我正在使用imageLoader类在后台加载图像，之后我在模拟器中设置图像它的工作。在设备中它不显示lazy downloaded图像。
private void queuePhoto(String url, Activity activity, ImageView imageView)
{
photosQueue.Clean(imageView);
PhotoToLoad p=new PhotoToLoad(url, imageView);
synchronized(photosQueue.photosToLoad)
{
photosQueue.photosToLoad.push(p);
photosQueue.photosToLoad.notifyAll();
}
(photoLoaderThread.getState()==Thread.State.NEW)
photoLoaderThread.start();
}
这是我的ImageLoader版本，每个 ImageView 都带有进度条。然后将动画应用于过渡。我还删除了 SD 卡缓存选项。你应该看到我修改的大部分内容。
/*
* Copyright (c)2012 Poohdish Rattanavijai
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.robgthai.lib.util;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.util.HashMap;
import java.util.Stack;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.widget.ImageView;
import android.widget.ProgressBar;
import com.robgthai.lib.R;
/**
* This class help handling the Lazyload of the image from given URL
* @author Poohdish Rattanavijai
*
*/
public class ImageLoader {
private static final String TAG = ImageLoader.class.getSimpleName();
private static final int LOG_LEVEL = (HelperUtil.FORCE_EVERY_LOG? Log.DEBUG: Log.INFO);
//the simplest in-memory cache implementation. This should be replaced with something like SoftReference or BitmapOptions.inPurgeable(since 1.6)
private HashMap<String, Bitmap> cache=new HashMap<String, Bitmap>();
private File cacheDir;
private Context context;
final int stub_id=R.drawable.ic_refresh; // Default icon to display before the image finish loaded
public ImageLoader(Context context){
//Make the background thead low priority. This way it will not affect the UI performance
photoLoaderThread.setPriority(Thread.NORM_PRIORITY-1);
this.context = context;
cacheDir=new File(context.getCacheDir(),"LazyList");
//Find the dir to save cached images
// if (android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))
// cacheDir=new File(android.os.Environment.getExternalStorageDirectory(),"LazyList");
// else
// cacheDir=context.getCacheDir();
if(!cacheDir.exists())
cacheDir.mkdirs();
}
/**
* Method for lazy-loading images
* @param url URL of the image
* @param activity Activity context, currently unused
* @param imageView ImageView to display the image
* @param progressBar ProgressBar for displaying while the image is being load
*/
public void DisplayImage(String url, Activity activity, ImageView imageView, ProgressBar progressBar)
{
if(cache.containsKey(url)) //If image is already in the cache
imageView.setImageBitmap(cache.get(url));
else
{
queuePhoto(url, activity, imageView, progressBar);
imageView.setImageResource(stub_id);
}
}
/**
* Method for lazy-loading images with the image sliding in from the left replacing the progress bar
* @param url URL of the image
* @param context Activity context, currently unused
* @param imageView ImageView to display the image
* @param progressBar ProgressBar for displaying while the image is being load
*/
public void DisplayImage(String url, Context context, ImageView imageView, ProgressBar progressBar)
{
if(cache.containsKey(url)){
if(LOG_LEVEL <= Log.DEBUG)Log.d(TAG, "Found in cache: " + url + "[" + cache.get(url) + "]");
imageView.setImageBitmap(cache.get(url));
Animation exitAnim = AnimationUtils.loadAnimation(ImageLoader.this.context, R.anim.list_image_slide_left_exit);
exitAnim.setFillAfter(true);
exitAnim.setFillEnabled(true);
Animation enterAnim = AnimationUtils.loadAnimation(ImageLoader.this.context, R.anim.list_image_slide_left_enter);
enterAnim.setFillAfter(true);
enterAnim.setFillEnabled(true);
progressBar.setVisibility(View.GONE);
imageView.setVisibility(View.VISIBLE);
progressBar.startAnimation(exitAnim);
imageView.startAnimation(enterAnim);
// if(bitmap!=null){
// imageView.setImageBitmap(bitmap);
// if(null != progress){
// progress.startAnimation(exitAnim);
// progress.setVisibility(View.GONE);
// }
// imageView.startAnimation(enterAnim);
//// imageView.setVisibility(View.VISIBLE);
// }else{
// if(null != progress){
// progress.startAnimation(enterAnim);
//// progress.setVisibility(View.VISIBLE);
// imageView.setVisibility(View.GONE);
// }else{
// imageView.setImageResource(stub_id);
// imageView.startAnimation(enterAnim);
//// imageView.setVisibility(View.VISIBLE);
// }
// }
}else
{
queuePhoto(url, context, imageView, progressBar);
imageView.setImageResource(stub_id);
}
}
/**
* Queue the image to download
* @param url
* @param context
* @param imageView
* @param progressBar
*/
private void queuePhoto(String url, Context context, ImageView imageView, ProgressBar progressBar)
{
//This ImageView may be used for other images before. So there may be some old tasks in the queue. We need to discard them.
photosQueue.Clean(imageView);
PhotoToLoad p= null;
if(null != progressBar){
p = new PhotoToLoad(url, imageView, progressBar);
}else{
p = new PhotoToLoad(url, imageView);
}
synchronized(photosQueue.photosToLoad){
photosQueue.photosToLoad.push(p);
photosQueue.photosToLoad.notifyAll();
}
//start thread if it's not started yet
if(photoLoaderThread.getState()==Thread.State.NEW)
photoLoaderThread.start();
}
/**
* Queue the image to download
* @param url
* @param context
* @param imageView
* @param progressBar
*/
private void queuePhoto(String url, Activity activity, ImageView imageView, ProgressBar progressBar)
{
//This ImageView may be used for other images before. So there may be some old tasks in the queue. We need to discard them.
photosQueue.Clean(imageView);
PhotoToLoad p= null;
if(null != progressBar){
p = new PhotoToLoad(url, imageView, progressBar);
}else{
p = new PhotoToLoad(url, imageView);
}
synchronized(photosQueue.photosToLoad){
photosQueue.photosToLoad.push(p);
photosQueue.photosToLoad.notifyAll();
}
//start thread if it's not started yet
if(photoLoaderThread.getState()==Thread.State.NEW)
photoLoaderThread.start();
}
/**
* Load image into the view preferably from Cache, otherwise url.
* @param url
* @return
*/
private Bitmap getBitmap(String url)
{
//identify images by hashcode. Not a perfect solution, good for the demo.
String filename=String.valueOf(url.hashCode());
File f=new File(cacheDir, filename);
//from cache
Bitmap b = decodeFile(f);
if(LOG_LEVEL <= Log.DEBUG)Log.d(TAG, "Looking for Image in cache");
if(b!=null){
if(LOG_LEVEL <= Log.DEBUG)Log.d(TAG, "Image found");
return b;
}
//from web
try {
if(LOG_LEVEL <= Log.DEBUG)Log.d(TAG, "Image not found, download from: " + url);
Bitmap bitmap=null;
InputStream is=new URL(url).openStream();
OutputStream os = new FileOutputStream(f);
HelperUtil.CopyStream(is, os);
os.close();
bitmap = decodeFile(f);
return bitmap;
} catch (Exception ex){
ex.printStackTrace();
return null;
}
}
//decodes image and scales it to reduce memory consumption
private Bitmap decodeFile(File f){
try {
//decode image size
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
BitmapFactory.decodeStream(new FileInputStream(f),null,o);
//Find the correct scale value. It should be the power of 2.
final int REQUIRED_SIZE=70;
int width_tmp=o.outWidth, height_tmp=o.outHeight;
int scale=1;
while(true){
if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE)
break;
width_tmp/=2;
height_tmp/=2;
scale*=2;
}
//decode with inSampleSize
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize=scale;
return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
} catch (FileNotFoundException e) {}
return null;
}
//Task for the queue
private class PhotoToLoad
{
public String url;
public ImageView imageView;
public ProgressBar progress;
public PhotoToLoad(String u, ImageView i, ProgressBar p){
url=u;
imageView=i;
progress = p;
}
public PhotoToLoad(String u, ImageView i){
url=u;
imageView=i;
}
}
PhotosQueue photosQueue=new PhotosQueue();
public void stopThread()
{
photoLoaderThread.interrupt();
}
//stores list of photos to download
class PhotosQueue
{
private Stack<PhotoToLoad> photosToLoad=new Stack<PhotoToLoad>();
//removes all instances of this ImageView
public void Clean(ImageView image)
{
for(int j=0 ;j<photosToLoad.size();){
if(photosToLoad.get(j).imageView==image)
photosToLoad.remove(j);
else
++j;
}
}
}
/**
* Controller of the image loader
* @author poohdishr
*
*/
class PhotosLoader extends Thread {
public void run() {
try {
while(true)
{
//thread waits until there are any images to load in the queue
if(photosQueue.photosToLoad.size()==0)
synchronized(photosQueue.photosToLoad){
photosQueue.photosToLoad.wait();
}
if(photosQueue.photosToLoad.size()!=0)
{
PhotoToLoad photoToLoad;
synchronized(photosQueue.photosToLoad){
photoToLoad=photosQueue.photosToLoad.pop();
}
Bitmap bmp=getBitmap(photoToLoad.url);
cache.put(photoToLoad.url, bmp);
Object tag=photoToLoad.imageView.getTag();
if(tag!=null && ((String)tag).equals(photoToLoad.url)){
BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad.imageView, photoToLoad.progress);
Activity a=(Activity)photoToLoad.imageView.getContext();
a.runOnUiThread(bd);
}
}
if(Thread.interrupted())
break;
}
} catch (InterruptedException e) {
//allow thread to exit
}
}
}
PhotosLoader photoLoaderThread=new PhotosLoader();
//Used to display bitmap in the UI thread
class BitmapDisplayer implements Runnable
{
Bitmap bitmap;
ImageView imageView;
ProgressBar progress;
public BitmapDisplayer(Bitmap b, ImageView i, ProgressBar p){bitmap=b;imageView=i;progress=p;}
public void run()
{
Animation exitAnim = AnimationUtils.loadAnimation(ImageLoader.this.context, R.anim.list_image_slide_left_exit);
exitAnim.setFillAfter(true);
exitAnim.setFillEnabled(true);
Animation enterAnim = AnimationUtils.loadAnimation(ImageLoader.this.context, R.anim.list_image_slide_left_enter);
enterAnim.setFillAfter(true);
enterAnim.setFillEnabled(true);
if(bitmap!=null){
imageView.setImageBitmap(bitmap);
if(null != progress){
progress.startAnimation(exitAnim);
progress.setVisibility(View.GONE);
}
imageView.startAnimation(enterAnim);
imageView.setVisibility(View.VISIBLE);
}else{
if(null != progress){
progress.startAnimation(enterAnim);
// progress.setVisibility(View.VISIBLE);
imageView.setVisibility(View.GONE);
}else{
imageView.setImageResource(stub_id);
imageView.startAnimation(enterAnim);
// imageView.setVisibility(View.VISIBLE);
}
}
}
}
public void clearCache() {
//clear memory cache
cache.clear();
//clear SD cache
File[] files=cacheDir.listFiles();
for(File f:files)
f.delete();
}
}