Android异步加载网络图片
Android图片的异步加载，主要原理：加载图片时先查看缓存中时候存在该图片，如果存在则返回该图片，否则先加载载一个默认的占位图片，同时创建一个通过网络获取图片的任务并添加，任务完成后放松消息给主线程更新界面。使用方法： view plaincopy[*]AsynImageLoader asynImageLoader = new AsynImageLoader();
[*]asynImageLoader.showImageAsyn(imageView, imageUrl, resId);
类代码： view plaincopy
[*]package com.wangge.uumao.http;
[*]
[*]import java.lang.ref.SoftReference;
[*]import java.util.ArrayList;
[*]import java.util.HashMap;
[*]import java.util.List;
[*]import java.util.Map;
[*]
[*]import android.graphics.Bitmap;
[*]import android.os.Handler;
[*]import android.os.Message;
[*]import android.util.Log;
[*]import android.widget.ImageView;
[*]
[*]import com.wangge.uumao.util.PicUtil;
[*]
[*]public class AsynImageLoader {
[*] private static final String TAG = "AsynImageLoader";
[*] // 缓存下载过的图片的Map
[*] private Map<String, SoftReference<Bitmap>> caches;
[*] // 任务队列
[*] private List<Task> taskQueue;
[*] private boolean isRunning = false;
[*]
[*] public AsynImageLoader(){
[*] // 初始化变量
[*] caches = new HashMap<String, SoftReference<Bitmap>>();
[*] taskQueue = new ArrayList<AsynImageLoader.Task>();
[*] // 启动图片下载线程
[*] isRunning = true;
[*] new Thread(runnable).start();
[*] }
[*]
[*] /**
[*] *
[*] * @param imageView 需要延迟加载图片的对象
[*] * @param url 图片的URL地址
[*] * @param resId 图片加载过程中显示的图片资源
[*] */
[*] public void showImageAsyn(ImageView imageView, String url, int resId){
[*] imageView.setTag(url);
[*] Bitmap bitmap = loadImageAsyn(url, getImageCallback(imageView, resId));
[*]
[*] if(bitmap == null){
[*] imageView.setImageResource(resId);
[*] }else{
[*] imageView.setImageBitmap(bitmap);
[*] }
[*] }
[*]
[*] public Bitmap loadImageAsyn(String path, ImageCallback callback){
[*] // 判断缓存中是否已经存在该图片
[*] if(caches.containsKey(path)){
[*] // 取出软引用
[*] SoftReference<Bitmap> rf = caches.get(path);
[*] // 通过软引用，获取图片
[*] Bitmap bitmap = rf.get();
[*] // 如果该图片已经被释放，则将该path对应的键从Map中移除掉
[*] if(bitmap == null){
[*] caches.remove(path);
[*] }else{
[*] // 如果图片未被释放，直接返回该图片
[*] Log.i(TAG, "return image in cache" + path);
[*] return bitmap;
[*] }
[*] }else{
[*] // 如果缓存中不常在该图片，则创建图片下载任务
[*] Task task = new Task();
[*] task.path = path;
[*] task.callback = callback;
[*] Log.i(TAG, "new Task ," + path);
[*] if(!taskQueue.contains(task)){
[*] taskQueue.add(task);
[*] // 唤醒任务下载队列
[*] synchronized (runnable) {
[*] runnable.notify();
[*] }
[*] }
[*] }
[*]
[*] // 缓存中没有图片则返回null
[*] return null;
[*] }
[*]
[*] /**
[*] *
[*] * @param imageView
[*] * @param resId 图片加载完成前显示的图片资源ID
[*] * @return
[*] */
[*] private ImageCallback getImageCallback(final ImageView imageView, final int resId){
[*] return new ImageCallback() {
[*]
[*] @Override
[*] public void loadImage(String path, Bitmap bitmap) {
[*] if(path.equals(imageView.getTag().toString())){
[*] imageView.setImageBitmap(bitmap);
[*] }else{
[*] imageView.setImageResource(resId);
[*] }
[*] }
[*] };
[*] }
[*]
[*] private Handler handler = new Handler(){
[*]
[*] @Override
[*] public void handleMessage(Message msg) {
[*] // 子线程中返回的下载完成的任务
[*] Task task = (Task)msg.obj;
[*] // 调用callback对象的loadImage方法，并将图片路径和图片回传给adapter
[*] task.callback.loadImage(task.path, task.bitmap);
[*] }
[*]
[*] };
[*]
[*] private Runnable runnable = new Runnable() {
[*]
[*] @Override
[*] public void run() {
[*] while(isRunning){
[*] // 当队列中还有未处理的任务时，执行下载任务
[*] while(taskQueue.size() > 0){
[*] // 获取第一个任务，并将之从任务队列中删除
[*] Task task = taskQueue.remove(0);
[*] // 将下载的图片添加到缓存
[*] task.bitmap = PicUtil.getbitmap(task.path);
[*] caches.put(task.path, new SoftReference<Bitmap>(task.bitmap));
[*] if(handler != null){
[*] // 创建消息对象，并将完成的任务添加到消息对象中
[*] Message msg = handler.obtainMessage();
[*] msg.obj = task;
[*] // 发送消息回主线程
[*] handler.sendMessage(msg);
[*] }
[*] }
[*]
[*] //如果队列为空,则令线程等待
[*] synchronized (this) {
[*] try {
[*] this.wait();
[*] } catch (InterruptedException e) {
[*] e.printStackTrace();
[*] }
[*] }
[*] }
[*] }
[*] };
[*]
[*] //回调接口
[*] public interface ImageCallback{
[*] void loadImage(String path, Bitmap bitmap);
[*] }
[*]
[*] class Task{
[*] // 下载任务的下载路径
[*] String path;
[*] // 下载的图片
[*] Bitmap bitmap;
[*] // 回调对象
[*] ImageCallback callback;
[*]
[*] @Override
[*] public boolean equals(Object o) {
[*] Task task = (Task)o;
[*] return task.path.equals(path);
[*] }
[*] }
[*]}
最后附上PicUtil类的代码，之前忘了贴这个类的代码，不好意识了~~ view plaincopy
[*]public class PicUtil {
[*] private static final String TAG = "PicUtil";
[*]
[*] /**
[*] * 根据一个网络连接(URL)获取bitmapDrawable图像
[*] *
[*] * @param imageUri
[*] * @return
[*] */
[*] public static BitmapDrawable getfriendicon(URL imageUri) {
[*]
[*] BitmapDrawable icon = null;
[*] try {
[*] HttpURLConnection hp = (HttpURLConnection) imageUri
[*] .openConnection();
[*] icon = new BitmapDrawable(hp.getInputStream());// 将输入流转换成bitmap
[*] hp.disconnect();// 关闭连接
[*] } catch (Exception e) {
[*] }
[*] return icon;
[*] }
[*]
[*] /**
[*] * 根据一个网络连接(String)获取bitmapDrawable图像
[*] *
[*] * @param imageUri
[*] * @return
[*] */
[*] public static BitmapDrawable getcontentPic(String imageUri) {
[*] URL imgUrl = null;
[*] try {
[*] imgUrl = new URL(imageUri);
[*] } catch (MalformedURLException e1) {
[*] e1.printStackTrace();
[*] }
[*] BitmapDrawable icon = null;
[*] try {
[*] HttpURLConnection hp = (HttpURLConnection) imgUrl.openConnection();
[*] icon = new BitmapDrawable(hp.getInputStream());// 将输入流转换成bitmap
[*] hp.disconnect();// 关闭连接
[*] } catch (Exception e) {
[*] }
[*] return icon;
[*] }
[*]
[*] /**
[*] * 根据一个网络连接(URL)获取bitmap图像
[*] *
[*] * @param imageUri
[*] * @return
[*] */
[*] public static Bitmap getusericon(URL imageUri) {
[*] // 显示网络上的图片
[*] URL myFileUrl = imageUri;
[*] Bitmap bitmap = null;
[*] try {
[*] HttpURLConnection conn = (HttpURLConnection) myFileUrl
[*] .openConnection();
[*] conn.setDoInput(true);
[*] conn.connect();
[*] InputStream is = conn.getInputStream();
[*] bitmap = BitmapFactory.decodeStream(is);
[*] is.close();
[*] } catch (IOException e) {
[*] e.printStackTrace();
[*] }
[*] return bitmap;
[*] }
[*]
[*] /**
[*] * 根据一个网络连接(String)获取bitmap图像
[*] *
[*] * @param imageUri
[*] * @return
[*] * @throws MalformedURLException
[*] */
[*] public static Bitmap getbitmap(String imageUri) {
[*] // 显示网络上的图片
[*] Bitmap bitmap = null;
[*] try {
[*] URL myFileUrl = new URL(imageUri);
[*] HttpURLConnection conn = (HttpURLConnection) myFileUrl
[*] .openConnection();
[*] conn.setDoInput(true);
[*] conn.connect();
[*] InputStream is = conn.getInputStream();
[*] bitmap = BitmapFactory.decodeStream(is);
[*] is.close();
[*]
[*] Log.i(TAG, "image download finished." + imageUri);
[*] } catch (IOException e) {
[*] e.printStackTrace();
[*] return null;
[*] }
[*] return bitmap;
[*] }
[*]
[*] /**
[*] * 下载图片 同时写道本地缓存文件中
[*] *
[*] * @param context
[*] * @param imageUri
[*] * @return
[*] * @throws MalformedURLException
[*] */
[*] public static Bitmap getbitmapAndwrite(String imageUri) {
[*] Bitmap bitmap = null;
[*] try {
[*] // 显示网络上的图片
[*] URL myFileUrl = new URL(imageUri);
[*] HttpURLConnection conn = (HttpURLConnection) myFileUrl
[*] .openConnection();
[*] conn.setDoInput(true);
[*] conn.connect();
[*]
[*] InputStream is = conn.getInputStream();
[*] File cacheFile = FileUtil.getCacheFile(imageUri);
[*] BufferedOutputStream bos = null;
[*] bos = new BufferedOutputStream(new FileOutputStream(cacheFile));
[*] Log.i(TAG, "write file to " + cacheFile.getCanonicalPath());
[*]
[*] byte[] buf = new byte;
[*] int len = 0;
[*] // 将网络上的图片存储到本地
[*] while ((len = is.read(buf)) > 0) {
[*] bos.write(buf, 0, len);
[*] }
[*]
[*] is.close();
[*] bos.close();
[*]
[*] // 从本地加载图片
[*] bitmap = BitmapFactory.decodeFile(cacheFile.getCanonicalPath());
[*] String name = MD5Util.MD5(imageUri);
[*]
[*] } catch (IOException e) {
[*] e.printStackTrace();
[*] }
[*] return bitmap;
[*] }
[*]
[*] public static boolean downpic(String picName, Bitmap bitmap) {
[*] boolean nowbol = false;
[*] try {
[*] File saveFile = new File("/mnt/sdcard/download/weibopic/" + picName
[*] + ".png");
[*] if (!saveFile.exists()) {
[*] saveFile.createNewFile();
[*] }
[*] FileOutputStream saveFileOutputStream;
[*] saveFileOutputStream = new FileOutputStream(saveFile);
[*] nowbol = bitmap.compress(Bitmap.CompressFormat.PNG, 100,
[*] saveFileOutputStream);
[*] saveFileOutputStream.close();
[*] } catch (FileNotFoundException e) {
[*] e.printStackTrace();
[*] } catch (IOException e) {
[*] e.printStackTrace();
[*] } catch (Exception e) {
[*] e.printStackTrace();
[*] }
[*] return nowbol;
[*] }
[*]
[*] public static void writeTofiles(Context context, Bitmap bitmap,
[*] String filename) {
[*] BufferedOutputStream outputStream = null;
[*] try {
[*] outputStream = new BufferedOutputStream(context.openFileOutput(
[*] filename, Context.MODE_PRIVATE));
[*] bitmap.compress(Bitmap.CompressFormat.PNG, 100, outputStream);
[*] } catch (FileNotFoundException e) {
[*] e.printStackTrace();
[*] }
[*] }
[*]
[*] /**
[*] * 将文件写入缓存系统中
[*] *
[*] * @param filename
[*] * @param is
[*] * @return
[*] */
[*] public static String writefile(Context context, String filename,
[*] InputStream is) {
[*] BufferedInputStream inputStream = null;
[*] BufferedOutputStream outputStream = null;
[*] try {
[*] inputStream = new BufferedInputStream(is);
[*] outputStream = new BufferedOutputStream(context.openFileOutput(
[*] filename, Context.MODE_PRIVATE));
[*] byte[] buffer = new byte;
[*] int length;
[*] while ((length = inputStream.read(buffer)) != -1) {
[*] outputStream.write(buffer, 0, length);
[*] }
[*] } catch (Exception e) {
[*] } finally {
[*] if (inputStream != null) {
[*] try {
[*] inputStream.close();
[*] } catch (IOException e) {
[*] e.printStackTrace();
[*] }
[*] }
[*] if (outputStream != null) {
[*] try {
[*] outputStream.flush();
[*] outputStream.close();
[*] } catch (IOException e) {
[*] e.printStackTrace();
[*] }
[*] }
[*] }
[*] return context.getFilesDir() + "/" + filename + ".jpg";
[*] }
[*]
[*] // 放大缩小图片
[*] public static Bitmap zoomBitmap(Bitmap bitmap, int w, int h) {
[*] int width = bitmap.getWidth();
[*] int height = bitmap.getHeight();
[*] Matrix matrix = new Matrix();
[*] float scaleWidht = ((float) w / width);
[*] float scaleHeight = ((float) h / height);
[*] matrix.postScale(scaleWidht, scaleHeight);
[*] Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, width, height,
[*] matrix, true);
[*] return newbmp;
[*] }
[*]
[*] // 将Drawable转化为Bitmap
[*] public static Bitmap drawableToBitmap(Drawable drawable) {
[*] int width = drawable.getIntrinsicWidth();
[*] int height = drawable.getIntrinsicHeight();
[*] Bitmap bitmap = Bitmap.createBitmap(width, height, drawable
[*] .getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
[*] : Bitmap.Config.RGB_565);
[*] Canvas canvas = new Canvas(bitmap);
[*] drawable.setBounds(0, 0, width, height);
[*] drawable.draw(canvas);
[*] return bitmap;
[*]
[*] }
[*]
[*] // 获得圆角图片的方法
[*] public static Bitmap getRoundedCornerBitmap(Bitmap bitmap, float roundPx) {
[*] if(bitmap == null){
[*] return null;
[*] }
[*]
[*] Bitmap output = Bitmap.createBitmap(bitmap.getWidth(),
[*] bitmap.getHeight(), Config.ARGB_8888);
[*] Canvas canvas = new Canvas(output);
[*]
[*] final int color = 0xff424242;
[*] final Paint paint = new Paint();
[*] final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
[*] final RectF rectF = new RectF(rect);
[*]
[*] paint.setAntiAlias(true);
[*] canvas.drawARGB(0, 0, 0, 0);
[*] paint.setColor(color);
[*] canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
[*]
[*] paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
[*] canvas.drawBitmap(bitmap, rect, rect, paint);
[*] return output;
[*] }
[*]
[*] // 获得带倒影的图片方法
[*] public static Bitmap createReflectionImageWithOrigin(Bitmap bitmap) {
[*] final int reflectionGap = 4;
[*] int width = bitmap.getWidth();
[*] int height = bitmap.getHeight();
[*]
[*] Matrix matrix = new Matrix();
[*] matrix.preScale(1, -1);
[*]
[*] Bitmap reflectionImage = Bitmap.createBitmap(bitmap, 0, height / 2,
[*] width, height / 2, matrix, false);
[*]
[*] Bitmap bitmapWithReflection = Bitmap.createBitmap(width,
[*] (height + height / 2), Config.ARGB_8888);
[*]
[*] Canvas canvas = new Canvas(bitmapWithReflection);
[*] canvas.drawBitmap(bitmap, 0, 0, null);
[*] Paint deafalutPaint = new Paint();
[*] canvas.drawRect(0, height, width, height + reflectionGap, deafalutPaint);
[*]
[*] canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);
[*]
[*] Paint paint = new Paint();
[*] LinearGradient shader = new LinearGradient(0, bitmap.getHeight(), 0,
[*] bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff,
[*] 0x00ffffff, TileMode.CLAMP);
[*] paint.setShader(shader);
[*] // Set the Transfer mode to be porter duff and destination in
[*] paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
[*] // Draw a rectangle using the paint with our linear gradient
[*] canvas.drawRect(0, height, width, bitmapWithReflection.getHeight()
[*] + reflectionGap, paint);
[*]
[*] return bitmapWithReflection;
[*] }
[*]
[*]}
FileUtil view plaincopy
[*]package com.wangge.coupon.util;
[*]
[*]import java.io.File;
[*]import java.io.IOException;
[*]
[*]import android.os.Environment;
[*]import android.util.Log;
[*]
[*]import com.wangge.coupon.http.AsynImageLoader;
[*]
[*]public class FileUtil {
[*] private static final String TAG = "FileUtil";
[*]
[*] public static File getCacheFile(String imageUri){
[*] File cacheFile = null;
[*] try {
[*] if (Environment.getExternalStorageState().equals(
[*] Environment.MEDIA_MOUNTED)) {
[*] File sdCardDir = Environment.getExternalStorageDirectory();
[*] String fileName = getFileName(imageUri);
[*] File dir = new File(sdCardDir.getCanonicalPath()
[*] + AsynImageLoader.CACHE_DIR);
[*] if (!dir.exists()) {
[*] dir.mkdirs();
[*] }
[*] cacheFile = new File(dir, fileName);
[*] Log.i(TAG, "exists:" + cacheFile.exists() + ",dir:" + dir + ",file:" + fileName);
[*] }
[*] } catch (IOException e) {
[*] e.printStackTrace();
[*] Log.e(TAG, "getCacheFileError:" + e.getMessage());
[*] }
[*]
[*] return cacheFile;
[*] }
[*]
[*] public static String getFileName(String path) {
[*] int index = path.lastIndexOf("/");
[*] return path.substring(index + 1);
[*] }
[*]}
[*]
转自：http://blog.csdn.net/geniusxiaoyu/article/details/7470163
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