如何使用的AsyncTask在PaperAdapter

Question

顯示URL圖像

最後，我改變我的代碼，並使用萬能圖像裝載機庫

我用paperadapter像代碼顯示網址的圖像，它工作正常。

@Override 
public Object instantiateItem(final ViewGroup container, final int position) { 
Drawable[] imageDrawable = new Drawable[3]; 
for (int i = 0; i < 3; i++) { 
imageDrawable[i] = LoadImageFromWebOperations(server_url+ image_name.replace(" ","")+ "_0" +String.valueOf(i + 1) + ".jpg"); 
} 
imageView = new ImageView(mContext); 
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP); 
imageView.setImageDrawable(imageDrawable[position]); 
container.addView(imageView, 0); 
return imageView; 
} 

，但我想用的AsyncTask要做到這一點，如代碼

@Override 
public Object instantiateItem(final ViewGroup container, final int position) { 

    AsyncTask<String, Void, Drawable[]> loadingImage = new AsyncTask<String, Void, Drawable[]>(){ 

     @Override 
     protected Drawable[] doInBackground(String... params) { 
      // TODO Auto-generated method stub 
      Drawable imageDrawable[] = new Drawable[3]; 
      for (int i = 0; i < 3; i++) { 
       imageDrawable[i] = LoadImageFromWebOperations(server_url 
         + image_name.replace(" ","")+ "_0" + String.valueOf(i + 1) + ".jpg"); 
       System.out.println("doInBackground="+position); 
      } 
      return imageDrawable; 
     } 
     @Override 
     protected void onPostExecute(Drawable[] result) { 
      System.out.println("onPostExecute="+position); 
      imageView = new ImageView(getBaseContext()); 
      imageView.setScaleType(ImageView.ScaleType.CENTER_CROP); 
      imageView.setImageDrawable(result[position]); 
      container.addView(imageView, 0); 
       } 
      }); 
     } 

    }; loadingImage.execute(); 
    return imageView; 
} 

它不工作fine.i發現該位置「1」爲空沒有圖像，但位置0 2不爲空，等待一些建議，謝謝！

Answer 1

這是所有代碼：

public class ProductDetailActivity1 extends FragmentActivity { 

     ImageAdapter mAdapter; 
     ViewPager mPager; 
     CirclePageIndicator mIndicator; 
     private String server_url; 
     ImageView imageView;  
     protected ScrollView mScrollView; 

     @Override 
     protected void onCreate(Bundle savedInstanceState) { 
      super.onCreate(savedInstanceState); 
      setContentView(R.layout.activity_product_detail1); 

      mScrollView = (ScrollView)findViewById(R.id.card_scrollview); 


      getActionBar(); 
      getActionBar().setHomeButtonEnabled(true); 
      getActionBar().setDisplayHomeAsUpEnabled(true); 
      getActionBar().setDisplayShowTitleEnabled(true); 
      getActionBar().setTitle(R.string.product_detail); 

      Intent intent = getIntent(); 
      server_url = intent.getStringExtra("SERVER_URL"); 

      mAdapter = new ImageAdapter(getApplicationContext()); 
      mPager = (ViewPager) findViewById(R.id.imageViewpager); 
      mPager.setAdapter(mAdapter); 


      mIndicator = (CirclePageIndicator) findViewById(R.id.indicator); 
      mIndicator.setViewPager(mPager); 
      mIndicator.setFillColor(0xFFFFFFFF); 
      mIndicator.setStrokeColor(0xFFFFFFFF); 
      mIndicator.setStrokeWidth(1); 
      mIndicator.setRadius(6 * getResources().getDisplayMetrics().density); 
      ((CirclePageIndicator) mIndicator).setSnap(true); 
      mIndicator 
        .setOnPageChangeListener(new ViewPager.OnPageChangeListener() { 
         @Override 
         public void onPageSelected(int position) { 
         } 

         @Override 
         public void onPageScrolled(int position, 
           float positionOffset, int positionOffsetPixels) { 
         } 

         @Override 
         public void onPageScrollStateChanged(int state) { 
         } 
        }); 
     } 

     @Override 
     public boolean onOptionsItemSelected(MenuItem item) { 

      switch (item.getItemId()) { 
      case android.R.id.home: 
       Intent intent = new Intent(ProductDetailActivity1.this, 
         com.wangrui.ams.MainActivity.class); 
       intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); 
       startActivity(intent); 
       return true; 
      default: 
       return super.onOptionsItemSelected(item); 
      } 
     } 

     @Override 
     public boolean onCreateOptionsMenu(Menu menu) { 
      // Inflate the menu; this adds items to the action bar if it is present. 
      getMenuInflater().inflate(R.menu.product_detail, menu); 
      return true; 
     } 

     public class ImageAdapter extends PagerAdapter { 
      private Context mContext; 
      private Drawable[] imageDrawable = new Drawable[3];; 

      public ImageAdapter(Context cx) { 
       mContext = cx.getApplicationContext(); 
      } 

      @Override 
      public Object instantiateItem(final ViewGroup container, final int position) { 
       AsyncTask<Void, Void, Drawable[]> loadingImage = new AsyncTask<Void, Void, Drawable[]>(){ 

        @Override 
        protected Drawable[] doInBackground(Void... params) { 
         // TODO Auto-generated method stub 

         for (int i = 0; i < 3; i++) { 
          imageDrawable[i] = LoadImageFromWebOperations(server_url 
            + image_name.replace(" ","")+ "_0" + String.valueOf(i + 1) + ".jpg"); 
          System.out.println("position="+i); 
         } 
         return imageDrawable; 
        } 
        @Override 
        protected void onPostExecute(Drawable[] result) { 
         imageView = new ImageView(mContext); 
         imageView.setScaleType(ImageView.ScaleType.CENTER_CROP); 
        imageView.setImageDrawable(result[position]); 
         mPager.getAdapter().notifyDataSetChanged(); 
         ((ViewPager) container).addView(imageView, position); 

        }    
       }; loadingImage.execute(); 

       return imageView; 
      } 

      @Override 
      public int getCount() { 
       // TODO Auto-generated method stub 
       return 3; 
      } 

      @Override 
      public boolean isViewFromObject(final View view, final Object object) { 
       // TODO Auto-generated method stub 
       //return arg0 == (View) arg1; 
       return view == ((ImageView) object); 
      } 

      @Override 
      public void destroyItem(ViewGroup container, int position, Object object) { 
       container.removeView((ImageView) object); 
      } 

     } 

     private void showAlertMessage(String msg){ 

      SuperToast superToast = new SuperToast(getApplicationContext()); 
      superToast.setAnimations(SuperToast.Animations.FLYIN); 
      superToast.setDuration(SuperToast.Duration.LONG); 
      superToast.setBackground(SuperToast.Background.RED); 
      superToast.setTextSize(SuperToast.TextSize.EXTRA_SMALL); 
      superToast.setText(msg); 
      superToast.show(); 
     } 

     private Drawable LoadImageFromWebOperations(String url) { 
      try { 
       StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder() 
         .permitAll().build(); 
       StrictMode.setThreadPolicy(policy); 
       InputStream is = (InputStream) new URL(url).getContent(); 
       Drawable d = Drawable.createFromStream(is, "src name"); 
       return d; 
      } catch (Exception e) { 
       System.out.println("Exc=" + e); 
       return null; 
      } 
     } 
    }