Android中使用Handler造成記憶體泄露的分析和解決

Android中使用Handler造成記憶體泄露的分析和解決

Handler 內部類持有 外部類Activity的引用，如果Activity退出而Handler還有延遲處理的訊息沒有處理完，會導致Activity不能回收，反覆如此會導致記憶體泄露。

解決方案一： onDestroy時清除訊息，mHandler.removeCallbacksAndMessages(null); // 參數為null時會清除所有訊息。

解決方案二：聲明Handler為static並持有Activity的弱引用。關鍵看程式中注釋的地方

 

 

public class MainActivity extends Activity {    private static final String tag = "MainActivity";    private TextView mTvShow;    private MyHandler mHandler;    private static final int DELAY_TIME = 10000; // set to 5s and 10s to check result.    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mHandler = new MyHandler(MainActivity.this);        Log.e(tag, "onCreate");        mTvShow = (TextView)findViewById(R.id.tv_show);        new Thread() {            @Override            public void run() {                mHandler.sendEmptyMessageDelayed(1, DELAY_TIME);                Log.e(tag, "msg send");            }        }.start();    }    @Override    protected void onDestroy() {        Log.e(tag, "onDestroy");        super.onDestroy();    }    static class MyHandler extends Handler{        WeakReference mWeakActivity;        public MyHandler(MainActivity activity) {            mWeakActivity = new WeakReference<>(activity);        }        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            MainActivity activity = mWeakActivity.get();            Log.e(tag, "handleMessage," + msg.what);            // 5s is not null, 10s is null, tell that activity is recycled.            if(null == activity){                Log.e(tag, "null");            }else{                Log.e(tag, "not null");                activity.mTvShow.setText("delay show");            }        }    }}