Android 内存泄漏的一些情况。

2. 静态 View

3. 非静态内部类

4. 匿名类

5. Handler

6. Thread

7. TimerTask

8. SensorManager

2.构造Adapter时，没有使用缓存的convertView

3.Bitmap对象不在使用时调用recycle()释放内存

4.试着使用关于application的context来替代和activity相关的context

5.注册没取消造成的内存泄漏

6.集合中对象没清理造成的内存泄漏

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interface 放在fragment内或者放在外面单独存在，一般不会造成activity泄漏

public interface DialogCallback {
    void showModifyInputDialog();
    void showTheMessageDialog();
}

其实一般的匿名内部类是不会导致activity释放不了的，只要你不在handle内进行奇怪的操作

private Handler uiHandler = new Handler(){

内存泄漏全解析

最近在维护代码，发现一个自定义View（这个View是在一个AsyncTask的工作线程doInBackground中新建的，在UI线程onPostExecute中添加进window中的）经常会泄漏内存，导致其引用的Activity一直得不到释放，每次退出再进去都会导致Activity的对象+1.

package com.xxx.launcher.view;

import android.content.Context;

import android.util.Log;

import android.view.View;

public class WeatherTextView extends SkinTextView {

    public WeatherTextView (Context context) {
        super(context);

        postDelayed(mShowCityRunnable, );//这一步有问题

    }

    @Override

    protected void onWindowVisibilityChanged(int visibility) {

        super.onWindowVisibilityChanged(visibility);

        if (visibility == View.VISIBLE) {

            post(mShowCityRunnable);

        }

    }

    @Override

    protected void onDetachedFromWindow() {

        super.onDetachedFromWindow();

        onCancel();

    };

    public void onCancel(){

        removeCallbacks(mShowCityRunnable);

    }

    private Runnable mShowCityRunnable = new Runnable() {

        @Override

        public void run() {

            Log.i("mShowCityRunnable-------TAG", "run"+mShowCityRunnable);

            setText(city);

        }

    };

}

最后通过MAT工具查看内存快照的比较，发现了如下的情况，把内存泄露的地方锁定在了WeatherTextView$2的第二个内部类中mShowCityRunnable ，一开始始终都想不到这个内部类到底有什么地方泄露了，最后突然灵光一闪，是不是View的post（）方法导致的，在网上一查，发现确实。

public boolean post(Runnable action) {

    Handler handler;

    AttachInfo attachInfo = mAttachInfo;

    if (attachInfo != null) {

        handler = attachInfo.mHandler;

    } else {

        // Assume that post will succeed later

        ViewRootImpl.getRunQueue().post(action);

        return true;

    }  

    return handler.post(action);

}

在post() 函数注释中，明确写着：This method can be invoked from outside of the UI thread only when this View is attached to a window.

当View还没有attach到当前window时，mAttachInfo 值为 null，故而执行 else语句，再看一下getRunQueue()和其post() 方法：

static final ThreadLocal<RunQueue> sRunQueues = new ThreadLocal<RunQueue>();  

static RunQueue getRunQueue() {

     RunQueue rq = sRunQueues.get();

     if (rq != null) {

         return rq;

     }

     rq = new RunQueue();

     sRunQueues.set(rq);

     return rq;

 }

 ……

 static final class RunQueue {

     private final ArrayList<HandlerAction> mActions = new ArrayList<HandlerAction>();  

     void post(Runnable action) {

         postDelayed(action, );

     }  

     void postDelayed(Runnable action, long delayMillis) {

         HandlerAction handlerAction = new HandlerAction();

         handlerAction.action = action;

         handlerAction.delay = delayMillis;  

         synchronized (mActions) {

             mActions.add(handlerAction);

         }

     }  

     void executeActions(Handler handler) {

         synchronized (mActions) {

             final ArrayList<handleraction> actions = mActions;

             final int count = actions.size();  

             for (int i = ; i < count; i++) {

                 final HandlerAction handlerAction = actions.get(i);

                 handler.postDelayed(handlerAction.action, handlerAction.delay);

             }  

             actions.clear();

         }

     }

     ……

 }

这样会把Runnable 插入到一个静态的ThreadLocal的RunQueue队列里（在工作线程中post，就会插入工作线程的RunQueue队列），针对本文开头给出的例子，那么插入的Runnable什么时候得到执行呢?

调用RunQueue.executeActions()方法只有一处，即在ViewRootImpl类的如下非静态方法中

private void performTraversals() {  

        if (mLayoutRequested && !mStopped) {

            // Execute enqueued actions on every layout in case a view that was detached

            // enqueued an action after being detached

            getRunQueue().executeActions(attachInfo.mHandler);

        }

}

该方法是在UI线程执行的（见ViewRootImpl.handleMessage()），故当UI线程执行到该performTraversals() 里的 getRunQueue() 时，得到的是UI线程中的RunQueue，这样AsyncTask 线程中的 RunQueue永远不会被执行到，并且AsyncTask的是用线程池实现的，AsyncTask启动的线程会长期存在，造成如下引用关系：

AsyncTask线程 => 静态的ThreadLocal的RunQueue => Runnable => View=> Activity；

如此即使activity finish 了，确始终存在一个静态引用链引用这该activity，而 Activity一般又引用着很多资源，比如图片等，最终造成严重资源泄漏。

最后我是写改成

package com.xxx.launcher.view;

import android.content.Context;

import android.util.Log;

import android.view.View;

public class WeatherTextView  extends SkinTextView {

    public WeatherTextView (Context context) {

        super(context);

    }

    @Override

    protected void onAttachedToWindow() {

        super.onAttachedToWindow();

        postDelayed(mShowCityRunnable, ); //在onAttachedToWindow方法中执行post方法

    }

    @Override

    protected void onWindowVisibilityChanged(int visibility) {

        super.onWindowVisibilityChanged(visibility);

        if (visibility == View.VISIBLE) {

            post(mShowCityRunnable);

        }

    }

    @Override

    protected void onDetachedFromWindow() {

        super.onDetachedFromWindow();

        onCancel();

    };

    public void onCancel(){

        removeCallbacks(mShowCityRunnable);

    }

    private Runnable mShowCityRunnable = new Runnable() {

        @Override

        public void run() {

            Log.i("mShowCityRunnable-------TAG", "run"+mShowCityRunnable);

            setText(city);

        }

    };

}

这样Activity就没有再被其他东西引用了，就不会发生Activity的泄漏了，Activity就可以被释放了。这样，不管进入退出进入这个MainMenuActivity多少次，MainMenuActivity的对象就只会保存一份。

ps：至于为什么在两个Histogram（直方图）的比较图中还是显示MainMenuActivity+1，则是因为这是类名，类被加载之后，在进程结束之前不会被回收

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这种泄漏一般是因为mStorageManager 注册了但是没有取消注册

mStorageManager = (StorageManager) mContext.getSystemService(Context.STORAGE_SERVICE);

mStorageManager.registerListener(mStoragelistener);

取消注册就可以了

if (mStorageManager != null) {

    mStorageManager.unregisterListener(mStoragelistener);

}