下面是一个覆盖imageView的简单示例，然后你也可以在布局设计器中使用它来预览。

public class RoundedImageView extends ImageView {

    public RoundedImageView(Context context) {
        super(context);
    }

    public RoundedImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public RoundedImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    public RoundedImageView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    @Override
    public void setImageDrawable(Drawable drawable) {
        float radius = 0.1f;
        Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
        RoundedBitmapDrawable rid = RoundedBitmapDrawableFactory.create(getResources(), bitmap);
        rid.setCornerRadius(bitmap.getWidth() * radius);
        super.setImageDrawable(rid);
    }
}

这是为了快速解决问题。半径用于所有角落，并基于位图宽度的百分比。

我只是覆盖了setImageDrawable，并使用支持v4方法绘制圆角位图。

用法:

<com.example.widgets.RoundedImageView
        android:layout_width="39dp"
        android:layout_height="39dp"
        android:src="@drawable/your_drawable" />

使用imageView和自定义imageView预览:

我的ImageView圆角小部件的实现，(下||上)大小图像到所需的尺寸。它利用了CaspNZ的代码形式。

public class ImageViewRounded extends ImageView {

    public ImageViewRounded(Context context) {
        super(context);
    }

    public ImageViewRounded(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public ImageViewRounded(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        BitmapDrawable drawable = (BitmapDrawable) getDrawable();

        if (drawable == null) {
            return;
        }

        if (getWidth() == 0 || getHeight() == 0) {
            return; 
        }

        Bitmap fullSizeBitmap = drawable.getBitmap();

        int scaledWidth = getMeasuredWidth();
        int scaledHeight = getMeasuredHeight();

        Bitmap mScaledBitmap;
        if (scaledWidth == fullSizeBitmap.getWidth() && scaledHeight == fullSizeBitmap.getHeight()) {
            mScaledBitmap = fullSizeBitmap;
        } else {
            mScaledBitmap = Bitmap.createScaledBitmap(fullSizeBitmap, scaledWidth, scaledHeight, true /* filter */);
        }

        Bitmap roundBitmap = ImageUtilities.getRoundedCornerBitmap(getContext(), mScaledBitmap, 5, scaledWidth, scaledHeight,
                false, false, false, false);
        canvas.drawBitmap(roundBitmap, 0, 0, null);

    }

}

我使用了一个自定义视图，我在其他视图的顶部布局，它只是画了4个小倒角，颜色与背景相同。

优点:

不分配位图。 适用于任何你想要应用圆角的视图。 适用于所有API级别;)

代码:

public class RoundedCornersView extends View {
    private float mRadius;
    private int mColor = Color.WHITE;
    private Paint mPaint;
    private Path mPath;

    public RoundedCornersView(Context context) {
        super(context);
        init();
    }

    public RoundedCornersView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();

        TypedArray a = context.getTheme().obtainStyledAttributes(
                attrs,
                R.styleable.RoundedCornersView,
                0, 0);

        try {
            setRadius(a.getDimension(R.styleable.RoundedCornersView_radius, 0));
            setColor(a.getColor(R.styleable.RoundedCornersView_cornersColor, Color.WHITE));
        } finally {
            a.recycle();
        }
    }

    private void init() {
        setColor(mColor);
        setRadius(mRadius);
    }

    private void setColor(int color) {
        mColor = color;
        mPaint = new Paint();
        mPaint.setColor(mColor);
        mPaint.setStyle(Paint.Style.FILL);
        mPaint.setAntiAlias(true);

        invalidate();
    }

    private void setRadius(float radius) {
        mRadius = radius;
        RectF r = new RectF(0, 0, 2 * mRadius, 2 * mRadius);
        mPath = new Path();
        mPath.moveTo(0,0);
        mPath.lineTo(0, mRadius);
        mPath.arcTo(r, 180, 90);
        mPath.lineTo(0,0);
        invalidate();
    }

    @Override
    protected void onDraw(Canvas canvas) {

        /*This just draws 4 little inverted corners */

        int w = getWidth();
        int h = getHeight();
        canvas.drawPath(mPath, mPaint);
        canvas.save();
        canvas.translate(w, 0);
        canvas.rotate(90);
        canvas.drawPath(mPath, mPaint);
        canvas.restore();
        canvas.save();
        canvas.translate(w, h);
        canvas.rotate(180);
        canvas.drawPath(mPath, mPaint);
        canvas.restore();
        canvas.translate(0, h);
        canvas.rotate(270);
        canvas.drawPath(mPath, mPaint);
    }
}

这不是确切的答案，但它是一个类似的解决方案。它可能会帮助那些和我有同样遭遇的人。

我的图像是一个应用程序logo，它的背景是透明的，我正在应用XML渐变作为图像背景。我在imageView中添加了必要的padding/margin，然后添加了这个作为我的背景:

<?xml version="1.0" encoding="utf-8"?>
<!-- This file defines the gradient used on the background of the main activity. -->
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape>
            <gradient
                android:type="linear"
                android:startColor="@color/app_color_light_background"
                android:endColor="@color/app_color_disabled"
                android:angle="90" />

            <!-- Round the top corners. -->
            <corners
                android:topLeftRadius="@dimen/radius_small"
                android:topRightRadius="@dimen/radius_small" />
        </shape>
    </item>
</selector>

对于那些使用Glide和Kotlin的，你可以通过扩展RequestBuilder来实现

fun <T> GlideRequest<T>.roundCorners(cornerRadius: Int) =
    apply(RequestOptions().transform(RoundedCorners(cornerRadius)))

并使用as;

 GlideApp.with(context)
            .load(url)
            .roundCorners(context.resources.getDimension(R.dimen.radius_in_dp).toInt())
            .into(imgView)

从材质组件库的1.2.0-alpha03版本开始，有了新的ShapeableImageView。

你可以这样使用:

<com.google.android.material.imageview.ShapeableImageView
    ...
    app:shapeAppearanceOverlay="@style/roundedImageView"
    app:srcCompat="@drawable/ic_image" />

在你的主题。xml:

<style name="roundedImageView" parent="">
    <item name="cornerFamily">rounded</item>
    <item name="cornerSize">8dp</item>
</style>

或通过编程:

float radius = getResources().getDimension(R.dimen.default_corner_radius);
imageView.setShapeAppearanceModel(imageView.getShapeAppearanceModel()
    .toBuilder()
    .setAllCorners(CornerFamily.ROUNDED,radius)
    .build());

使用jetpack compose，您可以使用RoundedCornerShape应用剪辑修饰器:

Image(
    painter = painterResource(R.drawable.xxxx),
    contentDescription = "xxxx",
    contentScale = ContentScale.Crop,            
    modifier = Modifier
        .size(64.dp)
        .clip(RoundedCornerShape(8.dp))             
)