Handler声明称静态内部类,实例化报错

安卓开发实现下载进度条
在使用Handler更新UI的时候,我是这样写的

handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            progressBar.setProgress((Integer)msg.obj);
            textView.setText("已下载"+msg.obj+"%");
        }
        };

编译器给出了这样的警告
This Handler class should be static or leaks might occur

查询资料后,使用静态内部类

 private static class MyHandler extends Handler {
        private final WeakReference<MainActivity> mActivity;
        public MyHandler(MainActivity activity) {
            mActivity = new WeakReference<MainActivity>(activity);
        }
    @Override
    public void handleMessage(Message msg) {
        if (mActivity.get() != null) {

        }
    }
}

实例化MyHandller的时候依旧给出这样的警告
This Handler class should be static or leaks might occur

以及我的静态内部类声明有问题吗?

完整的代码

public class MainActivity extends AppCompatActivity {
    private ProgressBar progressBar;
    private TextView textView;
    private int downloadStatus = 0;

    private static class MyHandler extends Handler {
        private final WeakReference<MainActivity> mActivity;
        public MyHandler(MainActivity activity) {
            mActivity = new WeakReference<MainActivity>(activity);
        }
        @Override
        public void handleMessage(Message msg) {
            if (mActivity.get() != null) {
            }
        }
    }
    private static MyHandler handler;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        progressBar = (ProgressBar) findViewById(R.id.progressBar);
        textView = (TextView) findViewById(R.id.textShow);

        handler = new MyHandler(this) {
            public void handleMessage(Message msg) {
                progressBar.setProgress((int) msg.obj);
                textView.setText("已下载" + msg.obj + "%");
            }

        };
        new MyThread().start();
    }

    class MyThread extends Thread {
        @Override
        public void run() {
            while (downloadStatus < 100) {
                downloadStatus = doWork();
                Message msg = new Message();
                msg.obj = downloadStatus;
                handler.sendMessage((Message) msg.obj);
            }
        }
    }

    //模拟下载过程
    int doWork() {
        downloadStatus += 1;
        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return downloadStatus;
    }
}
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