進度條給NullPointerException

我有兩個類。 A級是活動我的進度條將被使用。和B類是無活動我的進度條將被更新。但是當我從非活動類B調用進度條時。我得到了空指針異常。進度條給NullPointerException

A類： -

ProgressBar progressBar; 
@Override 
public void onCreate(Bundle icicle) { 
    super.onCreate(icicle); 
    setContentView(R.layout.main); 
progressBar = (ProgressBar) findViewById(R.id.progressBar1);}

B類： -

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 
        ((Activity) cnt).runOnUiThread(new Runnable() { 

         public void run() { 
          XMPPClient xc = new XMPPClient(); 
          xc.progressBar = new ProgressBar(cnt); 
          xc.progressBar.setProgress(progressStatus); 
         // Toast.makeText(cnt, "ok", Toast.LENGTH_SHORT).show(); 
          i++; 
         } 
        }); 
       } 
      } 
      private int doWork() { 

       return i * 3; 
       } 
     }).start(); 

when i added this line :- xc.progressBar = new ProgressBar(cnt); 
then i did not get nullpointerexception. But now my progress bar is **not updating.**

請任何一個幫助我。

來源

2013-06-18 user2160008

你必須給B類進度條的參考。然後使用它，並解僱它 – abhi

但我怎麼可能做plz？ – user2160008

發送進度條作爲參數在classB構造函數中從ActivityA中使用它在classb中 – abhi

ProgressBar progressBar; 

@Override 
public void onCreate(Bundle icicle) { 
    super.onCreate(icicle); 
    setContentView(R.layout.main); 
    progressBar = (ProgressBar) findViewById(R.id.progressBar1); 

    ClassB classb = new ClassB(this, progressBar); 
} 

public class ClassB{ 

    private Context cnt; 
    private ProgressBar progressBar; 

    public ClassB(Context context, ProgressBar pBar){ 
     cnt = context; 
     progressBar = pBar; 
    } 
}

現在，您可以使用progressBar而不是像以前的代碼那樣創建一個新的！只是一個快速的概述...

來源

2013-06-18 13:06:43 Carnal

在ClassA的

： -

ProgressBar progressBar; 
     @Override 
     public void onCreate(Bundle icicle) { 
      super.onCreate(icicle); 
      setContentView(R.layout.main); 
     progressBar = (ProgressBar) findViewById(R.id.progressBar1); 


     ////Then Use the Reference on Progressbar 

     ClassB classb = new ClassB(this, progressBar); 
    }

然後在ClassB的： -

public class ClassB{ 

    private Context cnt; 
    private ProgressBar progressBar; 

    public ClassB(Context context, ProgressBar pBar){ 
     cnt = context; 
     progressBar = pBar; 

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 
        ((Activity) cnt).runOnUiThread(new Runnable() { 

         public void run() { 
          XMPPClient xc = new XMPPClient(); 
          xc.progressBar = new ProgressBar(cnt); 
          xc.progressBar.setProgress(progressStatus); 
         // Toast.makeText(cnt, "ok", Toast.LENGTH_SHORT).show(); 
          i++; 
         } 
        }); 
       } 
      } 
      private int doWork() { 

       return i * 3; 
       } 
     }).start(); 


    }

來源

2013-06-18 13:19:25 abhi

進度條給NullPointerException

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