对于上面提到的乔治·沃尔特斯二世，我只是把他的答案扩展了一下，以支持不同的圆角。这可以进一步优化(一些目标矩形重叠)，但不是很多。

我知道这个线程有点老了，但它是谷歌上关于如何在Android上圆角ImageViews的查询的顶级结果之一。

/**
 * Use this method to scale a bitmap and give it specific rounded corners.
 * @param context Context object used to ascertain display density.
 * @param bitmap The original bitmap that will be scaled and have rounded corners applied to it.
 * @param upperLeft Corner radius for upper left.
 * @param upperRight Corner radius for upper right.
 * @param lowerRight Corner radius for lower right.
 * @param lowerLeft Corner radius for lower left.
 * @param endWidth Width to which to scale original bitmap.
 * @param endHeight Height to which to scale original bitmap.
 * @return Scaled bitmap with rounded corners.
 */
public static Bitmap getRoundedCornerBitmap(Context context, Bitmap bitmap, float upperLeft,
        float upperRight, float lowerRight, float lowerLeft, int endWidth,
        int endHeight) {
    float densityMultiplier = context.getResources().getDisplayMetrics().density;

    // scale incoming bitmap to appropriate px size given arguments and display dpi
    bitmap = Bitmap.createScaledBitmap(bitmap, 
            Math.round(endWidth * densityMultiplier),
            Math.round(endHeight * densityMultiplier), true);

    // create empty bitmap for drawing
    Bitmap output = Bitmap.createBitmap(
            Math.round(endWidth * densityMultiplier),
            Math.round(endHeight * densityMultiplier), Config.ARGB_8888);

    // get canvas for empty bitmap
    Canvas canvas = new Canvas(output);
    int width = canvas.getWidth();
    int height = canvas.getHeight();

    // scale the rounded corners appropriately given dpi
    upperLeft *= densityMultiplier;
    upperRight *= densityMultiplier;
    lowerRight *= densityMultiplier;
    lowerLeft *= densityMultiplier;

    Paint paint = new Paint();
    paint.setAntiAlias(true);
    paint.setColor(Color.WHITE);

    // fill the canvas with transparency
    canvas.drawARGB(0, 0, 0, 0);

    // draw the rounded corners around the image rect. clockwise, starting in upper left.
    canvas.drawCircle(upperLeft, upperLeft, upperLeft, paint);
    canvas.drawCircle(width - upperRight, upperRight, upperRight, paint);
    canvas.drawCircle(width - lowerRight, height - lowerRight, lowerRight, paint);
    canvas.drawCircle(lowerLeft, height - lowerLeft, lowerLeft, paint);

    // fill in all the gaps between circles. clockwise, starting at top.
    RectF rectT = new RectF(upperLeft, 0, width - upperRight, height / 2);
    RectF rectR = new RectF(width / 2, upperRight, width, height - lowerRight);
    RectF rectB = new RectF(lowerLeft, height / 2, width - lowerRight, height);
    RectF rectL = new RectF(0, upperLeft, width / 2, height - lowerLeft);

    canvas.drawRect(rectT, paint);
    canvas.drawRect(rectR, paint);
    canvas.drawRect(rectB, paint);
    canvas.drawRect(rectL, paint);

    // set up the rect for the image
    Rect imageRect = new Rect(0, 0, width, height);

    // set up paint object such that it only paints on Color.WHITE
    paint.setXfermode(new AvoidXfermode(Color.WHITE, 255, AvoidXfermode.Mode.TARGET));

    // draw resized bitmap onto imageRect in canvas, using paint as configured above
    canvas.drawBitmap(bitmap, imageRect, imageRect, paint);

    return output;
}

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))             
)

虽然前两个答案是可行的，但我希望再多描述一点。 比如说，ImageView所在的地方有一个活动或片段。您希望绘制图像并按比例缩放。然后你应该在onCreate或onCreateView中写入如下代码:

LinearLayout rootLayout = (LinearLayout) findViewById(R.id.rootLayout);
ImageView image = (ImageView) findViewById(R.id.image);
// Wait till an activity is visible and image can be measured.
rootLayout.post(new Runnable() {
    @Override
    public void run() {
        // Setting ImageView height with aspect ratio.
        Drawable drawable = ContextCompat.getDrawable(getActivity(), R.drawable.your_image);
        int height = getImageViewHeight(drawable, image);

        // Rounding image corners.
        float radius = getResources().getDimension(R.dimen.your_radius_in_dp);
        Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
        Bitmap result = getRoundedBitmap(bitmap, image.getWidth(), height, radius);
        image.setImageBitmap(result);
    }
});

其中设置新的图像高度为:

public static int getImageViewHeight(Drawable drawable, ImageView imageView) {
    imageView.setImageDrawable(drawable);
    int width = drawable.getIntrinsicWidth();
    int height = 0;
    if (width > 0) {
        height = (drawable.getIntrinsicHeight() * imageView.getWidth()) / width;
        imageView.getLayoutParams().height = height;
        imageView.requestLayout();
    }
    return height;
}

然后，您应该编写一个方法来缩放图像并使其圆角。这里的width和height是位图的新维度(更小或更大)。在下面的例子中，我只圆角上的两个角。

private Bitmap getRoundedBitmap(Bitmap bitmap, int width, int height, float radius) {
    // Create scaled bitmap.
    Bitmap scaledBitmap = Bitmap.createScaledBitmap(bitmap, width, height, false);
    BitmapShader shader = new BitmapShader(scaledBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);

    Paint paint = new Paint();
    paint.setAntiAlias(true);
    paint.setShader(shader);

    Bitmap result = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(result);
    // First make all corners round.
    canvas.drawRoundRect(new RectF(0, 0, width, height), radius, radius, paint);
    // Then draw bottom rectangle.
    canvas.drawRect(0, height - radius, radius, height, paint);
    canvas.drawRect(width - radius, height - radius, width, height, paint);
    return result;
}

因为所有的答案对我来说都太复杂了，只是为了圆角，我想到了另一个解决方案，我认为值得分享，只是XML，以防你在图像周围有一些空间:

创建一个带有透明内容的带边框的形状，如下所示:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <corners 
        android:radius="30dp" />
    <stroke 
        android:color="#ffffffff"
        android:width="10dp" />
</shape> 

然后在RelativeLayout中，你可以先放置你的图像，然后在相同的位置上面的形状与另一个ImageView。封面形状的大小应与边框宽度相等。注意，要取一个较大的角半径，因为外半径已被定义，但内半径是覆盖你的图像。

希望它也能帮助到别人。

根据CQM请求编辑相关布局示例:

<?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" >

    <ImageView
        android:id="@+id/imageToShow"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/imgCorners"
        android:layout_alignLeft="@+id/imgCorners"
        android:layout_alignRight="@+id/imgCorners"
        android:layout_alignTop="@+id/imgCorners"
        android:background="#ffffff"
        android:contentDescription="@string/desc"
        android:padding="5dp"
        android:scaleType="centerCrop" />

    <ImageView
        android:id="@+id/imgCorners"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:adjustViewBounds="true"
        android:contentDescription="@string/desc"
        android:src="@drawable/corners_white" />

</RelativeLayout>

答案中提供的方法没有一个对我有用。我发现如果你的android版本是5.0或以上，以下方法是有效的:

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {

    ViewOutlineProvider provider = new ViewOutlineProvider() {
        @Override
        public void getOutline(View view, Outline outline) {
            int curveRadius = 24;
            outline.setRoundRect(0, 0, view.getWidth(), (view.getHeight()+curveRadius), curveRadius);
        }
    };
    imageview.setOutlineProvider(provider);
    imageview.setClipToOutline(true);
}

不需要定义xml形状，上面的代码只为顶部创建角，这是普通方法无法实现的。如果你需要4个圆角，移除:

"+ curveRadius"  

从setRoundRect中底部的参数。您可以通过指定适合您需要的轮廓来进一步将该形状扩展到任何其他形状。请查看以下链接:

Android开发者文档。

注意，与Android中的任何度量一样，你必须从DP“转换”大小。在上面的例子中，假设你想让半径为24

                            int curveRadius = 24;

例如，您可能稍后在可绘制对象中添加半径设置为“24”的边界，并希望它与之匹配。因此,

    float desiredRadius = 24;
    float radiusConverted = TypedValue.applyDimension(
            TypedValue.COMPLEX_UNIT_DIP,
            desiredRadius,
            itemView.getContext().getResources().getDisplayMetrics());

然后

                            int curveRadius = radiusConverted;

科特林

import android.graphics.BitmapFactory
import android.os.Bundle
import android.support.v4.graphics.drawable.RoundedBitmapDrawableFactory
import kotlinx.android.synthetic.main.activity_main.*

val bitmap = BitmapFactory.decodeResource(resources, R.drawable.myImage)
val rounded = RoundedBitmapDrawableFactory.create(resources, bitmap)
rounded.cornerRadius = 20f
profileImageView.setImageDrawable(rounded)

为了使ImageView成为圆形，我们可以改变拐角半径:

rounded.isCircular = true