从图像URL下载图像到图像视图

Question

我想从imageurl下载图像该图像来自该网址是一个高分辨率image.it工作正常在所有高分辨率手机，当我试图加载到一个图像它正在抛出内存泄漏异常的mdpi模拟器。

我如何处理这种情况，我想在每个这一形象和每一个屏幕，所以我声明位图作为一个全局变量

有没有什么办法，以减少图像的大小，同时下载。使用IAM下面的代码下载的图像

C1是参考图像视图

bitmap = BitmapFactory.decodeStream((InputStream)new URL(logourltop.get(0)).getContent()); 
cl.setImageBitmap(bitmap) ; 

（或）

最好是使用urlimagehelper项目下载的图像时需要

UrlImageViewHelper.setUrlDrawable(cl,logourltop.get(0)); 

还有一个疑问是我正在改变在同一活动中的意见，通过使用

setContentView(R.layout.filename). 

如果我更改列表项的视图中单击分配给位图的内存将被释放或没有。

可以请你建议我到一个更好的办法（分配的对象和位图该视图的内存）避免内存泄漏。

Answer 1

import java.io.BufferedInputStream; 
import java.io.BufferedOutputStream; 
import java.io.FileOutputStream; 
import java.io.InputStream; 
import java.net.URL; 

import android.app.Activity; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.graphics.drawable.BitmapDrawable; 
import android.graphics.drawable.Drawable; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.util.Log; 
import android.widget.ImageView; 

public class downloadimg extends Activity { 

// 
private ImageView mImageView; 

/** Called when the activity is first created. */ 
@Override 
public void onCreate(Bundle savedInstanceState) { 

    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 

    //Find the reference to the ImageView 
    mImageView = (ImageView) findViewById(R.id.test_image); 

    // You can set a temporary background here 
    //image.setImageResource(null); 

    // Start the DownloadImage task with the given url 
    new DownloadImage().execute("http://demo.imgur.com/CQzlM.jpg"); 
} 


/** 
* Simple functin to set a Drawable to the image View 
* @param drawable 
*/ 
private void setImage(Drawable drawable) 
{ 
    mImageView.setBackgroundDrawable(drawable); 
} 

public class DownloadImage extends AsyncTask<String, Integer, Drawable> { 

    @Override 
    protected Drawable doInBackground(String... arg0) { 
     // This is done in a background thread 
     return downloadImage(arg0[0]); 
    } 

    /** 
    * Called after the image has been downloaded 
    * -> this calls a function on the main thread again 
    */ 
    protected void onPostExecute(Drawable image) 
    { 
     setImage(image); 
    } 


    /** 
    * Actually download the Image from the _url 
    * @param _url 
    * @return 
    */ 
    private Drawable downloadImage(String _url) 
    { 
     //Prepare to download image 
     URL url;   
     BufferedOutputStream out; 
     InputStream in; 
     BufferedInputStream buf; 

     //BufferedInputStream buf; 
     try { 
      url = new URL(_url); 
      in = url.openStream(); 



      // Read the inputstream 
      buf = new BufferedInputStream(in); 

      // Convert the BufferedInputStream to a Bitmap 
      Bitmap bMap = BitmapFactory.decodeStream(buf); 
      if (in != null) { 
       in.close(); 
      } 
      if (buf != null) { 
       buf.close(); 
      } 

      return new BitmapDrawable(bMap); 

     } catch (Exception e) { 
      Log.e("Error reading file", e.toString()); 
     } 

     return null; 
    } 

} 

} 

Answer 2

基本上，你必须下载图像数据，并在流或字节数组形式的图像数据，可以使用从BitmapFactory的方便的方法，会给你一个位图出来，并与此位图在手中，您可以将其直接设置为ImageView。

请确保您在网络中以单独的线程执行下载，例如，使用AsyncTask .doInBackground()并在UI线程上的ImageView上设置位图。通过将其设置为AsyncTask的方法onPostExecute()或致电Activity.runOnUIThread()。

Answer 3

希望这将有助于...

public class BitmapResizer { 

    public static Bitmap decodeFile(File f,int requiredSize){ 
    try { 
     //decode image size 
     BitmapFactory.Options o = new BitmapFactory.Options(); 
     o.inJustDecodeBounds = true; 
     BitmapFactory.decodeStream(new FileInputStream(f),null,o); 

     //Find the correct scale value. It should be the power of 2. 
     final int REQUIRED_SIZE=requiredSize; 
     int width_tmp=o.outWidth, height_tmp=o.outHeight; 
     int scale=1; 
     while(true){ 
      if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE) 
       break; 
      width_tmp/=2; 
      height_tmp/=2; 
      scale*=2; 
     } 

     //decode with inSampleSize 
     BitmapFactory.Options o2 = new BitmapFactory.Options(); 
     o2.inSampleSize=scale; 
     return BitmapFactory.decodeStream(new FileInputStream(f), null, o2); 
    } catch (FileNotFoundException e) { 

    } 
    return null; 
}}