从线程将bmp图像保存到SD卡

Question

I'm trying the openCV sample on Android. When I'm trying to save a bmp file to my SDcard every thread using following code:

String filePath = "/sdcard"; // some times it may be only /sdcard not /mnt/sdcard
        filePath += "newFileName.jpg";
        try {
             bmp.compress(Bitmap.CompressFormat.JPEG, 100, new FileOutputStream(new File(filePath)));
        } catch (FileNotFoundException e) {
                    // TODO Auto-generated catch block
        e.printStackTrace();
        Log.i(TAG, "IOException Occurred!!!");   
        }

The log always shows up "IOException Occurred" and no file have been saved on SDcard.

The full class code is below

public abstract class SampleCvViewBase extends SurfaceView implements SurfaceHolder.Callback, Runnable {
private static final String TAG = "Sample::SurfaceView";

private SurfaceHolder       mHolder;
private VideoCapture        mCamera;
private FpsMeter            mFps;

public SampleCvViewBase(Context context) {
    super(context);
    mHolder = getHolder();
    mHolder.addCallback(this);
    mFps = new FpsMeter();
    Log.i(TAG, "Instantiated new " + this.getClass());
}

public void surfaceChanged(SurfaceHolder _holder, int format, int width, int height) {//called immediately after the structural change of surface
    Log.i(TAG, "surfaceCreated");
    synchronized (this) {
        if (mCamera != null && mCamera.isOpened()) {
            Log.i(TAG, "before mCamera.getSupportedPreviewSizes()");
            List<Size> sizes = mCamera.getSupportedPreviewSizes();
            Log.i(TAG, "after mCamera.getSupportedPreviewSizes()");
            int mFrameWidth = width;
            int mFrameHeight = height;

            // selecting optimal camera preview size
            {
                double minDiff = Double.MAX_VALUE;
                for (Size size : sizes) {
                    if (Math.abs(size.height - height) < minDiff) {
                        mFrameWidth = (int) size.width;
                        mFrameHeight = (int) size.height;
                        minDiff = Math.abs(size.height - height);
                    }
                }
            }

            mCamera.set(Highgui.CV_CAP_PROP_FRAME_WIDTH, mFrameWidth);
            mCamera.set(Highgui.CV_CAP_PROP_FRAME_HEIGHT, mFrameHeight);
        }
    }
}

public void surfaceCreated(SurfaceHolder holder) {
    Log.i(TAG, "surfaceCreated");
    mCamera = new VideoCapture(Highgui.CV_CAP_ANDROID);
    if (mCamera.isOpened()) {
        (new Thread(this)).start();     //new thread
    } else {
        mCamera.release();
        mCamera = null;
        Log.e(TAG, "Failed to open native camera");
    }
}

public void surfaceDestroyed(SurfaceHolder holder) {
    Log.i(TAG, "surfaceDestroyed");
    if (mCamera != null) {
        synchronized (this) {
            mCamera.release();                      
            mCamera = null;
        }
    }
}

protected abstract Bitmap processFrame(VideoCapture capture) throws IOException;

public void run() {
    Log.i(TAG, "Starting processing thread");       //send out log notice
    mFps.init();                                //instance of Fps meter    

    while (true) {
        Bitmap bmp = null;

        synchronized (this) {
            if (mCamera == null)                    //instance of video capture
                break;

            if (!mCamera.grab()) {
                Log.e(TAG, "mCamera.grab() failed");
                break;
            }

            try {
                bmp = processFrame(mCamera);
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            mFps.measure();
        }

        if (bmp != null) {
            Canvas canvas = mHolder.lockCanvas();
            if (canvas != null) {
                canvas.drawBitmap(bmp, (canvas.getWidth() - bmp.getWidth()) / 2, (canvas.getHeight() - bmp.getHeight()) / 2, null);
                mFps.draw(canvas, (canvas.getWidth() - bmp.getWidth()) / 2, 0);
                mHolder.unlockCanvasAndPost(canvas);
            }
            String filePath = "/sdcard"; // some times it may be only /sdcard not /mnt/sdcard
            filePath += "newFileName.jpg";
            try {
                 bmp.compress(Bitmap.CompressFormat.JPEG, 100, new FileOutputStream(new File(filePath)));
            } catch (FileNotFoundException e) {
                        // TODO Auto-generated catch block
            e.printStackTrace();
            Log.i(TAG, "IOExcpetion Occurred!!!");   
            }
        }

Here is what I've got in DDMS:

03-07 08:58:11.639: W/TextLayoutCache(986): computeValuesWithHarfbuzz -- need to force to single run
03-07 08:58:11.709: W/System.err(986): java.io.FileNotFoundException: /sdcardnewFileName.jpg: open failed: EROFS (Read-only file system)
03-07 08:58:11.769: W/System.err(986):  at libcore.io.IoBridge.open(IoBridge.java:406)
03-07 08:58:11.769: W/System.err(986):  at java.io.FileOutputStream.<init>(FileOutputStream.java:88)
03-07 08:58:11.809: W/System.err(986):  at java.io.FileOutputStream.<init>(FileOutputStream.java:73)
03-07 08:58:11.829: W/System.err(986):  at org.opencv.samples.fd.SampleCvViewBase.run(SampleCvViewBase.java:125)
03-07 08:58:11.829: W/System.err(986):  at org.opencv.samples.fd.FdView.run(FdView.java:107)
03-07 08:58:11.829: W/System.err(986):  at java.lang.Thread.run(Thread.java:856)
03-07 08:58:11.829: W/System.err(986): Caused by: libcore.io.ErrnoException: open failed: EROFS (Read-only file system)
03-07 08:58:11.859: W/System.err(986):  at libcore.io.Posix.open(Native Method)
03-07 08:58:11.859: W/System.err(986):  at libcore.io.BlockGuardOs.open(BlockGuardOs.java:98)
03-07 08:58:11.889: W/System.err(986):  at libcore.io.IoBridge.open(IoBridge.java:390)
03-07 08:58:11.889: W/System.err(986):  ... 5 more

03-07 08:58:11.919: I/Sample::SurfaceView(986): IOExcpetion Occurred!!!

03-07 08:58:12.489: D/dalvikvm(986): GC_FOR_ALLOC freed 1209K, 14% free 9902K/11399K, paused 29ms
03-07 08:58:12.489: I/dalvikvm-heap(986): Grow heap (frag case) to 10.925MB for 1228816-byte allocation
03-07 08:58:12.619: D/dalvikvm(986): GC_CONCURRENT freed <1K, 3% free 11102K/11399K, paused 3ms+45ms

I'm trying to save one bmp image as soon as the detection has completed once. Can anyone help me?Thank you

Answer 1

You are trying to write into the filesystem root because you missed a forward slash in your file path: You use /sdcardnewFileName.jpg instead of /sdcard/newFileName.jpg . But you got no permission to write there, so you get an exception.

Also: Please don't hardcode the path to the SD-card like this at all. Instead use Environment.getExternalStorageDirectory() . Some devices mount the card on a different path or have flash memory instead. This method always returns the correct path. If you don't do this, you will run into problems when using your app across multiple devices.

Answer 2

1/ you lack a slash in your path.

2/ that is not the proper way of finding the sdcard path and creating a file on it: http://developer.android.com/reference/android/os/Environment.html#getExternalStorageDirectory%28%29

File root = Environment.getExternalStorageDirectory();
File imgFile = new File(root, "newFileName.jpg");
FileOutputStream fos = new FileOutputStream(imgFile);