android - 使用 Runnable 和 postDelayed 更新 UI 不适用于计时器应用程序

Question

我已经查看了我可以找到的所有讨论和线程，但事实并非如此。我有一个简单的计时器来更新 TextView (下面示例中的 mTimeTextField)。 mUpdateTimeTask 运行方法正在正确执行(每秒)，但 UI/文本字段未更新。

我有基于此处找到的信息的代码:

http://android-developers.blogspot.com/2007/11/stitch-in-time.html http://developer.android.com/resources/articles/timed-ui-updates.html

代码如下:

package com.something.handlertest;

import com.something.handlertest.R;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.os.SystemClock;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class Test extends Activity {

    private Handler mHandler = new Handler(); 
    private int labelNo    = 0;
    private long currTime  = 0L;
    private long mStartTime = 0L;
    TextView mTimeTextField;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mTimeTextField = (TextView)findViewById(R.id.timeTextFieldl);

        Button startButton = (Button)findViewById(R.id.start_button);
        startButton.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {
                   if (mStartTime == 0L) {
                        mStartTime = System.currentTimeMillis();
                        mHandler.removeCallbacks(mUpdateTimeTask);
                        mHandler.postDelayed(mUpdateTimeTask, 100);
                   }
            }
        });
    }

    private Runnable mUpdateTimeTask = new Runnable() {
           public void run() {
               final long start = mStartTime;
               //long millis = SystemClock.uptimeMillis() - start;
               long millis = SystemClock.uptimeMillis();
               int seconds = (int) (millis / 1000);
               int minutes = seconds / 60;
               seconds     = seconds % 60;

               //setContentView(mTimeTextField);  This will blow up if I use it

               if (seconds < 10) {
                   mTimeTextField.setText("" + minutes + ":0" + seconds);
               } else {
                   mTimeTextField.setText("" + minutes + ":" + seconds);            
               }

               //mHandler.postAtTime(this,
                   //    start + (((minutes * 60) + seconds + 1) * 1000));

               mHandler.postAtTime(this, 1000);
           }
        };

}

---

根据一些建议，我尝试添加:

setContentView(mTimeLabel);

但这会崩溃提示 View 没有父级。仅供引用，我确实有一个:

setContentView(R.layout.main);

调用我的onCreate()。

Answer 1

替换

mHandler.postAtTime(this, 1000);

与

mHandler.postDelayed(this, 1000);