Question

我通过组合两个图像来创建位图。我现在尝试存储它，保存它，看到它并在应用程序中使用它。

这就是我创建新位图的方法：

        string OnePath = "backgroundimage";
        string TwoPath = "objectimage";

        var OneImage = BitmapFactory.DecodeResource(Resources, Resources.GetIdentifier(OnePath, "drawable", PackageName));
        var TwoImage = BitmapFactory.DecodeResource(Resources, Resources.GetIdentifier(TwoPath, "mipmap", PackageName));

        Bitmap bitmap = OneImage.Copy(Bitmap.Config.Argb8888, true);
        Canvas canvas = new Canvas(bitmap);
        Rect baseRect = new Rect(0, 0, OneImage.Width, OneImage.Height);
        Rect frontRect = new Rect(22, 31, 79, 79);
        canvas.DrawBitmap(TwoImage, frontRect, baseRect, null);

所以我现在想要保存我创建的这个新位图。我试图做的是以下几点：

        var documentsDirectory = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal);
        string jpgFilename = System.IO.Path.Combine(documentsDirectory, OnePath);

        App.AppFileName = System.IO.Path.Combine(documentsDirectory, OnePath);
        System.Diagnostics.Debug.WriteLine(App.AppFileName);

其中App.AppFileName是存储图像路径的字符串。我现在不确定创建的图像是否实际保存在那里。如果我用连接到我的电脑的Android手机打开android文件管理器，我在App.AppFileName路径中看不到该图像。

Answer 1

因为图片是大文件，我建议您将其保存在外部存储空间 Here you can find what is external storage上，路径如：/storage/sdcard/Pictures，我为您制作了一个演示：

using Android.App;
using Android.Widget;
using Android.OS;
using Android.Util;
using Android.Graphics;
using System.IO;

namespace SaveBitmap
{
    [Activity(Label = "SaveBitmap", MainLauncher = true)]
    public class MainActivity : Activity
    {
        string bitmapPath;
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.Main);
            bitmapPath = getPath("bitmap.png");
            Bitmap bitmap = BitmapFactory.DecodeResource(Resources, Resource.Drawable.capture);
            //save bitamp
            saveBitmap(bitmap);
            ImageView iv = FindViewById<ImageView>(Resource.Id.iv);
            //load bitmap
            Bitmap bi = BitmapFactory.DecodeFile(bitmapPath);
            iv.SetImageBitmap(bi);

        }
        public string getPath(string fileName) {
            var sdCardPath = Environment.GetExternalStoragePublicDirectory(Environment.DirectoryPictures);
            Log.Error("lv", sdCardPath.AbsolutePath);
            string filePath = System.IO.Path.Combine(sdCardPath.AbsolutePath, fileName);
            return filePath;

        }
        public void saveBitmap(Bitmap bitmap ) {
            FileStream stream = new FileStream(bitmapPath, FileMode.Create);
            bitmap.Compress(Bitmap.CompressFormat.Png, 100, stream);
            stream.Close();

        }
    }
}

不要忘记在清单中添加这些：

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

如果您在Android 6.0以上运行您的应用，则需要运行时权限。

更新

我添加了运行时权限。

using Android.App;
using Android.Widget;
using Android.OS;
using Android.Util;
using Android.Graphics;
using System.IO;
using System;
using Android;
using Android.Content.PM;
using Android.Runtime;

namespace SaveBitmap
{
    [Activity(Label = "SaveBitmap", MainLauncher = true)]
    public class MainActivity : Activity
    {
        string bitmapPath;
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.Main);
            bitmapPath = getPath("bitmap.png");
            permissionCheck();
        }

        private void permissionCheck()
        {
            if (CheckSelfPermission(Manifest.Permission.ReadExternalStorage) != Permission.Granted)
            {
                // Should we show an explanation? 
                if (ShouldShowRequestPermissionRationale(Manifest.Permission.ReadExternalStorage))
                {
                    // Show an expanation to the user *asynchronously* -- don't block 
                    // this thread waiting for the user's response! After the user 
                    // sees the explanation, try again to request the permission. 
                }
                else
                {
                    // No explanation needed, we can request the permission. 
                    RequestPermissions(new String[] { Manifest.Permission.ReadExternalStorage }, 1);
                    // MY_PERMISSIONS_REQUEST_READ_CONTACTS is an 
                    // app-defined int constant. The callback method gets the 
                    // result of the request. 
                }
            }
            else {
                saveAndLoadBitmap();
            }
        }

        public string getPath(string fileName) {
            var sdCardPath = Android.OS.Environment.GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryPictures);
            Log.Error("lv", sdCardPath.AbsolutePath);
            string filePath = System.IO.Path.Combine(sdCardPath.AbsolutePath, fileName);
            return filePath;

        }
        public void saveBitmap(Bitmap bitmap ) {
            FileStream stream = new FileStream(bitmapPath, FileMode.Create);
            bitmap.Compress(Bitmap.CompressFormat.Png, 100, stream);
            stream.Close();

        }

        public void saveAndLoadBitmap() {
            Bitmap bitmap = BitmapFactory.DecodeResource(Resources, Resource.Drawable.capture);
            saveBitmap(bitmap);
            ImageView iv = FindViewById<ImageView>(Resource.Id.iv);
            Bitmap bi = BitmapFactory.DecodeFile(bitmapPath);
            iv.SetImageBitmap(bi);
        }
        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Permission[] grantResults)
        {
            switch (requestCode)
            {
                case 1:
                    {
                        // If request is cancelled, the result arrays are empty. 
                        if (grantResults.Length > 0 && grantResults[0] == Permission.Granted)
                        {
                            // permission was granted, yay! Do the 
                            // contacts-related task you need to do. 
                            saveAndLoadBitmap();
                        }
                        else
                        {

                            // permission denied, boo! Disable the 
                            // functionality that depends on this permission. 
                        }
                        return;
                    }

                    // other 'case' lines to check for other 
                    // permissions this app might request 
            }
        }
    }
}

如何在Xamarin.Android中保存，访问和使用位图？

1 个答案:

更新