发一个异步图片加载控件。网上也有大把的异步网络加载图片的控件，但是有一个问题，异步加载会造成列表中的图片混乱，因为列表的每一项的View都可能被重用，异步加载的时候多个异步线程引用到了同一个View将造成图片加载错乱。该控件解决这个问题：文章地址https://www.yii666.com/article/764396.html网址:yii666.com文章来源地址:https://www.yii666.com/article/764396.html
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLConnection; import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.Drawable;
import android.net.Uri;
import android.os.AsyncTask;
import android.util.AttributeSet;
import android.widget.ImageView; /**
* 异步图片控件
* 使用：new AsyncImageView().asyncLoadBitmapFromUrl("http://xxxx","缓存路径"){
*
* @author gaoomei@gmail.com
* @site http://obatu.sinaapp.com
* @version 1.0
* @2011-12-3
*/
public class AsyncImageView extends ImageView { /**
* 异步task加载器
*/
private AsyncLoadImage mAsyncLoad; /**
* 下载回来的图片缓存存活时间，单位：秒(s),默认30分钟
*/
private long mCacheLiveTime = 1800; public AsyncImageView(Context context) {
super(context);
} public AsyncImageView(Context context, AttributeSet attrs) {
super(context, attrs);
} public AsyncImageView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
} /**
*
*/
@Override
public void setImageDrawable(Drawable drawable) {
if (mAsyncLoad != null) {
mAsyncLoad.cancel(true);
mAsyncLoad = null;
}
super.setImageDrawable(drawable);
} /**
* 重写下面几个设置图片资源的方法，目地是取消网络加载
*/
@Override
public void setImageResource(int resId) {
cancelLoad();
super.setImageResource(resId);
} @Override
public void setImageURI(Uri uri) {
cancelLoad();
super.setImageURI(uri);
} @Override
public void setImageBitmap(Bitmap bitmap) {
cancelLoad();
super.setImageBitmap(bitmap);
} /**
* 取消正在进行的异步task
*/
public void cancelLoad() {
if (mAsyncLoad != null) {
mAsyncLoad.cancel(true);
mAsyncLoad = null;
}
} /**
* 设置图片存活时间
*
* @param second
* 存活时间，单位【秒】，如果等于0或null，则不缓存
*/
public void setCacheLiveTime(long second) {
if (second == 0) {
this.mCacheLiveTime = 0;
} else if (second >= 0) {
this.mCacheLiveTime = second * 1000;
}
} /**
* 从网络异步加载
*
* @param url
* @param saveFileName
*/
public void asyncLoadBitmapFromUrl(String url, String saveFileName) {
if (mAsyncLoad != null) {
mAsyncLoad.cancel(true);
}
// AsyncTask不可重用，所以每次重新实例
mAsyncLoad = new AsyncLoadImage();
mAsyncLoad.execute(url, saveFileName);
} /**
* 异步加载器
*/
private class AsyncLoadImage extends AsyncTask {
/**
* 是否取消
*/
private boolean isCancel = false; @Override
protected Bitmap doInBackground(String... params) {
if (isCancel) {
return null;
}
String url = params[0];
String fileName = params[1];
try {
return getBitmap(url, fileName);
} catch (IOException e) {
e.printStackTrace();
}
return null;
} @Override
protected void onCancelled() {
System.out.println("async load imgae cancel");
isCancel = true;
} @Override
protected void onPostExecute(Bitmap result) {
if (!isCancel && result != null) {
AsyncImageView.this.setImageBitmap(result);
}
}
} /**
* 下载图片
*
* @param urlString
* url下载地址
* @param fileName
* 缓存文件路径
* @throws IOException
*/
private Bitmap getBitmap(String urlString, String fileName)
throws IOException {
if (fileName == null || fileName.trim().isEmpty()) {
InputStream input = getBitmapInputStreamFromUrl(urlString);
return BitmapFactory.decodeStream(input);
} File file = new File(fileName);
if (!file.isFile()
|| (mCacheLiveTime > 0 && (System.currentTimeMillis()
- file.lastModified() > mCacheLiveTime))) {
InputStream input = getBitmapInputStreamFromUrl(urlString);
file = saveImage(input, fileName);
// 如果文件结构创建失败，则直接从输入流解码图片
if (file == null || !file.exists() || !file.canWrite()
|| !file.canRead()) {
return BitmapFactory.decodeStream(input);
}
}
return BitmapFactory.decodeFile(file.getAbsolutePath());
} /**
* 下载图片，输入InputStream
*
* @param urlString
* @return
* @throws IOException
*/
private InputStream getBitmapInputStreamFromUrl(String urlString)
throws IOException {
URL url = new URL(urlString);
URLConnection connection = url.openConnection();
connection.setConnectTimeout(25000);
connection.setReadTimeout(90000);
return connection.getInputStream();
} /**
* 从输入流保存图片到文件系统
*
* @param fileName
* @param input
* @return
*/
private File saveImage(InputStream input, String fileName) {
if (fileName.trim().isEmpty() || input == null) {
return null;
}
File file = new File(fileName);
OutputStream output = null;
try {
file.getParentFile().mkdirs();
if (file.exists() && file.isFile()) {
file.delete();
}
if (!file.createNewFile()) {
return null;
}
output = new FileOutputStream(file);
byte[] buffer = new byte[4 * 1024];
do {
// 循环读取
int numread = input.read(buffer);
if (numread == -1) {
break;
}
output.write(buffer, 0, numread);
} while (true);
output.flush();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
output.close();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e2) {
e2.printStackTrace();
}
}
return file;
}
}