在glide库和RoundedBitmapDrawableFactory类的帮助下，很容易实现。您可能需要创建圆形占位符映像。

    Glide.with(context)
        .load(imgUrl)
        .asBitmap()
        .placeholder(R.drawable.placeholder)
        .error(R.drawable.placeholder)
        .into(new BitmapImageViewTarget(imgProfilePicture) {
            @Override
            protected void setResource(Bitmap resource) {
                RoundedBitmapDrawable drawable = RoundedBitmapDrawableFactory.create(context.getResources(),
                        Bitmap.createScaledBitmap(resource, 50, 50, false));
                drawable.setCornerRadius(10); //drawable.setCircular(true);
                imgProfilePicture.setImageDrawable(drawable);
            }
        });

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;
}

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)

通过使用下面的代码，您可以改变顶部角半径

val image = findViewById<ImageView>(R.id.image)
val curveRadius = 20F

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

    image.outlineProvider = object : ViewOutlineProvider() {

        @RequiresApi(Build.VERSION_CODES.LOLLIPOP)
        override fun getOutline(view: View?, outline: Outline?) {
            outline?.setRoundRect(0, 0, view!!.width, (view.height+curveRadius).toInt(), curveRadius)
        }
    }

    image.clipToOutline = true

}

    /**
 * Background Async task to load user profile picture from url
 */
private class LoadProfileImage extends AsyncTask<String, Void, RoundedBitmapDrawable> {
    ImageView profileImageView;

    public LoadProfileImage(ImageView profileImageView) {
        this.profileImageView = profileImageView;
    }

    protected RoundedBitmapDrawable doInBackground(String... urls) {
        String photoUrl = urls[0];
        RoundedBitmapDrawable profileRoundedDrawable = null;
        try {
            InputStream inputStream = new java.net.URL(photoUrl).openStream();
            Resources res = getResources();

            profileRoundedDrawable = RoundedBitmapDrawableFactory.create(res, inputStream);
            profileRoundedDrawable.setCircular(true);
        } catch (Exception e) {
            Log.e("Error", e.getMessage());
            e.printStackTrace();
        }
        return profileRoundedDrawable;
    }

    protected void onPostExecute(RoundedBitmapDrawable result) {
        profileImageView.setImageDrawable(result);
    }
}

为什么不在draw()中进行剪辑?

以下是我的解决方案:

用剪切扩展RelativeLayout 将ImageView(或其他视图)放入布局中:

代码:

public class RoundRelativeLayout extends RelativeLayout {

    private final float radius;

    public RoundRelativeLayout(Context context, AttributeSet attrs) {
        super(context, attrs);

        TypedArray attrArray = context.obtainStyledAttributes(attrs,
                R.styleable.RoundRelativeLayout);
        radius = attrArray.getDimension(
                R.styleable.RoundRelativeLayout_radius, 0);
    }

    private boolean isPathValid;
    private final Path path = new Path();

    private Path getRoundRectPath() {
        if (isPathValid) {
            return path;
        }

        path.reset();

        int width = getWidth();
        int height = getHeight();
        RectF bounds = new RectF(0, 0, width, height);

        path.addRoundRect(bounds, radius, radius, Direction.CCW);
        isPathValid = true;
        return path;
    }

    @Override
    protected void dispatchDraw(Canvas canvas) {
        canvas.clipPath(getRoundRectPath());
        super.dispatchDraw(canvas);
    }

    @Override
    public void draw(Canvas canvas) {
        canvas.clipPath(getRoundRectPath());
        super.draw(canvas);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

        int oldWidth = getMeasuredWidth();
        int oldHeight = getMeasuredHeight();
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        int newWidth = getMeasuredWidth();
        int newHeight = getMeasuredHeight();
        if (newWidth != oldWidth || newHeight != oldHeight) {
            isPathValid = false;
        }
    }

}