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java - handler.postDelayed 无法正常工作

问题描述

我有一个简单的秒表代码片段。线程在自定义类中运行，它通过接口连接到主活动

public class MainActivity extends AppCompatActivity implements MainActivityInteractionInterface{

public static boolean isRunning = false;
Stopwatch stopWatch;
private TextView textViewMilliSeconds;
private TextView textViewSeconds;

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

    textViewMilliSeconds = findViewById(R.id.textViewStopwatchMilliseconds);
    textViewSeconds = findViewById(R.id.textViewStopwatchSeconds);

    stopWatch = new Stopwatch(this, getApplicationContext());
    stopWatch.runThread();
}

@Override
public void updateUI() {
    String time = String.format(Locale.getDefault(), "%03d", stopWatch.getMilliseconds());
    textViewMilliSeconds.setText(time);

    String timeSeconds = String.format(Locale.getDefault(), "%02d", stopWatch.getSeconds());
    textViewSeconds.setText(timeSeconds);
}

public void startTimer(View view) {
    isRunning = !isRunning;
}

public class Stopwatch {
private int milliseconds = 0;
private int seconds = 0;

public int getMilliseconds() {
    return milliseconds;
}

public int getSeconds() {
    return seconds;
}

private MainActivityInteractionInterface interactionInterface;
private Context applicationContext;

public Stopwatch(MainActivityInteractionInterface interactionInterface, Context applicationContext){
    this.interactionInterface = interactionInterface;
    this.applicationContext = applicationContext;
}

public void runThread(){
    final Handler handler = new Handler();
    handler.post(new Runnable(){
        @Override
        public void run(){
            if(isRunning) {
                milliseconds++;
                if (milliseconds == 1000) {
                    milliseconds = 0;
                    seconds++;
                    if(seconds == 60){
                        seconds = 0;
                    }
                }
            }
            interactionInterface.updateUI();
            handler.postDelayed(this, 1);
        }
    });
}

处理程序应该每 1 毫秒更新一次，当有 1000 毫秒时，经过 1 秒如果我设置 handler.postDelayed 延迟，任何低于 15 的时间达到 1000 毫秒都需要 18 秒，为什么？

标签： javaandroidandroid-handler

解决方案

我不知道为什么最多需要 18 秒，但我可以告诉你：Android 每 16 毫秒刷新一次 UI（以达到 60 fps 的速率），因此在更短的时间内将处理程序设置为updateUI是没有意义的，并且也许也干扰它。

以我的拙见，让它在 20 毫秒内更新并相应地更改计数器值，如下所示：

handler.post(new Runnable(){
    @Override
    public void run(){
        if(isRunning) {
            milliseconds++;
            if (milliseconds == 50) {
                milliseconds = 0;
                seconds++;
                if(seconds == 60){
                    seconds = 0;
                }
            }
        }
        interactionInterface.updateUI();
        handler.postDelayed(this, 20);
    }
});

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