線程教程需要

我有一個應用程序，從互聯網加載圖像，並使用圖庫小部件和imageview的組合顯示。我想把下載的圖像部分放到一個單獨的線程中，但即使經過幾次谷歌搜索，我也不知道如何去做。以下是我的代碼，任何人都可以請幫助我。提前致謝。線程教程需要

package com.example.gallery; 

import java.io.BufferedInputStream; 
import java.io.File; 
import java.io.IOException; 
import java.io.InputStream; 
import java.net.MalformedURLException; 
import java.net.URL; 
import java.net.URLConnection; 
import java.util.ArrayList; 
import java.util.List; 

import android.app.Activity; 
import android.content.Context; 
import android.content.res.TypedArray; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.os.Bundle; 
import android.os.Environment; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.AdapterView; 
import android.widget.AdapterView.OnItemClickListener; 
import android.widget.BaseAdapter; 
import android.widget.Gallery; 
import android.widget.ImageView; 
import android.widget.Toast; 

public class GalleryActivity extends Activity { 
public Bitmap[] bmps; 
    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 

    Gallery gal = (Gallery)findViewById(R.id.gallery); 

    final ImageView iv = (ImageView)findViewById(R.id.imageView); 

    gal.setAdapter(new ImageAdapter(this)); 

    gal.setOnItemClickListener(new OnItemClickListener() { 
     public void onItemClick(AdapterView<?> parent, 
      View v, int position, long id) {   

      Bitmap bm = bmps[position]; 
      if(bm.getHeight() > 800 || bm.getWidth() > 600) 
      { 
       Bitmap rbm = Bitmap.createScaledBitmap(bm, bm.getWidth()/2, bm.getHeight()/2, true); 
       iv.setImageBitmap(rbm); 
      } 
      else 
      { 
       iv.setImageBitmap(bm); 
      } 

     } 
    }); 
} 

public void initBmps(int length) 
{ 
    bmps = new Bitmap[length]; 
} 

public void setBmps(Bitmap bm, int pos) 
{ 
    bmps[pos] = bm; 
} 

public class ImageAdapter extends BaseAdapter 
{ 
    int mGalleryItemBackground; 
    private Context mContext; 

    private String[] mImageIds = {"http://4.bp.blogspot.com/-bQQ6UcJhpoA/TfOeymYKMeI/AAAAAAAAAIo/30kj0KUAgxo/s1600/snsd1.jpg", 
            "http://www.sweetslyrics.com/images/img_gal/13192_snsd-group-31.jpg", 
            "http://kojaproductions.files.wordpress.com/2008/12/snsd_teases_kjp.jpg", 
            "http://solar.envirohub.net/images/solar-power.jpg", 
            "http://scm-l3.technorati.com/11/05/27/35419/solar-power.jpg?t=20110527104336", 
            "http://www.solarstorms.org/Pictures/GridMap.gif", 
            "http://static.electro-tech-online.com/imgcache/11039-power%20lines.jpg"}; 


    public ImageAdapter(Context c) 
    { 
     mContext = c; 
     TypedArray a = mContext.obtainStyledAttributes(R.styleable.Theme); 
     mGalleryItemBackground = a.getResourceId(R.styleable.Theme_android_galleryItemBackground, 0); 
     initBmps(mImageIds.length); 
     a.recycle(); 
    } 

    public int getCount() 
    { 
     return mImageIds.length; 
    } 

    public Object getItem(int position) 
    { 
     return position; 
    } 

    public long getItemId(int position) 
    { 
     return position; 
    } 

    public View getView(int position, View convertView, ViewGroup parent) 
    { 
     ImageView i = new ImageView(mContext); 

      DownloadImageTask down = new DownloadImageTask(); 
      down.excecute(mImageIds[position]); 

      if(down..getStatus() == AsyncTask.Status.FINISHED) 
      { 

       Bitmap rbm = Bitmap.createScaledBitmap(bm, 200, 200, true); 

       i.setImageBitmap(rbm); 
       i.setLayoutParams(new Gallery.LayoutParams(150, 150)); 
       i.setScaleType(ImageView.ScaleType.FIT_XY); 
       i.setBackgroundResource(mGalleryItemBackground); 
      } 
      return i; 
    } 

private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> { 
     @Override 
     protected Bitmap doInBackground(String... url) { 
      // TODO Auto-generated method stub 
      Toast.makeText(getApplicationContext(), url[0], Toast.LENGTH_SHORT).show(); 
      URL aURL; 
      Bitmap bm = null; 
      try { 
       aURL = new URL(url[0]); 
       URLConnection conn = aURL.openConnection(); 
       conn.connect(); 
       InputStream is = conn.getInputStream(); 
       BufferedInputStream bis = new BufferedInputStream(is); 
       bm = BitmapFactory.decodeStream(bis); 
       //setBmps(bm, position); 
       bis.close(); 
       is.close(); 
      } catch (MalformedURLException e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } catch (IOException e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } 

      return null; 
     } 

     protected void onPostExecute (Bitmap result) { 
      setBm(result); 
     } 

    } 

} 
}

來源

2011-09-25 chenhou90

我已經加入的AsyncTask我的代碼，但我的應用程序將只突然死了。而且錯誤總是一樣的。有人知道爲什麼調用AsyncTask後，它與代碼有什麼關係？ – chenhou90

看起來您不止一次地啓動了調試器？我沒有看到你開始下載的ImageImageTask，我錯過了嗎？ –

我重新啓動了android虛擬機，錯誤消失了。在AsyncTask完成後，我修改了我的代碼以執行某些任務，但似乎沒有進入if語句。問題是我可以多次調用AsyncTask？ – chenhou90

線程教程需要

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