[转]Android图片异步加载
获取图片工具类：
public class ApacheUtility {
/**
* 获取图片流
*
* @param uri 图片地址
* @return
* @throws MalformedURLException
*/
public static InputStream GetImageByUrl(String uri) throws MalformedURLException {
URL url = new URL(uri);
URLConnection conn;
InputStream is;
try {
conn = url.openConnection();
conn.connect();
is = conn.getInputStream();
// 或者用如下方法
// is=(InputStream)url.getContent();
return is;
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
/**
* 获取Bitmap
*
* @param uri 图片地址
* @return
*/
public static Bitmap GetBitmapByUrl(String uri) {
Bitmap bitmap;
InputStream is;
try {
is = GetImageByUrl(uri);
bitmap = BitmapFactory.decodeStream(is);
is.close();
return bitmap;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
/**
* 获取Drawable
*
* @param uri 图片地址
* @return
*/
public static Drawable GetDrawableByUrl(String uri) {
Drawable drawable;
InputStream is;
try {
is = GetImageByUrl(uri);
drawable= Drawable.createFromStream(is, "src");
is.close();
return drawable;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
异步任务加载图片类：
/**
* 异步加载图片
*
*/
public class LoadImageAsyncTask extends AsyncTask<String, Integer, Bitmap> {
private ImageView imageView;
@Override
protected void onPostExecute(Bitmap bitmap) {
if (null != imageView) {
imageView.setImageBitmap(bitmap);
}
}
// 设置图片视图实例
public void setImageView(ImageView image) {
this.imageView = image;
}
@Override
protected Bitmap doInBackground(String... params) {
Bitmap bitmap = ApacheUtility.GetBitmapByUrl(params[0]); // 调用前面 ApacheUtility 类的方法
return bitmap;
}
}
调用过程如下：
String imgUrl="http://www.streetcar.org/mim/cable/images/cable-01.jpg"; // 图片路径
LoadImageAsyncTask task = new LoadImageAsyncTask();
task.setImageView(iv); // iv为获取的ImageView对象实例
tast.execute(imgUrl); // 执行任务,参数与 doInBackground(String... params) 方法参数一致
异步图片加载类：
参考文章：http://blog.163.com/guozioo@126/blog/static/64086947201136102838503/
public class AsyncImageLoader {
// SoftReference是软引用，是为了更好的为了系统回收变量
private HashMap<String, SoftReference<Drawable>> imagesCache;
public AsyncImageLoader() {
imagesCache = new HashMap<String, SoftReference<Drawable>>();
}
public Drawable loadDrawable(final String imageUrl,final ImageView imageView,final ILoadImageCallback callback){
if(imagesCache.containsKey(imageUrl)){
// 从缓存中获取
SoftReference<Drawable> softReference=imagesCache.get(imageUrl);
Drawable drawable=softReference.get();
if(null!=drawable){
return drawable;
}
}
final Handler handler=new Handler(){
public void handleMessage(Message message){
callback.onObtainDrawable((Drawable)message.obj, imageView);
}
};
//建立一个新的线程下载图片
new Thread(){
public void run(){
Drawable drawable=ApacheUtility.GetBitmapByUrl(imageUrl); // 调用前面 ApacheUtility 类的方法
imagesCache.put(imageUrl, new SoftReference<Drawable>(drawable));
Message msg=handler.obtainMessage(0, drawable);
handler.sendMessage(msg);
}
}.start();
return null;
}
/**
* 异步加载图片的回调接口
*/
public interface ILoadImageCallback {
public void onObtainDrawable (Drawable drawable, ImageView imageView);
}
}
调用过程如下：
String imgUrl="http://www.streetcar.org/mim/cable/images/cable-01.jpg"; // 图片路径
AsyncImageLoader imagLoader = new AsyncImageLoader();
Drawable cachedImage= imagLoader.loadDrawable(imgUrl,iv,new ILoadImageCallback(){
public void onObtainDrawable (Drawable drawable, ImageView imageView){
imageView.setImageDrawable(drawable);
}
});
if(null!=cachedImage){
iv.setImageDrawable(cachedImage);
}
类似于上面的另一种实现方式：
public class AsyncImageLoader{
private HashMap<String, Bitmap> imageMap; // 存放图片列表：key-图片路径；value-Bitmap
private Handler handler;
// 构造函数
public AsyncImageLoader(){
imageMap = new HashMap<String, Bitmap>();
handler = new Handler();
}
// 异步加载图片
public void loadImage(final String imageUrl,final ImageView imageView){
new Thread(new Runnable() {
public void run() {
Bitmap image = imageMap.get(imageUrl); // 从缓存中获取数据
if (image == null) {
image = ApacheUtility.GetBitmapByUrl(imageUrl); // 调用前面 ApacheUtility 类的方法
imageMap.put(status.getId(), image);
}
final Bitmap bitmap = image;
handler.post(new Runnable() {
public void run() {
imgView.setImageBitmap(bitmap);
}
});
}
}).start();
}
}
调用过程如下：
String imgUrl="http://www.streetcar.org/mim/cable/images/cable-01.jpg"; // 图片路径
AsyncImageLoader imagLoader = new AsyncImageLoader();
imageLoader.loadImage(imgUrl,iv); // iv为ImageView实例