为什么TextView的Text值即使在UI线程上也没有更改

Question

我有一个带按钮的活动。在ACTION_DOWN上，我开始录制并在按下此按钮的同时继续录制。在ACTION_UP上，我必须停止录制。录音线程是独立的。有一个关于活动的文本视图，显示录制时间。时间的默认值为"00:00:00:000"从记录线程我调用活动类的updateTime方法：

public void updateTime(final String time) {
    Log.d("***UPDATE TIME Thread", "Current time:" + time);
    runOnUiThread(new Runnable() {
        public void run() {
            timerTextView.setText(time);
            Log.d("UPDATE TIME Thread", "Current time:"+time);
        }
    });
}

当我第一次调用此活动时，它工作正常，并正确更新时间值。但是，如果我从上一个屏幕中选择相同的选项来开始记录第二次时间，时间文本视图的值将保持与"00:00:00:000"相同，其中第二个Log.d代码行显示了正确的值。这是LogCat

02-25 16:07:10.660: D/Recording(5075):  Start
02-25 16:07:10.695: D/***UPDATE TIME Thread(5075): Current time:00:00:00:032
02-25 16:07:10.711: D/UPDATE TIME Thread(5075): Current time:00:00:00:032
02-25 16:07:10.843: D/***UPDATE TIME Thread(5075): Current time:00:00:00:174
02-25 16:07:10.863: D/UPDATE TIME Thread(5075): Current time:00:00:00:174
02-25 16:07:10.945: D/***UPDATE TIME Thread(5075): Current time:00:00:00:280
02-25 16:07:10.972: D/UPDATE TIME Thread(5075): Current time:00:00:00:280
02-25 16:07:11.082: D/***UPDATE TIME Thread(5075): Current time:00:00:00:418
02-25 16:07:11.089: D/UPDATE TIME Thread(5075): Current time:00:00:00:418
02-25 16:07:11.203: D/***UPDATE TIME Thread(5075): Current time:00:00:00:535
02-25 16:07:11.222: D/UPDATE TIME Thread(5075): Current time:00:00:00:535
02-25 16:07:11.351: D/***UPDATE TIME Thread(5075): Current time:00:00:00:676
......
Here is my Activity Class Code

公共类VerficationPBActivity扩展Activity实现VoiceManagerListener、OnTouchListener{私人索赔人current索赔人=无效；TextView屏幕标题=null；private字符串screenHeadingText=null；TextView textToSpeakTextView=null；TextView timerTextView=null；TextView状态提示TextView=null；私有按钮pushToRecordButton；

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_verfication_pb);
    ActivityController.getActivityController().setCurrentActivity(this);
    screenHeading = (TextView) findViewById(R.id.screenHeading);
    textToSpeakTextView = (TextView) findViewById(R.id.text_to_speek);
    timerTextView = (TextView) findViewById(R.id.timer);
    statusHintTextView = (TextView) findViewById(R.id.status_hint);
    screenHeadingText = (String) getIntent().getSerializableExtra("heading");
    currentClaimant = (Claimant) getIntent().getSerializableExtra("claimant");
    screenHeading.setText(screenHeadingText);
    if (currentClaimant != null) {
        textToSpeakTextView.setText(currentClaimant.getNextPrompt());
        statusHintTextView.setText(currentClaimant.getStatusHint());
    }
    pushToRecordButton = (Button) findViewById(R.id.pushToRecord);
    pushToRecordButton.setOnTouchListener(this);
}
@Override
public void updateTime(final String time) {
    Log.d("***UPDATE TIME Thread", "Current time:" + time);
    runOnUiThread(new Runnable() {
     public void run() {
     timerTextView.setText(time);
     Log.d("UPDATE TIME Thread", "Current time:"+time);
     Log.d("UPDATE TIME Thread", "Current value:"+timerTextView.getText());
     }
     });
}


@Override
public boolean onTouch(View v, MotionEvent event) {
    switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN:
        VoiceManager.getInstance().startRecording();
        break;
    case MotionEvent.ACTION_UP:
        Log.d("Push Button Down", "Up Event Fired");
        VoiceManager.getInstance().stop();
        String audioDataBase64 = VoiceManager.getInstance().getAudioDateinBase64Encoding();
        if (screenHeadingText.equals("Verification")) {
            VBSServiceManager.getInstance().processVerification(currentClaimant, audioDataBase64);
        } else {
            VBSServiceManager.getInstance().processEnrollment(currentClaimant, audioDataBase64);
        }
        break;
    }
    return false;
}

}

Answer 1

在android中，您不能从另一个线程更新UI。这是android开发中的限制(我认为这是一个删除不必要错误的功能(。您可以对此使用AsyncTask。。。

在使用中，您可以在donInBackground((中执行长任务，然后使用onProgressUpdate((更新UI。。。请参阅此处的AsyncTask示例

编辑

有关更多信息，请参阅此类似问题。。。

Answer 2

查看日志，我意识到您几乎每100毫秒更新一次TextView，这就是为什么它没有显示任何内容。

这就是我模拟你正在做的事情的方式，我的文本视图在第100次迭代后显示了最终值：-

for(int i=0;i<100;i++)
{
    ((TextView) findViewById(R.id.timerTextView)).setText(""
            + System.currentTimeMillis());
    try {
        Thread.sleep(100);
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

试着每秒钟更新一次UI，你可能也会消耗CPU周期。