GridView图片异步显示

http://www.eoeandroid.com/thread-210082-1-1.html
Handler+ExecutorService(线程池)+MessageQueue模式+缓存模式

朋友们，先上效果图：
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工程结构图：
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RemoteImageView

package com.amaker.pic;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.Drawable;
import android.os.AsyncTask;
import android.util.AttributeSet;
import android.widget.ImageView;

import java.io.IOException;
import java.io.InputStream;
import java.lang.ref.SoftReference;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;
import java.util.concurrent.RejectedExecutionException;


/**
 * ImageView extended class allowing easy downloading
 * of remote images
 */
public class RemoteImageView extends ImageView{

    public static HashMap<String,Bitmap> imageCache = new HashMap<String, Bitmap>();
    
    private static final int MAX_FAIL_TIME = 5;
    private int mFails = 0;
    
    private String mUrl;
    //========
    private ImageCache mapCache;
    public RemoteImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
    
    public void setDefaultImage(int resId){
        this.setImageResource(resId);
    }
    
    public void setImageUrl(String url){
        
        if(mUrl != null && mUrl.equals(url)){
            mFails++;
        }else{
            mFails = 0;
            mUrl = url;
        }
        
        if(mFails >= MAX_FAIL_TIME)
            return;
        
        mUrl = url;
        
        if(isCached(url))
            return;
        
        startDownload(url);
    }
    
    public boolean isCached(String url){
        if(imageCache.containsKey(url)){
            this.setImageBitmap(imageCache.get(url));
            return true;
        }
        
        return false;
    }
    
    private void startDownload(String url){
        try{
            new DownloadTask().execute(url);
        }catch (RejectedExecutionException e) {
            //捕获RejectedExecutionException同时加载的图片过多而导致程序崩溃
        }
    }
    
    private void reDownload(String url){
        setImageUrl(url);
    }
    
    class DownloadTask extends AsyncTask<String, Void, String>{

        private String imageUrl;
        
        @Override
        protected String doInBackground(String... params) {
            imageUrl = params[0];
            InputStream is = null;
            Bitmap bmp = null;
            
            try {
                URL url = new URL(imageUrl);
                is = url.openStream();
                bmp = BitmapFactory.decodeStream(is);
                if(bmp != null){
                    imageCache.put(imageUrl, bmp);
                }else{
                    reDownload(imageUrl);
                }
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if(is != null){
                    try {
                        is.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
            
            return imageUrl;
        }

        @Override
        protected void onPostExecute(String result) {
            Bitmap bmp = null;
            if(imageCache.containsKey(result)){
                bmp = imageCache.get(result);
                RemoteImageView.this.setImageBitmap(bmp);
            }else{
                reDownload(imageUrl);
            }
            
            super.onPostExecute(result);
        }
        
    }

}

RemoteAdapter

package com.amaker.pic;


import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import java.util.List;

public class RemoteAdapter extends BaseAdapter {

    private Context mContext;
    private List<String> urls;
    private LayoutInflater inflater;
    
    public RemoteAdapter(Context context,List<String> urls){
        mContext = context;
        this.urls = urls;
        inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }
    
    @Override
    public int getCount() {
        return urls.size();
    }

    @Override
    public Object getItem(int arg0) {
        return urls.get(arg0);
    }

    @Override
    public long getItemId(int arg0) {
        return arg0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup root) {
        
        final ViewHolder holder;
        
        if(convertView == null){
            convertView = inflater.inflate(R.layout.item_layout, null);
            holder = new ViewHolder();
            holder.imageView = (RemoteImageView)convertView.findViewById(R.id.remote_image_view);
            convertView.setTag(holder);
        }else{
            holder = (ViewHolder)convertView.getTag();
        }
        
        holder.imageView.setDefaultImage(R.drawable.default_image);
        holder.imageView.setImageUrl(urls.get(position));
        
        return convertView;
    }
    
    class ViewHolder{
        RemoteImageView imageView;
    }

}

ImageCache

package com.amaker.pic;

import java.util.WeakHashMap;

import android.graphics.Bitmap;

public class ImageCache extends WeakHashMap<String, Bitmap> {

	private static final long serialVersionUID = 1L;
	
	public boolean isCached(String url){
		return containsKey(url) && get(url) != null;
	}

}

AsyncDownPicDemoActivity

package com.amaker.pic;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.widget.GridView;

import java.util.Arrays;
import java.util.List;

public class AsyncDownPicDemoActivity extends Activity {
    
    private GridView mGridView;
    private Context mContext;
    private List<String> urlList;
    private RemoteAdapter mRemoteAdapter;
    
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        init();
    }
    private void init(){
        mContext = this;
        mGridView = (GridView)findViewById(R.id.grid_view);
        urlList = Arrays.asList(new String[]{
                "http://www.chinatelecom.com.cn/images/logo_new.gif"
                ,"http://t03.pic.sogou.com/945b578c3b6057be.jpg"
                ,"http://t03.pic.sogou.com/3a4feb9c3b6057be.jpg"
                ,"http://t02.pic.sogou.com/eb95234678ecb28d.jpg"
                ,"http://t01.pic.sogou.com/a240ade96f0fbe20.jpg"
                ,"http://t04.pic.sogou.com/e72ead334e356f27.jpg"
                ,"http://t01.pic.sogou.com/166bb3e4026f1294.jpg"
                ,"http://t01.pic.sogou.com/bf593d46dc85ff10.jpg"
                ,"http://t04.pic.sogou.com/a7bedc2a13f3045f.jpg"
                ,"http://t02.pic.sogou.com/c323b5e10071eed5.jpg"
                ,"http://www.baidu.com/img/baidu_logo.gif"
                ,"http://t01.pic.sogou.com/0165d7241d6cd80c.jpg"
                ,"http://cache.soso.com/30d/img/web/logo.gif",
                "http://csdnimg.cn/www/images/csdnindex_logo.gif"
                ,"http://samsung.tgbus.com/UploadFiles_3297/201207/2012071009241894.jpg"
                ,"http://t01.pic.sogou.com/746bf1a4484d8dd4.jpg"
                ,"http://www.icoou.com/news_img/20110301/1109150.jpg"
                ,"http://images.cnblogs.com/logo_small.gif"
                ,"http://t04.pic.sogou.com/84b8341f7346b9c7.jpg"
                ,"http://t03.pic.sogou.com/ca11112c3b6057be.jpg"
                ,"http://t02.pic.sogou.com/56cbda8df459a4e1.jpg"
                ,"http://t04.pic.sogou.com/64918bba09a4884b.jpg"
                ,"http://t04.pic.sogou.com/bda625f4bff15e0b.jpg"
                ,"http://t01.pic.sogou.com/5d9a94e179fb5f08.jpg"
                ,"http://www.chinatelecom.com.cn/images/logo_new.gif"
                ,"http://t03.pic.sogou.com/945b578c3b6057be.jpg"
                ,"http://t03.pic.sogou.com/3a4feb9c3b6057be.jpg"
                ,"http://t02.pic.sogou.com/eb95234678ecb28d.jpg"
                ,"http://t01.pic.sogou.com/a240ade96f0fbe20.jpg"
                ,"http://t04.pic.sogou.com/e72ead334e356f27.jpg"
                ,"http://t01.pic.sogou.com/166bb3e4026f1294.jpg"
                ,"http://t01.pic.sogou.com/bf593d46dc85ff10.jpg"
                ,"http://t04.pic.sogou.com/a7bedc2a13f3045f.jpg"
                ,"http://t02.pic.sogou.com/c323b5e10071eed5.jpg"
                ,"http://www.baidu.com/img/baidu_logo.gif"
                ,"http://t01.pic.sogou.com/0165d7241d6cd80c.jpg"
                ,"http://cache.soso.com/30d/img/web/logo.gif",
                "http://csdnimg.cn/www/images/csdnindex_logo.gif"
                ,"http://samsung.tgbus.com/UploadFiles_3297/201207/2012071009241894.jpg"
                ,"http://t01.pic.sogou.com/746bf1a4484d8dd4.jpg"
                ,"http://www.icoou.com/news_img/20110301/1109150.jpg"
                ,"http://images.cnblogs.com/logo_small.gif"
                ,"http://t04.pic.sogou.com/84b8341f7346b9c7.jpg"
                ,"http://t03.pic.sogou.com/ca11112c3b6057be.jpg"
                ,"http://t02.pic.sogou.com/56cbda8df459a4e1.jpg"
                ,"http://t04.pic.sogou.com/64918bba09a4884b.jpg"
                ,"http://t04.pic.sogou.com/bda625f4bff15e0b.jpg"
                ,"http://t01.pic.sogou.com/5d9a94e179fb5f08.jpg"
        });
        mRemoteAdapter = new RemoteAdapter(mContext, urlList);
        mGridView.setAdapter(mRemoteAdapter);
    }
}

item_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    
    <com.amaker.pic.RemoteImageView
        android:id="@+id/remote_image_view"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:scaleType="fitXY"
        />

</LinearLayout>

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <GridView
        android:id="@+id/grid_view"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:numColumns="3" 
        />

</LinearLayout>

AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.amaker.pic"
      android:versionCode="1"
      android:versionName="1.0">
    <uses-sdk android:minSdkVersion="8" />

    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name="AsyncDownPicDemoActivity"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

    </application>
    <uses-permission android:name="android.permission.INTERNET"/>
</manifest>

GridView图片异步显示

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