library/src/main/java/com/bumptech/glide/manager/RequestManagerRetriever.java

package com.bumptech.glide.manager;

import android.annotation.TargetApi;
import android.app.Activity;
import android.app.Application;
import android.content.Context;
import android.content.ContextWrapper;
import android.os.Build;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentActivity;
import androidx.fragment.app.FragmentManager;
import android.util.Log;

import com.bumptech.glide.RequestManager;
import com.bumptech.glide.util.Util;

import java.util.HashMap;
import java.util.Map;

/**
 * A collection of static methods for creating new {@link com.bumptech.glide.RequestManager}s or retrieving existing
 * ones from activities and fragment.
 */
public class RequestManagerRetriever implements Handler.Callback {
    static final String TAG = "com.bumptech.glide.manager";

    /** The singleton instance of RequestManagerRetriever. */
    private static final RequestManagerRetriever INSTANCE = new RequestManagerRetriever();

    private static final int ID_REMOVE_FRAGMENT_MANAGER = 1;
    private static final int ID_REMOVE_SUPPORT_FRAGMENT_MANAGER = 2;

    /** The top application level RequestManager. */
    private volatile RequestManager applicationManager;

    // Visible for testing.
    /** Pending adds for RequestManagerFragments. */
    final Map<android.app.FragmentManager, RequestManagerFragment> pendingRequestManagerFragments =
            new HashMap<android.app.FragmentManager, RequestManagerFragment>();

    // Visible for testing.
    /** Pending adds for SupportRequestManagerFragments. */
    final Map<FragmentManager, SupportRequestManagerFragment> pendingSupportRequestManagerFragments =
            new HashMap<FragmentManager, SupportRequestManagerFragment>();

    /** Main thread handler to handle cleaning up pending fragment maps. */
    private final Handler handler;

    /**
     * Retrieves and returns the RequestManagerRetriever singleton.
     */
    public static RequestManagerRetriever get() {
        return INSTANCE;
    }

    // Visible for testing.
    RequestManagerRetriever() {
        handler = new Handler(Looper.getMainLooper(), this /* Callback */);
    }

    private RequestManager getApplicationManager(Context context) {
        // Either an application context or we're on a background thread.
        if (applicationManager == null) {
            synchronized (this) {
                if (applicationManager == null) {
                    // Normally pause/resume is taken care of by the fragment we add to the fragment or activity.
                    // However, in this case since the manager attached to the application will not receive lifecycle
                    // events, we must force the manager to start resumed using ApplicationLifecycle.
                    applicationManager = new RequestManager(context.getApplicationContext(),
                            new ApplicationLifecycle());
                }
            }
        }

        return applicationManager;
    }

    public RequestManager get(Context context) {
        if (context == null) {
            throw new IllegalArgumentException("You cannot start a load on a null Context");
        } else if (Util.isOnMainThread() && !(context instanceof Application)) {
            if (context instanceof FragmentActivity) {
                return get((FragmentActivity) context);
            } else if (context instanceof Activity) {
                return get((Activity) context);
            } else if (context instanceof ContextWrapper) {
                return get(((ContextWrapper) context).getBaseContext());
            }
        }

        return getApplicationManager(context);
    }

    public RequestManager get(FragmentActivity activity) {
        if (Util.isOnBackgroundThread()) {
            return get(activity.getApplicationContext());
        } else {
            assertNotDestroyed(activity);
            FragmentManager fm = activity.getSupportFragmentManager();
            return supportFragmentGet(activity, fm);
        }
    }

    public RequestManager get(Fragment fragment) {
        if (fragment.getActivity() == null) {
            throw new IllegalArgumentException("You cannot start a load on a fragment before it is attached");
        }
        if (Util.isOnBackgroundThread()) {
            return get(fragment.getActivity().getApplicationContext());
        } else {
            if (fragment.isDetached()) {
                throw new IllegalArgumentException("You cannot start a load on a detached fragment");
            }
            FragmentManager fm = fragment.getChildFragmentManager();
            return supportFragmentGet(fragment.getActivity(), fm);
        }
    }

    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    public RequestManager get(Activity activity) {
        if (Util.isOnBackgroundThread() || Build.VERSION.SDK_INT < Build.VERSION_CODES.HONEYCOMB) {
            return get(activity.getApplicationContext());
        } else {
            assertNotDestroyed(activity);
            android.app.FragmentManager fm = activity.getFragmentManager();
            return fragmentGet(activity, fm);
        }
    }

    @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
    private static void assertNotDestroyed(Activity activity) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1 && activity.isDestroyed()) {
            throw new IllegalArgumentException("You cannot start a load for a destroyed activity");
        }
    }

    @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
    public RequestManager get(android.app.Fragment fragment) {
        if (fragment.getActivity() == null) {
            throw new IllegalArgumentException("You cannot start a load on a fragment before it is attached");
        }
        if (Util.isOnBackgroundThread() || Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN_MR1) {
            return get(fragment.getActivity().getApplicationContext());
        } else {
            assertNotDetached(fragment);
            android.app.FragmentManager fm = fragment.getChildFragmentManager();
            return fragmentGet(fragment.getActivity(), fm);
        }
    }

    @TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2)
    private static void assertNotDetached(android.app.Fragment fragment) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR2 && fragment.isDetached()) {
            throw new IllegalArgumentException("You cannot start a load on a detached fragment");
        }
    }

    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    RequestManager fragmentGet(Context context, final android.app.FragmentManager fm) {
        RequestManagerFragment current = (RequestManagerFragment) fm.findFragmentByTag(TAG);
        if (current == null) {
            current = pendingRequestManagerFragments.get(fm);
            if (current == null) {
                current = new RequestManagerFragment();
                pendingRequestManagerFragments.put(fm, current);
                fm.beginTransaction().add(current, TAG).commitAllowingStateLoss();
                handler.obtainMessage(ID_REMOVE_FRAGMENT_MANAGER, fm).sendToTarget();
            }
        }
        RequestManager requestManager = current.getRequestManager();
        if (requestManager == null) {
            requestManager = new RequestManager(context, current.getGlideLifecycle());
            current.setRequestManager(requestManager);
        }
        return requestManager;

    }

    RequestManager supportFragmentGet(Context context, final FragmentManager fm) {
        SupportRequestManagerFragment current = (SupportRequestManagerFragment) fm.findFragmentByTag(TAG);
        if (current == null) {
            current = pendingSupportRequestManagerFragments.get(fm);
            if (current == null) {
                current = new SupportRequestManagerFragment();
                pendingSupportRequestManagerFragments.put(fm, current);
                fm.beginTransaction().add(current, TAG).commitAllowingStateLoss();
                handler.obtainMessage(ID_REMOVE_SUPPORT_FRAGMENT_MANAGER, fm).sendToTarget();
            }
        }
        RequestManager requestManager = current.getRequestManager();
        if (requestManager == null) {
            requestManager = new RequestManager(context, current.getGlideLifecycle());
            current.setRequestManager(requestManager);
        }
        return requestManager;
    }

    @Override
    public boolean handleMessage(Message message) {
        boolean handled = true;
        Object removed = null;
        Object key = null;
        switch (message.what) {
            case ID_REMOVE_FRAGMENT_MANAGER:
                android.app.FragmentManager fm = (android.app.FragmentManager) message.obj;
                key = fm;
                removed = pendingRequestManagerFragments.remove(fm);
                break;
            case ID_REMOVE_SUPPORT_FRAGMENT_MANAGER:
                FragmentManager supportFm = (FragmentManager) message.obj;
                key = supportFm;
                removed = pendingSupportRequestManagerFragments.remove(supportFm);
                break;
            default:
                handled = false;
        }
        if (handled && removed == null && Log.isLoggable(TAG, Log.WARN)) {
            Log.w(TAG, "Failed to remove expected request manager fragment, manager: " + key);
        }
        return handled;
    }
}