根据我的应用程序，首先我将所有图像从我的资源复制到内部存储器，然后在图像向左或向右滑动上，我从内存中获取图像及其索引并将其显示在那里。我正在用 AsynTask 做这件事。在显示大约 10 张图像后，应用程序进入黑屏，并且 log cat 说“外部分配对于这个过程来说太大了”。根据我在这里阅读的内容，我认为问题出在 AsyncTask 上，我无法释放已用于这些任务的内存。我有三个不同的活动，用于将图像显示为图库，并且每个活动都使用 asyncTask 来显示图像。
下面是我的一些代码，任何帮助将不胜感激，在此先感谢。这是我用来根据滑动图像执行图像下载器的 Activity。
lid1 = new LocalImageDownloader(imageSwitcher, myContext, path, nameList.get(curIndex) );
lid1.execute();
imageSwitcher.setOnTouchListener(new OnTouchListener() {
public boolean onTouch(View v, MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
downX = (int) event.getX();
Log.i("event.getX()", " downX " + downX);
return true;
}
else if (event.getAction() == MotionEvent.ACTION_UP) {
upX = (int) event.getX();
Log.i("event.getX()", " upX " + downX);
if (upX - downX > 100) {
//curIndex current image index in array viewed by user
curIndex--;
if (curIndex < 0) {
curIndex = imageList.size()-1;
}
imageSwitcher.setInAnimation(AnimationUtils.loadAnimation(Activities.this,R.anim.slide_in_left));
imageSwitcher.setOutAnimation(AnimationUtils.loadAnimation(Activities.this,R.anim.slide_out_right));
lid1.cancel(true);
lid1 = new LocalImageDownloader(imageSwitcher, myContext, path, nameList.get(curIndex) );
lid1.execute();
}
else if (downX - upX > -100) {
curIndex++;
if (curIndex == imageList.size() ) {
curIndex = 0;
}
imageSwitcher.setInAnimation(AnimationUtils.loadAnimation(Activities.this,R.anim.slide_in_right));
imageSwitcher.setOutAnimation(AnimationUtils.loadAnimation(Activities.this,R.anim.slide_out_left));
lid1.cancel(true);
lid1 = new LocalImageDownloader(imageSwitcher, myContext, path, nameList.get(curIndex) );
lid1.execute();
}
return true;
}
return false;
}
});
这是我的 AsyncTask 从内存中获取图像，
public class LocalImageDownloader extends AsyncTask<String, Void, Bitmap> {
String url;
Drawable d;
Context myContext;
String path;
String fileName;
ProgressDialog dialog;
int REQUIRED_SIZE=600;
private final WeakReference<ImageSwitcher> imageViewReference;
public LocalImageDownloader(ImageSwitcher imageSwitcher,Context myContext, String path, String fileName) {
this.myContext = myContext;
this.path = path;
this.fileName = fileName;
imageViewReference = new WeakReference<ImageSwitcher>(imageSwitcher);
}
@Override
protected Bitmap doInBackground(String... urls) {
publishProgress();
return null;
}
@Override
protected void onPreExecute() {
dialog = ProgressDialog.show(myContext, "", "Loading Images...", true);
super.onPreExecute();
}
@Override
protected void onPostExecute(Bitmap result) {
try {
if (imageViewReference != null) {
ImageSwitcher imageSwitcher = imageViewReference.get();
if (imageSwitcher != null) {
imageSwitcher.setImageDrawable(getLocalImage());
}
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
dialog.dismiss();
}
public Drawable getLocalImage() throws IOException {
File file = new File(path,fileName);
//Decode image size
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
BitmapFactory.decodeStream(new FileInputStream(file),null,o);
//The new size we want to scale to
//Find the correct scale value. It should be the power of 2.
int scale=1;
while(o.outWidth/scale/2>=this.REQUIRED_SIZE && o.outHeight/scale/2>=this.REQUIRED_SIZE)
scale*=2;
//Decode with inSampleSize
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize=scale;
o.inJustDecodeBounds = false;
return new BitmapDrawable(BitmapFactory.decodeStream(new FileInputStream(file), null, o2));
}
}
编辑： 我已经应用了一些方法来更有效地使用位图，现在我将它们推送到内存中，但我仍然遇到几乎相同的错误。一些图像存储在内存中后，对于一些图像，我会黑屏并出现相同的错误。“此过程的外部分配太大。” 知道怎么做吗？
下面是内存缓存代码，我将 MemoryCache 对象作为参数发送到 AsyncTask。
public class MemoryCache {
private static final String TAG = "MemoryCache";
private Map<String, Bitmap> cache=Collections.synchronizedMap(
new LinkedHashMap<String, Bitmap>(10,1.5f,true));//Last argument true for LRU ordering
private long size=0;//current allocated size
private long limit=1000000;//max memory in bytes
public MemoryCache(){
//use 50% of available heap size
setLimit(Runtime.getRuntime().maxMemory()/2);
}
public void setLimit(long new_limit){
limit=new_limit;
Log.i(TAG, "MemoryCache will use up to "+limit/1024./1024.+"MB");
}
public Bitmap get(String id){
try{
if(!cache.containsKey(id))
return null;
//NullPointerException sometimes happen here http://code.google.com/p/osmdroid/issues/detail?id=78
return cache.get(id);
}catch(NullPointerException ex){
return null;
}
}
public void put(String id, Bitmap bitmap){
try{
if(cache.containsKey(id))
size-=getSizeInBytes(cache.get(id));
cache.put(id, bitmap);
size+=getSizeInBytes(bitmap);
checkSize();
}catch(Throwable th){
th.printStackTrace();
}
}
private void checkSize() {
Log.i(TAG, "cache size="+size+" length="+cache.size());
if(size>limit){
Iterator<Entry<String, Bitmap>> iter=cache.entrySet().iterator();//least recently accessed item will be the first one iterated
while(iter.hasNext()){
Entry<String, Bitmap> entry=iter.next();
size-=getSizeInBytes(entry.getValue());
iter.remove();
if(size<=limit)
break;
}
Log.i(TAG, "Clean cache. New size "+cache.size());
}
}
public void clear() {
cache.clear();
}
long getSizeInBytes(Bitmap bitmap) {
if(bitmap==null)
return 0;
return bitmap.getRowBytes() * bitmap.getHeight();
}
public boolean contains(String key) {
if(cache.containsKey(key)) {
return true;
}
return false;
}
}