我开发了下面的类来接收带有标头(22字节)发送的图像，首先我解码标头以检查图像正确性，然后我解码图像，但并非所有图像都被解码，有时它返回SkImageDecoder::Factory returned null。我正在使用这个Android教程来inSampleImage。
public class SocketServerStreamDataThread extends Thread {
private Socket streamSocket;
MainActivity mainActivity ;
ImageView displayedImage ;
Bitmap bitmapImageToDisplay = null;
byte[] dataBuffer = new byte[1048576];
boolean result ;
protected static boolean mReceivingStop; // Flag used to start and stop transmitting data
SocketServerStreamDataThread(Socket socket, MainActivity mainActivityReceived, ImageView displayedImageView) {
streamSocket = socket;
// received activity to work on it in our java file
mainActivity = mainActivityReceived ;
// received image UI component to display
displayedImage = displayedImageView;
}
@Override
public void run() {
/* Receiving the image */
try {
DecodeData decodeData = new DecodeData();
// call DecodeData to get Image data from stream
while (mReceivingStop == false) {
if (bitmapImageToDisplay == null) {
InputStream inputStream = streamSocket.getInputStream();
if (inputStream.read(dataBuffer) > -1) {
// Call the class to decode received stream and return integer with the state of the decoding of the received data
// result = 0 ; means that decoding header is successful.
// result = -1 ; means that there is a problem in decoding header.
byte [] dataHeaderReceived = Arrays.copyOf(dataBuffer, 23) ;
result = decodeData.iDecodeReceiveData(dataHeaderReceived);
// Evalute the received data
if (result == false) {
/* Fault on application */
/* Close socket */
streamSocket.close();
mReceivingStop = true;
}
if (result == true) {
/* Data have been received */
/* Show image */
BitmapFactory.Options imageOption = new BitmapFactory.Options();
imageOption.inJustDecodeBounds = true;
BitmapFactory.decodeResource(mainActivity.getResources(), R.id.display_image, imageOption);
imageOption.inSampleSize = calculateInSampleSize (imageOption, 550, 435) ;
imageOption.inJustDecodeBounds = false;
bitmapImageToDisplay = BitmapFactory.decodeByteArray(dataBuffer, 23, decodeData.imageSize, imageOption);
if (bitmapImageToDisplay != null) {
mainActivity.runOnUiThread(new Runnable() {
@Override
public void run() {
//try to display to image
displayedImage.setImageBitmap(bitmapImageToDisplay);
}
});
}
}
}
SystemClock.sleep(300);
bitmapImageToDisplay = null ;
}
}
streamSocket.close();
mReceivingStop = true;
mainActivity.runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(mainActivity, "Finished", Toast.LENGTH_LONG).show();
}
});
} catch (IOException e) {
e.printStackTrace();
StringBuilder eMsg = new StringBuilder();
eMsg.append("Something wrong: " + e.getMessage());
final String eMessage=eMsg.toString();
// final String eMsg = "Something wrong: " + e.getMessage();
mainActivity.runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(mainActivity, eMessage, Toast.LENGTH_LONG).show();
}
});
} finally {
if(streamSocket != null){
try {
streamSocket.close();
mReceivingStop = true ;
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
Logcat输出:
GC_FOR_ALLOC freed 1307K, 27% free 13676K/18596K, paused 34ms, total 34ms
D/dalvikvm: GC_FOR_ALLOC freed 1306K, 27% free 13676K/18596K, paused 8ms, total 8ms
D/skia: --- SkImageDecoder::Factory returned null
D/skia: --- SkImageDecoder::Factory returned null
D/dalvikvm: GC_FOR_ALLOC freed 1607K, 29% free 13376K/18596K, paused 24ms, total 24ms
D/skia: --- SkImageDecoder::Factory returned null
D/dalvikvm: GC_FOR_ALLOC freed 1255K, 27% free 13728K/18596K, paused 9ms, total 9ms
在Android上加载位图是一个庞大且相当复杂的主题。这就是为什么我建议使用一个经过验证的库来为您处理它;比如格莱德、毕加索或弗雷斯科。这些库将为您处理加载位图时出现的许多陷阱;包括内存约束、缓存和线程。
如果你真的想单独行动，你就得自己面对这些问题。如果位图不能正确解码，SkImageDecoder::Factory returned null是BitmapFactory.decode...方法吐出的，这可能是由许多问题引起的。我不知道到底是什么原因造成的，但我确实看到一些问题在你的代码。
首先，您将MainActivity传递给Thread，这只是自找麻烦。相反，您只需要将ImageView传递给Thread。确保你使用WeakReference，否则你有泄露Context的风险:
WeakReference<ImageView> mDisplayedImageView;
SocketServerStreamDataThread(Socket socket, ImageView imageView) {
mDisplayedImageView = new WeakReference<>(imageView);
...
}
接下来，您使用可绘制的资源来解码Bitmap的边界，但随后您试图从Socket连接获得Bitmap。相反，您应该使用InputStream:
BufferedInputStream inBounds = new BufferedInputStream(streamSocket.getInputStream());
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeStream(inBounds, null, options);
options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
inBounds.close();
并且您不需要单独的DecodeData类，因为BitmapFactory也有解码流的方法:
options.inJustDecodeBounds = false;
BufferedInputStream in = new BufferedInputStream(streamSocket.getInputStream());
Bitmap bitmap = BitmapFactory.decodeStream(in, null, options);
in.close();
最后，如果您使用Thread.sleep()或SystemClock.sleep()来克服某些障碍，您可能应该重新考虑您的解决方案。这些只是我在快速浏览中注意到的问题。如果你真的想在没有库的帮助下继续，我建议你多研究一下如何有效地加载位图;文档是一个很好的起点。