前几天在修复电池项目内存泄漏的地方学到了一个新的知识点.

私有内部类（匿名的私有内部类也算）中会有一个外部类的引用，那么当内部类对象没有被销毁，外部类也不会被销毁，这一点很容易忽略从而造成内存泄漏.

代码如下：这样的匿名内部类使用会导致OutOfMemActivity的内存泄漏

public class OutOfMemActivity extends Activity implements View.OnClickListener{

    public static final String ACTION_INTENT_FILTER = "ACTION_INTENT_FILTER";

    private Button btn;

    private BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            new Thread(){
                @Override
                public void run() {
                    super.run();
                    while (true){
                        try {
                            Thread.sleep(1000);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        Log.i("tag","running ... "+OutOfMemActivity.this);
                    }
                }
            }.start();
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_out_of_mem);
        btn = (Button)findViewById(R.id.btn_send);
        btn.setOnClickListener(this);
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(ACTION_INTENT_FILTER);
        registerReceiver(broadcastReceiver,intentFilter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(broadcastReceiver);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.btn_send:
                Intent intent = new Intent();
                intent.setAction(ACTION_INTENT_FILTER);
                sendBroadcast(intent);
                break;
        }
    }
}

我们可用通过弱引用解决该问题（关于强引用,软引用,弱引用,虚引用传送门https://my.oschina.net/ydsakyclguozi/blog/404389），我们改写这个广播接收器使它成为静态内部类如下:

private static class MyBroadcastReceiver extends BroadcastReceiver{



    private WeakReference<OutOfMemActivity> outOfMemActivityWeakReference;

    public MyBroadcastReceiver(WeakReference<OutOfMemActivity> outOfMemActivityWeakReference) {

        this.outOfMemActivityWeakReference = outOfMemActivityWeakReference;
    }



    @Override
    public void onReceive(Context context, Intent intent) {

        new Thread(){

            @Override
            public void run() {

                super.run();
                while (true){

                    try {

                        Thread.sleep(1000);
                    } catch (InterruptedException e) {

                        e.printStackTrace();
                    }

                    OutOfMemActivity outOfMemActivity = outOfMemActivityWeakReference.get();
                    Log.i("tag","running ... "+outOfMemActivity);
                }

            }

        }.start();
    }

}

这样如果使用OutOfMemActivity对象，它是以弱引用传送进来，在垃圾回收器扫描到该对象的时候就会回收掉它.