Faced the same and thanks to @CommonsWare for the discussion.
Posting the full solution here so it helps more people coming here for the same issue.
Edits and Comments are welcomed. Cheers
When should I recycle a bitmap using LRUCache?
当你的Bitmap既不在缓存 也不在任何图像视图中被引用时
To maintain the reference count of bitmap we have to extend the BitmapDrawable class and add
reference attributes to them.
This android sample has the answer to it exactly.
DisplayingBitmaps.zip
我们会找到下面的细节和代码
(don t recycle the bitmaps in the entryRemoved() call).
不尽然
In entryRemoved delegate check whether Bitmap is still referenced from any ImageView.
If not. Recycle it there itself.
而反之亦然,在公认的答案中也提到了这一点,即当视图即将被再利用或被倾弃时检查其位图(在视图被再利用时,前位位图)在缓存中。如果存在的话,就让它单独回收它。
关键是我们要在这两个地方 检查一下我们是否可以回收比特图
I will explain my specific case where i am using LruCache to hold bitmaps for me.
And displaying them in ListView. And calling recycle on bitmaps when there are no longer in use.
RecyclingBitmapDrawable.java and RecyclingImageView.java of the sample mentioned above are the core pieces we need here. They are handling things beautifully.
Their setIsCached and setIsDisplayed methods are doing what we need.
代码可以在上文提到的样本链接中找到。 但也可以在答案底部张贴完整的文件代码, 以防链接今后会下降或更改。 略微修改了超标设置图像Resource, 以检查上一个位图的状态 。
- 这是给你的密码...
所以,你的LruCache经理应该 看起来像这样。
LruCacheManache.java 管理者.java
package com.example.cache;
import android.os.Build;
import android.support.v4.util.LruCache;
public class LruCacheManager {
private LruCache<String, RecyclingBitmapDrawable> mMemoryCache;
private static LruCacheManager instance;
public static LruCacheManager getInstance() {
if(instance == null) {
instance = new LruCacheManager();
instance.init();
}
return instance;
}
private void init() {
// We are declaring a cache of 6Mb for our use.
// You need to calculate this on the basis of your need
mMemoryCache = new LruCache<String, RecyclingBitmapDrawable>(6 * 1024 * 1024) {
@Override
protected int sizeOf(String key, RecyclingBitmapDrawable bitmapDrawable) {
// The cache size will be measured in kilobytes rather than
// number of items.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR1) {
return bitmapDrawable.getBitmap().getByteCount() ;
} else {
return bitmapDrawable.getBitmap().getRowBytes() * bitmapDrawable.getBitmap().getHeight();
}
}
@Override
protected void entryRemoved(boolean evicted, String key, RecyclingBitmapDrawable oldValue, RecyclingBitmapDrawable newValue) {
super.entryRemoved(evicted, key, oldValue, newValue);
oldValue.setIsCached(false);
}
};
}
public void addBitmapToMemoryCache(String key, RecyclingBitmapDrawable bitmapDrawable) {
if (getBitmapFromMemCache(key) == null) {
// The removed entry is a recycling drawable, so notify it
// that it has been added into the memory cache
bitmapDrawable.setIsCached(true);
mMemoryCache.put(key, bitmapDrawable);
}
}
public RecyclingBitmapDrawable getBitmapFromMemCache(String key) {
return mMemoryCache.get(key);
}
public void clear() {
mMemoryCache.evictAll();
}
}
And your getView() of ListView/GridView adapter should look normal like usual.
As when you are setting a new image on ImageView using setImageDrawable method.
Its internally checking the reference count on previous bitmap and will call recycle on it internally if not in lrucache.
@Override
public View getView(int position, View convertView, ViewGroup parent) {
RecyclingImageView imageView;
if (convertView == null) { // if it s not recycled, initialize some attributes
imageView = new RecyclingImageView(getActivity());
imageView.setLayoutParams(new GridView.LayoutParams(
GridView.LayoutParams.WRAP_CONTENT,
GridView.LayoutParams.WRAP_CONTENT));
imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
imageView.setPadding(5, 5, 5, 5);
} else {
imageView = (RecyclingImageView) convertView;
}
MyDataObject dataItem = (MyDataObject) getItem(position);
RecyclingBitmapDrawable image = lruCacheManager.getBitmapFromMemCache(dataItem.getId());
if(image != null) {
// This internally is checking reference count on previous bitmap it used.
imageView.setImageDrawable(image);
} else {
// You have to implement this method as per your code structure.
// But it basically doing is preparing bitmap in the background
// and adding that to LruCache.
// Also it is setting the empty view till bitmap gets loaded.
// once loaded it just need to call notifyDataSetChanged of adapter.
loadImage(dataItem.getId(), R.drawable.empty_view);
}
return imageView;
}
这里是您的 回收图像View.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.example.cache;
import android.content.Context;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.LayerDrawable;
import android.util.AttributeSet;
import android.widget.ImageView;
/**
* Sub-class of ImageView which automatically notifies the drawable when it is
* being displayed.
*/
public class RecyclingImageView extends ImageView {
public RecyclingImageView(Context context) {
super(context);
}
public RecyclingImageView(Context context, AttributeSet attrs) {
super(context, attrs);
}
/**
* @see android.widget.ImageView#onDetachedFromWindow()
*/
@Override
protected void onDetachedFromWindow() {
// This has been detached from Window, so clear the drawable
setImageDrawable(null);
super.onDetachedFromWindow();
}
/**
* @see android.widget.ImageView#setImageDrawable(android.graphics.drawable.Drawable)
*/
@Override
public void setImageDrawable(Drawable drawable) {
// Keep hold of previous Drawable
final Drawable previousDrawable = getDrawable();
// Call super to set new Drawable
super.setImageDrawable(drawable);
// Notify new Drawable that it is being displayed
notifyDrawable(drawable, true);
// Notify old Drawable so it is no longer being displayed
notifyDrawable(previousDrawable, false);
}
/**
* @see android.widget.ImageView#setImageResource(android.graphics.drawable.Drawable)
*/
@Override
public void setImageResource(int resId) {
// Keep hold of previous Drawable
final Drawable previousDrawable = getDrawable();
// Call super to set new Drawable
super.setImageResource(resId);
// Notify old Drawable so it is no longer being displayed
notifyDrawable(previousDrawable, false);
}
/**
* Notifies the drawable that it s displayed state has changed.
*
* @param drawable
* @param isDisplayed
*/
private static void notifyDrawable(Drawable drawable, final boolean isDisplayed) {
if (drawable instanceof RecyclingBitmapDrawable) {
// The drawable is a CountingBitmapDrawable, so notify it
((RecyclingBitmapDrawable) drawable).setIsDisplayed(isDisplayed);
} else if (drawable instanceof LayerDrawable) {
// The drawable is a LayerDrawable, so recurse on each layer
LayerDrawable layerDrawable = (LayerDrawable) drawable;
for (int i = 0, z = layerDrawable.getNumberOfLayers(); i < z; i++) {
notifyDrawable(layerDrawable.getDrawable(i), isDisplayed);
}
}
}
}
这里是您的 回收BitmapDrawable.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.example.cache;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.drawable.BitmapDrawable;
import android.util.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 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();
//END_INCLUDE(set_is_displayed)
}
/**
* 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()) {
Log.d(TAG, "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();
}
}
