对于圆形边界使用下面的代码

  <com.google.android.material.card.MaterialCardView
                        android:id="@+id/circle"
                        android:layout_width="45dp"
                        android:layout_height="45dp"
                        android:layout_marginStart="5dp"

                        app:cardCornerRadius="25dp"
                        app:strokeColor="@color/colorDarkGreen"

                        app:strokeWidth="1dp">

                        <ImageView
                            android:id="@+id/toolbarProfile"
                            android:scaleType="fitXY"

                            android:layout_width="match_parent"
                            android:layout_height="match_parent"

                            android:src="@drawable/avater" />
                    </com.google.android.material.card.MaterialCardView>

我发现这两种方法在提出可行的解决方案时都非常有用。这是我的合成版本，它与像素无关，允许你有一些正方形的角，其余的角具有相同的半径(这是通常的用例)。 感谢以上两种解决方案:

public static Bitmap getRoundedCornerBitmap(Context context, Bitmap input, int pixels , int w , int h , boolean squareTL, boolean squareTR, boolean squareBL, boolean squareBR  ) {

    Bitmap output = Bitmap.createBitmap(w, h, Config.ARGB_8888);
    Canvas canvas = new Canvas(output);
    final float densityMultiplier = context.getResources().getDisplayMetrics().density;

    final int color = 0xff424242;
    final Paint paint = new Paint();
    final Rect rect = new Rect(0, 0, w, h);
    final RectF rectF = new RectF(rect);

    //make sure that our rounded corner is scaled appropriately
    final float roundPx = pixels*densityMultiplier;

    paint.setAntiAlias(true);
    canvas.drawARGB(0, 0, 0, 0);
    paint.setColor(color);
    canvas.drawRoundRect(rectF, roundPx, roundPx, paint);


    //draw rectangles over the corners we want to be square
    if (squareTL ){
        canvas.drawRect(0, h/2, w/2, h, paint);
    }
    if (squareTR ){
        canvas.drawRect(w/2, h/2, w, h, paint);
    }
    if (squareBL ){
        canvas.drawRect(0, 0, w/2, h/2, paint);
    }
    if (squareBR ){
        canvas.drawRect(w/2, 0, w, h/2, paint);
    }


    paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
    canvas.drawBitmap(input, 0,0, paint);

    return output;
}

我重写了ImageView，把这个放进去，这样我就可以用xml定义它了。 您可能想在这里添加一些super调用所做的逻辑，但我已经对其进行了注释，因为它对我的情况没有帮助。

    @Override
protected void onDraw(Canvas canvas) {
    //super.onDraw(canvas);
        Drawable drawable = getDrawable();

        Bitmap b =  ((BitmapDrawable)drawable).getBitmap() ;
        Bitmap bitmap = b.copy(Bitmap.Config.ARGB_8888, true);

        int w = getWidth(), h = getHeight();


        Bitmap roundBitmap =  CropImageView.getRoundedCornerBitmap( getContext(), bitmap,10 , w, h , true, false,true, false);
        canvas.drawBitmap(roundBitmap, 0,0 , null);
}

希望这能有所帮助!

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;
        }
    }

}

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)

尝试材质组件库并使用ShapeableImageView。 大概是这样的:

Java:

imageView=new ShapeableImageView(context);
imageView.setShapeAppearanceModel(
        imageView.getShapeAppearanceModel()
                 .toBuilder()
                 .setAllCornerSizes(20)
                 .build());

芬兰湾的科特林:

val imageView = ShapeableImageView(context)
imageView.setShapeAppearanceModel(
        imageView.getShapeAppearanceModel()
                 .toBuilder()
                 .setAllCornerSizes(20f)
                 .build())

你可以很容易地使用roundedImageView库:

compile 'com.makeramen:roundedimageview:2.3.0'

然后:

<com.makeramen.roundedimageview.RoundedImageView
  xmlns:app="http://schemas.android.com/apk/res-auto"
  android:id="@+id/img_episode"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:elevation="7dp"
  app:riv_border_color="@color/colorPrimary"
  app:riv_border_width="1dip"
  app:riv_corner_radius="10dip"
  app:riv_mutate_background="true"
  />