Handler我們經常用在程序中,發送消息,然而這裏涉及到內存泄漏隱患,非靜態內部類引起的。
非靜態內部類引起內存泄漏,詳見http://blog.csdn.net/qq_29266921/article/details/54847402
舉個栗子:
public class MainActivity extends AppCompatActivity {
private Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
//...
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
loadData();
}
private void loadData(){
//...request
Message message = Message.obtain();
mHandler.sendMessage(message);
}
}
建議去看上面的鏈接,然後你就會知道非靜態匿名內部類,和非靜態內部類引起內存泄漏原因是一樣的。
上面的代碼可以更加安全,修改如下:
public class MainActivity extends AppCompatActivity {
private MyHandler mHandler = new MyHandler(this);
private TextView mTextView ;
private static class MyHandler extends Handler {
private WeakReference<Context> reference;
public MyHandler(Context context) {
reference = new WeakReference<>(context);
}
@Override
public void handleMessage(Message msg) {
MainActivity activity = (MainActivity) reference.get();
if(activity != null){
activity.mTextView.setText("");
}
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTextView = (TextView)findViewById(R.id.textview);
loadData();
}
private void loadData() {
//...request
Message message = Message.obtain();
mHandler.sendMessage(message);
}
@Override
protected void onDestroy() {
super.onDestroy();
mHandler.removeCallbacksAndMessages(null);
}
}
1.創建一個靜態Handler內部類,然後對Handler持有的對象使用弱引用,這樣在回收時也可以回收Handler持有的對象。
2.mHandler.removeCallbacksAndMessages(null)移除消息隊列中所有消息和所有的Runnable。當然也可以使用mHandler.removeCallbacks()或mHandler.removeMessages()來移除指定的Runnable和Message