RecyclingBitmapDrawable.java

/*
 * Copyright (C) 2013 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.pc.ioc.image;

import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.drawable.BitmapDrawable;

import com.android.pc.ioc.app.Ioc;

/**
 * A BitmapDrawable that keeps track of whether it is being displayed or cached. When the drawable is no longer being displayed or cached, {@link android.graphics.Bitmap#recycle() recycle()} will be called on this drawable's bitmap.
 */
public class RecyclingBitmapDrawable extends BitmapDrawable {

	static final String TAG = "CountingBitmapDrawable";

	private int mCacheRefCount = 0;
	private int mDisplayRefCount = 0;

	private boolean mHasBeenDisplayed;

	public RecyclingBitmapDrawable(Resources res, Bitmap bitmap) {
		super(res, bitmap);
	}

	/**
	 * Notify the drawable that the displayed state has changed. Internally a count is kept so that the drawable knows when it is no longer being displayed.
	 * 
	 * @param isDisplayed
	 *            - Whether the drawable is being displayed or not
	 */
	public void setIsDisplayed(boolean isDisplayed) {
		// BEGIN_INCLUDE(set_is_displayed)
		synchronized (this) {
			if (isDisplayed) {
				mDisplayRefCount++;
				mHasBeenDisplayed = true;
			} else {
				mDisplayRefCount--;
			}
		}

		// Check to see if recycle() can be called
		checkState();
	}

	/**
	 * Notify the drawable that the cache state has changed. Internally a count is kept so that the drawable knows when it is no longer being cached.
	 * 
	 * @param isCached
	 *            - Whether the drawable is being cached or not
	 */
	public void setIsCached(boolean isCached) {
		// BEGIN_INCLUDE(set_is_cached)
		synchronized (this) {
			if (isCached) {
				mCacheRefCount++;
			} else {
				mCacheRefCount--;
			}
		}

		// Check to see if recycle() can be called
		checkState();
		// END_INCLUDE(set_is_cached)
	}

	private synchronized void checkState() {
		// BEGIN_INCLUDE(check_state)
		// If the drawable cache and display ref counts = 0, and this drawable
		// has been displayed, then recycle
		if (mCacheRefCount <= 0 && mDisplayRefCount <= 0 && mHasBeenDisplayed && hasValidBitmap()) {
			Ioc.getIoc().getLogger().d("No longer being used or cached so recycling. " + toString());
			getBitmap().recycle();
		}
		// END_INCLUDE(check_state)
	}

	private synchronized boolean hasValidBitmap() {
		Bitmap bitmap = getBitmap();
		return bitmap != null && !bitmap.isRecycled();
	}
}