我正在编写一个简单的地图应用程序,从服务器为每个图块产生一个新的AsyncTask,下载osm图块。一些AsyncTasks运行完成,一些AsyncTasks在他们有机会运行之前被取消(以防万一我平移了屏幕)。它可能是,当他们似乎泄漏。我首先通过检查我的瓦片位图的寿命并发现它们泄漏来发现它。在将AsyncTask中的位图的(间接)引用归零后,位图停止泄漏,但它让我思索为什么说引用很重要,并发现AsycTasks的数量不断增长,尽管尽力关闭对引用的引用。我运行MAT分析,这是当我需要帮助。任何人都可以帮我解释image(对不起,我没有足够的棕色点来直接附加图片)。AsyncTask和内存泄漏
显示的树条目呈现了许多泄漏的AsyncTasks(类型FileCacheTask)中的一个,子节点表示对它的所有传入引用。我明白'指涉'是垃圾收集器。另外两个,表示为$ 0(表示与外部类的关联),类型为android.os.AsyncTask(这与FileCacheTask的外部类没有任何关系,无可否认,FileCacheTask是一个瓦片工厂内的非静态内部类) ,似乎通过mWorker成员持有对我的泄露对象的引用,这是我无法解释并且无法明显摆脱的。我试着按照路径寻找传入的对android.os.AsyncTask对象的引用,但看到了一些调度内部和与我的代码无关的东西)。 任何想法可能是android.os.AsyncTask对象被称为这个$ 0?
编辑。 接下来的建议,我有(类)的问题蒸馏为易消化的代码片段。我说过,因为它似乎表现出同样的行为,但我不能确定它确实遭受同样的问题。它仍然具有隐密性。下面的代码:
public class TaskLeak {
static public int DDeletedTasks; //these are all for debug/tracing purposes
static public int DCreatedTasks;
static public int DCancelled;
private class PrivateTask extends AsyncTask<Void, Void, Void>
{
private int mTaskId;
private boolean mFinished;
private Bitmap mBitmap;
public PrivateTask()
{
mTaskId = ++DCreatedTasks;
//allocating a bitmap to give this object a meaningful weight for GC to consider.
mBitmap = Bitmap.createBitmap(256, 256, Bitmap.Config.ARGB_8888);
//Log.d("Tasks", "(constructor) Task count:"+ mTaskId+" tasks in existence:"+(DCreatedTasks-DDeletedTasks));
execute();
}
@Override
protected Void doInBackground(Void... params) {
try {
int sleepForMs = mRandomGenerator.nextInt(100);
//emulating blocking download action for a random few milliseconds.
Thread.sleep(sleepForMs);
//Log.d("Tasks", "Waking up from sleep, task:" + mTaskId);
} catch (InterruptedException e) {
//Log.d("Tasks", "Can't sleep, task:" + mTaskId);
}
return null;
}
@Override
protected void onPostExecute(Void result)
{
mFinished = true;
maintain();
}
@Override
protected void onCancelled()
{
DCancelled++;
onPostExecute(null);
}
@Override
protected void finalize()
{
++DDeletedTasks;
Log.d("Tasks", "(destructor) Task count:"+ mTaskId+" tasks in existence:"+(DCreatedTasks-DDeletedTasks));
}
public boolean finished()
{
return mFinished;
}
}
private final static int KMaxTasks = 100;
private Random mRandomGenerator;
private final int mMaxCycles;
private int mCycles;
private final Vector<PrivateTask> mTasks;
public TaskLeak(int maxCycles)
{
mMaxCycles = maxCycles;
mRandomGenerator = new Random();
mTasks = new Vector<PrivateTask>();
for (int i = 0; i < KMaxTasks; i++)
{
mTasks.add(new PrivateTask());
}
}
public void maintain()
{
Log.d("Tasks", "***maintain(), tasks held:"+mTasks.size()+" there are "+ (mMaxCycles - ++mCycles)+" cycles left to go");
for (int i = 0; i < mTasks.size();)
{
if (mTasks.get(i).finished())
{
mTasks.remove(i);
if (mCycles < mMaxCycles)
{
mTasks.add(new PrivateTask());
}
}
else
{
i++;
}
}
if ((mCycles % 10) == 0)
{
DCancelled++;
mTasks.get(5).cancel(true);
}
if (mTasks.size() == 0)
{
new TestMemoryGrabber(200).test();
Log.d("Tasks", "maintain() has finished!");
Log.d("Tasks", "maintain(). There have been "+DCreatedTasks+" tasks created.");
Log.d("Tasks", "maintain(). There have been "+DDeletedTasks+" tasks deleted.");
Log.d("Tasks", "maintain(). There have been "+(DCreatedTasks-DDeletedTasks)+" tasks remaining.");
Log.d("Tasks", "maintain(). There have been "+DCancelled+" tasks cancelled.");
}
}
当这1000个周期内执行,它无法中途(在周期#570)的内存溢出异常,尽管,在任何时候,我保持不超过100个引用到PrivateTask对象。这本身有点令人费解,因为GC应该不断为新参赛者腾出空间。为什么不呢?
这里的logcat的关于当OOM发生异常:
01-12 16:37:50.902: D/Tasks(3235): (destructor) Task count:568 tasks in existence:156
01-12 16:37:50.993: D/Tasks(3235): ***maintain(), tasks held:100 there are 430 cycles left to go
01-12 16:37:51.062: I/dalvikvm-heap(3235): Clamp target GC heap from 49.251MB to 48.000MB
01-12 16:37:51.062: D/dalvikvm(3235): GC_FOR_ALLOC freed 257K, 2% free 48337K/48903K, paused 70ms, total 71ms
01-12 16:37:51.062: D/Tasks(3235): (destructor) Task count:569 tasks in existence:156
01-12 16:37:51.092: D/Tasks(3235): ***maintain(), tasks held:100 there are 429 cycles left to go
01-12 16:37:51.222: I/dalvikvm-heap(3235): Clamp target GC heap from 49.251MB to 48.000MB
01-12 16:37:51.232: D/dalvikvm(3235): GC_FOR_ALLOC freed 257K, 2% free 48337K/48903K, paused 139ms, total 139ms
01-12 16:37:51.242: D/Tasks(3235): ***maintain(), tasks held:100 there are 428 cycles left to go
01-12 16:37:51.312: I/dalvikvm-heap(3235): Clamp target GC heap from 49.502MB to 48.000MB
01-12 16:37:51.322: D/dalvikvm(3235): GC_FOR_ALLOC freed <1K, 1% free 48593K/48903K, paused 70ms, total 72ms
01-12 16:37:51.322: I/dalvikvm-heap(3235): Forcing collection of SoftReferences for 262160-byte allocation
01-12 16:37:51.412: I/dalvikvm-heap(3235): Clamp target GC heap from 49.494MB to 48.000MB
01-12 16:37:51.412: D/dalvikvm(3235): GC_BEFORE_OOM freed 9K, 1% free 48584K/48903K, paused 86ms, total 86ms
01-12 16:37:51.412: E/dalvikvm-heap(3235): Out of memory on a 262160-byte allocation.
01-12 16:37:51.412: I/dalvikvm(3235): "main" prio=5 tid=1 RUNNABLE
01-12 16:37:51.412: I/dalvikvm(3235): | group="main" sCount=0 dsCount=0 obj=0x40a14568 self=0x2a00b9e0
01-12 16:37:51.412: I/dalvikvm(3235): | sysTid=3235 nice=0 sched=0/0 cgrp=apps handle=1073870640
01-12 16:37:51.412: I/dalvikvm(3235): | schedstat=(21236163363 7517071458 4002) utm=1940 stm=183 core=0
01-12 16:37:51.412: I/dalvikvm(3235): at android.graphics.Bitmap.nativeCreate(Native Method)
01-12 16:37:51.412: I/dalvikvm(3235): at android.graphics.Bitmap.createBitmap(Bitmap.java:640)
01-12 16:37:51.412: I/dalvikvm(3235): at android.graphics.Bitmap.createBitmap(Bitmap.java:620)
logcat /部分代码与异步任务 - 请放在这里,请 – deadfish
没有发布代码很难帮助您,但在阅读您的文章后,这里有一个提示:它违背了最佳实践,以您的方式发射AsyncTasks描述。查看这里的“执行顺序”部分。 http://developer.android.com/reference/android/os/AsyncTask.html从Honeycomb(Android 3.0)开始,AsyncTask池中只有一个线程,所以你的磁贴下载将在任何Android版本的post-姜饼。使用自定义的ThreadPool将缓解这个潜在的问题,并且在这个过程中也可能帮助你解决内存泄漏问题。 – MattDavis
感谢您的第一次尝试。我要做的就是尝试将问题提炼成一段代码,用来演示behvaiour和转发。可能需要我一两天。 @Matt:我的实施的哪一方面违背了最佳实践?我正在产生每个任务的瓦片,而不是实现一个瓦片队列并让单个任务处理队列? – Remster