如何从文件管理器中获取位图？

Question

我将在我的 android 应用程序中创建附件。我需要附上图片。这是我的代码：

...
attachButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
            intent.setType("image/*");
            startActivityForResult(Intent.createChooser(intent, "Select image"), CHOOSE_IMAGE);
        }
    });
...


@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if(requestCode == CHOOSE_IMAGE) {
        if(resultCode == RESULT_OK) {
            Uri uri = data.getData();
            ImageView imageView = new ImageView(this);

            Bitmap bitmap = getDecodedImageFromUri(uri);
            imageView.setImageBitmap(bitmap);
         }
    }
 }

 private Bitmap getDecodedImageFromUri(Uri uri) {
    InputStream inputStream = null;
    try {
        inputStream = getContentResolver().openInputStream(uri);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
    Rect rect = new Rect(0, 0, 0, 0);
    BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;

    BitmapFactory.decodeStream(inputStream, rect, options);
    options.inSampleSize = getInSampleSize(options, 128, 128);

    options.inJustDecodeBounds = false;
    Bitmap bitmap = BitmapFactory.decodeStream(inputStream, rect, options); //HERE IS PROBLEM - bitmap = null.
    return bitmap;
}

private int getInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
    int width = options.outWidth;
    int height = options.outHeight;
    int inSampleSize = 1;

    if(height > reqHeight || width > reqWidth) {
        int halfHeight = height / 2;
        int halfWidth = width / 2;

        while ((halfHeight / inSampleSize) > reqHeight &&
                (halfWidth / inSampleSize) > reqWidth) {
            inSampleSize *= 2;
        }
    }

    return inSampleSize;
}

我在问题的地方添加评论。所以，我调试了一下，在这一刻：

 Bitmap bitmap = BitmapFactory.decodeStream(inputStream, rect, options);

位图等于空。

有什么问题吗？我做错了什么？

如您所见，这些辅助方法来自 android 开发人员指南。

已更新

我需要解码两次，因为我需要获取选项，然后获取图像大小来计算 InSampleSize 以压缩此图像。

第二次，选项不等于 null - 我通过调试检查了它。

但是，在第二次解码选项后，outWidth 和 outHeight 为 -1。所以，它设置为默认值。我不知道这一刻会发生什么。

Answer 1

你可以试试BitmapFactory.decodeStream(inputStream, null, options);

Answer 2

我猜你的问题可能是因为调用 decodeStream 两次

BitmapFactory.decodeStream(inputStream, rect, options); //HERE
options.inSampleSize = getInSampleSize(options, 128, 128);

options.inJustDecodeBounds = false;
Bitmap bitmap = BitmapFactory.decodeStream(inputStream, rect, options); //HERE AGAIN
return bitmap;

Answer 3

根据文档，BitmapFactory.Options 的默认构造函数可能会给您带来这个麻烦：

BitmapFactory.Options() Create a default Options object, which if left unchanged will give the same result from the decoder as if null were passed.

如果选项参数为空（或行为为空），则结果将为空：

The decoded bitmap, or null if the image data could not be decoded, or, if opts is non-null, if opts requested only the size be returned (in opts.outWidth and opts.outHeight)

尝试制作更好的选项对象或使用方法

public static Bitmap decodeStream (InputStream is)

Answer 4

如果你这样尝试会怎样：

protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
    super.onActivityResult(requestCode, resultCode, data);
    if (resultCode == RESULT_OK)
    {
        Uri imageUri = data.getData();
        Bitmap bitmap = MediaStore.Images.Media.getBitmap(this.getContentResolver(), imageUri);
    }
}

如何从文件管理器中获取位图？

How to get bitmap from file manager?

android

bitmap

android-intent

bitmapfactory