【1】异步加载图片类AsyncImageLoader
package com.example.testdddleapk.cus;
import java.io.IOException;
import java.lang.ref.SoftReference;
import java.util.HashMap;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.CoreConnectionPNames;
import android.graphics.drawable.Drawable;
import android.os.Handler;
import android.os.Message;
/**
* 异步加载图片
*/
public class AsyncImageLoader {
// 软引用,使用内存做临时缓存 (程序退出,或内存不够则清除软引用)
private HashMap<String, SoftReference<Drawable>> p_w_picpathCache;
public AsyncImageLoader() {
p_w_picpathCache = new HashMap<String, SoftReference<Drawable>>();
}
/**
* 定义回调接口
*/
public interface ImageCallback {
public void p_w_picpathLoaded(Drawable p_w_picpathDrawable, String p_w_picpathUrl);
}
/**
* 创建子线程加载图片
* 子线程加载完图片交给handler处理(子线程不能更新ui,而handler处在主线程,可以更新ui)
* handler又交给p_w_picpathCallback,p_w_picpathCallback须要自己来实现,在这里可以对回调参数进行处理
* @param p_w_picpathUrl :须要加载的图片url
* @param p_w_picpathCallback:
* @return
*/
public Drawable loadDrawable(final String p_w_picpathUrl,final ImageCallback p_w_picpathCallback) {
//如果缓存中存在图片 ,则首先使用缓存
if (p_w_picpathCache.containsKey(p_w_picpathUrl)) {
SoftReference<Drawable> softReference = p_w_picpathCache.get(p_w_picpathUrl);
Drawable drawable = softReference.get();
if (drawable != null) {
System.out.println("loadDrawable");
p_w_picpathCallback.p_w_picpathLoaded(drawable, p_w_picpathUrl);//执行回调
return drawable;
}
}
/**
* 在主线程里执行回调,更新视图
*/
final Handler handler = new Handler() {
public void handleMessage(Message message) {
System.out.println("handleMessage");
p_w_picpathCallback.p_w_picpathLoaded((Drawable) message.obj, p_w_picpathUrl);
}
};
/**
* 创建子线程访问网络并加载图片 ,把结果交给handler处理
*/
new Thread() {
@Override
public void run() {
Drawable drawable = loadImageFromUrl(p_w_picpathUrl);
// 下载完的图片放到缓存里
p_w_picpathCache.put(p_w_picpathUrl, new SoftReference<Drawable>(drawable));
Message message = handler.obtainMessage(0, drawable);
handler.sendMessage(message);
}
}.start();
return null;
}
/**
* 下载图片 (注意HttpClient 和httpUrlConnection的区别)
*/
public Drawable loadImageFromUrl(String url) {
try {
HttpClient client = new DefaultHttpClient();
client.getParams().setParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, 1000*15);
HttpGet get = new HttpGet(url);
HttpResponse response;
response = client.execute(get);
if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
HttpEntity entity = response.getEntity();
Drawable d = Drawable.createFromStream(entity.getContent(),"src");
return d;
} else {
return null;
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
//清除缓存
public void clearCache() {
if (this.p_w_picpathCache.size() > 0) {
this.p_w_picpathCache.clear();
}
}
}
【2】 pagerAdapter的instantiateItem方法
@SuppressLint("NewApi") @Override
public Object instantiateItem(final ViewGroup container, final int position) {
String url=imgsUrls[position];
Drawable cachedImage = asyncImageLoader.loadDrawable(url, new ImageCallback() {
@SuppressLint("NewApi") public void p_w_picpathLoaded(Drawable p_w_picpathDrawable,String p_w_picpathUrl) {
ImageView img=(ImageView) viewList.get(position).findViewById(R.id.img);
img.setBackground(p_w_picpathDrawable);
container.addView(view);
}
});
return viewList.get(position);
}
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