SoftReference+Thread进行图片加载(一)

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" >

    <ListView
        android:id="@+id/list"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" />

</LinearLayout>

book_item_adapter.xml

<?xml version="1.0" encoding="UTF-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="70.0dip"
    android:background="@drawable/item"
    android:drawingCacheQuality="high"
    android:minHeight="70.0dip"
    android:orientation="horizontal" >

    <ImageView
        android:id="@+id/sItemIcon"
        android:layout_width="42.0dip"
        android:layout_height="54.0dip"
        android:layout_margin="10.0dip"
        android:background="@drawable/rc_item_bg"
        android:padding="2.0dip"
        android:scaleType="fitXY" />

    <TextView
        android:text="斗破苍穹"
        android:id="@+id/sItemTitle"
        android:layout_width="fill_parent"
        android:layout_height="30.0dip"
        android:layout_alignTop="@+id/sItemIcon"
        android:layout_toRightOf="@+id/sItemIcon"
        android:gravity="center_vertical"
        android:singleLine="true"
        android:textColor="#ffffff"
        android:textSize="18.0sp" />
</RelativeLayout>

ImageAndText

package cn.wangmeng.test;

public class ImageAndText {
	    private String imageUrl;
	    private String text;

	    public ImageAndText(String imageUrl, String text) {
	        this.imageUrl = imageUrl;
	        this.text = text;
	    }
	    public String getImageUrl() {
	        return imageUrl;
	    }
	    public String getText() {
	        return text;
	    }
}

AsyncListImage

package cn.wangmeng.test;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;

public class AsyncListImage extends Activity {
	private ListView list;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //布局只是一个listView控件
        setContentView(R.layout.main);
        //listView
        list=(ListView)findViewById(R.id.list);
        //data
        List<ImageAndText> dataArray=new ArrayList<ImageAndText>();
        for (int i = 0; i < 100; i++) {
       	 ImageAndText test=new ImageAndText("http://www.wangmeng.cn/images/logo.gif", "test");
         ImageAndText test1=new ImageAndText("http://www.pfwx.com/files/article/image/0/54/54s.jpg", "test1");
         ImageAndText test2=new ImageAndText("http://www.pfwx.com/files/article/image/0/4/4s.jpg","test2");
         ImageAndText test3=new ImageAndText("http://www.pfwx.com/files/article/image/9/9760/9760s.jpg","test3");
         ImageAndText test4=new ImageAndText("http://www.pfwx.com/files/article/image/3/3382/3382s.jpg","test4");
         ImageAndText test5=new ImageAndText("http://www.pfwx.com/files/article/image/3/3237/3237s.jpg","test5");
         dataArray.add(test);
         dataArray.add(test1);
         dataArray.add(test2);	
         dataArray.add(test3);	
         dataArray.add(test4);	
         dataArray.add(test5);	
		}
       //adapter
        ImageAndTextListAdapter adapter=new ImageAndTextListAdapter(this, dataArray, list);
        //setAdapter
        list.setAdapter(adapter);
        
    }
}

ImageAndTextListAdapter

package cn.wangmeng.test;

import java.util.ArrayList;
import java.util.List;

import cn.wangmeng.test.AsyncImageLoader.ImageCallback;

import android.app.Activity;
import android.graphics.drawable.Drawable;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;

public class ImageAndTextListAdapter extends BaseAdapter {

	private ListView listView;
	private List<ImageAndText> dataArray = new ArrayList<ImageAndText>();
	
	private LayoutInflater inflater;
	private AsyncImageLoader asyncImageLoader;


	/**
	 * data和adapter
	 */
	public ImageAndTextListAdapter(Activity activity,
			List<ImageAndText> imageAndTexts, ListView listView) {

		this.listView = listView;
		dataArray = imageAndTexts;
		
		asyncImageLoader = new AsyncImageLoader();
		inflater = activity.getLayoutInflater();
	}

	@Override
	public int getCount() {
		return dataArray.size();
	}

	@Override
	public Object getItem(int position) {
		if (position >= getCount()) {
			return null;
		}
		return dataArray.get(position);
	}

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

	public View getView(int position, View convertView, ViewGroup parent) {
		/**页面一旦加载，就获取可显示item的布局，并且设置tag，待滑动时候，复用布局*/
		if (convertView == null) {
			convertView = inflater.inflate(R.layout.book_item_adapter, null);
		}
		convertView.setTag(position);

		/**
		 * 获取可见item的data数据
		 */
		ImageAndText imageAndText = (ImageAndText) getItem(position);
		String imageUrl = imageAndText.getImageUrl();
		//设置值
		TextView textView = (TextView) convertView
				.findViewById(R.id.sItemTitle);
		textView.setText(imageAndText.getText());
		ImageView iv = (ImageView) convertView.findViewById(R.id.sItemIcon);
		//一上来就先加载默认的图片
		iv.setBackgroundResource(R.drawable.rc_item_bg);

		/**
		 * 在加载默认的图片同时，也进行异步请求图片下载
		 */
		asyncImageLoader.loadDrawable(position, imageUrl, new ImageCallback() {
			@Override
			public void onImageLoad(Integer pos, Drawable drawable) {
				//获取设置标记的视图
				View view = listView.findViewWithTag(pos);
				if (view != null) {
					ImageView iv = (ImageView) view
							.findViewById(R.id.sItemIcon);
					iv.setBackgroundDrawable(drawable);
				}
			}

			// 加载不成功的图片处理
			@Override
			public void onError(Integer pos) {
				View view = listView.findViewWithTag(pos);
				if (view != null) {
					ImageView iv = (ImageView) view
							.findViewById(R.id.sItemIcon);
					iv.setBackgroundResource(R.drawable.rc_item_bg);
				}
			}

		});
		return convertView;
	}
}

AsyncImageLoader

package cn.wangmeng.test;

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

import android.graphics.drawable.Drawable;
import android.os.Handler;

public class AsyncImageLoader {
	final Handler handler = new Handler();
	private HashMap<String, SoftReference<Drawable>> imageCache;

	/**
	 * 构造器--初始化图片缓存（软引用）
	 */
	public AsyncImageLoader() {
		imageCache = new HashMap<String, SoftReference<Drawable>>();
	}

	/**
	 * 进行图片异步加载的方法 参数：pos,url,接口
	 */
	public Drawable loadDrawable(final Integer pos, final String imageUrl,
			final ImageCallback imageCallback) {
		/** 开启分线程进行下载图片 */
		new Thread() {
			@Override
			public void run() {

				LoadImg(pos, imageUrl, imageCallback);

			}
		}.start();
		return null;
	}

	public void LoadImg(final Integer pos, final String imageUrl,
			final ImageCallback imageCallback) {
		/**
		 * 首先先判断缓存中有没有，如果缓存中包含某个Key值，
		 * 就从缓存中获取某个url,得到软引用内存里面的对象
		 * 
		 */
		if (imageCache.containsKey(imageUrl)) {
			SoftReference<Drawable> softReference = imageCache.get(imageUrl);
			final Drawable drawable = softReference.get();
			//如果软引用里面的图片没有被回收，就进行页面加载即可
			if (drawable != null) {
				//通过handler消息机制，在主线程进行更新ui即可
				handler.post(new Runnable() {
					@Override
					public void run() {
						imageCallback.onImageLoad(pos, drawable);
					}
				});
				return;
			}
		}
		// 尝试从URL中加载
		try {
			final Drawable drawable = loadImageFromUrl(imageUrl);
			//如果图片获取成功了
			if (drawable != null) {
				//放到缓存中
				imageCache.put(imageUrl, new SoftReference<Drawable>(drawable));
			}
			//通过handler消息机制，在主线程进行更新ui即可
			handler.post(new Runnable() {
				@Override
				public void run() {
					imageCallback.onImageLoad(pos, drawable);
				}
			});
		} catch (IOException e) {
			handler.post(new Runnable() {
				@Override
				public void run() {
					imageCallback.onError(pos);
				}
			});
			e.printStackTrace();
		}

	}

	// 根据URL加载图片,如果出现错误throws IOException式的错误，以便在LoadImg中捕获，执行OnError（）函数
	public static Drawable loadImageFromUrl(String url) throws IOException {
		URL m;
		InputStream i = null;
		m = new URL(url);
		i = (InputStream) m.getContent();
		Drawable d = Drawable.createFromStream(i, "src");
		return d;
	}

	// 回调函数
	public interface ImageCallback {
		public void onImageLoad(Integer t, Drawable drawable);

		public void onError(Integer t);
	}

}