Android - 显示进度条时出现 'Cant create handler' 错误

Question

我试图在我的应用程序中显示进度条，但遇到线程问题。这是我用来执行此操作的代码:

package com.integrated.mpr;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;

public class Progess extends Activity {

   static String[] display = new String[Choose.n];
   private static final int Progress = 0;

   ProgressBar bar;
   TextView label;
   Handler handler = new Handler();

   @Override
   protected void onCreate(Bundle savedInstanceState) {
      // TODO Auto-generated method stub
      super.onCreate(savedInstanceState);
      setContentView(R.layout.progress);

      bar = (ProgressBar) findViewById(R.id.progBar);

      new Thread(new Runnable() {

         int i = 0;
         int progressStatus = 0;

         public void run() {
            while (progressStatus < 100) {
               progressStatus += doWork();
               try {
                  Thread.sleep(500);
               } catch (InterruptedException e) {
                  e.printStackTrace();
               }

               // Update the progress bar
               handler.post(new Runnable() {
                  public void run() {
                     bar.setProgress(progressStatus);
                     i++;
                  }
               });
            }
         }

         private int doWork() {
            display = new Logic().finaldata();
            return i * 3;
         }

      }).start();

      Intent openList = new Intent("com.integrated.mpr.SENSITIVELIST");
      startActivity(openList);
   }
}

我收到以下 logcat 消息:

05-30 12:38:00.082: E/AndroidRuntime(17332): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()

请帮助我，我是线程新手。

Answer 1

与其以这种方式实现线程，我建议您实现 AsyncTask 被称为 Painless Threading在 Android 中。

1. 在onPreExecute()中显示进度条
2. 在 doInBackground()
中执行后台任务
3. 关闭 onPostExecute() 中的进度条
4. 在 onProgressUpdate() 内更新进度条