src/com/android/settings/accessibility/PaletteListPreference.java

/*
 * Copyright (C) 2020 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.accessibility;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewTreeObserver;
import android.widget.FrameLayout;
import android.widget.ListView;

import androidx.preference.Preference;
import androidx.preference.PreferenceViewHolder;

import com.android.settings.R;

/** Preference that easier preview by matching name to color. */
public class PaletteListPreference extends Preference {

    private ListView mListView;
    private ViewTreeObserver.OnPreDrawListener mPreDrawListener;

    /**
     * Constructs a new PaletteListPreference with the given context's theme and the supplied
     * attribute set.
     *
     * @param context The Context this is associated with, through which it can access the current
     *                theme, resources, etc.
     * @param attrs The attributes of the XML tag that is inflating the view.
     */
    public PaletteListPreference(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    /**
     * Constructs a new PaletteListPreference with the given context's theme, the supplied
     * attribute set, and default style attribute.
     *
     * @param context The Context this is associated with, through which it can access the
     *                current theme, resources, etc.
     * @param attrs The attributes of the XML tag that is inflating the view.
     * @param defStyleAttr An attribute in the current theme that contains a reference to a style
     *                     resource that supplies default
     *                     values for the view. Can be 0 to not look for
     *                     defaults.
     */
    public PaletteListPreference(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        setLayoutResource(R.layout.daltonizer_preview);
        initPreDrawListener();
    }

    @Override
    public void onBindViewHolder(PreferenceViewHolder holder) {
        super.onBindViewHolder(holder);

        final View rootView = holder.itemView;
        mListView = rootView.findViewById(R.id.palette_listView);
        if (mPreDrawListener != null) {
            mListView.getViewTreeObserver().addOnPreDrawListener(mPreDrawListener);
        }
    }

    private void initPreDrawListener() {
        mPreDrawListener = new ViewTreeObserver.OnPreDrawListener() {
            @Override
            public boolean onPreDraw() {
                if (mListView == null) {
                    return false;
                }

                final int listViewHeight = mListView.getMeasuredHeight();
                final int listViewWidth = mListView.getMeasuredWidth();

                // Removes the callback after get result of measure view.
                final ViewTreeObserver viewTreeObserver = mListView.getViewTreeObserver();
                if (viewTreeObserver.isAlive()) {
                    viewTreeObserver.removeOnPreDrawListener(this);
                }
                mPreDrawListener = null;

                // Resets layout parameters to display whole items from listView.
                final FrameLayout.LayoutParams layoutParams =
                        (FrameLayout.LayoutParams) mListView.getLayoutParams();
                layoutParams.height = listViewHeight * mListView.getAdapter().getCount();
                layoutParams.width = listViewWidth;
                mListView.setLayoutParams(layoutParams);

                return true;
            }
        };
    }
}