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!

如果你不希望边框影响图像，使用这个类。不幸的是，我没有找到任何方法来绘制画布上的透明区域来到onDraw()。这里创建了一个新的位图它是画在一个真实的画布上的。

如果您想要创建一个消失的边界，该视图非常有用。如果你将borderWidth设置为0，边框将会消失，图像仍然保持圆角，就像边界一样。也就是说，它看起来就像边界完全由图像边缘绘制。

import android.annotation.SuppressLint
import android.content.Context
import android.graphics.Bitmap
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.Paint
import android.graphics.PorterDuff
import android.graphics.PorterDuffXfermode
import android.graphics.RectF
import android.util.AttributeSet
import androidx.appcompat.widget.AppCompatImageView


class RoundedImageViewWithBorder @JvmOverloads constructor(
        context: Context,
        attrs: AttributeSet? = null,
        defStyleAttr: Int = 0) : AppCompatImageView(context, attrs, defStyleAttr) {

    var borderColor: Int = 0
        set(value) {
            invalidate()
            field = value
        }
    var borderWidth: Int = 0
        set(value) {
            invalidate()
            field = value
        }
    var cornerRadius: Float = 0f
        set(value) {
            invalidate()
            field = value
        }

    private var bitmapForDraw: Bitmap? = null
    private var canvasForDraw: Canvas? = null
    private val transparentPaint = Paint().apply {
        isAntiAlias = true
        color = Color.TRANSPARENT
        style = Paint.Style.STROKE
        xfermode = PorterDuffXfermode(PorterDuff.Mode.SRC)
    }

    private val borderPaint = Paint().apply {
        isAntiAlias = true
        style = Paint.Style.STROKE
    }

    private val transparentAreaRect = RectF()
    private val borderRect = RectF()

    init {
        val typedArray = context.obtainStyledAttributes(attrs, R.styleable.RoundedImageViewWithBorder)

        try {
            borderWidth = typedArray.getDimensionPixelSize(R.styleable.RoundedImageViewWithBorder_border_width, 0)
            borderColor = typedArray.getColor(R.styleable.RoundedImageViewWithBorder_border_color, 0)
            cornerRadius = typedArray.getDimensionPixelSize(R.styleable.RoundedImageViewWithBorder_corner_radius, 0).toFloat()

        } finally {
            typedArray.recycle()
        }
    }

    @SuppressLint("CanvasSize", "DrawAllocation")
    override fun onDraw(canvas: Canvas) {
        if (canvas.height <=0 || canvas.width <=0) {
            return
        }

        if (canvasForDraw?.height != canvas.height || canvasForDraw?.width != canvas.width) {
            val newBitmap = Bitmap.createBitmap(canvas.width, canvas.height, Bitmap.Config.ARGB_8888)
            bitmapForDraw = newBitmap
            canvasForDraw = Canvas(newBitmap)
        }
        
        bitmapForDraw?.eraseColor(Color.TRANSPARENT)

        // Draw existing content
        super.onDraw(canvasForDraw)

        if (borderWidth > 0) {
            canvasForDraw?.let { drawWithBorder(it) }
        } else {
            canvasForDraw?.let { drawWithoutBorder(it) }
        }

        // Draw everything on real canvas
        bitmapForDraw?.let { canvas.drawBitmap(it, 0f, 0f, null) }
    }

    private fun drawWithBorder(canvas: Canvas) {
        // Draw transparent area
        transparentPaint.strokeWidth = borderWidth.toFloat() * 4
        transparentAreaRect.apply {
            left = -borderWidth.toFloat() * 1.5f
            top = -borderWidth.toFloat() * 1.5f
            right = canvas.width.toFloat() + borderWidth.toFloat() * 1.5f
            bottom = canvas.height.toFloat() + borderWidth.toFloat() * 1.5f
        }
        canvasForDraw?.drawRoundRect(transparentAreaRect, borderWidth.toFloat() * 2 + cornerRadius, borderWidth.toFloat() * 2 + cornerRadius, transparentPaint)

        // Draw border
        borderPaint.color = borderColor
        borderPaint.strokeWidth = borderWidth.toFloat()
        borderRect.apply {
            left = borderWidth.toFloat() / 2
            top = borderWidth.toFloat() / 2
            right = canvas.width.toFloat() - borderWidth.toFloat() / 2
            bottom = canvas.height.toFloat() - borderWidth.toFloat() / 2
        }
        canvas.drawRoundRect(borderRect, cornerRadius - borderWidth.toFloat() / 2, cornerRadius - borderWidth.toFloat() / 2, borderPaint)
    }

    private fun drawWithoutBorder(canvas: Canvas) {
        // Draw transparent area
        transparentPaint.strokeWidth = cornerRadius * 4
        transparentAreaRect.apply {
            left = -cornerRadius * 2
            top = -cornerRadius * 2
            right = canvas.width.toFloat() + cornerRadius * 2
            bottom = canvas.height.toFloat() + cornerRadius * 2
        }
        canvasForDraw?.drawRoundRect(transparentAreaRect, cornerRadius * 3, cornerRadius * 3, transparentPaint)
    }

}

值:

<declare-styleable name="RoundedImageViewWithBorder">
    <attr name="corner_radius" format="dimension|string" />
    <attr name="border_width" format="dimension|reference" />
    <attr name="border_color" format="color|reference" />
</declare-styleable>

让你的ImageView像这样:

<com.example..CircularImageView
    android:id="@+id/profile_image_round_corner"
    android:layout_width="80dp"
    android:layout_height="80dp"
    android:scaleType="fitCenter"
    android:padding="2dp"
    android:background="@null"
    android:adjustViewBounds="true"
    android:layout_centerInParent="true"
    android:src="@drawable/dummy"
    />

并创建一个类:

package com.example;

import java.util.Formatter.BigDecimalLayoutForm;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.widget.ImageView;

public class CircularImageView extends ImageView {

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

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

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

    @Override
    protected void onDraw(Canvas canvas) {

        Drawable drawable = getDrawable();

        if (drawable == null) {
            return;
        }

        if (getWidth() == 0 || getHeight() == 0) {
            return;
        }
        Bitmap b = ((BitmapDrawable) drawable).getBitmap();
        Bitmap bitmap = b.copy(Bitmap.Config.ARGB_8888, true);

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

        Bitmap roundBitmap = getRoundBitmap(bitmap, w);
        canvas.drawBitmap(roundBitmap, 0, 0, null);

    }

    public static Bitmap getRoundBitmap(Bitmap bmp, int radius) {
        Bitmap sBmp;

        if (bmp.getWidth() != radius || bmp.getHeight() != radius) {
            float smallest = Math.min(bmp.getWidth(), bmp.getHeight());
            float factor = smallest / radius;
            sBmp = Bitmap.createScaledBitmap(bmp, (int)(bmp.getWidth() / factor), (int)(bmp.getHeight() / factor), false);
        } else {
            sBmp = bmp;
        }

        Bitmap output = Bitmap.createBitmap(radius, radius, Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(output);
        final int color = 0xffa19774;
        final Paint paint = new Paint();
        final Rect rect = new Rect(0, 0, radius, radius);
        paint.setAntiAlias(true);
        paint.setFilterBitmap(true);
        paint.setDither(true);
        canvas.drawARGB(0, 0, 0, 0);
        paint.setColor(Color.parseColor("#BAB399"));
        canvas.drawCircle(radius / 2 + 0.7f,
                radius / 2 + 0.7f, radius / 2 + 0.1f, paint);
        paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
        canvas.drawBitmap(sBmp, rect, rect, paint);

        return output;
    }

}

相当多的答案!

我遵循了一些人也建议的这个例子:http://www.techrepublic.com/article/pro-tip-round-corners-on-an-android-imageview-with-this-hack/

然而，我需要的是一个透明图像后面的彩色圆圈。对于任何有兴趣做同样事情的人…

1)设置FrameLayout的宽度和高度-在我的情况下，图像的大小(50dp)。 2)将带有src = "@drawable/…"的ImageView放在带有图像的ImageView之上。给它一个id，在我的例子中，我叫它iconShape 3) Drawable mask.xml应该是纯色的#ffffffff 4)如果你想在你的代码中动态地改变圆圈的颜色，可以这样做

ImageView iv2 = (ImageView) v.findViewById(R.id.iconShape);
Drawable shape = getResources().getDrawable(R.drawable.mask);
shape.setColorFilter(Color.BLUE, Mode.MULTIPLY);
iv2.setImageDrawable(shape);

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"
  />

您应该扩展ImageView并绘制自己的圆角矩形。

如果你想在图像周围添加一个框架，你也可以在布局中将圆形框架叠加在图像视图的顶部。

例如，通过使用FrameLayout将帧叠加到原始图像上。FrameLayout的第一个元素将是你想要显示的图像。然后添加另一个ImageView与框架。第二个ImageView将显示在原始ImageView的顶部，因此Android将在原始ImageView上方绘制它的内容。