計時器的Android 執行緒
提供的程式碼建立一個從5 分鐘倒數到0 的計時器:00，但它沒有按預期工作。問題在於從 UI 執行緒以外的執行緒內更新 UI。
在 Android 中使用執行緒時，必須避免從非 UI 執行緒更新 UI 。以下是建立倒數計時器的三種替代方法，同時確保在 UI 執行緒上執行 UI 更新：
範例：
<code class="java">public class MainActivity extends Activity {
private TextView timer1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
timer1 = findViewById(R.id.timer1);
startTimer(5 * 60 * 1000); // 5 minutes in milliseconds
}
private void startTimer(long time) {
CountDownTimer timer = new CountDownTimer(time, 1000) {
@Override
public void onTick(long millisUntilFinished) {
int minutes = (int) (millisUntilFinished / (1000 * 60));
int seconds = (int) (millisUntilFinished / 1000) % 60;
timer1.setText(String.format("%02d:%02d", minutes, seconds));
}
@Override
public void onFinish() {
timer1.setText("00:00");
}
};
timer.start();
}
}</code>範例：
<code class="java">public class MainActivity extends Activity {
private Handler mHandler;
private Runnable mRunnable;
private int timeleft = 5 * 60; // 5 minutes
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mHandler = new Handler();
mRunnable = new Runnable() {
@Override
public void run() {
if (timeleft >= 0) {
int minutes = timeleft / 60;
int seconds = timeleft % 60;
timer1.setText(String.format("%02d:%02d", minutes, seconds));
timeleft--;
} else {
// Stop the timer
mHandler.removeCallbacks(mRunnable);
}
mHandler.postDelayed(mRunnable, 1000);
}
};
mRunnable.run();
}
}</code>範例：
<code class="java">public class MainActivity extends Activity {
private Timer timer;
private TimerTask timerTask;
private int timeleft = 5 * 60; // 5 minutes
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
timer = new Timer();
timerTask = new TimerTask() {
@Override
public void run() {
runOnUiThread(new Runnable() {
@Override
public void run() {
if (timeleft >= 0) {
int minutes = timeleft / 60;
int seconds = timeleft % 60;
timer1.setText(String.format("%02d:%02d", minutes, seconds));
timeleft--;
} else {
// Cancel the timer
timer.cancel();
}
}
});
}
};
timer.scheduleAtFixedRate(timerTask, 1000, 1000);
}
}</code>以上是如何從 Android 計時器中的執行緒安全地更新 UI？的詳細內容。更多資訊請關注PHP中文網其他相關文章！
