src/com/android/settings/SettingsPreferenceFragment.java - platform/packages/apps/Settings - Git at Google

 /*
  * Copyright (C) 2010 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package com.android.settings;

 import android.app.Activity;
 import android.app.Dialog;
 import android.content.ContentResolver;
 import android.content.Context;
 import android.content.DialogInterface;
 import android.content.Intent;
 import android.content.pm.PackageManager;
 import android.os.Bundle;
 import android.text.TextUtils;
 import android.util.ArrayMap;
 import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.Button;

 import androidx.annotation.VisibleForTesting;
 import androidx.annotation.XmlRes;
 import androidx.fragment.app.DialogFragment;
 import androidx.fragment.app.Fragment;
 import androidx.preference.Preference;
 import androidx.preference.PreferenceGroup;
 import androidx.preference.PreferenceScreen;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;

 import com.android.settings.core.InstrumentedPreferenceFragment;
 import com.android.settings.core.instrumentation.InstrumentedDialogFragment;
 import com.android.settings.search.actionbar.SearchMenuController;
 import com.android.settings.support.actionbar.HelpMenuController;
 import com.android.settings.support.actionbar.HelpResourceProvider;
 import com.android.settings.widget.HighlightablePreferenceGroupAdapter;
 import com.android.settings.widget.LoadingViewController;
 import com.android.settingslib.CustomDialogPreferenceCompat;
 import com.android.settingslib.CustomEditTextPreferenceCompat;
 import com.android.settingslib.core.instrumentation.Instrumentable;
 import com.android.settingslib.search.Indexable;
 import com.android.settingslib.widget.LayoutPreference;

 import java.util.UUID;

 /**
  * Base class for Settings fragments, with some helper functions and dialog management.
  */
 public abstract class SettingsPreferenceFragment extends InstrumentedPreferenceFragment
         implements DialogCreatable, HelpResourceProvider, Indexable {

     private static final String TAG = "SettingsPreference";

     private static final String SAVE_HIGHLIGHTED_KEY = "android:preference_highlighted";

     private static final int ORDER_FIRST = -1;

     private SettingsDialogFragment mDialogFragment;
     // Cache the content resolver for async callbacks
     private ContentResolver mContentResolver;

     private RecyclerView.Adapter mCurrentRootAdapter;
     private boolean mIsDataSetObserverRegistered = false;
     private RecyclerView.AdapterDataObserver mDataSetObserver =
             new RecyclerView.AdapterDataObserver() {
                 @Override
                 public void onChanged() {
                     onDataSetChanged();
                 }

                 @Override
                 public void onItemRangeChanged(int positionStart, int itemCount) {
                     onDataSetChanged();
                 }

                 @Override
                 public void onItemRangeChanged(int positionStart, int itemCount, Object payload) {
                     onDataSetChanged();
                 }

                 @Override
                 public void onItemRangeInserted(int positionStart, int itemCount) {
                     onDataSetChanged();
                 }

                 @Override
                 public void onItemRangeRemoved(int positionStart, int itemCount) {
                     onDataSetChanged();
                 }

                 @Override
                 public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
                     onDataSetChanged();
                 }
             };

     @VisibleForTesting
     ViewGroup mPinnedHeaderFrameLayout;

     private LayoutPreference mHeader;

     private View mEmptyView;
     private LinearLayoutManager mLayoutManager;
     private ArrayMap<String, Preference> mPreferenceCache;
     private boolean mAnimationAllowed;

     @VisibleForTesting
     public HighlightablePreferenceGroupAdapter mAdapter;
     @VisibleForTesting
     public boolean mPreferenceHighlighted = false;

     @Override
     public void onCreate(Bundle icicle) {
         super.onCreate(icicle);
         SearchMenuController.init(this /* host */);
         HelpMenuController.init(this /* host */);

         if (icicle != null) {
             mPreferenceHighlighted = icicle.getBoolean(SAVE_HIGHLIGHTED_KEY);
         }
         HighlightablePreferenceGroupAdapter.adjustInitialExpandedChildCount(this /* host */);
     }

     @Override
     public View onCreateView(LayoutInflater inflater, ViewGroup container,
             Bundle savedInstanceState) {
         final View root = super.onCreateView(inflater, container, savedInstanceState);
         mPinnedHeaderFrameLayout = root.findViewById(R.id.pinned_header);
         return root;
     }

     @Override
     public void addPreferencesFromResource(@XmlRes int preferencesResId) {
         super.addPreferencesFromResource(preferencesResId);
         checkAvailablePrefs(getPreferenceScreen());
     }

     @VisibleForTesting
     void checkAvailablePrefs(PreferenceGroup preferenceGroup) {
         if (preferenceGroup == null) return;
         for (int i = 0; i < preferenceGroup.getPreferenceCount(); i++) {
             Preference pref = preferenceGroup.getPreference(i);
             if (pref instanceof SelfAvailablePreference
                     && !((SelfAvailablePreference) pref).isAvailable(getContext())) {
                 pref.setVisible(false);
             } else if (pref instanceof PreferenceGroup) {
                 checkAvailablePrefs((PreferenceGroup) pref);
             }
         }
     }

     public View setPinnedHeaderView(int layoutResId) {
         final LayoutInflater inflater = getActivity().getLayoutInflater();
         final View pinnedHeader =
                 inflater.inflate(layoutResId, mPinnedHeaderFrameLayout, false);
         setPinnedHeaderView(pinnedHeader);
         return pinnedHeader;
     }

     public void setPinnedHeaderView(View pinnedHeader) {
         mPinnedHeaderFrameLayout.addView(pinnedHeader);
         mPinnedHeaderFrameLayout.setVisibility(View.VISIBLE);
     }

     public void showPinnedHeader(boolean show) {
         mPinnedHeaderFrameLayout.setVisibility(show ? View.VISIBLE : View.INVISIBLE);
     }

     @Override
     public void onSaveInstanceState(Bundle outState) {
         super.onSaveInstanceState(outState);

         if (mAdapter != null) {
             outState.putBoolean(SAVE_HIGHLIGHTED_KEY, mAdapter.isHighlightRequested());
         }
     }

     @Override
     public void onActivityCreated(Bundle savedInstanceState) {
         super.onActivityCreated(savedInstanceState);
         setHasOptionsMenu(true);
     }

     @Override
     public void onResume() {
         super.onResume();
         highlightPreferenceIfNeeded();
     }

     @Override
     protected void onBindPreferences() {
         registerObserverIfNeeded();
     }

     @Override
     protected void onUnbindPreferences() {
         unregisterObserverIfNeeded();
     }

     public void setLoading(boolean loading, boolean animate) {
         View loadingContainer = getView().findViewById(R.id.loading_container);
         LoadingViewController.handleLoadingContainer(loadingContainer, getListView(),
                 !loading /* done */,
                 animate);
     }

     public void registerObserverIfNeeded() {
         if (!mIsDataSetObserverRegistered) {
             if (mCurrentRootAdapter != null) {
                 mCurrentRootAdapter.unregisterAdapterDataObserver(mDataSetObserver);
             }
             mCurrentRootAdapter = getListView().getAdapter();
             mCurrentRootAdapter.registerAdapterDataObserver(mDataSetObserver);
             mIsDataSetObserverRegistered = true;
             onDataSetChanged();
         }
     }

     public void unregisterObserverIfNeeded() {
         if (mIsDataSetObserverRegistered) {
             if (mCurrentRootAdapter != null) {
                 mCurrentRootAdapter.unregisterAdapterDataObserver(mDataSetObserver);
                 mCurrentRootAdapter = null;
             }
             mIsDataSetObserverRegistered = false;
         }
     }

     public void highlightPreferenceIfNeeded() {
         if (!isAdded()) {
             return;
         }
         if (mAdapter != null) {
             mAdapter.requestHighlight(getView(), getListView());
         }
     }

     /**
      * Returns initial expanded child count.
      * <p/>
      * Only override this method if the initial expanded child must be determined at run time.
      */
     public int getInitialExpandedChildCount() {
         return 0;
     }

     /**
      * Whether preference is allowing to be displayed to the user.
      *
      * @param preference to check if it can be displayed to the user (not hidding in expand area).
      * @return {@code true} when preference is allowing to be displayed to the user.
      * {@code false} when preference is hidden in expand area and not been displayed to the user.
      */
     protected boolean isPreferenceExpanded(Preference preference) {
         return ((mAdapter == null)
                 || (mAdapter.getPreferenceAdapterPosition(preference) != RecyclerView.NO_POSITION));
     }

     protected void onDataSetChanged() {
         highlightPreferenceIfNeeded();
         updateEmptyView();
     }

     public LayoutPreference getHeaderView() {
         return mHeader;
     }

     protected void setHeaderView(int resource) {
         mHeader = new LayoutPreference(getPrefContext(), resource);
         mHeader.setSelectable(false);
         addPreferenceToTop(mHeader);
     }

     protected void setHeaderView(View view) {
         mHeader = new LayoutPreference(getPrefContext(), view);
         mHeader.setSelectable(false);
         addPreferenceToTop(mHeader);
     }

     private void addPreferenceToTop(LayoutPreference preference) {
         preference.setOrder(ORDER_FIRST);
         if (getPreferenceScreen() != null) {
             getPreferenceScreen().addPreference(preference);
         }
     }

     @Override
     public void setPreferenceScreen(PreferenceScreen preferenceScreen) {
         if (preferenceScreen != null && !preferenceScreen.isAttached()) {
             // Without ids generated, the RecyclerView won't animate changes to the preferences.
             preferenceScreen.setShouldUseGeneratedIds(mAnimationAllowed);
         }
         super.setPreferenceScreen(preferenceScreen);
         if (preferenceScreen != null) {
             if (mHeader != null) {
                 preferenceScreen.addPreference(mHeader);
             }
         }
     }

     @VisibleForTesting
     void updateEmptyView() {
         if (mEmptyView == null) return;
         if (getPreferenceScreen() != null) {
             final View listContainer = getActivity().findViewById(android.R.id.list_container);
             boolean show = (getPreferenceScreen().getPreferenceCount()
                     - (mHeader != null ? 1 : 0)) <= 0
                     || (listContainer != null && listContainer.getVisibility() != View.VISIBLE);
             mEmptyView.setVisibility(show ? View.VISIBLE : View.GONE);
         } else {
             mEmptyView.setVisibility(View.VISIBLE);
         }
     }

     public void setEmptyView(View v) {
         if (mEmptyView != null) {
             mEmptyView.setVisibility(View.GONE);
         }
         mEmptyView = v;
         updateEmptyView();
     }

     public View getEmptyView() {
         return mEmptyView;
     }

     @Override
     public RecyclerView.LayoutManager onCreateLayoutManager() {
         mLayoutManager = new LinearLayoutManager(getContext());
         return mLayoutManager;
     }

     @Override
     protected RecyclerView.Adapter onCreateAdapter(PreferenceScreen preferenceScreen) {
         final Bundle arguments = getArguments();
         mAdapter = new HighlightablePreferenceGroupAdapter(preferenceScreen,
                 arguments == null
                         ? null : arguments.getString(SettingsActivity.EXTRA_FRAGMENT_ARG_KEY),
                 mPreferenceHighlighted);
         return mAdapter;
     }

     protected void setAnimationAllowed(boolean animationAllowed) {
         mAnimationAllowed = animationAllowed;
     }

     protected void cacheRemoveAllPrefs(PreferenceGroup group) {
         mPreferenceCache = new ArrayMap<>();
         final int N = group.getPreferenceCount();
         for (int i = 0; i < N; i++) {
             Preference p = group.getPreference(i);
             if (TextUtils.isEmpty(p.getKey())) {
                 continue;
             }
             mPreferenceCache.put(p.getKey(), p);
         }
     }

     protected Preference getCachedPreference(String key) {
         return mPreferenceCache != null ? mPreferenceCache.remove(key) : null;
     }

     protected void removeCachedPrefs(PreferenceGroup group) {
         for (Preference p : mPreferenceCache.values()) {
             group.removePreference(p);
         }
         mPreferenceCache = null;
     }

     protected int getCachedCount() {
         return mPreferenceCache != null ? mPreferenceCache.size() : 0;
     }

     @VisibleForTesting(otherwise = VisibleForTesting.PROTECTED)
     public boolean removePreference(String key) {
         return removePreference(getPreferenceScreen(), key);
     }

     @VisibleForTesting
     boolean removePreference(PreferenceGroup group, String key) {
         final int preferenceCount = group.getPreferenceCount();
         for (int i = 0; i < preferenceCount; i++) {
             final Preference preference = group.getPreference(i);
             final String curKey = preference.getKey();

             if (TextUtils.equals(curKey, key)) {
                 return group.removePreference(preference);
             }

             if (preference instanceof PreferenceGroup) {
                 if (removePreference((PreferenceGroup) preference, key)) {
                     return true;
                 }
             }
         }
         return false;
     }

     /*
      * The name is intentionally made different from Activity#finish(), so that
      * users won't misunderstand its meaning.
      */
     public final void finishFragment() {
         getActivity().onBackPressed();
     }

     // Some helpers for functions used by the settings fragments when they were activities

     /**
      * Returns the ContentResolver from the owning Activity.
      */
     protected ContentResolver getContentResolver() {
         Context context = getActivity();
         if (context != null) {
             mContentResolver = context.getContentResolver();
         }
         return mContentResolver;
     }

     /**
      * Returns the specified system service from the owning Activity.
      */
     protected Object getSystemService(final String name) {
         return getActivity().getSystemService(name);
     }

     /**
      * Returns the PackageManager from the owning Activity.
      */
     protected PackageManager getPackageManager() {
         return getActivity().getPackageManager();
     }

     @Override
     public void onDetach() {
         if (isRemoving()) {
             if (mDialogFragment != null) {
                 mDialogFragment.dismiss();
                 mDialogFragment = null;
             }
         }
         super.onDetach();
     }

     // Dialog management

     protected void showDialog(int dialogId) {
         if (mDialogFragment != null) {
             Log.e(TAG, "Old dialog fragment not null!");
         }
         mDialogFragment = SettingsDialogFragment.newInstance(this, dialogId);
         mDialogFragment.show(getChildFragmentManager(), Integer.toString(dialogId));
     }

     @Override
     public Dialog onCreateDialog(int dialogId) {
         return null;
     }

     @Override
     public int getDialogMetricsCategory(int dialogId) {
         return 0;
     }

     protected void removeDialog(int dialogId) {
         // mDialogFragment may not be visible yet in parent fragment's onResume().
         // To be able to dismiss dialog at that time, don't check
         // mDialogFragment.isVisible().
         if (mDialogFragment != null && mDialogFragment.getDialogId() == dialogId) {
             mDialogFragment.dismissAllowingStateLoss();
         }
         mDialogFragment = null;
     }

     /**
      * Sets the OnCancelListener of the dialog shown. This method can only be
      * called after showDialog(int) and before removeDialog(int). The method
      * does nothing otherwise.
      */
     protected void setOnCancelListener(DialogInterface.OnCancelListener listener) {
         if (mDialogFragment != null) {
             mDialogFragment.mOnCancelListener = listener;
         }
     }

     /**
      * Sets the OnDismissListener of the dialog shown. This method can only be
      * called after showDialog(int) and before removeDialog(int). The method
      * does nothing otherwise.
      */
     protected void setOnDismissListener(DialogInterface.OnDismissListener listener) {
         if (mDialogFragment != null) {
             mDialogFragment.mOnDismissListener = listener;
         }
     }

     public void onDialogShowing() {
         // override in subclass to attach a dismiss listener, for instance
     }

     @Override
     public void onDisplayPreferenceDialog(Preference preference) {
         if (preference.getKey() == null) {
             // Auto-key preferences that don't have a key, so the dialog can find them.
             preference.setKey(UUID.randomUUID().toString());
         }
         DialogFragment f = null;
         if (preference instanceof RestrictedListPreference) {
             f = RestrictedListPreference.RestrictedListPreferenceDialogFragment
                     .newInstance(preference.getKey());
         } else if (preference instanceof CustomListPreference) {
             f = CustomListPreference.CustomListPreferenceDialogFragment
                     .newInstance(preference.getKey());
         } else if (preference instanceof CustomDialogPreferenceCompat) {
             f = CustomDialogPreferenceCompat.CustomPreferenceDialogFragment
                     .newInstance(preference.getKey());
         } else if (preference instanceof CustomEditTextPreferenceCompat) {
             f = CustomEditTextPreferenceCompat.CustomPreferenceDialogFragment
                     .newInstance(preference.getKey());
         } else {
             super.onDisplayPreferenceDialog(preference);
             return;
         }
         f.setTargetFragment(this, 0);
         f.show(getFragmentManager(), "dialog_preference");
         onDialogShowing();
     }

     public static class SettingsDialogFragment extends InstrumentedDialogFragment {
         private static final String KEY_DIALOG_ID = "key_dialog_id";
         private static final String KEY_PARENT_FRAGMENT_ID = "key_parent_fragment_id";

         private Fragment mParentFragment;

         private DialogInterface.OnCancelListener mOnCancelListener;
         private DialogInterface.OnDismissListener mOnDismissListener;

         public static SettingsDialogFragment newInstance(DialogCreatable fragment, int dialogId) {
             if (!(fragment instanceof Fragment)) {
                 throw new IllegalArgumentException("fragment argument must be an instance of "
                         + Fragment.class.getName());
             }

             final SettingsDialogFragment settingsDialogFragment = new SettingsDialogFragment();
             settingsDialogFragment.setParentFragment(fragment);
             settingsDialogFragment.setDialogId(dialogId);

             return settingsDialogFragment;
         }

         @Override
         public int getMetricsCategory() {
             if (mParentFragment == null) {
                 return Instrumentable.METRICS_CATEGORY_UNKNOWN;
             }
             final int metricsCategory =
                     ((DialogCreatable) mParentFragment).getDialogMetricsCategory(mDialogId);
             if (metricsCategory <= 0) {
                 throw new IllegalStateException("Dialog must provide a metrics category");
             }
             return metricsCategory;
         }

         @Override
         public void onSaveInstanceState(Bundle outState) {
             super.onSaveInstanceState(outState);
             if (mParentFragment != null) {
                 outState.putInt(KEY_DIALOG_ID, mDialogId);
                 outState.putInt(KEY_PARENT_FRAGMENT_ID, mParentFragment.getId());
             }
         }

         @Override
         public void onStart() {
             super.onStart();

             if (mParentFragment != null && mParentFragment instanceof SettingsPreferenceFragment) {
                 ((SettingsPreferenceFragment) mParentFragment).onDialogShowing();
             }
         }

         @Override
         public Dialog onCreateDialog(Bundle savedInstanceState) {
             if (savedInstanceState != null) {
                 mDialogId = savedInstanceState.getInt(KEY_DIALOG_ID, 0);
                 mParentFragment = getParentFragment();
                 int mParentFragmentId = savedInstanceState.getInt(KEY_PARENT_FRAGMENT_ID, -1);
                 if (mParentFragment == null) {
                     mParentFragment = getFragmentManager().findFragmentById(mParentFragmentId);
                 }
                 if (!(mParentFragment instanceof DialogCreatable)) {
                     throw new IllegalArgumentException(
                             (mParentFragment != null
                                     ? mParentFragment.getClass().getName()
                                     : mParentFragmentId)
                                     + " must implement "
                                     + DialogCreatable.class.getName());
                 }
                 // This dialog fragment could be created from non-SettingsPreferenceFragment
                 if (mParentFragment instanceof SettingsPreferenceFragment) {
                     // restore mDialogFragment in mParentFragment
                     ((SettingsPreferenceFragment) mParentFragment).mDialogFragment = this;
                 }
             }
             return ((DialogCreatable) mParentFragment).onCreateDialog(mDialogId);
         }

         @Override
         public void onCancel(DialogInterface dialog) {
             super.onCancel(dialog);
             if (mOnCancelListener != null) {
                 mOnCancelListener.onCancel(dialog);
             }
         }

         @Override
         public void onDismiss(DialogInterface dialog) {
             super.onDismiss(dialog);
             if (mOnDismissListener != null) {
                 mOnDismissListener.onDismiss(dialog);
             }
         }

         public int getDialogId() {
             return mDialogId;
         }

         @Override
         public void onDetach() {
             super.onDetach();

             // This dialog fragment could be created from non-SettingsPreferenceFragment
             if (mParentFragment instanceof SettingsPreferenceFragment) {
                 // in case the dialog is not explicitly removed by removeDialog()
                 if (((SettingsPreferenceFragment) mParentFragment).mDialogFragment == this) {
                     ((SettingsPreferenceFragment) mParentFragment).mDialogFragment = null;
                 }
             }
         }

         private void setParentFragment(DialogCreatable fragment) {
             mParentFragment = (Fragment) fragment;
         }

         private void setDialogId(int dialogId) {
             mDialogId = dialogId;
         }
     }

     protected boolean hasNextButton() {
         return ((ButtonBarHandler) getActivity()).hasNextButton();
     }

     protected Button getNextButton() {
         return ((ButtonBarHandler) getActivity()).getNextButton();
     }

     public void finish() {
         Activity activity = getActivity();
         if (activity == null) return;
         if (getFragmentManager().getBackStackEntryCount() > 0) {
             getFragmentManager().popBackStack();
         } else {
             activity.finish();
         }
     }

     protected Intent getIntent() {
         if (getActivity() == null) {
             return null;
         }
         return getActivity().getIntent();
     }

     protected void setResult(int result, Intent intent) {
         if (getActivity() == null) {
             return;
         }
         getActivity().setResult(result, intent);
     }

     protected void setResult(int result) {
         if (getActivity() == null) {
             return;
         }
         getActivity().setResult(result);
     }

     protected boolean isFinishingOrDestroyed() {
         final Activity activity = getActivity();
         return activity == null || activity.isFinishing() || activity.isDestroyed();
     }
 }
	/*
	* Copyright (C) 2010 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package com.android.settings;

	import android.app.Activity;
	import android.app.Dialog;
	import android.content.ContentResolver;
	import android.content.Context;
	import android.content.DialogInterface;
	import android.content.Intent;
	import android.content.pm.PackageManager;
	import android.os.Bundle;
	import android.text.TextUtils;
	import android.util.ArrayMap;
	import android.util.Log;
	import android.view.LayoutInflater;
	import android.view.View;
	import android.view.ViewGroup;
	import android.widget.Button;

	import androidx.annotation.VisibleForTesting;
	import androidx.annotation.XmlRes;
	import androidx.fragment.app.DialogFragment;
	import androidx.fragment.app.Fragment;
	import androidx.preference.Preference;
	import androidx.preference.PreferenceGroup;
	import androidx.preference.PreferenceScreen;
	import androidx.recyclerview.widget.LinearLayoutManager;
	import androidx.recyclerview.widget.RecyclerView;

	import com.android.settings.core.InstrumentedPreferenceFragment;
	import com.android.settings.core.instrumentation.InstrumentedDialogFragment;
	import com.android.settings.search.actionbar.SearchMenuController;
	import com.android.settings.support.actionbar.HelpMenuController;
	import com.android.settings.support.actionbar.HelpResourceProvider;
	import com.android.settings.widget.HighlightablePreferenceGroupAdapter;
	import com.android.settings.widget.LoadingViewController;
	import com.android.settingslib.CustomDialogPreferenceCompat;
	import com.android.settingslib.CustomEditTextPreferenceCompat;
	import com.android.settingslib.core.instrumentation.Instrumentable;
	import com.android.settingslib.search.Indexable;
	import com.android.settingslib.widget.LayoutPreference;

	import java.util.UUID;

	/**
	* Base class for Settings fragments, with some helper functions and dialog management.
	*/
	public abstract class SettingsPreferenceFragment extends InstrumentedPreferenceFragment
	implements DialogCreatable, HelpResourceProvider, Indexable {

	private static final String TAG = "SettingsPreference";

	private static final String SAVE_HIGHLIGHTED_KEY = "android:preference_highlighted";

	private static final int ORDER_FIRST = -1;

	private SettingsDialogFragment mDialogFragment;
	// Cache the content resolver for async callbacks
	private ContentResolver mContentResolver;

	private RecyclerView.Adapter mCurrentRootAdapter;
	private boolean mIsDataSetObserverRegistered = false;
	private RecyclerView.AdapterDataObserver mDataSetObserver =
	new RecyclerView.AdapterDataObserver() {
	@Override
	public void onChanged() {
	onDataSetChanged();
	}

	@Override
	public void onItemRangeChanged(int positionStart, int itemCount) {
	onDataSetChanged();
	}

	@Override
	public void onItemRangeChanged(int positionStart, int itemCount, Object payload) {
	onDataSetChanged();
	}

	@Override
	public void onItemRangeInserted(int positionStart, int itemCount) {
	onDataSetChanged();
	}

	@Override
	public void onItemRangeRemoved(int positionStart, int itemCount) {
	onDataSetChanged();
	}

	@Override
	public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
	onDataSetChanged();
	}
	};

	@VisibleForTesting
	ViewGroup mPinnedHeaderFrameLayout;

	private LayoutPreference mHeader;

	private View mEmptyView;
	private LinearLayoutManager mLayoutManager;
	private ArrayMap<String, Preference> mPreferenceCache;
	private boolean mAnimationAllowed;

	@VisibleForTesting
	public HighlightablePreferenceGroupAdapter mAdapter;
	@VisibleForTesting
	public boolean mPreferenceHighlighted = false;

	@Override
	public void onCreate(Bundle icicle) {
	super.onCreate(icicle);
	SearchMenuController.init(this /* host */);
	HelpMenuController.init(this /* host */);

	if (icicle != null) {
	mPreferenceHighlighted = icicle.getBoolean(SAVE_HIGHLIGHTED_KEY);
	}
	HighlightablePreferenceGroupAdapter.adjustInitialExpandedChildCount(this /* host */);
	}

	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
	Bundle savedInstanceState) {
	final View root = super.onCreateView(inflater, container, savedInstanceState);
	mPinnedHeaderFrameLayout = root.findViewById(R.id.pinned_header);
	return root;
	}

	@Override
	public void addPreferencesFromResource(@XmlRes int preferencesResId) {
	super.addPreferencesFromResource(preferencesResId);
	checkAvailablePrefs(getPreferenceScreen());
	}

	@VisibleForTesting
	void checkAvailablePrefs(PreferenceGroup preferenceGroup) {
	if (preferenceGroup == null) return;
	for (int i = 0; i < preferenceGroup.getPreferenceCount(); i++) {
	Preference pref = preferenceGroup.getPreference(i);
	if (pref instanceof SelfAvailablePreference
	&& !((SelfAvailablePreference) pref).isAvailable(getContext())) {
	pref.setVisible(false);
	} else if (pref instanceof PreferenceGroup) {
	checkAvailablePrefs((PreferenceGroup) pref);
	}
	}
	}

	public View setPinnedHeaderView(int layoutResId) {
	final LayoutInflater inflater = getActivity().getLayoutInflater();
	final View pinnedHeader =
	inflater.inflate(layoutResId, mPinnedHeaderFrameLayout, false);
	setPinnedHeaderView(pinnedHeader);
	return pinnedHeader;
	}

	public void setPinnedHeaderView(View pinnedHeader) {
	mPinnedHeaderFrameLayout.addView(pinnedHeader);
	mPinnedHeaderFrameLayout.setVisibility(View.VISIBLE);
	}

	public void showPinnedHeader(boolean show) {
	mPinnedHeaderFrameLayout.setVisibility(show ? View.VISIBLE : View.INVISIBLE);
	}

	@Override
	public void onSaveInstanceState(Bundle outState) {
	super.onSaveInstanceState(outState);

	if (mAdapter != null) {
	outState.putBoolean(SAVE_HIGHLIGHTED_KEY, mAdapter.isHighlightRequested());
	}
	}

	@Override
	public void onActivityCreated(Bundle savedInstanceState) {
	super.onActivityCreated(savedInstanceState);
	setHasOptionsMenu(true);
	}

	@Override
	public void onResume() {
	super.onResume();
	highlightPreferenceIfNeeded();
	}

	@Override
	protected void onBindPreferences() {
	registerObserverIfNeeded();
	}

	@Override
	protected void onUnbindPreferences() {
	unregisterObserverIfNeeded();
	}

	public void setLoading(boolean loading, boolean animate) {
	View loadingContainer = getView().findViewById(R.id.loading_container);
	LoadingViewController.handleLoadingContainer(loadingContainer, getListView(),
	!loading /* done */,
	animate);
	}

	public void registerObserverIfNeeded() {
	if (!mIsDataSetObserverRegistered) {
	if (mCurrentRootAdapter != null) {
	mCurrentRootAdapter.unregisterAdapterDataObserver(mDataSetObserver);
	}
	mCurrentRootAdapter = getListView().getAdapter();
	mCurrentRootAdapter.registerAdapterDataObserver(mDataSetObserver);
	mIsDataSetObserverRegistered = true;
	onDataSetChanged();
	}
	}

	public void unregisterObserverIfNeeded() {
	if (mIsDataSetObserverRegistered) {
	if (mCurrentRootAdapter != null) {
	mCurrentRootAdapter.unregisterAdapterDataObserver(mDataSetObserver);
	mCurrentRootAdapter = null;
	}
	mIsDataSetObserverRegistered = false;
	}
	}

	public void highlightPreferenceIfNeeded() {
	if (!isAdded()) {
	return;
	}
	if (mAdapter != null) {
	mAdapter.requestHighlight(getView(), getListView());
	}
	}

	/**
	* Returns initial expanded child count.
	* <p/>
	* Only override this method if the initial expanded child must be determined at run time.
	*/
	public int getInitialExpandedChildCount() {
	return 0;
	}

	/**
	* Whether preference is allowing to be displayed to the user.
	*
	* @param preference to check if it can be displayed to the user (not hidding in expand area).
	* @return {@code true} when preference is allowing to be displayed to the user.
	* {@code false} when preference is hidden in expand area and not been displayed to the user.
	*/
	protected boolean isPreferenceExpanded(Preference preference) {
	return ((mAdapter == null)
	\|\| (mAdapter.getPreferenceAdapterPosition(preference) != RecyclerView.NO_POSITION));
	}

	protected void onDataSetChanged() {
	highlightPreferenceIfNeeded();
	updateEmptyView();
	}

	public LayoutPreference getHeaderView() {
	return mHeader;
	}

	protected void setHeaderView(int resource) {
	mHeader = new LayoutPreference(getPrefContext(), resource);
	mHeader.setSelectable(false);
	addPreferenceToTop(mHeader);
	}

	protected void setHeaderView(View view) {
	mHeader = new LayoutPreference(getPrefContext(), view);
	mHeader.setSelectable(false);
	addPreferenceToTop(mHeader);
	}

	private void addPreferenceToTop(LayoutPreference preference) {
	preference.setOrder(ORDER_FIRST);
	if (getPreferenceScreen() != null) {
	getPreferenceScreen().addPreference(preference);
	}
	}

	@Override
	public void setPreferenceScreen(PreferenceScreen preferenceScreen) {
	if (preferenceScreen != null && !preferenceScreen.isAttached()) {
	// Without ids generated, the RecyclerView won't animate changes to the preferences.
	preferenceScreen.setShouldUseGeneratedIds(mAnimationAllowed);
	}
	super.setPreferenceScreen(preferenceScreen);
	if (preferenceScreen != null) {
	if (mHeader != null) {
	preferenceScreen.addPreference(mHeader);
	}
	}
	}

	@VisibleForTesting
	void updateEmptyView() {
	if (mEmptyView == null) return;
	if (getPreferenceScreen() != null) {
	final View listContainer = getActivity().findViewById(android.R.id.list_container);
	boolean show = (getPreferenceScreen().getPreferenceCount()
	- (mHeader != null ? 1 : 0)) <= 0
	\|\| (listContainer != null && listContainer.getVisibility() != View.VISIBLE);
	mEmptyView.setVisibility(show ? View.VISIBLE : View.GONE);
	} else {
	mEmptyView.setVisibility(View.VISIBLE);
	}
	}

	public void setEmptyView(View v) {
	if (mEmptyView != null) {
	mEmptyView.setVisibility(View.GONE);
	}
	mEmptyView = v;
	updateEmptyView();
	}

	public View getEmptyView() {
	return mEmptyView;
	}

	@Override
	public RecyclerView.LayoutManager onCreateLayoutManager() {
	mLayoutManager = new LinearLayoutManager(getContext());
	return mLayoutManager;
	}

	@Override
	protected RecyclerView.Adapter onCreateAdapter(PreferenceScreen preferenceScreen) {
	final Bundle arguments = getArguments();
	mAdapter = new HighlightablePreferenceGroupAdapter(preferenceScreen,
	arguments == null
	? null : arguments.getString(SettingsActivity.EXTRA_FRAGMENT_ARG_KEY),
	mPreferenceHighlighted);
	return mAdapter;
	}

	protected void setAnimationAllowed(boolean animationAllowed) {
	mAnimationAllowed = animationAllowed;
	}

	protected void cacheRemoveAllPrefs(PreferenceGroup group) {
	mPreferenceCache = new ArrayMap<>();
	final int N = group.getPreferenceCount();
	for (int i = 0; i < N; i++) {
	Preference p = group.getPreference(i);
	if (TextUtils.isEmpty(p.getKey())) {
	continue;
	}
	mPreferenceCache.put(p.getKey(), p);
	}
	}

	protected Preference getCachedPreference(String key) {
	return mPreferenceCache != null ? mPreferenceCache.remove(key) : null;
	}

	protected void removeCachedPrefs(PreferenceGroup group) {
	for (Preference p : mPreferenceCache.values()) {
	group.removePreference(p);
	}
	mPreferenceCache = null;
	}

	protected int getCachedCount() {
	return mPreferenceCache != null ? mPreferenceCache.size() : 0;
	}

	@VisibleForTesting(otherwise = VisibleForTesting.PROTECTED)
	public boolean removePreference(String key) {
	return removePreference(getPreferenceScreen(), key);
	}

	@VisibleForTesting
	boolean removePreference(PreferenceGroup group, String key) {
	final int preferenceCount = group.getPreferenceCount();
	for (int i = 0; i < preferenceCount; i++) {
	final Preference preference = group.getPreference(i);
	final String curKey = preference.getKey();

	if (TextUtils.equals(curKey, key)) {
	return group.removePreference(preference);
	}

	if (preference instanceof PreferenceGroup) {
	if (removePreference((PreferenceGroup) preference, key)) {
	return true;
	}
	}
	}
	return false;
	}

	/*
	* The name is intentionally made different from Activity#finish(), so that
	* users won't misunderstand its meaning.
	*/
	public final void finishFragment() {
	getActivity().onBackPressed();
	}

	// Some helpers for functions used by the settings fragments when they were activities

	/**
	* Returns the ContentResolver from the owning Activity.
	*/
	protected ContentResolver getContentResolver() {
	Context context = getActivity();
	if (context != null) {
	mContentResolver = context.getContentResolver();
	}
	return mContentResolver;
	}

	/**
	* Returns the specified system service from the owning Activity.
	*/
	protected Object getSystemService(final String name) {
	return getActivity().getSystemService(name);
	}

	/**
	* Returns the PackageManager from the owning Activity.
	*/
	protected PackageManager getPackageManager() {
	return getActivity().getPackageManager();
	}

	@Override
	public void onDetach() {
	if (isRemoving()) {
	if (mDialogFragment != null) {
	mDialogFragment.dismiss();
	mDialogFragment = null;
	}
	}
	super.onDetach();
	}

	// Dialog management

	protected void showDialog(int dialogId) {
	if (mDialogFragment != null) {
	Log.e(TAG, "Old dialog fragment not null!");
	}
	mDialogFragment = SettingsDialogFragment.newInstance(this, dialogId);
	mDialogFragment.show(getChildFragmentManager(), Integer.toString(dialogId));
	}

	@Override
	public Dialog onCreateDialog(int dialogId) {
	return null;
	}

	@Override
	public int getDialogMetricsCategory(int dialogId) {
	return 0;
	}

	protected void removeDialog(int dialogId) {
	// mDialogFragment may not be visible yet in parent fragment's onResume().
	// To be able to dismiss dialog at that time, don't check
	// mDialogFragment.isVisible().
	if (mDialogFragment != null && mDialogFragment.getDialogId() == dialogId) {
	mDialogFragment.dismissAllowingStateLoss();
	}
	mDialogFragment = null;
	}

	/**
	* Sets the OnCancelListener of the dialog shown. This method can only be
	* called after showDialog(int) and before removeDialog(int). The method
	* does nothing otherwise.
	*/
	protected void setOnCancelListener(DialogInterface.OnCancelListener listener) {
	if (mDialogFragment != null) {
	mDialogFragment.mOnCancelListener = listener;
	}
	}

	/**
	* Sets the OnDismissListener of the dialog shown. This method can only be
	* called after showDialog(int) and before removeDialog(int). The method
	* does nothing otherwise.
	*/
	protected void setOnDismissListener(DialogInterface.OnDismissListener listener) {
	if (mDialogFragment != null) {
	mDialogFragment.mOnDismissListener = listener;
	}
	}

	public void onDialogShowing() {
	// override in subclass to attach a dismiss listener, for instance
	}

	@Override
	public void onDisplayPreferenceDialog(Preference preference) {
	if (preference.getKey() == null) {
	// Auto-key preferences that don't have a key, so the dialog can find them.
	preference.setKey(UUID.randomUUID().toString());
	}
	DialogFragment f = null;
	if (preference instanceof RestrictedListPreference) {
	f = RestrictedListPreference.RestrictedListPreferenceDialogFragment
	.newInstance(preference.getKey());
	} else if (preference instanceof CustomListPreference) {
	f = CustomListPreference.CustomListPreferenceDialogFragment
	.newInstance(preference.getKey());
	} else if (preference instanceof CustomDialogPreferenceCompat) {
	f = CustomDialogPreferenceCompat.CustomPreferenceDialogFragment
	.newInstance(preference.getKey());
	} else if (preference instanceof CustomEditTextPreferenceCompat) {
	f = CustomEditTextPreferenceCompat.CustomPreferenceDialogFragment
	.newInstance(preference.getKey());
	} else {
	super.onDisplayPreferenceDialog(preference);
	return;
	}
	f.setTargetFragment(this, 0);
	f.show(getFragmentManager(), "dialog_preference");
	onDialogShowing();
	}

	public static class SettingsDialogFragment extends InstrumentedDialogFragment {
	private static final String KEY_DIALOG_ID = "key_dialog_id";
	private static final String KEY_PARENT_FRAGMENT_ID = "key_parent_fragment_id";

	private Fragment mParentFragment;

	private DialogInterface.OnCancelListener mOnCancelListener;
	private DialogInterface.OnDismissListener mOnDismissListener;

	public static SettingsDialogFragment newInstance(DialogCreatable fragment, int dialogId) {
	if (!(fragment instanceof Fragment)) {
	throw new IllegalArgumentException("fragment argument must be an instance of "
	+ Fragment.class.getName());
	}

	final SettingsDialogFragment settingsDialogFragment = new SettingsDialogFragment();
	settingsDialogFragment.setParentFragment(fragment);
	settingsDialogFragment.setDialogId(dialogId);

	return settingsDialogFragment;
	}

	@Override
	public int getMetricsCategory() {
	if (mParentFragment == null) {
	return Instrumentable.METRICS_CATEGORY_UNKNOWN;
	}
	final int metricsCategory =
	((DialogCreatable) mParentFragment).getDialogMetricsCategory(mDialogId);
	if (metricsCategory <= 0) {
	throw new IllegalStateException("Dialog must provide a metrics category");
	}
	return metricsCategory;
	}

	@Override
	public void onSaveInstanceState(Bundle outState) {
	super.onSaveInstanceState(outState);
	if (mParentFragment != null) {
	outState.putInt(KEY_DIALOG_ID, mDialogId);
	outState.putInt(KEY_PARENT_FRAGMENT_ID, mParentFragment.getId());
	}
	}

	@Override
	public void onStart() {
	super.onStart();

	if (mParentFragment != null && mParentFragment instanceof SettingsPreferenceFragment) {
	((SettingsPreferenceFragment) mParentFragment).onDialogShowing();
	}
	}

	@Override
	public Dialog onCreateDialog(Bundle savedInstanceState) {
	if (savedInstanceState != null) {
	mDialogId = savedInstanceState.getInt(KEY_DIALOG_ID, 0);
	mParentFragment = getParentFragment();
	int mParentFragmentId = savedInstanceState.getInt(KEY_PARENT_FRAGMENT_ID, -1);
	if (mParentFragment == null) {
	mParentFragment = getFragmentManager().findFragmentById(mParentFragmentId);
	}
	if (!(mParentFragment instanceof DialogCreatable)) {
	throw new IllegalArgumentException(
	(mParentFragment != null
	? mParentFragment.getClass().getName()
	: mParentFragmentId)
	+ " must implement "
	+ DialogCreatable.class.getName());
	}
	// This dialog fragment could be created from non-SettingsPreferenceFragment
	if (mParentFragment instanceof SettingsPreferenceFragment) {
	// restore mDialogFragment in mParentFragment
	((SettingsPreferenceFragment) mParentFragment).mDialogFragment = this;
	}
	}
	return ((DialogCreatable) mParentFragment).onCreateDialog(mDialogId);
	}

	@Override
	public void onCancel(DialogInterface dialog) {
	super.onCancel(dialog);
	if (mOnCancelListener != null) {
	mOnCancelListener.onCancel(dialog);
	}
	}

	@Override
	public void onDismiss(DialogInterface dialog) {
	super.onDismiss(dialog);
	if (mOnDismissListener != null) {
	mOnDismissListener.onDismiss(dialog);
	}
	}

	public int getDialogId() {
	return mDialogId;
	}

	@Override
	public void onDetach() {
	super.onDetach();

	// This dialog fragment could be created from non-SettingsPreferenceFragment
	if (mParentFragment instanceof SettingsPreferenceFragment) {
	// in case the dialog is not explicitly removed by removeDialog()
	if (((SettingsPreferenceFragment) mParentFragment).mDialogFragment == this) {
	((SettingsPreferenceFragment) mParentFragment).mDialogFragment = null;
	}
	}
	}

	private void setParentFragment(DialogCreatable fragment) {
	mParentFragment = (Fragment) fragment;
	}

	private void setDialogId(int dialogId) {
	mDialogId = dialogId;
	}
	}

	protected boolean hasNextButton() {
	return ((ButtonBarHandler) getActivity()).hasNextButton();
	}

	protected Button getNextButton() {
	return ((ButtonBarHandler) getActivity()).getNextButton();
	}

	public void finish() {
	Activity activity = getActivity();
	if (activity == null) return;
	if (getFragmentManager().getBackStackEntryCount() > 0) {
	getFragmentManager().popBackStack();
	} else {
	activity.finish();
	}
	}

	protected Intent getIntent() {
	if (getActivity() == null) {
	return null;
	}
	return getActivity().getIntent();
	}

	protected void setResult(int result, Intent intent) {
	if (getActivity() == null) {
	return;
	}
	getActivity().setResult(result, intent);
	}

	protected void setResult(int result) {
	if (getActivity() == null) {
	return;
	}
	getActivity().setResult(result);
	}

	protected boolean isFinishingOrDestroyed() {
	final Activity activity = getActivity();
	return activity == null \|\| activity.isFinishing() \|\| activity.isDestroyed();
	}
	}