Camera的onActivityResult数据为null

Question

我试图使用户能够从他的相机拍摄照片并将其内部存储在内存中，并且可以正常工作。 问题是当我尝试调整该图像的大小时，我创建了一个方法并找到一种方法来实现该目的，但问题是onActivity仅对数据返回null，因此我无法访问它

  public void takePicture() {
    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new      Date());
    File imagesFolder = new File(Environment.getExternalStorageDirectory(), "App");
    imagesFolder.mkdirs();

    Intent imageIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
    File image = new File(imagesFolder, "QR_" + timeStamp + ".jpg");
    Uri uriSavedImage = Uri.fromFile(image);
    uriString=uriSavedImage.toString();
    imageIntent.putExtra(MediaStore.EXTRA_OUTPUT, uriSavedImage);
    startActivityForResult(imageIntent, CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE);

}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode==CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE){
        Uri uri =data.getData();
        changeImageSize(uri,500,500);


    }
}

 private Bitmap changeImageSize(Uri fileUri, int width, int height) {
    Bitmap bitmap = null;
    File imgFile = new File(getRealPathFromURI(getApplicationContext(),fileUri));
    if (imgFile.exists()) {
        bitmap = BitmapFactory.decodeFile(imgFile.getAbsolutePath());
    }
    if (bitmap != null) {
        return bitmap = (Bitmap.createScaledBitmap(bitmap, width, height, false));
    }
    return null;
}



  public String getRealPathFromURI(Context context, Uri contentUri) {
    Cursor cursor = getActivity().getContentResolver().query(contentUri, null, null, null, null);
    cursor.moveToFirst();
    String document_id = cursor.getString(0);
    document_id = document_id.substring(document_id.lastIndexOf(":")+1);
    cursor.close();

    cursor = getActivity().getContentResolver().query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,null
            , MediaStore.Images.Media._ID + " = ? ", new String[]{document_id}, null);
    cursor.moveToFirst();
    String path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));
    cursor.close();

    return path;
}

我试图添加下面的一些解决方案，现在我的getRealPathFromURI方法出现错误，说明了这一点：

Logcat

Attempt to invoke interface method 'boolean android.database.Cursor.moveToFirst()' on a null object reference
java.lang.RuntimeException: Failure delivering result 
ResultInfo{who=null, request=65636, result=-1, data=null} to activity {com.app/com.app.MainPostLogin}: java.lang.NullPointerException: 
Attempt to invoke interface method 'boolean android.database.Cursor.moveToFirst()' on a null object reference

Answer 1

当您将Uri传递给相机时，它不会返回任何数据。 将此文件存储在本地变量File image = new File(imagesFolder, "QR_" + timeStamp + ".jpg"); 并尝试

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode==CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE && resultCode == RESULT_OK){
    changeImageSize(Uri.fromFile(image),500,500);
    }
}

Answer 2

这是我在项目中用来调整图像大小的工作代码。 创建此方法（只需复制粘贴）：

private String decodeFile(String path, int DESIREDWIDTH, int DESIREDHEIGHT) {
    String strMyImagePath = null;
    Bitmap scaledBitmap = null;

    try {
        // Part 1: Decode image
        Bitmap unscaledBitmap = ScalingUtilities.decodeFile(path, DESIREDWIDTH, DESIREDHEIGHT, ScalingUtilities.ScalingLogic.FIT);

        if (!(unscaledBitmap.getWidth() <= DESIREDWIDTH && unscaledBitmap.getHeight() <= DESIREDHEIGHT)) {
            // Part 2: Scale image
            scaledBitmap = ScalingUtilities.createScaledBitmap(unscaledBitmap, DESIREDWIDTH, DESIREDHEIGHT, ScalingUtilities.ScalingLogic.FIT);
        } else {
            unscaledBitmap.recycle();
            return path;
        }

        // Store to tmp file

        String extr = Environment.getExternalStorageDirectory().toString();
        File mFolder = new File(extr + "/TMMFOLDER");
        if (!mFolder.exists()) {
            mFolder.mkdir();
        }

        String s = "tmp.png";

        File f = new File(mFolder.getAbsolutePath(), s);

        strMyImagePath = f.getAbsolutePath();
        FileOutputStream fos = null;
        try {
            fos = new FileOutputStream(f);
            scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 75, fos);
            fos.flush();
            fos.close();
        } catch (FileNotFoundException e) {

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

            e.printStackTrace();
        }

        scaledBitmap.recycle();
    } catch (Throwable e) {
    }

    if (strMyImagePath == null) {
        return path;
    }
    return strMyImagePath;
}

创建此类（只需复制粘贴）：

package com.katariya.pomoc.utils;

/**
 * Created by Danish.sharma on 5/31/2016.
 */
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.BitmapFactory.Options;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;

/**
 * Class containing static utility methods for bitmap decoding and scaling
 *
 * @author
 */
public class ScalingUtilities {

    /**
     * Utility function for decoding an image resource. The decoded bitmap will
     * be optimized for further scaling to the requested destination dimensions
     * and scaling logic.
     *
     * @param res The resources object containing the image data
     * @param resId The resource id of the image data
     * @param dstWidth Width of destination area
     * @param dstHeight Height of destination area
     * @param scalingLogic Logic to use to avoid image stretching
     * @return Decoded bitmap
     */
    public static Bitmap decodeResource(Resources res, int resId, int dstWidth, int dstHeight,
                                        ScalingLogic scalingLogic) {
        Options options = new Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeResource(res, resId, options);
        options.inJustDecodeBounds = false;
        options.inSampleSize = calculateSampleSize(options.outWidth, options.outHeight, dstWidth,
                dstHeight, scalingLogic);
        Bitmap unscaledBitmap = BitmapFactory.decodeResource(res, resId, options);

        return unscaledBitmap;
    }
    public static Bitmap decodeFile(String path, int dstWidth, int dstHeight,
                                    ScalingLogic scalingLogic) {
        Options options = new Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(path, options);
        options.inJustDecodeBounds = false;
        options.inSampleSize = calculateSampleSize(options.outWidth, options.outHeight, dstWidth,
                dstHeight, scalingLogic);
        Bitmap unscaledBitmap = BitmapFactory.decodeFile(path, options);

        return unscaledBitmap;
    }

    /**
     * Utility function for creating a scaled version of an existing bitmap
     *
     * @param unscaledBitmap Bitmap to scale
     * @param dstWidth Wanted width of destination bitmap
     * @param dstHeight Wanted height of destination bitmap
     * @param scalingLogic Logic to use to avoid image stretching
     * @return New scaled bitmap object
     */
    public static Bitmap createScaledBitmap(Bitmap unscaledBitmap, int dstWidth, int dstHeight,
                                            ScalingLogic scalingLogic) {
        Rect srcRect = calculateSrcRect(unscaledBitmap.getWidth(), unscaledBitmap.getHeight(),
                dstWidth, dstHeight, scalingLogic);
        Rect dstRect = calculateDstRect(unscaledBitmap.getWidth(), unscaledBitmap.getHeight(),
                dstWidth, dstHeight, scalingLogic);
        Bitmap scaledBitmap = Bitmap.createBitmap(dstRect.width(), dstRect.height(),
                Config.ARGB_8888);
        Canvas canvas = new Canvas(scaledBitmap);
        canvas.drawBitmap(unscaledBitmap, srcRect, dstRect, new Paint(Paint.FILTER_BITMAP_FLAG));

        return scaledBitmap;
    }

    /**
     * ScalingLogic defines how scaling should be carried out if source and
     * destination image has different aspect ratio.
     *
     * CROP: Scales the image the minimum amount while making sure that at least
     * one of the two dimensions fit inside the requested destination area.
     * Parts of the source image will be cropped to realize this.
     *
     * FIT: Scales the image the minimum amount while making sure both
     * dimensions fit inside the requested destination area. The resulting
     * destination dimensions might be adjusted to a smaller size than
     * requested.
     */
    public static enum ScalingLogic {
        CROP, FIT
    }

    /**
     * Calculate optimal down-sampling factor given the dimensions of a source
     * image, the dimensions of a destination area and a scaling logic.
     *
     * @param srcWidth Width of source image
     * @param srcHeight Height of source image
     * @param dstWidth Width of destination area
     * @param dstHeight Height of destination area
     * @param scalingLogic Logic to use to avoid image stretching
     * @return Optimal down scaling sample size for decoding
     */
    public static int calculateSampleSize(int srcWidth, int srcHeight, int dstWidth, int dstHeight,
                                          ScalingLogic scalingLogic) {
        if (scalingLogic == ScalingLogic.FIT) {
            final float srcAspect = (float)srcWidth / (float)srcHeight;
            final float dstAspect = (float)dstWidth / (float)dstHeight;

            if (srcAspect > dstAspect) {
                return srcWidth / dstWidth;
            } else {
                return srcHeight / dstHeight;
            }
        } else {
            final float srcAspect = (float)srcWidth / (float)srcHeight;
            final float dstAspect = (float)dstWidth / (float)dstHeight;

            if (srcAspect > dstAspect) {
                return srcHeight / dstHeight;
            } else {
                return srcWidth / dstWidth;
            }
        }
    }

    /**
     * Calculates source rectangle for scaling bitmap
     *
     * @param srcWidth Width of source image
     * @param srcHeight Height of source image
     * @param dstWidth Width of destination area
     * @param dstHeight Height of destination area
     * @param scalingLogic Logic to use to avoid image stretching
     * @return Optimal source rectangle
     */
    public static Rect calculateSrcRect(int srcWidth, int srcHeight, int dstWidth, int dstHeight,
                                        ScalingLogic scalingLogic) {
        if (scalingLogic == ScalingLogic.CROP) {
            final float srcAspect = (float)srcWidth / (float)srcHeight;
            final float dstAspect = (float)dstWidth / (float)dstHeight;

            if (srcAspect > dstAspect) {
                final int srcRectWidth = (int)(srcHeight * dstAspect);
                final int srcRectLeft = (srcWidth - srcRectWidth) / 2;
                return new Rect(srcRectLeft, 0, srcRectLeft + srcRectWidth, srcHeight);
            } else {
                final int srcRectHeight = (int)(srcWidth / dstAspect);
                final int scrRectTop = (int)(srcHeight - srcRectHeight) / 2;
                return new Rect(0, scrRectTop, srcWidth, scrRectTop + srcRectHeight);
            }
        } else {
            return new Rect(0, 0, srcWidth, srcHeight);
        }
    }

    /**
     * Calculates destination rectangle for scaling bitmap
     *
     * @param srcWidth Width of source image
     * @param srcHeight Height of source image
     * @param dstWidth Width of destination area
     * @param dstHeight Height of destination area
     * @param scalingLogic Logic to use to avoid image stretching
     * @return Optimal destination rectangle
     */
    public static Rect calculateDstRect(int srcWidth, int srcHeight, int dstWidth, int dstHeight,
                                        ScalingLogic scalingLogic) {
        if (scalingLogic == ScalingLogic.FIT) {
            final float srcAspect = (float)srcWidth / (float)srcHeight;
            final float dstAspect = (float)dstWidth / (float)dstHeight;

            if (srcAspect > dstAspect) {
                return new Rect(0, 0, dstWidth, (int)(dstWidth / srcAspect));
            } else {
                return new Rect(0, 0, (int)(dstHeight * srcAspect), dstHeight);
            }
        } else {
            return new Rect(0, 0, dstWidth, dstHeight);
        }
    }

}

这是调整图像大小的主线

 Bitmap bmp = BitmapFactory.decodeFile(decodeFile(file.toString(), 600, 600));
                                imageView.setImageBitmap(bmp);

看看我的onActivityResult如何以及在哪里使用这些行：

  @Override
    protected void onActivityResult(int requestCode, int resultCode, final Intent data) {
        super.onActivityResult(requestCode, resultCode, data);


        if (requestCode == PICK_IMAGE_REQUEST) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    runOnUiThread(new Runnable() {
                        public void run() {
                            try {
                                Bitmap thumbnail = (Bitmap) data.getExtras().get("data");
                                ByteArrayOutputStream bytes = new ByteArrayOutputStream();
                                thumbnail.compress(Bitmap.CompressFormat.JPEG, 90, bytes);

                                File destination = new File(Environment.getExternalStorageDirectory() + "/Guesp");
                                if (!destination.exists()) {
                                    File f = new File("/sdcard/POMOC/");
                                    f.mkdir();
                                }
                                File file = new File(new File("/sdcard/POMOC/"), System.currentTimeMillis() + ".jpg");

                                FileOutputStream fo;
                                try {
                                    file.createNewFile();
                                    fo = new FileOutputStream(file);
                                    fo.write(bytes.toByteArray());
                                    fo.close();
                                    picturePath = file.toString();
                                } catch (FileNotFoundException e) {
                                    e.printStackTrace();
                                } catch (IOException e) {
                                    e.printStackTrace();
                                }

                                Bitmap bmp = BitmapFactory.decodeFile(decodeFile(file.toString(), 600, 600));
                                img_profilePhoto.setImageBitmap(bmp);
                            } catch (Exception e) {

                                e.printStackTrace();
                            }
                        }
                    });
                }
            }).start();
        }
    }

而已。