參考《android開發藝術探索》
1.圖片壓縮功能類ImageResizer
<pre>
public class ImageResizer{
private static final String TAG = "ImageResizer";
public ImageResizer(){
}
public Bitmap decodeSampledBitmapFromResource(Resource res,int resId,int reqWidth,int reqHeight){
//First decode with inJustDecodeBounds=true to check dimensions
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeResource(res,resId,options);
//calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options,reqWidth,reqHeight);
//decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
return BitmapFactory.decodeResource(res,resId,options);
}
public Bitmap decodeSampledBitmapFromFileDescriptor(FileDescriptor fd,int reqWidth, int reqHeight){
//First decode with inJustDecodeBounds=true to check dimensions
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFileDescriptor(fd,null,options);
//calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options,reqWidth,reqHeight);
//decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
return BitmapFactory.decodeFileDescriptor(fd,null,options);
}
public int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight){
if(reqWidth == 0 || reqHeight == 0){
return 1;
}
//Raw height and width of image
final int width = options.outWidth;
final int height = options.outHeight;
Log.d(TAG,"origin,w="+width+"h="+height);
int inSampleSize = 1;
if(height > reqHeight || width > reqWidth){
final int halfHeight = height / 2;
final int halfWidth = width / 2;
while((halfHeight / inSampleSize) >= reqHeight && (halfWidth / inSampleSize) >= reqWidth){
inSampleSize *= 2;
}
}
Log.d(TAG,"sampleSize:"+inSampleSize);
return inSampleSize;
}
}
</pre>
2.ImageLoader完整代碼
<pre>
public class ImageLoader{
private static final String TAG = "ImageLoader";
public static final int MESSAGE_POST_RESULT = 1;
private static final int CPU_COUNT = Runtime.getRuntime().availableProcessors();
private static final int CORE_POOL_SIZE = CPU_COUNT + 1;
private static final int MAXIMUM_POOL_SIZE = CPU_COUNT * 2 + 1;
private static final long KEEP_ALIVE = 10L;
private static final int TAG_KEY_URI = R.id.imageloader_uri;
private static final long DISK_CACHE_SIZE = 1024 * 1024 * 50;
private static final int IO_BUFFER_SIZE = 8 * 1024;
private static final int DISK_CACHE_INDEX = 0;
private boolean mIsDiskLruCacheCreated = false;
private static final ThreadFactory sThreadFactory = new ThreadFactory(){
private final AtomicInteger mCount = new AtomicInteger(1);
public Thread newThread(Runnable r){
return new Thread(r, "ImageLoader#" + mCount.getAndIncrement());
}
}
public static final Executor THREAD_POOL_EXECUTOR = new ThreadPoolExecutor(
CORE_POOL_SIZE,MAXIMUM_POOL_SIZE,KEEP_ALIVE,TimeUnit.SECONDS,
new LinkedBlockingQueue<>(Runnable),sThreadFactory);
private Handler mMainHandler = new Handler(Looper.getMainLooper()){
public void handleMessage(Message msg){
LoaderResult result = (LoaderResult) msg.obj;
ImageView imageView = result.imageView;
String uri= (String) imageView.getTag(TAG_KEY_URI);
if(uri.equals(result.uri)){
imageView.setImageBitmap(result.bitmap);
}else{
Log.w(TAG,"set image bitmap,but url has changed,ignored!");
}
}
};
private Context mContext;
private ImageResizer mImageResizer = new ImageResizer();
private LruCache<String,Bitmap> mMemoryCache;
private DiskLruCache mDiskLruCache;
private ImageLoader(Context context){
mContext = context.getApplicationContext();
int maxMemory = (int) (Runtime.getRuntime().maxMemory / 1024);
int cacheSize = maxMemory / 8;
mMemoryCache = new LruCache<String, Bitmap>(cacheSize){
protected int sizeOf(String key,Bitmap bitmap){
return bitmap.getRowBytes() * bitmap.getHeight() / 1024;
}
};
File diskCacheDir = getDiskCacheDir(mContext, "bitmap");
if(!diskCacheDir.exists()){
diskCacheDir.mkdirs();
}
if(getUsableSpace(diskCacheDir) > DISK_CACHE_SIZE){
try{
mDiskLruCache = DiskLruCache.open(diskCacheDir,1,1,DISK_CACHE_SIZE);
mIsDiskLruCacheCreated = true;
}catch(IOException e){
e.printStackTrace();
}
}
}
public static ImageLoader build(Context context){
return new ImageLoader(context);
}
private void addBitmapToMemoryCache(String key,Bitmap bitmap){
if(getBitmapFromMemCache(key) == null){
mMemoryCache.put(key, bitmap);
}
}
private Bitmap getBitmapFromMemCache(String key){
return mMemoryCache.get(key);
}
public void bindBitmap(final String uri, final ImageView imageView){
bindBitmap(uri,imageView,0,0);
}
/**
* load bitmap from memory cache or disk or network async,then bind imageview and bitmap
* NOTE THAT: should run in UI thread
*/
public void bindBitmap(final String uri, final ImageView imageView, final int reqWidth,final int reqHeight){
imageView.setTag(TAG_KEY_URI,uri);
Bitmap bitmap = loadBitmapFromMemCache(uri);
if(bitmap != null){
imageView.setImageBitmap(bitmap);
return;
}
Runnable loadBitmapTask = new Runnable(){
public void run(){
Bitmap bitmap = loadBitmap(uri, reqWidth, reqHeight);
if(bitmap != null){
LoaderResult result = new LoaderResult(imageView,uri,bitmap);
mMainHandler.obtainMessage(MESSAGE_POST_RESULT,result).sendToTarget();
}
}
}
THREAD_POOL_EXECUTOR.execute(loadBitmapTask);
}
public Bitmap loadBitmap(String uri,int reqWidth,int reqHeight){
Bitmap bitmap = loadBitmapFromMemCache(uri);
if(bitmap != null){
Log.d(TAG,"loadBitmapFromMemCache,url:"+uri);
return bitmap;
}
try{
bitmap = loadBitmapFromDiskCache(uri,reqWidth,reqHeight);
if(bitmap != null){
Log.d(TAG,"loadBitmapFromDiskCache,url:"+uri);
return bitmap;
}
bitmap = loadBitmapFromHttp(uri,reqWidth,reqHeight);
Log.d(TAG,"loadBitmapFromHttp,url:"+uri);
}catch(IOException e){
e.printStackTrace();
}
if(bitmap == null && !mIsDiskLruCacheCreated){
Log.w(TAG, "encounter error,DiskLruCache is not created.");
bitmap = downloadBitmapFromUrl(uri);
}
return bitmap;
}
private Bitmap loadBitmapFromMemCache(String url){
final String key = hashKeyFromUrl(url);
Bitmap bitmap = getBitmapFromMemCache(key);
return bitmap;
}
private Bitmap loadBitmapFromHttp(String url,int reqWidth, int reqHeight) throws IOException{
if(Looper.myLooper() == Looper.getMainLooper()){
throw new RuntimeException("can not visit network from UI Thread.");
}
if(mDiskLruCache == null){
return null;
}
String key = hashKeyFromUrl(url);
DiskLruCache.Editor editor = mDiskLruCache.edit(key);
if(editor != null){
OutputStream outputStream = editor.newOutputStream(DISK_CACHE_INDEX);
if(downloadUrlToStream(url,outputStream)){
editor.commit();
}else{
editor.abort();
}
mDiskLruCache.flush();
}
return loadBitmapFromDiskCache(url,reqWidth,reqHeight);
}
private Bitmap loadBitmapFromDiskCache(String url,int reqWidth,int reqHeight){
if(Looper.myLooper() == Looper.getMainLooper()){
Log.w(TAG,"load bitmap from UI Thread,it is not recommended!");
}
if(mDiskLruCache == null){
return null;
}
Bitmap bitmap = null;
String key = hashKeyFromUrl(url);
DiskLruCache.SnapShot snapShot = mDiskLruCache.get(key);
if(snapShot != null){
FileInputStream fileInputStream = (FileInputStream)snapShot.getInputStream(DISK_CACHE_INDEX);
FileDescriptor fileDescriptor = fileInputStream.getFD();
bitmap = mImageResizer.decodeSampledBitmapFromFileDescriptor(fileDescriptor,reqWidth,reqHeight);
if(bitmap != null){
addBitmapToMemoryCache(key,bitmap);
}
}
return bitmap;
}
public boolean downloadUrlToStream(String urlString,OutputStream outputStream){
HttpURLConnection urlConnection = null;
BufferedOutputStream out = null;
BufferedInputStream in = null;
try{
final URL url = new URL(urlString);
urlConnection = (HttpURLConnection) url.openConnection();
in = new BufferedInputStream(urlConnection.getInputStream(),IO_BUFFER_SIZE);
out = new BufferedOutputStream(outputStream,IO_BUFFER_SIZE);
int b;
while((b = in.read()) != -1){
out.write(b);
}
return true;
}catch(IOException e){
Log.e(TAG,"downloadBitmap failed."+e);
}finally{
if(urlConnection != null){
urlConnection.disconnect();
}
MyUtils.close(out);
MyUtils.close(in);
}
return false;
}
private Bitmap downloadBitmapFromUrl(String urlString){
Bitmap bitmap = null;
HttpURLConnection urlConnection = null;
BufferedInputStream in = null;
try{
final URL url = new URL(urlString);
urlConnection = (HttpURLConnection) url.openConnection();
in = new BufferedInputStream(urlConnection.getInputStream(),IO_BUFFER_SIZE);
bitmap = BitmapFactory.decodeStream(in);
}catch(IOException e){
Log.e(TAG,"Error in downloadBitmap:"+e);
}finally{
if(urlConnection != null){
urlConnection.disconnect();
}
MyUtils.close(in);
}
return bitmap;
}
private String hashKeyFromUrl(String url){
String cacheKey;
try{
final MessageDigest mDigest = MessageDigest.getInstance("MD5");
mDigest.update(url.getBytes());
cacheKey = bytesToHexString(mDigest.digest());
}catch(NoSuchAlgorithmException e){
cacheKey = String.valueOf(url.hasCode());
}
return cacheKey;
}
private String bytesToHexString(byte[] bytes){
StringBuilder sb = new StringBuilder();
for(int i = 0; i < bytes.length; i ++){
String hex = Integer.toHexString(0xFF & byte[i]);
if(hex.length() == 1){
sb.append('0');
}
sb.append(hex);
}
return sb.toString();
}
public File getDiskCacheDir(Context context,String uniqueName){
boolean externalStorageAvailable = Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED);
final String cachePath;
if(externalStorageAvailable){
cachePath = context.getExternalCacheDir().getPath();
}else{
cachePath = context.getCacheDir().getPath();
}
return new File(cachePath + File.separator + uniqueName);
}
private long getUsableSpace(File path){
if(Build.VERSION.SDK_INT >= VERSION_CODES.GINGERBREAD){
return path.getUsableSpace();
}
final StatFs stats = new StatFs(path.getPath());
return (long) stats.getBloackSize() * (long)stats.getAvailableBlocks();
}
private static class LoaderResult{
public ImageView imageView;
public String uri;
public Bitmap bitmap;
public LoaderResult(ImageView imageView,String uri,Bitmap bitmap){
this.imageView = imageView;
this.uri = uri;
this.bitmap = bitmap;
}
}
}
</pre>
