android - 循环中的计数器

Question

如何在Activity中做sample counter？这是行不通的。

public class MainActivity extends AppCompatActivity implements Runnable {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        run();
    }

    @Override
    public void run() {
        while (true) {
            updateTv();

            try {
                Thread.sleep(17);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public void updateTv() {
        int counter = 100;
        final TextView tv = (TextView) findViewById(R.id.tv);
        tv.setText(String.valueOf(counter));
        counter--;
    }
}

Answer 1

在 onCreate() 中，您将在 UI 线程内启动一个无限循环，将其完全阻塞。或者你可以使用 Handler定期更新。也许使用更大的延迟并在某个时候停止它。

public class MainActivity extends AppCompatActivity implements Runnable {
    private final Handler mHandler = new Handler();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        run();
    }

    @Override
    public void run() {
        updateTv();
        mHandler.postDelayed(this, 17);
    }

    public void updateTv() {
        int counter = 100;
        final TextView tv = (TextView) findViewById(R.id.tv);
        tv.setText(String.valueOf(counter));
        counter--;
    }
}

无论如何你应该阅读What is the Android UiThread (UI thread)当然。