Android的教程 - setImageResource和網格視圖

Question

我實現了一個網格視圖按照本教程：

http://developer.android.com/guide/topics/ui/layout/gridview.html

適配器具有以下圖片引用：

// references to our images 
private Integer[] mThumbIds = { 
     R.drawable.sample_2, R.drawable.sample_3, 
     R.drawable.sample_4, R.drawable.sample_5, 
     R.drawable.sample_6, R.drawable.sample_7, 
     R.drawable.sample_0, R.drawable.sample_1, 
     R.drawable.sample_2, R.drawable.sample_3, 
     R.drawable.sample_4, R.drawable.sample_5, 
     R.drawable.sample_6, R.drawable.sample_7, 
     R.drawable.sample_0, R.drawable.sample_1, 
     R.drawable.sample_2, R.drawable.sample_3, 
     R.drawable.sample_4, R.drawable.sample_5, 
     R.drawable.sample_6, R.drawable.sample_7 
}; 

和圖案，然後使用顯示setImageResource：

imageView.setImageResource(mThumbIds[position]); 

從互聯網

1. 下載圖片（我會提供的URI）
2. 緩存圖像
3. 顯示他們在GridView

：

我想提高這一點，...

我該怎麼做？請點我到正確的方向，並提供任何相關教程如果可能的話

Answer 1

• 下載圖片來自互聯網（我將提供URI）

本教程會幫助你https://stackoverflow.com/questions/15549421/how-to-download-and-save-an-image-in-android

• 緩存

你可以在你的類，如果你想擁有緩存爲一個應用程序生命週期只使用HashMap的或創建的SQLite數據庫中的圖像具有高速緩存可以存儲數據永遠https://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html

• 顯示他們在GridView

您需要擴展BaseAdapter類。本教程應該可以幫助您：http://www.stealthcopter.com/blog/2010/09/android-creating-a-custom-adapter-for-gridview-buttonadapter/

如果你有相關的這個話題什麼的另一個問題是，不明確的只是問，我會盡力幫助你

Answer 2

的AsyncTask上加載一個ImageView的照片：

private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> { 
    private ImageView bmImage; 

    public DownloadImageTask(ImageView bmImage) { 
     this.bmImage = bmImage; 
    } 

    protected Bitmap doInBackground(String... urls) { 
     final File cacheDir = getCacheDir(); 
     Bitmap bitmap = null; 
     if (Utill.isMemoryAvaliable(dir.getPath())){ 
      String url = urls[0]; 
      String filename = url.substring(url.lastIndexOf("/")+1,url.contains("?")?url.indexOf("?"):url.length()); 
      File f = new File(cacheDir, filename); 
      //from SD cache 
      if(!f.exists()){ 
       try { 
        Utill.DownloadFromUrl(url, filename, cacheDir); 
       } catch (IOException ex) { 
        Log.e("Error", "Download", ex); 
       } 
      } 
      if(f.exists()) 
       bitmap = decodeFile(new File(cacheDir, filename)); 
     } 
     return bitmap; 
    } 

    protected void onPostExecute(Bitmap result) { 
     bmImage.setImageBitmap(result); 
    } 

    private Bitmap decodeFile(File f) { 
     try { 
      BitmapFactory.Options o = new BitmapFactory.Options(); 
      o.inJustDecodeBounds = true; 
      BitmapFactory.decodeStream(new FileInputStream(f), null, o); 
      return BitmapFactory.decodeStream(new FileInputStream(f)); 
     } catch (FileNotFoundException e) { 
      Log.e("Error", "Decode File", e); 
     } 
     return null; 
    } 

} 

要下載圖片：

public static boolean downloadFromUrl(String downloadUrl, String fileName, File dir) throws IOException { 
     if (URLUtil.isValidUrl(downloadUrl)) { 
      System.setProperty("http.keepAlive", "false"); 
      URL url = new URL(downloadUrl); 
      HttpURLConnection ucon = (HttpURLConnection) url.openConnection(); 
      ucon.setRequestProperty("Connection", "Keep-Alive"); 
      ucon.setConnectTimeout(50000); 
      ucon.connect(); 
      if (ucon.getResponseCode() == HttpURLConnection.HTTP_OK) { 
       InputStream is = url.openStream(); 
       if (is.available() > 0) { 
        BufferedInputStream bis = new BufferedInputStream(is); 
        ByteArrayBuffer baf = new ByteArrayBuffer(5000); 
        int current = 0; 
        while ((current = bis.read()) != -1) { 
         baf.append((byte) current); 
        } 
        File file = new File(dir, fileName); 
        FileOutputStream fos = new FileOutputStream(file); 
        fos.write(baf.toByteArray()); 
        fos.flush(); 
        fos.close(); 
       } 
       is.close(); 
       return true; 
      } else { 
       return false; 
      } 
     } 
     return false; 
    }