如何动态设置VideoView与ImageView的边距、宽度和高度？

Hey there! I totally get the frustration—most Android image display guides are written for native Android Studio (Java/Kotlin), so they don’t play nicely with Xamarin’s C# environment. Let’s fix that by walking through exactly how to show images from Android resources or the filesystem in your Main.axml layout.

1. Displaying an Image from Android Resources #

This is the simplest case for static images bundled with your app.

Step 1: Add the Image to Your Project #

• Place your image file (e.g., my_photo.png) in the Resources/drawable folder of your Xamarin.Android project.
  • Important: Use lowercase filenames with no spaces or special characters (e.g., my_photo.png instead of My Photo!.png).

Step 2: Reference the Image in Main.axml #

You can set the image directly in XML or dynamically via C#.

XML Approach

Update your Main.axml to include an ImageView with the android:src attribute pointing to your drawable:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <!-- Static ImageView from resources -->
    <ImageView
        android:id="@+id/resourceImageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/my_photo" /> <!-- No file extension needed -->

</RelativeLayout>

C# Dynamic Approach

If you need to change the image at runtime, use this code in your MainActivity.cs:

protected override void OnCreate(Bundle savedInstanceState)
{
    base.OnCreate(savedInstanceState);
    SetContentView(Resource.Layout.Main);

    // Get reference to the ImageView
    ImageView resourceImageView = FindViewById<ImageView>(Resource.Id.resourceImageView);
    // Set the image from resources
    resourceImageView.SetImageResource(Resource.Drawable.my_photo);
}

2. Displaying an Image from the Filesystem #

For images stored on the device’s internal or external storage, we’ll use BitmapFactory to load the file.

Step 1: Add Permissions #

First, ensure your app has permission to read external storage. Add these lines to AndroidManifest.xml:

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<!-- Add this if you need to write to storage too -->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

Note: For Android 6.0 (API 23+) and above, you’ll also need to request these permissions dynamically at runtime.

Step 2: Load the Image via C# #

Use BitmapFactory.DecodeFile to load the image file and set it to your ImageView:

protected override void OnCreate(Bundle savedInstanceState)
{
    base.OnCreate(savedInstanceState);
    SetContentView(Resource.Layout.Main);

    ImageView fileImageView = FindViewById<ImageView>(Resource.Id.fileImageView);
    // Example path: External storage root + your image file
    string imageFilePath = Path.Combine(Android.OS.Environment.ExternalStorageDirectory.AbsolutePath, "my_external_photo.png");

    // Load the bitmap
    Bitmap imageBitmap = BitmapFactory.DecodeFile(imageFilePath);
    // Set it to the ImageView
    fileImageView.SetImageBitmap(imageBitmap);
}

Optional: Compress Large Images #

To avoid OutOfMemory errors with big images, add compression options:

BitmapFactory.Options options = new BitmapFactory.Options();
options.InSampleSize = 2; // Reduces image size to 1/2 of original (adjust as needed)
Bitmap compressedBitmap = BitmapFactory.DecodeFile(imageFilePath, options);
fileImageView.SetImageBitmap(compressedBitmap);

Key Difference from Android Studio Code #

The main reason your previous code didn’t work is that Xamarin uses C# syntax instead of Java. For example:

• Java: imageView.setImageResource(R.drawable.my_photo);
• Xamarin C#: imageView.SetImageResource(Resource.Drawable.my_photo);

Capitalization and namespace differences matter!

内容的提问来源于stack exchange，提问作者Luiey