Question

我要在我的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;
}

我添加评论哪里有问题。所以，我做了调试，在这一刻：

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

位图等于null。

有什么问题？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debug检查它。

但是，在第二个解码选项的outWidth和outHeight为-1之后。所以，它设置为默认值。我不知道这一刻发生了什么。

Answer 1

我猜您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 2

您可以尝试BitmapFactory.decodeStream(inputStream, null, options);

Answer 3

从文档中，BitmapFactory.Options的默认构造函数可能会给你这个麻烦：

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options paramter为null（或表现为null），那么结果将为null：

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

如果你这样尝试怎么办：

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);
    }
}

如何从文件管理器获取位图？

4 个答案: