功能详解点击 ：https://www.jianshu.com/p/0cd4b6bd516e
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();//得到cpu的个数
private static final int CORE_POOL_SIZE=CPU_COUNT+1;
private static final int MAXIMUM_POOL_SIZE= CPU_COUNT*2+1;//2倍的cpu个数加1
private static final long KEEP_ALIVE=10L;
private static final int TAG_KEY_URI=R.id.image_demo6;//R.id.image_uri
private static final long DISK_CACHCE_SIZE=1024*1024*8;
private static final int IO_BUFFER_SIZE=1024*8;
private static final int DISK_CACHCE_INFEX=0;
private boolean mIsDiskLruCacheCreated=false;
//创建线程工厂
private static final ThreadFactory sThreadFactory =new ThreadFactory() {
private final AtomicInteger mCount=new AtomicInteger(1);
@Override
public Thread newThread(@NonNull Runnable r) {
return new Thread(r,"ImageLoader:"+mCount.getAndIncrement());
}
};
//线程池创建
public static final Executor THERAD_POOL_EXECUTOR=new ThreadPoolExecutor(CORE_POOL_SIZE,MAXIMUM_POOL_SIZE,
KEEP_ALIVE, TimeUnit.SECONDS,new LinkedBlockingQueue<Runnable>(),sThreadFactory);
//通过handler 在设置图片之前都会检查它的url有没有改变，如果发生改变就不再给它设置图片。这样可以解决图片错位问题
private Handler mMainHandler=new Handler(Looper.getMainLooper()){
@Override
public void handleMessage(Message msg) {
LoaderResult result= (LoaderResult) msg.obj;
ImageView imageView=result.imageView;
imageView.setImageBitmap(result.bitmap);
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();
//maxMemory是拿到的程序最大可以使用的内存以k为单位
int maxMemory=(int)(Runtime.getRuntime().maxMemory()/1024);
int cacheSize=maxMemory/8;
mMemoryCache=new LruCache<String, Bitmap>(cacheSize){
@Override
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_CACHCE_SIZE){
try {
mDiskLruCache=DiskLruCache.open(diskCacheDir,1,1,DISK_CACHCE_SIZE);
} catch (IOException e) {
e.printStackTrace();
}
mIsDiskLruCacheCreated=true;
}
}
public static ImageLoader build(Context context){
return new ImageLoader(context);
}
//添加缓存数据
private void addBitmapToMemoryCache(String key,Bitmap bitmap){
if (getBitmapFromMemCache(key)==null){
mMemoryCache.put(key,bitmap);
}
}
//添加读取数据
private Bitmap getBitmapFromMemCache(String key) {
return mMemoryCache.get(key);
}
public void bindBitmap(final String uri, final ImageView imageView){
bindBitmap(uri,imageView,0,0);
}
//异步加载
public void bindBitmap(final String uri, final ImageView imageView, final int reqWidth,final int reqHeight){
imageView.setTag(TAG_KEY_URI,uri);
final Bitmap bitmap=loadBitmapFromMemCache(uri);
if (bitmap!=null){
imageView.setImageBitmap(bitmap);
return;
}
final Runnable loadBitmapTask=new Runnable() {
@Override
public void run() {
Bitmap bitmapp=loadBitmap(uri,reqWidth,reqHeight);
if (bitmap!=null){
LoaderResult result=new LoaderResult(imageView,uri,bitmap);
mMainHandler.obtainMessage(MESSAGE_POST_RESULT,result).sendToTarget();
}
}
};
THERAD_POOL_EXECUTOR.execute(loadBitmapTask);
}
//同步加载
private Bitmap loadBitmap(String uri, int reqWidth, int reqHeight) {
Bitmap bitmap=loadBitmapFromMemCache(uri);
if (bitmap!=null){
Log.d(TAG, "loadBitmapFromMemCache: uri = "+uri);
return bitmap;
}
try {
bitmap=loadBitmapFromMemDiskCache(uri,reqWidth,reqHeight);
if (bitmap!=null){
Log.d(TAG, "loadBitmapFromMemDiskCache: uri = "+uri);
return bitmap;
}
bitmap=loadBitmapFromHttp(uri,reqWidth,reqHeight);
if (bitmap!=null){
Log.d(TAG, "loadBitmapFromHttp: uri = "+uri);
return bitmap;
}
}catch (Exception 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 uri) {
final String key=hashKeyFormUrl(uri);
Bitmap bitmap=getBitmapFromMemCache(key);
return bitmap;
}
//磁盘缓存读取
private Bitmap loadBitmapFromMemDiskCache(String uri, 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;
}
Bitmap bitmap=null;
String key=hashKeyFormUrl(uri);
DiskLruCache.Snapshot snapshot=mDiskLruCache.get(key);
if (snapshot!=null){
FileInputStream fileInputStream=(FileInputStream)snapshot.getInputStream(DISK_CACHCE_INFEX);
FileDescriptor fileDescriptor=fileInputStream.getFD();
bitmap=mImageResizer.decodeSampledBitmapFromFileDescriptor(fileDescriptor,reqWidth,reqHeight);
if (bitmap!=null){
addBitmapToMemoryCache(key,bitmap);
}
}
return bitmap;
}
private Bitmap loadBitmapFromHttp(String uri, int reqWidth, int reqHeight) throws IOException{
//判断当前线程是不是主线程
if (Looper.myLooper()==Looper.getMainLooper()){
throw new RuntimeException("can not visit network from UI Thread .");
}
if (mDiskLruCache==null){
return null;
}
String key=hashKeyFormUrl(uri);
//通过 Editor 可以得到一个文件输出流
DiskLruCache.Editor editor =mDiskLruCache.edit(key);
if (editor !=null){
//由于DiskLruCache的 open 方法在前面设置了一个节点只能有一个数据，所以 DISK_CACHCE_INFEX 设为0就可
OutputStream outputStream=editor.newOutputStream(DISK_CACHCE_INFEX);
if (downloadUrlToStream(uri,outputStream)){
editor.commit();
}else {
editor.abort();
}
mDiskLruCache.flush();
}
return loadBitmapFromMemDiskCache(uri,reqWidth,reqHeight);
}
//通过文件输出流写入到文件系统上
private boolean downloadUrlToStream(String uriString, OutputStream outputStream) {
HttpURLConnection urlConnection=null;
BufferedOutputStream out=null;
BufferedInputStream in=null;
try {
final URL url =new URL(uriString);
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();
}
try {
out.close();
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return false;
}
private Bitmap downloadBitmapFromUrl(String uri) {
Bitmap bitmap=null;
HttpURLConnection urlConnection=null;
BufferedInputStream in=null;
try {
final URL url = new URL(uri);
urlConnection= (HttpURLConnection) url.openConnection();
in=new BufferedInputStream(urlConnection.getInputStream(),IO_BUFFER_SIZE);
bitmap= BitmapFactory.decodeStream(in);
} catch (IOException e) {
Log.e(TAG, "downLoadBitmap failed ,"+e );
}finally {
if (urlConnection!=null){
urlConnection.disconnect();
}
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return bitmap;
}
//磁盘缓存添加
private String hashKeyFormUrl(String uri) {
String cacheKey = null;
try {
//图片的url中很可能有特殊字符，这将影响url在android中的使用，所以一般采用url的md5值作为key
final MessageDigest mDigest=MessageDigest.getInstance("MD5");
mDigest.update(uri.getBytes());
cacheKey=bytesToHexString(mDigest.digest());
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
}
return cacheKey;
}
private String bytesToHexString(byte[] bytes) {
StringBuilder sb=new StringBuilder();
for (int i = 0; i < bytes.length; i++) {
//此方法返回的字符串表示的无符号整数参数所表示的值以十六进制（基数为16）
String hex=Integer.toHexString(0xFF & bytes[i]);
if (hex.length()==1){
sb.append('0');
}
sb.append(hex);
}
return sb.toString();
}
private File getDiskCacheDir(Context mContext, String uniqueName) {
boolean externalStorageAvailable= Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED);
final String cachePath;
if (externalStorageAvailable){
cachePath=mContext.getExternalCacheDir().getPath();
}else {
cachePath=mContext.getCacheDir().getPath();
}
return new File(cachePath+File.separator+uniqueName);
}
//StatFs类 获取系统/sdcard存储空间信息
@TargetApi(Build.VERSION_CODES.GINGERBREAD)
private long getUsableSpace(File path){
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD){
return path.getUsableSpace();
}
final StatFs statFs =new StatFs(path.getPath());
return statFs.getBlockSizeLong()*statFs.getAvailableBlocksLong();
}
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;
}
}
}
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