android异步加载网络图片

android异步加载网络图片
1.异步加载图片类
package com.mingda.show.util.image;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import ng.ref.SoftReference;
import java.util.HashMap;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.os.Message;
import android.widget.ImageView;
/**
* 异步图片加载类
*
* @author wanghao
*
*/
public class AsyncBitmapLoader {
/**
* 内存图片软应用缓存
*/
private HashMap<String, SoftReference<Bitmap>> imageCache = null;
/**
* 本地图片缓存路径
*/
private static final String cacheLocation =
"/mnt/sdcard/test/";
/**
* 构造函数
*/
public AsyncBitmapLoader() {
imageCache= new HashMap<String, SoftReference<Bitmap>>();
}
public Bitmap loadBitmap(final ImageView imageView, final String imageURL, final ImageCallBack imageCallBack) {
/**
* 如果在内存缓存中，则返回Bitmap对象
*/
if (imageCache.containsKey(imageURL)) {
SoftReference<Bitmap> reference =
imageCache.get(imageURL);
Bitmap bitmap = reference.get();
if (bitmap != null) {
return bitmap;
}
} else {
/**
* 如果没有缓存，则在本地缓存中查找
*/
String bitmapName =
imageURL.substring(stIndexOf("/") + 1);
File cacheDir = new File(cacheLocation);
File[] cacheFiles = cacheDir.listFiles();
int i = 0;
if (null != cacheFiles) {
for (; i < cacheFiles.length; i++) {
if (bitmapName.equals(cacheFiles[i].getName())) {
break;
}
}
if (i < cacheFiles.length) {
return BitmapFactory.decodeFile(cacheLocation + bitmapName);
}
}
}
final Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
imageCallBack.imageLoad(imageView, (Bitmap)
msg.obj);
}
};
/**
* 如果不在本地内存缓存中，也不在本地（被JVM回收掉），则开启线程下载图片
*/
new Thread(){
@Override
public void run() {
InputStream bitmapIs =
HttpUtils.getStreamFromURL(imageURL);
Bitmap bitmap =
BitmapFactory.decodeStream(bitmapIs);
imageCache.put(imageURL, new
SoftReference<Bitmap>(bitmap));
Message msg = handler.obtainMessage(0, bitmap);
handler.sendMessage(msg);
File dir = new File(cacheLocation);
if (!dir.exists()) {
dir.mkdirs();
}
File bitmapFile = new File(cacheLocation + imageURL.substring(stIndexOf("/") + 1));
if (!bitmapFile.exists()) {
try {
bitmapFile.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
}
FileOutputStream fos;
try {
fos = new FileOutputStream(bitmapFile);
press(pressFormat.PNG, 100, fos);
} catch (Exception e) {
e.printStackTrace();
}
}
}.start();
return null;
}
public interface ImageCallBack {
public void imageLoad(ImageView imageView, Bitmap bitmap);
}
}
2.网络获取类
package com.mingda.show.util.image;
import java.io.InputStream;
import .HttpURLConnection;
import .URL;
/**
*
* 网络获取类
*
* @author wanghao
*
*/
public class HttpUtils {
/**
*
* 根据URL获取输入流对象
*
* @param imageURL 文件URL地址
*
* @return输入流对象
*
*/
public static InputStream getStreamFromURL(String imageURL) { InputStream in = null;
try {
URL url = new URL(imageURL);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
in = connection.getInputStream();
} catch (Exception e) {
e.printStackTrace();
}
return in;
}
}
3.适配器类getview方法加载图片片段
/**
* 设置图片
*/
String image_path = info.getImageUrl();
//异步加载图片
Bitmap bitmap =
asyncBitmapLoader.loadBitmap(holder.appImage, image_path, new ImageCallBack() {
public void imageLoad(ImageView imageView, Bitmap bitmap) {
imageView.setImageBitmap(bitmap);
}
});
//设置默认图片
if (bitmap == null) {
holder.appImage.setImageResource(R.drawable.empty_photo);
} else {
holder.appImage.setImageBitmap(bitmap);
}
4.注意在AndroidManifest.xml文件中加入网络访问和写SDCard的权限,不然会报.SocketException: Permission denied和FileNotFound的异常。

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