如何从相机意图中提取文件URI

Question

我正在查看一些示例，这些示例触发android.media.action.IMAGE_CAPTURE意图并使用类级别变量来存储结果图像。我不想那么做。我认为我应该能够给intent文件的URI然后在它完成时从intent取回那个URI。我正在尝试做这个:

void snapPixButton_Click(object sender, EventArgs e)
{
    Intent cameraIntent = new Intent(MediaStore.ActionImageCapture);
    File file = new File(Home.SnapStorageLocation, string.Format("{0}.jpg", Guid.NewGuid()));
    cameraIntent.PutExtra(MediaStore.ExtraOutput, file.ToURI().ToString());
    StartActivityForResult(cameraIntent, SnapPixIntentRequestCode);
}
protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
    if (requestCode == SnapPixIntentRequestCode && resultCode == Result.Ok)
    {
        URI uri = new URI(data.GetStringExtra(MediaStore.ExtraOutput));
        File file = new File(uri);
        using (Bitmap bitmap = LoadAndResizeBitmap(file.Path, this.ImageView.Width, this.ImageView.Height))
        {
            this.ImageView.SetImageBitmap(bitmap);
        }
    }
}

但是在OnActivityResult中，对data.GetStringExtra(MediaStore.ExtraOutput)的调用导致消息:未知标识符:MediaStore

我做错了什么?我不认为我应该保持类级变量，我应该能够传递数据到一个意图，然后提取它之后，对吗?

Answer 1

我用这种方式检索Uri

    String[] filePathColumn = { MediaStore.Images.Media.DATA };
    Uri imageFilePathUri = null;
    if (cameraImagePath != null) {
        Cursor imageCursor = getContentResolver().query(
            cameraImagePath, filePathColumn, null, null, null);
    if (imageCursor != null && imageCursor.moveToFirst()) {
        int columnIndex = imageCursor.getColumnIndex(filePathColumn[0]);
        String filePath = imageCursor.getString(columnIndex);
        imageCursor.close();
        imageFilePathUri = filePath != null ? Uri
                .parse(filePath) : null;
    }

并以这个Intent

开头

    Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    ContentValues values = new ContentValues(3);
    values.put(MediaStore.Images.Media.MIME_TYPE, "image/jpeg");
    cameraImagePath = getContentResolver().insert(
            MediaStore.Images.Media.EXTERNAL_CONTENT_URI, values);
    takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, cameraImagePath);
    startActivityForResult(takePictureIntent, CAMERA_REQUEST);

Answer 2

我这样做的方式是使用一个新的File对象。在我拍照之前，我先创建一个新文件，这样我就知道用哪个文件了。

我的代码开始在Intent:

var cameraIntent = new Intent(MediaStore.ActionImageCapture);
var availableActivies = PackageManager.QueryIntentActivities(cameraIntent,
                                                             PackageInfoFlags.Permissions);
if (availableActivies != null && availableActivies.Count > 0)
{
    var dir =
        new File(
            Android.OS.Environment.GetExternalStoragePublicDirectory(
                Android.OS.Environment.DirectoryPictures), "Map name");
    if (!dir.Exists())
    {
        dir.Mkdirs();
    }
    _imageFile = new File(dir, string.Format("CP2{0}.jpg", DateTime.Now.Ticks));
    cameraIntent.PutExtra(MediaStore.ExtraOutput, Android.Net.Uri.FromFile(_imageFile));
    StartActivityForResult(cameraIntent,100);
}

然后在Activity Result中，我只需要这样做:

using (Bitmap usedBitmap = BitmapFactory.DecodeFile(_imageFile.AbsolutePath))
{
    _usedImageView = FindViewById<ImageView>(Resource.Id.imageView1);
    _usedImageView.SetImageBitmap(usedBitmap);
    _usedImageView.Dispose();
    usedBitmap.Dispose();
}