Saving a byte array as jpg file in android device folder

问题

I am trying to save an image in a folder of the Android device. The code I am using is as follows

var newFolder = AndroidEnvironment.GetExternalStoragePublicDirectory(AndroidEnvironment.DirectoryPictures).AbsolutePath + "/NewFolder";

Directory.CreateDirectory(cameraFolder);

byte[] reducedImage = ResizeImageAndroid(imageData, 50, 50, 70);

Image image = new Image {Source = ImageSource.FromStream(() => new MemoryStream(reducedImage))};

I want to save reduced image as jpg file in "newFolder". I am not sure if I am in right direction, it would be great if I save reducedImage or image as a jpg file in newFolder. I am using Xamarin and this code is in Android project.

I already checked this post and I don't understand whats happening there.

回答1:

Use Directory.CreateDirectory to create your folder in the public Picture directory and FileOutputStream to write your byte[] to a file.

Example:

byte[] reducedImage = `some jpeg-based byte array`

var filename = System.IO.Path.Combine(Environment.GetExternalStoragePublicDirectory(Environment.DirectoryPictures).ToString(), "NewFolder");
Directory.CreateDirectory(filename);
filename = System.IO.Path.Combine(filename, "filename.jpg");
using (var fileOutputStream = new FileOutputStream(filename))
{
    await fileOutputStream.WriteAsync(reducedImage);
}

回答2:

I would just like to share my solution, which I found after some research and worked well.

 var btnSave = FindViewById<Button>(Resource.Id.btnSave);
            btnSave.Click += async delegate
                {
                    if (signature.IsBlank)
                    {
                        // display the base line for the user to sign on.
                        Android.Support.V7.App.AlertDialog.Builder alert = new Android.Support.V7.App.AlertDialog.Builder(this);
                        alert.SetMessage(Resources.GetString(Resource.String.signature_isempty));
                        alert.SetNeutralButton("OK", delegate { });
                        alert.Create().Show();
                    }
                    else
                    {
                        points = signature.Points;
                        try
                        {

                            string nString = String.Format("mySign_{0}.png", Guid.NewGuid());
                            string absolutePath = String.Format("{0}/{1}", Android.OS.Environment.GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryPictures).ToString(), GetString(Resource.String.app_name).ToString());
                            var filePath = System.IO.Path.Combine(absolutePath, nString);

                            /**

                             You can get base64 and save your database
                            **/
                            /*var img = await signature.GetImageStreamAsync(SignatureImageFormat.Jpeg);
                            var signatureMemoryStream = (MemoryStream)img;
                            byte[] data = signatureMemoryStream.ToArray();
                            string base64img = Convert.ToBase64String(data);
                            Log.Info(NativeConfig.TAG_DROID, base64img.ToString());

                            File.WriteAllBytes(filePath, data);*/

                            var img = await signature.GetImageStreamAsync(SignatureImageFormat.Png, Color.Black, Color.White, true);
                            var ms = (MemoryStream)img;
                            using (FileStream file = new FileStream(filePath, FileMode.Create, System.IO.FileAccess.Write))
                            {
                                byte[] bytes = new byte[ms.Length];
                                ms.Read(bytes, 0, (int)ms.Length);
                                file.Write(bytes, 0, bytes.Length);
                                ms.Close();
                            }

                        }
                        catch (Exception e)
                        {
                            Log.Info(NativeConfig.TAG_DROID, e.Message);
                            Toast.MakeText(this, "No se pudo guardar", ToastLength.Short).Show();
                        }
                    }
                };
            btnSave.Dispose();

I adapted the code from the sample page and added the filestream.

来源：https://stackoverflow.com/questions/46103368/saving-a-byte-array-as-jpg-file-in-android-device-folder