Android Paint，Path，Canvas

public class PkLeftView extends View {

    private static final String TAG = "GradientLayout";
    private int mW, mH; // 控件，宽高
    Path stampPath = new Path();
    public int startX1, startY1;
    public int startX2, startY2;
    public int startX3, startY3;
    public int startX4, startY4;
    public RectF arcRect;
    private Shader mShader;
    private Bitmap mBitmap;

    private Paint mPaint;
    private Paint mPaintLine;

    private int lineH = PixelDpUtils.dp2px(1); // 画线宽度1/2

    public int xDown = 40; // 折角宽度 X

    public PkLeftView(Context context) {
        this(context, null);
    }

    public PkLeftView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public PkLeftView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        mPaintLine = new Paint(); //初始化
        mPaintLine.setColor(Color.BLACK);// 设置颜色
        mPaintLine.setStyle(Paint.Style.STROKE); //描边效果
        mPaintLine.setAntiAlias(true); // 抗锯齿
        mPaintLine.setStyle(Paint.Style.STROKE); //描边效果
        mPaintLine.setStrokeWidth(lineH * 2);//描边宽度

        mPaint = new Paint(); //初始化
        mPaint.setAntiAlias(true); // 抗锯齿
        mPaint.setStyle(Paint.Style.FILL); //描边效果
        mPaint.setStrokeWidth(lineH * 2);//描边宽度
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        mW = getMeasuredWidth();
        mH = getMeasuredHeight();
        Log.i(TAG, "mW: " + mW);
        Log.i(TAG, "mW: " + mH);
        xDown = mW / 10;
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        Log.i(TAG, "left: " + left);
        Log.i(TAG, "top: " + top);
        Log.i(TAG, "right: " + right);
        Log.i(TAG, "bottom: " + bottom);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        mShader = new LinearGradient(0, 0, 500, 500, new int[]{Color.RED, Color.BLUE, Color.GREEN}, new float[]{0.f, 0.7f, 1}, Shader.TileMode.REPEAT);
        mPaint.setShader(mShader);

        // 1. 首先移动到起始点
        startX1 = mH / 2;
        startY1 = lineH;
        stampPath.moveTo(startX1, startY1);

        // 2. 画水平线
        startX2 = mW - lineH;
        startY2 = lineH;

        stampPath.lineTo(startX2, startY2);

        // 3. 画倒角
        startX3 = startX2 - xDown;
        startY3 = mH - lineH;
        stampPath.lineTo(startX3, startY3);

        // 4. 画下边
        startX4 = mH / 2;
        startY4 = startY3;
        stampPath.lineTo(startX4, startY4);

//        // 5. 画圆弧
        if (arcRect == null) {
            arcRect = new RectF(lineH, lineH, mH - lineH, mH - lineH);
        }
        stampPath.addArc(arcRect, 90, 180);

        // 6. 将Path利用Paint绘制出来
        canvas.drawPath(stampPath, mPaint);

        canvas.save();

        // 7.
        canvas.drawPath(stampPath, mPaintLine);

    }

}

public class GradientLayout extends View {

    private Paint mPaint;
    private Shader mShader;
    private Bitmap mBitmap;

    public GradientLayout(Context context) {
        this(context, null);
    }

    public GradientLayout(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public GradientLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {

        mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.beauty);

        mPaint = new Paint(); //初始化
//        mPaint.setColor(Color.RED);// 设置颜色
//        mPaint.setARGB(255, 255, 255, 0); // 设置 Paint对象颜色,范围为0~255
//        mPaint.setAlpha(200); // 设置alpha不透明度,范围为0~255
        mPaint.setAntiAlias(true); // 抗锯齿
        mPaint.setStyle(Paint.Style.FILL); //描边效果
//        mPaint.setStrokeWidth(4);//描边宽度
//        mPaint.setStrokeCap(Paint.Cap.ROUND); //圆角效果
//        mPaint.setStrokeJoin(Paint.Join.MITER);//拐角风格
//        mPaint.setShader(new SweepGradient(200, 200, Color.BLUE, Color.RED)); //设置环形渲染器
//        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DARKEN)); //设置图层混合模式
//        mPaint.setColorFilter(new LightingColorFilter(0x00ffff, 0x000000)); //设置颜色过滤器
//        mPaint.setFilterBitmap(true); //设置双线性过滤
//        mPaint.setMaskFilter(new BlurMaskFilter(10, BlurMaskFilter.Blur.NORMAL));//设置画笔遮罩滤镜 ,传入度数和样式
//        mPaint.setTextScaleX(2);// 设置文本缩放倍数
//        mPaint.setTextSize(38);// 设置字体大小
//        mPaint.setTextAlign(Paint.Align.LEFT);//对其方式
//        mPaint.setUnderlineText(true);// 设置下划线
//
//        String str = "Android高级工程师";
//        Rect rect = new Rect();
//        mPaint.getTextBounds(str, 0, str.length(), rect); //测量文本大小，将文本大小信息存放在rect中
//        mPaint.measureText(str); //获取文本的宽
//        mPaint.getFontMetrics(); //获取字体度量对象

    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
       /**
        * 1.线性渲染,LinearGradient(float x0, float y0, float x1, float y1, @NonNull @ColorInt int colors[], @Nullable float positions[], @NonNull TileMode tile)
        * (x0,y0)：渐变起始点坐标
        * (x1,y1):渐变结束点坐标
        * color0:渐变开始点颜色,16进制的颜色表示，必须要带有透明度
        * color1:渐变结束颜色
        * colors:渐变数组
        * positions:位置数组，position的取值范围[0,1],作用是指定某个位置的颜色值，如果传null，渐变就线性变化。
        * tile:用于指定控件区域大于指定的渐变区域时，空白区域的颜色填充方法
        */
//        mShader = new LinearGradient(0, 0, 500, 500, new int[]{Color.RED, Color.BLUE, Color.GREEN}, new float[]{0.f,0.7f,1}, Shader.TileMode.REPEAT);
//        mPaint.setShader(mShader);
//        canvas.drawCircle(250, 250, 250, mPaint);
//        canvas.drawRect(0,0,1000,1000, mPaint);

       /**
        * 环形渲染，RadialGradient(float centerX, float centerY, float radius, @ColorInt int colors[], @Nullable float stops[], TileMode tileMode)
        * centerX ,centerY：shader的中心坐标，开始渐变的坐标
        * radius:渐变的半径
        * centerColor,edgeColor:中心点渐变颜色，边界的渐变颜色
        * colors:渐变颜色数组
        * stoops:渐变位置数组，类似扫描渐变的positions数组，取值[0,1],中心点为0，半径到达位置为1.0f
        * tileMode:shader未覆盖以外的填充模式。
        */
//        mShader = new RadialGradient(250, 250, 250, new int[]{Color.GREEN, Color.YELLOW, Color.RED}, null, Shader.TileMode.CLAMP);
//        mPaint.setShader(mShader);
//        canvas.drawCircle(250, 250, 250, mPaint);

        /**
        * 扫描渲染，SweepGradient(float cx, float cy, @ColorInt int color0,int color1)
        * cx,cy 渐变中心坐标
        * color0,color1：渐变开始结束颜色
        * colors，positions：类似LinearGradient,用于多颜色渐变,positions为null时，根据颜色线性渐变
        */
//        mShader = new SweepGradient(250, 250, Color.RED, Color.GREEN);
//        mPaint.setShader(mShader);
//        canvas.drawCircle(250, 250, 250, mPaint);

        /**
        * 位图渲染，BitmapShader(@NonNull Bitmap bitmap, @NonNull TileMode tileX, @NonNull TileMode tileY)
        * Bitmap:构造shader使用的bitmap
        * tileX：X轴方向的TileMode
        * tileY:Y轴方向的TileMode
              REPEAT, 绘制区域超过渲染区域的部分，重复排版
              CLAMP， 绘制区域超过渲染区域的部分，会以最后一个像素拉伸排版
              MIRROR, 绘制区域超过渲染区域的部分，镜像翻转排版
        */
//        mShader = new BitmapShader(mBitmap, Shader.TileMode.REPEAT, Shader.TileMode.MIRROR);
//        mPaint.setShader(mShader);
//        canvas.drawRect(0,0,500, 500, mPaint);
//        canvas.drawCircle(250, 250, 250, mPaint);

        /**
         * 组合渲染，
         * ComposeShader(@NonNull Shader shaderA, @NonNull Shader shaderB, Xfermode mode)
         * ComposeShader(@NonNull Shader shaderA, @NonNull Shader shaderB, PorterDuff.Mode mode)
         * shaderA,shaderB:要混合的两种shader
         * Xfermode mode： 组合两种shader颜色的模式
         * PorterDuff.Mode mode: 组合两种shader颜色的模式
         */
        BitmapShader bitmapShader = new BitmapShader(mBitmap, Shader.TileMode.REPEAT, Shader.TileMode.REPEAT);
        LinearGradient linearGradient = new LinearGradient(0, 0, 1000, 1600, new int[]{Color.RED, Color.GREEN, Color.BLUE}, null, Shader.TileMode.CLAMP);
        mShader = new ComposeShader(bitmapShader, linearGradient, PorterDuff.Mode.MULTIPLY);
        mPaint.setShader(mShader);
        canvas.drawCircle(250, 250, 250, mPaint);
    }
}

mPaint.setStrokeCap(Paint.Cap.ROUND); // 圆角效果