查看带有 xamarin 表单的图像

Question

I should be viewing an image from internal memory.

Code:

public partial class MainPage : ContentPage
{
    static readonly File file = new File(Android.OS.Environment.GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryPictures), "tmp.jpg");

    public MainPage()
    {
        InitializeComponent();
    }

    private void Button_Clicked(object sender, EventArgs e)
    {
        bool exists = file.Exists(); // exists = true
        ImageExample.Source = ImageSource.FromFile(file.Path);
    }
}

xaml:

<StackLayout>
    <Button HeightRequest="100" 
            WidthRequest="200"
            HorizontalOptions="Center" 
            VerticalOptions="Center" 
            Clicked="Button_Clicked"/>
    <Image x:Name="ImageExample" 
           HorizontalOptions="FillAndExpand" 
           VerticalOptions="FillAndExpand"
           WidthRequest="200" 
           HeightRequest="100"/>
</StackLayout>

Why is the image not displayed?

Thanks in advance!

Answer 1

I figured it out. It looks like your app doesn't have permissions to read from file storage.

You should add the line

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

into the AndroidManifest.xml file (located in Properties subfolder of the <your-app-name>.Android folder).

Also, you should add to the MainActivity.cs file:

 using Android;
 using Android.Support.V4.App;
 .... 
    const int OurRequest = 2;

    protected override void OnCreate(Bundle savedInstanceState)
    {
        ....
        var permission = new string[1];
        if (Android.Support.V4.Content.ContextCompat.CheckSelfPermission(this, Manifest.Permission.ReadExternalStorage) != Permission.Granted)
        {
            permission[0] = Manifest.Permission.ReadExternalStorage;
            ActivityCompat.RequestPermissions(this, permission, OurRequest);
        }

Now if you run the app, it will ask about permission and (in case of positive answer, obviously) image will be loaded.