Android中如何将Bitmap适配自定义圆角矩形并保持宽高比？

Got it, let's tackle this non-standard rounded rectangle ImageView issue you're facing. Since RoundedBitmapDrawable only handles circles or uniform rounded corners, we need a custom approach here—here's how to do it step by step, including support for dynamic image updates:

1. Build a Custom Drawable for Non-Uniform Rounded Corners #

We'll create a custom BitmapDrawable that uses Canvas.clipPath to define our exact rounded shape. This lets us set different radii for each corner, matching your attachment's style.

public class CustomRoundRectDrawable extends BitmapDrawable {
    private final Path clipPath;
    private final RectF bitmapBounds;
    private final float[] cornerRadii;

    // Constructor takes corner radii (in dp) for each corner: top-left, top-right, bottom-right, bottom-left
    public CustomRoundRectDrawable(Resources res, Bitmap bitmap, float tlRadius, float trRadius, float brRadius, float blRadius) {
        super(res, bitmap);
        clipPath = new Path();
        bitmapBounds = new RectF();
        
        // Convert dp to pixels for proper scaling across devices
        float density = res.getDisplayMetrics().density;
        cornerRadii = new float[]{
                tlRadius * density, tlRadius * density,
                trRadius * density, trRadius * density,
                brRadius * density, brRadius * density,
                blRadius * density, blRadius * density
        };
    }

    @Override
    protected void onBoundsChange(Rect bounds) {
        super.onBoundsChange(bounds);
        bitmapBounds.set(bounds);
        clipPath.reset();
        // Add our custom rounded rectangle path to the clip
        clipPath.addRoundRect(bitmapBounds, cornerRadii, Path.Direction.CW);
    }

    @Override
    public void draw(Canvas canvas) {
        // Clip the canvas so only the rounded area is drawn
        canvas.clipPath(clipPath);
        super.draw(canvas);
    }
}

2. Keep Your Aspect Ratio Scaling Logic #

Your existing scaleBitmapAndKeepRation method is perfect for preserving the image's original aspect ratio while fitting it to the ImageView. Keep using that:

private Bitmap scaleBitmapAndKeepRation(Bitmap bitmap, int targetWidth, int targetHeight) {
    int originalWidth = bitmap.getWidth();
    int originalHeight = bitmap.getHeight();
    
    float scaleFactor = Math.min(
            (float) targetWidth / originalWidth,
            (float) targetHeight / originalHeight
    );

    Matrix scaleMatrix = new Matrix();
    scaleMatrix.postScale(scaleFactor, scaleFactor);

    return Bitmap.createBitmap(bitmap, 0, 0, originalWidth, originalHeight, scaleMatrix, true);
}

3. Replace the Circular Logic with Custom Rounded Rect #

Update your image loading code to use our new custom drawable instead of RoundedBitmapDrawable. Adjust the corner radii values to match your attachment's style:

// After picking image from gallery
Bitmap FixBitmap = MediaStore.Images.Media.getBitmap(getContentResolver(), uri);

// Get ImageView's target dimensions (convert dp to pixels)
int targetWidth = (int) getResources().getDimension(R.dimen._137sdp);
int targetHeight = (int) getResources().getDimension(R.dimen._150sdp);

// Scale image while keeping aspect ratio
Bitmap scaledBitmap = scaleBitmapAndKeepRation(FixBitmap, targetWidth, targetHeight);

// Create custom drawable with your desired corner radii (example: 20dp top-left, 0dp top-right, 20dp bottom-right, 0dp bottom-left)
CustomRoundRectDrawable customDrawable = new CustomRoundRectDrawable(
        getResources(), 
        scaledBitmap, 
        20f, 0f, 20f, 0f
);

// Set the drawable to your ImageView
p_avatar.setImageDrawable(customDrawable);

4. Support Dynamic Image Updates #

For swapping images dynamically (when the user picks a new photo), just repeat the above steps: fetch the new Bitmap, scale it, create a new CustomRoundRectDrawable, and call p_avatar.setImageDrawable() with the new drawable. It works exactly like your current circular image update flow—just swap the drawable creation part.

5. Alternative: XML Shape Overlay (Less Reliable for Aspect Ratio) #

If your rounded shape is fixed, you could use a shape drawable as the ImageView's foreground, but this can cause image stretching if your scaleType isn't set perfectly. Here's how that looks, but I recommend the custom Drawable approach for better control:

Create drawable/custom_round_rect_overlay.xml:

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <solid android:color="@android:color/transparent" />
    <corners
        android:topLeftRadius="20dp"
        android:topRightRadius="0dp"
        android:bottomRightRadius="20dp"
        android:bottomLeftRadius="0dp" />
</shape>

Update your ImageView XML:

<ImageView
    android:id="@+id/avatar"
    android:layout_width="137dp"
    android:layout_height="150dp"
    android:clickable="true"
    android:paddingTop="@dimen/_10sdp"
    android:paddingBottom="@dimen/_10sdp"
    android:foreground="@drawable/custom_round_rect_overlay"
    android:scaleType="centerCrop" />

That should get you exactly the custom rounded shape you need, while keeping your image's aspect ratio intact and supporting dynamic image swaps.

内容的提问来源于stack exchange，提问作者Marcus Barnet