糖葫芦

• build gradle配置

  debugImplementation 'com.squareup.leakcanary:leakcanary-android:1.6.1'
  releaseImplementation 'com.squareup.leakcanary:leakcanary-android-no-op:1.6.1'
  // Optional, if you use support library fragments:
  debugImplementation 'com.squareup.leakcanary:leakcanary-support-fragment:1.6.1'

• 配置 application

  private RefWatcher refWatcher;
  
      public static RefWatcher getRefWatcher(Context context){
  
          HealthApplication application = (HealthApplication) context.getApplicationContext();
  
          return application.refWatcher;
      }

• 监测

  RefWatcher refWatcher = MyApplication.getRefWatcher(this);//1
         refWatcher.watch(this);

例如：我们写一个泄漏的代码

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.layout_event_bus);

        RefWatcher refWatcher = MyApplication.getRefWatcher(this);//1
        refWatcher.watch(this);


        Message message = Message.obtain();
        message.obj = "qianqian";
        message.what = 666;
        handler.sendMessageDelayed(message,600000);
    }

    Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            Log.i("xx","handle message");
        }
    };

    public void sendMessage(View view){
        finish();
    }

界面上一个按钮，点击按钮退出程序，在程序 onCreate 方法中我们发送了一个延时的消息，按照我们的分析，肯定会发生泄漏的。来我们看下leakcannary 给我们的提示：

我们知道当我们退出程序的时候 MessageQueue 中的消息还没执行完毕，MessageQueue.mMessages 这个变量持有的是Message 这个对象，而 Message.target中的 target持有的该Activity的 handler引用，所以此时finish 掉的 activity 并不会被回收，导致LeakActivity 发生内存泄漏。

• 其中一种解决办法呢，就是我们可以通过在点击或activity 退出时，removeMessage，例如：

  public void sendMessage(View view){
          handler.removeMessages(666);
          finish();
      }

这样就不会有警告了。

也可以通过静态内部类+弱引用的方式：

private static class MyHandler extends Handler {
    private final WeakReference<LeakActivity> mActivity;

    public MyHandler(SampleActivity activity) {
      mActivity = new WeakReference<LeakActivity>(activity);
    }

    @Override
    public void handleMessage(Message msg) {
      LeakActivityactivity = mActivity.get();
      if (activity != null) {
        ...
      }
    }
  }
private final MyHandler handler= new MyHandler(this);

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.layout_event_bus);
        Message message = Message.obtain();
        message.obj = "qianqian";
        message.what = 666;
        handler.sendMessageDelayed(message,600000);
    }
}

在实际项目中，可以用这个工具筛查一遍。