您可以创建自定义绘图来动态更改圆的颜色和半径

import android.graphics.Canvas;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.drawable.Drawable;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;

public class CircleDrawable extends Drawable {

    private Paint circlePaint;
    private int fillColor;
    private int strokeColor;
    private float radius;

    public CircleDrawable(int fillColor, int strokeColor, float radius) {
        this.fillColor = fillColor;
        this.strokeColor = strokeColor;
        this.radius = radius;
        circlePaint=new Paint(Paint.ANTI_ALIAS_FLAG);
    }

    @Override
    public void draw(@NonNull Canvas canvas) {
        int x=getBounds().centerX();
        int y=getBounds().centerY();
        //draw fill color circle
        circlePaint.setStyle(Paint.Style.FILL);
        circlePaint.setColor(fillColor);
        canvas.drawCircle(x,y,radius,circlePaint);
        // draw stroke circle
        circlePaint.setStyle(Paint.Style.STROKE);
        circlePaint.setColor(strokeColor);
        circlePaint.setStrokeWidth(5);
        canvas.drawCircle(x,y,radius,circlePaint);
    }

    @Override
    public void setAlpha(int alpha) {
        circlePaint.setAlpha(alpha);
    }

    @Override
    public void setColorFilter(@Nullable ColorFilter colorFilter) {
         circlePaint.setColorFilter(colorFilter);
    }

    @Override
    public int getOpacity() {
        return PixelFormat.TRANSLUCENT;
    }
}

从UI设置此项以获得圆形

imageView.setImageDrawable(new CircleDrawable(Color.RED,Color.YELLOW,100));

输出将是这样的

只需使用

ShapeDrawable circle = new ShapeDrawable( new  OvalShape() );

查看Android SDK示例。ApiDemos项目中有几个示例：

/ApiDemos/res/可绘制/

黑色_箱.xml形状_5.xml等

对于带有渐变填充的圆，它看起来像这样：

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="oval" >
    <gradient android:startColor="#FFFF0000" android:endColor="#80FF00FF"
            android:angle="270"/>
</shape>

由于某种原因，我无法在ConstraintLayout中画一个圆圈，我只是无法使用上面的任何答案。

当你按下“Alt+7”时，一个简单的文本视图显示了文本，效果很好：

 <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textColor="#0075bc"
            android:textSize="40dp"
            android:text="•"></TextView>

尝试以下带破折号的代码：

<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="oval">
<size
    android:width="@dimen/_60sdp"
    android:height="@dimen/_60sdp" />

<solid android:color="@color/black" />

<stroke
    android:width="@dimen/_1sdp"
    android:color="@color/white"
    android:dashWidth="@dimen/_1sdp"
    android:dashGap="@dimen/_1sdp" />

尝试不带破折号的代码：

<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="oval">

<size
    android:width="@dimen/_60sdp"
    android:height="@dimen/_60sdp" />

<solid android:color="@color/black" />

<stroke
    android:width="@dimen/_1sdp"
    android:color="@color/white" />

将此设置为视图背景

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval">
    <stroke
        android:width="1dp"
        android:color="#78d9ff"/>
</shape>

对于实心圆使用：

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval">
    <solid
        android:color="#48b3ff"/>
</shape>

实心带笔划：

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval">
    <solid android:color="#199fff"/>
    <stroke
        android:width="2dp"
        android:color="#444444"/>
</shape>

注意：要使椭圆形显示为圆形，在这些示例中，使用此形状作为背景的视图应该是正方形，或者必须将形状标记的高度和宽度财产设置为相等的值。