Java tutorial
/* * 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.tangjd.displayingbitmaps.util; import android.content.res.Resources; import android.graphics.Bitmap; import android.graphics.drawable.BitmapDrawable; import android.support.v4.BuildConfig; import com.tangjd.common.utils.Log; /** * A BitmapDrawable that keeps track of whether it is being displayed or cached. * When the drawable is no longer being displayed or cached, * {@link 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) { 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) { synchronized (this) { if (isCached) { mCacheRefCount++; } else { mCacheRefCount--; } } // Check to see if recycle() can be called checkState(); } private synchronized void checkState() { // If the drawable cache and display ref counts = 0, and this drawable // has been displayed, then recycle if (mCacheRefCount <= 0 && mDisplayRefCount <= 0 && mHasBeenDisplayed && hasValidBitmap()) { if (BuildConfig.DEBUG) { Log.d(TAG, "No longer being used or cached so recycling. " + toString()); } getBitmap().recycle(); } } private synchronized boolean hasValidBitmap() { Bitmap bitmap = getBitmap(); return bitmap != null && !bitmap.isRecycled(); } }