单例

public class AppManager {

    //有内存泄漏的问题：
//    private static AppManager instance;
//    private Context context;
//    private AppManager(Context context) {
//        this.context = context;
//    }
//    public static AppManager getInstance(Context context) {
//        if (instance == null) {
//传入的Activity回收时由于被单例持有无法回收
//            instance = new AppManager(context);
//        }
//        return instance;
//    }
//    修复内存泄漏的写法：
    private static AppManager instance;
    private Context context;
    private AppManager(Context context) {
        this.context = context.getApplicationContext();// 使用Application 的context
    }
    public static AppManager getInstance(Context context) {
        if (instance == null) {
            instance = new AppManager(context);
        }
        return instance;
    }
}

匿名内部类handler

public class MainActivity extends AppCompatActivity {
    //容易造成内存泄漏的写法：
//非静态内部类
//    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);
//    }
//
//    static class TestResource {
//该静态实例持有activity的引用，内存资源得不到正常回收，应该设为静态内部类
//        private static final String TAG = "";
//        //...
//    }

//    修复内存泄漏的方法：
//1.设为静态内部类2.在handler内部持有外部类Activity的弱引用
    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);
        loadData();
    }

    private void loadData() {
        //...request
        Message message = Message.obtain();
        mHandler.sendMessage(message);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        mHandler.removeCallbacksAndMessages(null);
    }
}