Java 只想在我手机的多媒体资料数据库中添加图像，但其间遇到了一些问题

我是Android Studio的新手。我正在尝试将手机图库中的图像添加到应用程序的数据库中。尝试了不同的方法，但没有成功

下面是应用程序的XML文件

activity_main.xml 应用程序的主java文件

MainActivity.java

---

在活动中，您需要获得用户选择的图像的结果。您已经在startActivityForResult上有了一个良好的开端。比如说：

 @Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
   if (requestCode == RESULT_LOAD_IMAGE && resultCode == AppCompatActivity.RESULT_OK) {
        Uri selectedImage = data.getData();
        ...
    }
    super.onActivityResult(requestCode, resultCode, data);
}

这为您提供了一个可以使用的图像URI，您可以将其存储在数据库中。否则，如果必须存储base64，则可以获得如下结果位图：

public Bitmap getBitmapFromUri(Context context, Uri selectedImage) {
    String[] filePathColumn = { MediaStore.Images.Media.DATA };
    Cursor cursor = context.getContentResolver().query(selectedImage, filePathColumn,
            null, null, null);
    cursor.moveToFirst();
    int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
    String picturePath = cursor.getString(columnIndex);
    cursor.close();
    return (getBitmapFromFileWithCorrectOrientation(picturePath, 4));
}

public Bitmap getBitmapFromFileWithCorrectOrientation(String filePath, int inSampleSize) {
    BitmapFactory.Options bounds = new BitmapFactory.Options();
    bounds.inJustDecodeBounds = true;
    bounds.inSampleSize = inSampleSize;
    BitmapFactory.decodeFile(filePath, bounds);

    BitmapFactory.Options opts = new BitmapFactory.Options();
    opts.inSampleSize = inSampleSize;
    Bitmap bm;
    try {
        bm = BitmapFactory.decodeFile(filePath, opts);
    } catch (OutOfMemoryError e) {
        BitmapFactory.Options opt2 = new BitmapFactory.Options();
        opt2.inSampleSize = inSampleSize * 2;
        bm = BitmapFactory.decodeFile(filePath, opt2);
    }

    int orientation = ExifInterface.ORIENTATION_NORMAL;
    try {
        ExifInterface exif = new ExifInterface(filePath);
        String orientString = exif.getAttribute(ExifInterface.TAG_ORIENTATION);
        orientation = orientString != null ? Integer.parseInt(orientString) :  ExifInterface.ORIENTATION_NORMAL;
    } catch (IOException e) {

    }

    int rotationAngle = 0;
    if (orientation == ExifInterface.ORIENTATION_ROTATE_90) rotationAngle = 90;
    if (orientation == ExifInterface.ORIENTATION_ROTATE_180) rotationAngle = 180;
    if (orientation == ExifInterface.ORIENTATION_ROTATE_270) rotationAngle = 270;

    Matrix matrix = new Matrix();
    matrix.setRotate(rotationAngle, (float) bm.getWidth() / 2, (float) bm.getHeight() / 2);
    return Bitmap.createBitmap(bm, 0, 0, bounds.outWidth, bounds.outHeight, matrix, true);
}

。。。。然后像这样的base64代码

 public String encodeToBase64(Bitmap image, Bitmap.CompressFormat compressFormat, int quality)
{
    ByteArrayOutputStream byteArrayOS = new ByteArrayOutputStream();
    image.compress(compressFormat, quality, byteArrayOS);
    return Base64.encodeToString(byteArrayOS.toByteArray(), Base64.DEFAULT);
}

---

它不是世界上最好的代码，但它可以满足您的需要

什么有效，什么无效？仅仅看一堆代码是很难分辨的我只是想知道如何将图像插入数据库。我陷入了无法将图像存储在数据库中的困境。将它们存储到文件系统，并将它们的路径保存在数据库中。记住使用合适的样本大小。如果用户选择了一个大得离谱的图像，那么当您尝试将Base64存储到数据库中时会遇到异常。你也不想选择太大的样本大小，否则你的图像在再次加载时会显得有点糟糕。

 @Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
   if (requestCode == RESULT_LOAD_IMAGE && resultCode == AppCompatActivity.RESULT_OK) {
        Uri selectedImage = data.getData();
        ...
    }
    super.onActivityResult(requestCode, resultCode, data);
}

public Bitmap getBitmapFromUri(Context context, Uri selectedImage) {
    String[] filePathColumn = { MediaStore.Images.Media.DATA };
    Cursor cursor = context.getContentResolver().query(selectedImage, filePathColumn,
            null, null, null);
    cursor.moveToFirst();
    int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
    String picturePath = cursor.getString(columnIndex);
    cursor.close();
    return (getBitmapFromFileWithCorrectOrientation(picturePath, 4));
}

public Bitmap getBitmapFromFileWithCorrectOrientation(String filePath, int inSampleSize) {
    BitmapFactory.Options bounds = new BitmapFactory.Options();
    bounds.inJustDecodeBounds = true;
    bounds.inSampleSize = inSampleSize;
    BitmapFactory.decodeFile(filePath, bounds);

    BitmapFactory.Options opts = new BitmapFactory.Options();
    opts.inSampleSize = inSampleSize;
    Bitmap bm;
    try {
        bm = BitmapFactory.decodeFile(filePath, opts);
    } catch (OutOfMemoryError e) {
        BitmapFactory.Options opt2 = new BitmapFactory.Options();
        opt2.inSampleSize = inSampleSize * 2;
        bm = BitmapFactory.decodeFile(filePath, opt2);
    }

    int orientation = ExifInterface.ORIENTATION_NORMAL;
    try {
        ExifInterface exif = new ExifInterface(filePath);
        String orientString = exif.getAttribute(ExifInterface.TAG_ORIENTATION);
        orientation = orientString != null ? Integer.parseInt(orientString) :  ExifInterface.ORIENTATION_NORMAL;
    } catch (IOException e) {

    }

    int rotationAngle = 0;
    if (orientation == ExifInterface.ORIENTATION_ROTATE_90) rotationAngle = 90;
    if (orientation == ExifInterface.ORIENTATION_ROTATE_180) rotationAngle = 180;
    if (orientation == ExifInterface.ORIENTATION_ROTATE_270) rotationAngle = 270;

    Matrix matrix = new Matrix();
    matrix.setRotate(rotationAngle, (float) bm.getWidth() / 2, (float) bm.getHeight() / 2);
    return Bitmap.createBitmap(bm, 0, 0, bounds.outWidth, bounds.outHeight, matrix, true);
}

 public String encodeToBase64(Bitmap image, Bitmap.CompressFormat compressFormat, int quality)
{
    ByteArrayOutputStream byteArrayOS = new ByteArrayOutputStream();
    image.compress(compressFormat, quality, byteArrayOS);
    return Base64.encodeToString(byteArrayOS.toByteArray(), Base64.DEFAULT);
}