在Android中捕獲圖像

Question

我想在android中捕獲圖像並將其顯示在imageview中。訪問相機並拍照沒有問題，但是每當我要拍照時我都會出現空指針錯誤。以下是我的代碼

public class New3Fragment extends Fragment implements OnClickListener,
    DialogClickListener {
EditText name_EditText, phonenumber_EditText, email_EditText;

ImageView photo1_ImageView, photo2_ImageView, photo3_ImageView;

String choice;

private Uri fileUri; // file url to store image/video

public static final int DIALOG_FRAGMENT = 1;

private int photo_number;

// Activity request codes
private static final int CAMERA_CAPTURE_IMAGE_REQUEST_CODE = 100;
public static final int MEDIA_TYPE_IMAGE = 1;
public static final int MEDIA_TYPE_VIDEO = 2;
private static int RESULT_LOAD_IMAGE = 1;

// directory name to store captured images and videos
private static final String IMAGE_DIRECTORY_NAME = "Safirisha";

public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_new3, container,
            false);

    name_EditText = (EditText) rootView
            .findViewById(R.id.new3_editText_name);
    phonenumber_EditText = (EditText) rootView
            .findViewById(R.id.new3_editText_phonenumber);
    email_EditText = (EditText) rootView
            .findViewById(R.id.new3_editText_email);

    photo1_ImageView = (ImageView) rootView
            .findViewById(R.id.new3_imageView_photo1);
    photo2_ImageView = (ImageView) rootView
            .findViewById(R.id.new3_imageView_photo2);
    photo3_ImageView = (ImageView) rootView
            .findViewById(R.id.new3_imageView_photo3);

    photo_number = 0;

    photo1_ImageView.setOnClickListener(this);
    photo2_ImageView.setOnClickListener(this);
    photo3_ImageView.setOnClickListener(this);
    return rootView;
}

/**
 * Select image from gallery
 */
private void selectFromGallery() {
    Intent i = new Intent(Intent.ACTION_PICK,
            android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);

    startActivityForResult(i, RESULT_LOAD_IMAGE);
}

/**
 * Capturing Camera Image will lauch camera app requrest image capture
 */
private void captureImage() {
    Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);

    fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE);

    intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri);

    // start the image capture Intent
    startActivityForResult(intent, CAMERA_CAPTURE_IMAGE_REQUEST_CODE);
}

/**
 * Here we store the file url as it will be null after returning from camera
 * app
 */
@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);

    // save file url in bundle as it will be null on scren orientation
    // changes
    outState.putParcelable("file_uri", fileUri);
}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    if (savedInstanceState != null) {
        // Restore last state for checked position.
        fileUri = savedInstanceState.getParcelable("file_uri");
    }
}

/**
 * Receiving activity result method will be called after closing the camera
 * */
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    // if the result is capturing Image
    if (requestCode == CAMERA_CAPTURE_IMAGE_REQUEST_CODE) {
        if (resultCode == Activity.RESULT_OK) {
            // successfully captured the image
            // display it in image view
            previewCapturedImage();
        } else if (resultCode == Activity.RESULT_CANCELED) {
            // user cancelled Image capture
            Toast.makeText(getActivity().getApplicationContext(),
                    "User cancelled image capture", Toast.LENGTH_SHORT)
                    .show();
        } else {
            // failed to capture image
            Toast.makeText(getActivity().getApplicationContext(),
                    "Sorry! Failed to capture image", Toast.LENGTH_SHORT)
                    .show();
        }
    } else if (requestCode == RESULT_LOAD_IMAGE
            && resultCode == Activity.RESULT_OK && null != data) {
        Uri selectedImage = data.getData();
        String[] filePathColumn = { MediaStore.Images.Media.DATA };

        Cursor cursor = getActivity().getContentResolver().query(
                selectedImage, filePathColumn, null, null, null);
        cursor.moveToFirst();

        int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
        String picturePath = cursor.getString(columnIndex);
        cursor.close();

        // String picturePath contains the path of selected Image
        previewFromGallery(picturePath);
    } else if (requestCode == DIALOG_FRAGMENT) {
        if (resultCode == Activity.RESULT_OK) {

        }
        // After Ok code.
        else if (resultCode == Activity.RESULT_CANCELED) {
            // After Cancel code.
        }
    }
}

/**
 * Display image from a path to ImageView
 */
private void previewCapturedImage() {
    try {

        // bimatp factory
        BitmapFactory.Options options = new BitmapFactory.Options();

        // downsizing image as it throws OutOfMemory Exception for larger
        // images
        options.inSampleSize = 8;

        final Bitmap bitmap = BitmapFactory.decodeFile(fileUri.getPath(),
                options);

        if (photo_number == 1) {
            photo1_ImageView.setImageBitmap(bitmap);
        } else if (photo_number == 2) {
            photo2_ImageView.setImageBitmap(bitmap);
        } else if (photo_number == 3) {
            photo3_ImageView.setImageBitmap(bitmap);
        }
    } catch (NullPointerException e) {
        e.printStackTrace();
    }
}

private void previewFromGallery(String picturePath) {
    photo1_ImageView.setImageBitmap(BitmapFactory.decodeFile(picturePath));
}

/**
 * ------------ Helper Methods ----------------------
 * */

/**
 * Creating file uri to store image/video
 */
public Uri getOutputMediaFileUri(int type) {
    return Uri.fromFile(getOutputMediaFile(type));
}

/**
 * returning image / video
 */
private static File getOutputMediaFile(int type) {

    // External sdcard location
    File mediaStorageDir = new File(
            Environment
                    .getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
            IMAGE_DIRECTORY_NAME);

    // Create the storage directory if it does not exist
    if (!mediaStorageDir.exists()) {
        if (!mediaStorageDir.mkdirs()) {
            Log.d(IMAGE_DIRECTORY_NAME, "Oops! Error creating "
                    + IMAGE_DIRECTORY_NAME + " directory.");
            return null;
        }
    }

    // Create a media file name
    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss",
            Locale.getDefault()).format(new Date());
    File mediaFile;
    if (type == MEDIA_TYPE_IMAGE) {
        mediaFile = new File(mediaStorageDir.getPath() + File.separator
                + "IMG_" + timeStamp + ".jpg");
    } else if (type == MEDIA_TYPE_VIDEO) {
        mediaFile = new File(mediaStorageDir.getPath() + File.separator
                + "VID_" + timeStamp + ".mp4");
    } else {
        return null;
    }

    return mediaFile;
}

@Override
public void onClick(View v) {
    switch (v.getId()) {
    case R.id.new3_imageView_photo1:
        photo_number = 1;
        UploadPhotoDialog uploadPhotoDialog = new UploadPhotoDialog()
                .newInstance(123);
        uploadPhotoDialog.setTargetFragment(this, DIALOG_FRAGMENT);
        uploadPhotoDialog.show(getFragmentManager().beginTransaction(),
                "dialog");
        break;

    case R.id.new3_imageView_photo2:
        photo_number = 2;
        UploadPhotoDialog uploadPhotoDialog2 = new UploadPhotoDialog()
                .newInstance(123);
        uploadPhotoDialog2.setTargetFragment(this, DIALOG_FRAGMENT);
        uploadPhotoDialog2.show(getFragmentManager().beginTransaction(),
                "dialog");
        break;

    case R.id.new3_imageView_photo3:
        photo_number = 3;
        UploadPhotoDialog uploadPhotoDialog3 = new UploadPhotoDialog()
                .newInstance(123);
        uploadPhotoDialog3.setTargetFragment(this, DIALOG_FRAGMENT);
        uploadPhotoDialog3.show(getFragmentManager().beginTransaction(),
                "dialog");
        break;
    }

}

@Override
public void onCameraClick() {
    Toast.makeText(getActivity(), "Camera", Toast.LENGTH_SHORT).show();
    captureImage();
}

@Override
public void onGalleryClick() {
    selectFromGallery();

}

和logcat輸出

07-07 14:05:23.225: E/AndroidRuntime(28851): FATAL EXCEPTION: main
07-07 14:05:23.225: E/AndroidRuntime(28851): java.lang.NullPointerException: file
07-07 14:05:23.225: E/AndroidRuntime(28851):    at android.net.Uri.fromFile(Uri.java:446)
07-07 14:05:23.225: E/AndroidRuntime(28851):    at com.koncious.safirisha.New3Fragment.getOutputMediaFileUri(New3Fragment.java:213)
07-07 14:05:23.225: E/AndroidRuntime(28851):    at com.koncious.safirisha.New3Fragment.captureImage(New3Fragment.java:95)
07-07 14:05:23.225: E/AndroidRuntime(28851):    at com.koncious.safirisha.New3Fragment.onCameraClick(New3Fragment.java:289)
07-07 14:05:23.225: E/AndroidRuntime(28851):    at com.koncious.safirisha.UploadPhotoDialog.onClick(UploadPhotoDialog.java:67)
07-07 14:05:23.225: E/AndroidRuntime(28851):    at android.view.View.performClick(View.java:3511)
07-07 14:05:23.225: E/AndroidRuntime(28851):    at android.view.View$PerformClick.run(View.java:14105)
07-07 14:05:23.225: E/AndroidRuntime(28851):    at android.os.Handler.handleCallback(Handler.java:605)
07-07 14:05:23.225: E/AndroidRuntime(28851):    at android.os.Handler.dispatchMessage(Handler.java:92)
07-07 14:05:23.225: E/AndroidRuntime(28851):    at android.os.Looper.loop(Looper.java:137)
07-07 14:05:23.225: E/AndroidRuntime(28851):    at android.app.ActivityThread.main(ActivityThread.java:4440)
07-07 14:05:23.225: E/AndroidRuntime(28851):    at java.lang.reflect.Method.invokeNative(Native Method)
07-07 14:05:23.225: E/AndroidRuntime(28851):    at java.lang.reflect.Method.invoke(Method.java:511)
07-07 14:05:23.225: E/AndroidRuntime(28851):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:787)
07-07 14:05:23.225: E/AndroidRuntime(28851):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:554)
07-07 14:05:23.225: E/AndroidRuntime(28851):    at dalvik.system.NativeStart.main(Native Method)

213行是

return Uri.fromFile(getOutputMediaFile(type));

如果有人能指出哪里出了問題，我將不勝感激。

Answer 1

您需要先運行媒體掃描器（ ACTION_MEDIA_SCANNER_SCAN_FILE ），然后才能訪問圖像

Intent mediaScanIntent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
mediaScanIntent.setData(fileUri);
getApplicationContext().sendBroadcast(mediaScanIntent);

這實際上是將您的圖像添加到圖庫數據庫。