Gallery异步加载图片

Gallery异步加载图片

activity:

package org.hwq.gallery.activity;

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

import android.app.Activity;
import android.content.pm.ActivityInfo;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;
import android.widget.Gallery;

public class Gallery1Activity extends Activity {
	public static HashMap<String,Bitmap> cache;//加载完毕的图片缓存到这里
	private Gallery gallery;
	private List<String> imgUrl;//加载到gallery中的所有图片路径
    @Override
    public void onCreate(Bundle savedInstanceState) {
    	//全屏
    	getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);//设置成全屏模式
    	//横屏
    	setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);//强制为横屏
    	//没标题
    	requestWindowFeature(Window.FEATURE_NO_TITLE);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        //初始化操作
        init();
    }
    /**
     * 启动线程加载指定路径的图片到cache
     * @param url
     */
    public void loadImage(String url){
    	new Thread(new LoadImageThread(url,cache)).start();
    }
    /**
     * 初始化下缓存cache
     * 要加载到gallery中的图片路径
     * 初始Gallery并设置其adapter
     */
    public void init(){
    	cache = new HashMap<String, Bitmap>();
    	imgUrl = new ArrayList<String>();
    	imgUrl.add("http://fujian.xabbs.com/forum/201109/02/160646nn9hjjiimixvkxhe.jpg");  
    	imgUrl.add("http://img1.cache.netease.com/catchpic/A/A9/A9D98040B397C366AE93E67871346561.jpg");  
    	imgUrl.add("http://new.aliyiyao.com/UpFiles/Image/2011/01/13/nc_129393721364387442.jpg");  
    	imgUrl.add("http://pic.viewpics.cn/2011/07/03/naichaMMzhangzetianzuixinzhaopian/18.jpg");  
    	imgUrl.add("http://i1.sinaimg.cn/ent/m/c/2010-01-18/U1819P28T3D2847679F326DT20100118115712.jpg");  
    	imgUrl.add("http://comic.sinaimg.cn/2011/0824/U5237P1157DT20110824161051.jpg");  
    	imgUrl.add("http://t2.baidu.com/it/u=3142230130,2486626207&fm=52&gp=0.jpg");
    	imgUrl.add("http://t1.baidu.com/it/u=195272205,3957438954&fm=52&gp=0.jpg");
    	imgUrl.add("http://t2.baidu.com/it/u=2728825411,1745149447&fm=52&gp=0.jpg");
    	imgUrl.add("http://t3.baidu.com/it/u=4049625789,880707762&fm=52&gp=0.jpg");
    	imgUrl.add("http://t2.baidu.com/it/u=251271316,3044182410&fm=51&gp=0.jpg");
    	imgUrl.add("http://t2.baidu.com/it/u=1909869261,3407648852&fm=51&gp=0.jpg");
    	imgUrl.add("http://t2.baidu.com/it/u=3904233276,4064970722&fm=52&gp=0.jpg");
    	imgUrl.add("http://t3.baidu.com/it/u=179128931,289390833&fm=52&gp=0.jpg");
    	imgUrl.add("http://t3.baidu.com/it/u=67631552,1181502930&fm=52&gp=0.jpg");
    	imgUrl.add("http://t1.baidu.com/it/u=3156928874,2848088324&fm=51&gp=0.jpg");
    	imgUrl.add("http://t1.baidu.com/it/u=382878650,3995372735&fm=51&gp=0.jpg");
    	gallery = (Gallery) findViewById(R.id.gallery1);
    	ImageAdapter adapter = new ImageAdapter(this, imgUrl);
    	gallery.setAdapter(adapter);
    }
    
}

Galleryd的自定义ImageAdapter:

package org.hwq.gallery.activity;

import java.util.List;

import android.content.Context;
import android.graphics.Bitmap;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;

public class ImageAdapter extends BaseAdapter{
	private List<String> imgUrl;
	private Context context;
	
	public ImageAdapter(Context context,List<String> imgUrl){
		this.imgUrl = imgUrl;
		this.context = context;
	}

	public int getCount() {
		return imgUrl.size();
	}

	public Object getItem(int position) {
		return imgUrl.get(position);
	}

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

	public View getView(int position, View convertView, ViewGroup parent) {
		ImageView imageView = new ImageView(context);
		//从前面定义的cache中找到该路径下的图片
		Bitmap map = Gallery1Activity.cache.get(imgUrl.get(position));
		imageView.setLayoutParams(new Gallery.LayoutParams(800,400));   
		imageView.setScaleType(ImageView.ScaleType.FIT_XY);
		if(map == null){
			//如果没加载的，则显示默认图片
			imageView.setImageResource(R.drawable.ic_launcher);
			//如果没有加载，则启动线程其加载
			((Gallery1Activity)context).loadImage(imgUrl.get(position));
		}else{
			//如果加载了的，则设置到Imageview
			imageView.setImageBitmap(map);
		}
		return imageView;
	}

}

加载图片线程LoadImageThread.java

package org.hwq.gallery.activity;

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

public class LoadImageThread implements Runnable{
	private String imageUrl;
	HashMap<String,Bitmap> cache;
	LoadImageThread(String url,HashMap<String,Bitmap> cache){
		this.imageUrl = url;
		this.cache = cache;
	}
	public void run(){
		try {
			System.out.println("开始加载"+imageUrl);
			//将指定的路径下的图片加载到定义的cache当中去
			InputStream imageStream = new URL(imageUrl).openStream();
			Bitmap map = BitmapFactory.decodeStream(imageStream);
			cache.put(imageUrl, map);
		} catch (MalformedURLException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

例中使用到了URL，所以需要在AndroidManifest.xml添加相应的网络权限

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

OK，完事。

评论

1 楼 shim 2012-10-11  

HashMap不是线程安全的，这么搞有风险