問題並無法將View.onClickListener的類與主類分開......幫助！

我需要一些幫助在android ..顯然，我試圖做一個進展對話框的學習目的，基本上這個進度對話框不會做任何事情，但顯示進度條...我有一個按鈕在我的主要活動，點擊該按鈕後，它的onClickListener將運行showDialog（1）方法，該方法將調用main的onCreateDialog方法，但是我已經將該按鈕的View.onClickListener作爲一個單獨的類，即ButtonOnClickListener，將所有必需的變量主要活動被引用，當我在avd模擬器中運行活動時。當我單擊按鈕時，它不會執行進度對話框，但會引發錯誤「抱歉！應用程序意外停止，請重試。「這迫使我退出...問題是與ButtonOnClickListener類..我仍然無法調試數小時..問題並無法將View.onClickListener的類與主類分開......幫助！

它只適用於onClickListener是匿名類...有些幫助嗎？

這是主要的活動課..

package edu.net.learn.android; 

import android.app.Activity; 
import android.os.Bundle; 
import android.app.AlertDialog; 
import android.app.Dialog; 
import android.view.View; 
import android.widget.Button; 
import android.widget.Toast; 
import android.app.ProgressDialog; 
import android.content.DialogInterface; 
import android.os.Handler; 
import android.os.Message; 

public class DialogImproved extends Activity{ 
CharSequence[] items = {"Google", "Apple", "Microsoft"}; 
boolean[] itemsChecked = new boolean[items.length]; 

private ProgressDialog _progressDialog; 
private int _progress = 0; 
private Handler _progressHandler; 

@Override 
public void onCreate(Bundle savedInstanceState){ 
    super.onCreate(savedInstanceState); 
    this.setContentView(R.layout.main); 

    Button btn = (Button)this.findViewById(R.id.btn_dialog); 

    _progressHandler = new Handler(){ 
     public void handleMessage(Message msg){ 
      super.handleMessage(msg); 
      if(_progress >= 100){ 
       _progressDialog.dismiss(); 
      }//end if 
      else { 
       _progress++; 
       _progressDialog.incrementProgressBy(1); 
       _progressHandler.sendEmptyMessageDelayed(0, 100); 
      } 
     } 
    }; 


    btn.setOnClickListener(new ButtonOnClickListener(this,_progress,_progressDialog, 
      _progressHandler)); 


}//end onCreate 

protected Dialog onCreateDialog(int id){ 
    switch(id){ 
    case 1: 
     _progressDialog = new ProgressDialog(this); 
     _progressDialog.setIcon(R.drawable.icon); 
     _progressDialog.setTitle("Downloading files.."); 
     _progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL); 

     _progressDialog.setButton(DialogInterface.BUTTON_POSITIVE, "Hide", new DialogInterface.OnClickListener() { 

      @Override 
      public void onClick(DialogInterface dialog, int which) { 
       Toast.makeText(getBaseContext(), "Hide clicked", Toast.LENGTH_SHORT).show(); 

      } 
     }); 

     _progressDialog.setButton(DialogInterface.BUTTON_NEGATIVE, "Cancel", new DialogInterface.OnClickListener(){ 

      @Override 
      public void onClick(DialogInterface dialog, int which) { 
       Toast.makeText(getBaseContext(), "Cancel clicked!", Toast.LENGTH_SHORT).show(); 

      } 
     }); 
     return _progressDialog; 

    } 

    return null; 
}

ButtonOnClickListener類...

package edu.net.learn.android; 

import android.app.Activity; 
import android.app.ProgressDialog; 
import android.os.Handler; 
import android.os.Message; 
import android.view.View; 


public class ButtonOnClickListener implements View.OnClickListener { 

private Activity main; 
private ProgressDialog _progressDialog; 
private int _progress = 0; 
private Handler _progressHandler; 

ButtonOnClickListener(Activity main,int _progress, 
     ProgressDialog _progressDialog, Handler _progressHandler){ 
    this.main = main; 
    this._progress = _progress; 
    this._progressDialog = _progressDialog; 
    this._progressHandler = _progressHandler; 
} 

public void onClick(View v){ 
    _progress = 0; 
    _progressDialog.setProgress(0); 
    _progressHandler.sendEmptyMessage(0); 
    main.showDialog(1); 


    _progressHandler = new Handler(){ 
     public void handleMessage(Message msg){ 
      super.handleMessage(msg); 
      if(_progress >= 100){ 
       _progressDialog.dismiss(); 
      }//end if 
      else { 
       _progress++; 
       _progressDialog.incrementProgressBy(1); 
       _progressHandler.sendEmptyMessageDelayed(0, 100); 
      } 
     } 
    }; 

} 




}

logcat的報道，在第27行ButtonOnClickListener類空指針異常......

來源

2011-07-25 Shizumaru18