在Activity或者Fragment中创建异步处理对象时，比如Handler、AsyncTask，要特别注意内存泄漏问题，这些异步对象在子线程处理请求，生命周期和外面Activity和Fragment存在不同步的问题，当Activity的生命周期结束时，若不显式在onDestroy中将这些异步控件结束，将会造成activity无法被回收，也就造成了内存泄漏。
下面我们从smali文件和内存堆栈两个角度分析内存泄漏问题。
public class HandlerTestActivity extends Activity { private static final int MESSAGE_WHAT = 1; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mHandler.sendMessageDelayed(mHandler.obtainMessage(MESSAGE_WHAT), 50000); startActivity(new Intent(this, TestActivity.class)); finish(); } private Handler mHandler = new Handler(){ @Override public void handleMessage(Message msg) { super.handleMessage(msg); switch (msg.what) { case MESSAGE_WHAT: doSomething();//handler调用外部类的方法，将会持有外部类的隐式调用 break; } } }; private void doSomething(){ Log.i("", "doSomething"); } } 测试类 # virtual methods .method public handleMessage(Landroid/os/Message;)V .locals 1 .param p1, "msg" # Landroid/os/Message; .prologue .line 38 invoke-super {p0, p1}, Landroid/os/Handler;->handleMessage(Landroid/os/Message;)V .line 40 iget-object v0, p0, Lcom/jason/handlertest/HandlerTestActivity$1;->this$0:Lcom/jason/handlertest/HandlerTestActivity; # invokes: Lcom/jason/handlertest/HandlerTestActivity;->doSomething()V invoke-static {v0}, Lcom/jason/handlertest/HandlerTestActivity;->access$000(Lcom/jason/handlertest/HandlerTestActivity;)V .line 43 return-void .end method handler延迟50s发送一条message，在此期间handleMessage方法中将会持有外部HandlerTestActivity的引用,50s内activity将无法释放，如果handler处理的是循环消息，那么activity将不会释放下面我们看一下内存情况
首次启动的内存
多次启动后，手动gc后的内存情况
怎么样避免这种情况？
@Override protected void onDestroy() { super.onDestroy(); mHandler.removeMessages(MESSAGE_WHAT); } 1.在activity结束时，清空handler的消息并退出 class MyHandler extends Handler{ WeakReference<Activity> activityWeakReference; public MyHandler(Activity activity){ activityWeakReference = new WeakReference<>(activity); } @Override public void handleMessage(Message msg) { super.handleMessage(msg); switch (msg.what){ case MESSAGE_WHAT: if (activityWeakReference.get() != null){ ((HandlerTestActivity)activityWeakReference.get()).doSomething(); } break; } } } 2.内部类Handler采用弱引用持有activity private static Handler mHandler = new Handler(){ @Override public void handleMessage(Message msg) { super.handleMessage(msg); switch (msg.what) { case MESSAGE_WHAT: doSomething();//handler调用外部类的方法，将会持有外部类的隐式调用 break; } } }; 3.handler采用静态，这种方式缺点是调用的方法也变为了静态 4.采用RxJava CompositeSubscription订阅的方式，在activity退出时调用CompositeSubscription.unsubscribe() 参考文章 http://www.jianshu.com/p/fa3b31f8f47d
