Getting Null pointer exception while capturing and saving an image using android emulator

问题

I am trying to capture and save an image through an Android emulator, image is being captured, but the file being saved is corrupted.

What could be causing this? can anyone help me identify possible error points?

Below is my code:

**public void onCreate**(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    **Intent** intent = new **Intent**("android.media.action.IMAGE_CAPTURE");
    try {
        fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE);
    } 

    catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    intent.putExtra(**MediaStore**.EXTRA_OUTPUT, fileUri);
    startActivityForResult(intent, CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE);
}

@Override
**protected void onActivityResult**(int requestCode, int resultCode, Intent data) {
    if (requestCode == CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE) {
        if (resultCode == RESULT_OK) {
            StoreImage(this, data.getData(),
            mediaFile);
            finish();
        } 

        else if (resultCode == RESULT_CANCELED) {
            // User cancelled the image capture
        } 

        else {
            finish();
            try {
            } 

            catch (Exception e) {
               e.printStackTrace();
            }
        }
    }

}

The Stack trace is below::

04-05 23:55:40.369: E/AndroidRuntime(534): FATAL EXCEPTION: main
04-05 23:55:40.369: E/AndroidRuntime(534): java.lang.RuntimeException: Unable to start activity ComponentInfo{camera.android/camera.android.CameraActivity}: java.lang.NullPointerException: file
04-05 23:55:40.369: E/AndroidRuntime(534):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955)

04-05 23:55:40.369: E/AndroidRuntime(534): Caused by: java.lang.NullPointerException: file
04-05 23:55:40.369: E/AndroidRuntime(534):  at android.net.Uri.fromFile(Uri.java:441)
04-05 23:55:40.369: E/AndroidRuntime(534):  at camera.android.CameraActivity.getOutputMediaFileUri(CameraActivity.java:72)
04-05 23:55:40.369: E/AndroidRuntime(534):  at camera.android.CameraActivity.onCreate(CameraActivity.java:34)
04-05 23:55:40.369: E/AndroidRuntime(534):  at android.app.Activity.performCreate(Activity.java:4465)
04-05 23:55:40.369: E/AndroidRuntime(534):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
04-05 23:55:40.369: E/AndroidRuntime(534):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)

回答1:

check whether you added the below permission in manifest file::

<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.CAMERA" />

also in the

fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE);

I think you must attach the file name that you want to save too, and giving only the path is not enough....

回答2:

Interchange this line,

if (requestCode == CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE) {
                if (resultCode == RESULT_OK) {

to

 if (resultCode == RESULT_OK) {
                    if (requestCode == CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE) {

First check whether the child activity is done its work successfully or not.

回答3:

"@ Agarwal : on calling the onActivityResult"

@Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE) {
            if (resultCode == RESULT_OK) {
                StoreImage(this, data.getData(), mediaFile);
                finish();

            } else if (resultCode == RESULT_CANCELED) {
                // User cancelled the image capture
            } else {
                finish();
                try {

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

        }

    }

"If the result is success, then the data from intern is stored n file which is created and saved as jpeg format"

public static void StoreImage(Context mContext, Uri imageLoc, File imageDir) {
        Bitmap bm = null;
        try {
            bm = Media.getBitmap(mContext.getContentResolver(), imageLoc);
            FileOutputStream out = new FileOutputStream(imageDir);
            bm.compress(Bitmap.CompressFormat.JPEG, 100, out);
            bm.recycle();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

回答4:

try below code,

Intent i = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);

    File file=getOutputMediaFile(1);
    picUri = Uri.fromFile(file); // create
    i.putExtra(MediaStore.EXTRA_OUTPUT,picUri); // set the image file

    startActivityForResult(i, CAPTURE_IMAGE);

where getOutputMediaFile(int) will be,

/** Create a File for saving an image */
private  File getOutputMediaFile(int type){
    File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(
              Environment.DIRECTORY_PICTURES), "MyApplication");

    /**Create the storage directory if it does not exist*/
    if (! mediaStorageDir.exists()){
        if (! mediaStorageDir.mkdirs()){
            return null;
        }
    }

    /**Create a media file name*/
    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
    File mediaFile;
    if (type == 1){
        mediaFile = new File(mediaStorageDir.getPath() + File.separator +
        "IMG_"+ timeStamp + ".png");
    } else {
        return null;
    }

    return mediaFile;
}

and finally,

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (resultCode == Activity.RESULT_OK) {
        Intent i;
        switch (requestCode) {
        case CAPTURE_IMAGE:
            //THIS IS YOUR Uri
            Uri uri=picUri; 
            break;
        }
    }   
}

cheers....:)

来源：https://stackoverflow.com/questions/10022758/getting-null-pointer-exception-while-capturing-and-saving-an-image-using-android