Android自定义Drawable，增加渐变阴影、部分渐变（圆角、部分圆角、圆形）

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自定义Drawable，增加渐变阴影、部分渐变（圆角、部分圆角、圆形）

一、先上效果图

效果图

二、思路

1、圆角
     1）绘制shadow
   * 2）绘制遮挡部分shadow
     3）绘制圆角图
2、部分圆角
     1）绘制shadow
   * 2）绘制遮挡部分shadow
     3）绘制圆角图
     4）绘制遮挡部分圆角
3、圆形
     1）绘制shadow
   * 2）绘制遮挡部分shadow
     3）绘制圆形图

四、实现

1）设置paint

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 /**
 * 阴影paint
 */
mShadowPaint = new Paint();
mShadowPaint.setAntiAlias(true);
mShadowPaint.setShadowLayer(shadowRadius, 0, 0, shadowColor);
/**
 * 覆盖部分背景的paint
 */
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));
/**
 * 背景paint
 */
mBgPaint = new Paint();
mBgPaint.setAntiAlias(true);
/**
 * 覆盖部分圆角的paint
 */
mBgPartPaint = new Paint();
mBgPartPaint.setAntiAlias(true);

图像合成效果示意图

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设置 覆盖部分背景的paint  DST_OUT  显示不重叠的部分

2）根据类型设置RectF

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  ***** 根据类型设置RectF ******

@Override
   public void setBounds(int left, int top, int right, int bottom) {
       super.setBounds(left, top, right, bottom);
       switch (type) {
           case All:
               left = left + mShadowRadius;
               top = top + mShadowRadius;
               right = right - mShadowRadius;
               bottom = bottom - mShadowRadius;
               break;
           case TOP:
           case BOTTOM:
               top = top + mShadowRadius;
               bottom = bottom - mShadowRadius;
               break;
           case LEFT:
           case RIGHT:
               left = left + mShadowRadius;
               right = right - mShadowRadius;
               break;
           default:
               break;
       }
       mRect = new RectF(left, top, right, bottom);
   }

3）根据类型设置覆盖阴影/圆角 的 RectF

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/**
 * 设置覆盖阴影/圆角 的 RectF
 */
RectF rect = new RectF();
RectF rect1 = new RectF();
switch (type) {
    case All:
        rect.left = 0;
        rect.right = 0;
        rect.top = 0;
        rect.bottom = 0;
        break;
    case TOP:
        rect.left = mRect.left;
        rect.right = mRect.right;
        rect.top = mRect.height() / 2;
        rect.bottom = mRect.bottom + mShadowRadius;
        rect1.left = mRect.left;
        rect1.right = mRect.right;
        rect1.top = mRect.height() / 2;
        rect1.bottom = mRect.bottom;
        break;
    case BOTTOM:
        rect.left = mRect.left;
        rect.right = mRect.right;
        rect.top = mRect.top - mShadowRadius;
        rect.bottom = mRect.height() / 2;

        rect1.left = mRect.left;
        rect1.right = mRect.right;
        rect1.top = mRect.top;
        rect1.bottom = mRect.height() / 2;

        break;
    case LEFT:
        rect.left = mRect.width() / 2;
        rect.right = mRect.right + mShadowRadius;
        rect.top = mRect.top;
        rect.bottom = mRect.bottom;

        rect1.left = mRect.width() / 2;
        rect1.right = mRect.right ;
        rect1.top = mRect.top;
        rect1.bottom = mRect.bottom;

        break;
    case RIGHT:
        rect.left = mRect.left-mShadowRadius;
        rect.right = mRect.width() / 2;
        rect.top = mRect.top;
        rect.bottom = mRect.bottom;

        rect1.left = mRect.left;
        rect1.right = mRect.width() / 2;
        rect1.top = mRect.top;
        rect1.bottom = mRect.bottom;
        break;

    default:
        break;
}

4）根据 类型绘制 背景

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if (mShape == SHAPE_ROUND) {
      /**
       * 绘制全圆角阴影
       */
      canvas.drawRoundRect(mRect, mShapeRadius, mShapeRadius, mShadowPaint);//绘制阴影
      canvas.drawRect(rect, mPaint);//绘制不需显示阴影部分的遮盖
      canvas.drawRoundRect(mRect, mShapeRadius, mShapeRadius, mBgPaint);//绘制中心的图
  } else if (mShape == SHAPE_ROUND_PART) {
      /**
       * 绘制部分圆角阴影
       */
      canvas.drawRoundRect(mRect, mShapeRadius, mShapeRadius, mShadowPaint);//绘制阴影
      canvas.drawRect(rect, mPaint);//绘制不需显示阴影部分的遮盖
      canvas.drawRoundRect(mRect, mShapeRadius, mShapeRadius, mBgPaint);//绘制中心的图
      canvas.drawRect(rect1, mBgPartPaint);//绘制不需显示圆角的部分
  } else {
      /**
       * 绘制圆形阴影
       */
      canvas.drawCircle(mRect.centerX(), mRect.centerY(), Math.min(mRect.width(), mRect.height()) / 2, mShadowPaint);//绘制带阴影的圆形
      canvas.drawRect(rect, mPaint);//绘制不需显示阴影部分的遮盖
      canvas.drawCircle(mRect.centerX(), mRect.centerY(), Math.min(mRect.width(), mRect.height()) / 2, mBgPaint);//绘制中心圆
  }

4）使用（就是这么简单）

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ShadowDrawableUtil.setShadowDrawable(round_tv, ShadowDrawableUtil.TypeEnum.LEFT);
ShadowDrawableUtil.setShadowDrawableTop(round_part_tv,"#A6000000");
ShadowDrawableUtil.setShadowDrawableCircle(circle_tv);

6）RoundImageView完整代码

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/**
 * view 添加阴影
 */
public class ShadowDrawableUtil extends Drawable {

    private Paint mShadowPaint;
    private Paint mBgPaint;
    private Paint mPaint;
    private Paint mBgPartPaint;
    private int mShadowRadius;
    private int mShape;
    private int mShapeRadius;
    private int mBgColor[];
    private RectF mRect;
    private TypeEnum type;
    private static int SHAPE_ROUND = 1;
    private static int SHAPE_CIRCLE = 2;
    private static int SHAPE_ROUND_PART = 3;

    public enum TypeEnum {
        All,
        LEFT,
        TOP,
        RIGHT,
        BOTTOM
    }


    private ShadowDrawableUtil(int shape, TypeEnum type, int[] bgColor, int shapeRadius, int shadowColor, int shadowRadius) {
        this.mShape = shape;
        this.type = type;
        this.mBgColor = bgColor;
        this.mShapeRadius = shapeRadius;
        this.mShadowRadius = shadowRadius;
        /**
         * 阴影paint
         */
        mShadowPaint = new Paint();
        mShadowPaint.setAntiAlias(true);
        mShadowPaint.setShadowLayer(shadowRadius, 0, 0, shadowColor);
        /**
         * 覆盖部分背景的paint
         */
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));
        /**
         * 背景paint
         */
        mBgPaint = new Paint();
        mBgPaint.setAntiAlias(true);
        /**
         * 覆盖部分圆角的paint
         */
        mBgPartPaint = new Paint();
        mBgPartPaint.setAntiAlias(true);
    }

    @Override
    public void setBounds(int left, int top, int right, int bottom) {
        super.setBounds(left, top, right, bottom);
        switch (type) {
            case All:
                left = left + mShadowRadius;
                top = top + mShadowRadius;
                right = right - mShadowRadius;
                bottom = bottom - mShadowRadius;
                break;
            case TOP:
            case BOTTOM:
                top = top + mShadowRadius;
                bottom = bottom - mShadowRadius;
                break;
            case LEFT:
            case RIGHT:
                left = left + mShadowRadius;
                right = right - mShadowRadius;
                break;
            default:
                break;
        }


        mRect = new RectF(left, top, right, bottom);
    }

    @Override
    public void draw(@NonNull Canvas canvas) {
        if (mBgColor != null) {
            if (mBgColor.length == 1) {
                mBgPaint.setColor(mBgColor[0]);
                mShadowPaint.setColor(mBgColor[0]);
                mBgPartPaint.setColor(mBgColor[0]);
            } else {
                mBgPaint.setShader(new LinearGradient(mRect.left, mRect.height() / 2, mRect.right,
                        mRect.height() / 2, mBgColor, null, Shader.TileMode.CLAMP));
            }
        }
        /**
         * 设置覆盖阴影/圆角 的 RectF
         */
        RectF rect = new RectF();
        RectF rect1 = new RectF();
        switch (type) {
            case All:
                rect.left = 0;
                rect.right = 0;
                rect.top = 0;
                rect.bottom = 0;
                break;
            case TOP:
                rect.left = mRect.left;
                rect.right = mRect.right;
                rect.top = mRect.height() / 2;
                rect.bottom = mRect.bottom + mShadowRadius;
                rect1.left = mRect.left;
                rect1.right = mRect.right;
                rect1.top = mRect.height() / 2;
                rect1.bottom = mRect.bottom;
                break;
            case BOTTOM:
                rect.left = mRect.left;
                rect.right = mRect.right;
                rect.top = mRect.top - mShadowRadius;
                rect.bottom = mRect.height() / 2;

                rect1.left = mRect.left;
                rect1.right = mRect.right;
                rect1.top = mRect.top;
                rect1.bottom = mRect.height() / 2;

                break;
            case LEFT:
                rect.left = mRect.width() / 2;
                rect.right = mRect.right + mShadowRadius;
                rect.top = mRect.top;
                rect.bottom = mRect.bottom;

                rect1.left = mRect.width() / 2;
                rect1.right = mRect.right ;
                rect1.top = mRect.top;
                rect1.bottom = mRect.bottom;

                break;
            case RIGHT:
                rect.left = mRect.left-mShadowRadius;
                rect.right = mRect.width() / 2;
                rect.top = mRect.top;
                rect.bottom = mRect.bottom;

                rect1.left = mRect.left;
                rect1.right = mRect.width() / 2;
                rect1.top = mRect.top;
                rect1.bottom = mRect.bottom;
                break;

            default:
                break;
        }

        if (mShape == SHAPE_ROUND) {
            /**
             * 绘制全圆角阴影
             */
            canvas.drawRoundRect(mRect, mShapeRadius, mShapeRadius, mShadowPaint);
            canvas.drawRect(rect, mPaint);
            canvas.drawRoundRect(mRect, mShapeRadius, mShapeRadius, mBgPaint);
        } else if (mShape == SHAPE_ROUND_PART) {
            /**
             * 绘制部分圆角阴影
             */
            canvas.drawRoundRect(mRect, mShapeRadius, mShapeRadius, mShadowPaint);
            canvas.drawRect(rect, mPaint);
            canvas.drawRoundRect(mRect, mShapeRadius, mShapeRadius, mBgPaint);
            canvas.drawRect(rect1, mBgPartPaint);
        } else {
            /**
             * 绘制圆形阴影
             */
            canvas.drawCircle(mRect.centerX(), mRect.centerY(), Math.min(mRect.width(), mRect.height()) / 2, mShadowPaint);
            canvas.drawRect(rect, mPaint);
            canvas.drawCircle(mRect.centerX(), mRect.centerY(), Math.min(mRect.width(), mRect.height()) / 2, mBgPaint);
        }
    }

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

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

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

    public static void setShadowDrawable(View view) {
        ShadowDrawableUtil drawable = new Builder()
                .setType(TypeEnum.BOTTOM)
                .builder();
        view.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        ViewCompat.setBackground(view, drawable);
    }

    public static void setShadowDrawable(View view, String bgColor) {
        ShadowDrawableUtil drawable = new Builder()
                .setType(TypeEnum.BOTTOM)
                .setBgColor(bgColor)
                .builder();
        view.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        ViewCompat.setBackground(view, drawable);
    }

    public static void setShadowDrawable(View view, TypeEnum type) {
        ShadowDrawableUtil drawable = new Builder()
                .setType(type)
                .builder();
        view.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        ViewCompat.setBackground(view, drawable);
    }

    public static void setShadowDrawableCircle(View view) {
        ShadowDrawableUtil drawable = new Builder()
                .setShape(SHAPE_CIRCLE)
                .setType(TypeEnum.All)
                .builder();
        view.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        ViewCompat.setBackground(view, drawable);
    }

    public static void setShadowDrawableTop(View view, String shapeColor) {
        ShadowDrawableUtil drawable = new Builder()
                .setShape(SHAPE_ROUND_PART)
                .setType(TypeEnum.TOP)
                .setShadowColor(shapeColor)
                .builder();
        view.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        ViewCompat.setBackground(view, drawable);
    }

    public static void setShadowDrawable(View view, String shapeColor, int shapeRadius, String shadowColor, int shadowRadius) {
        ShadowDrawableUtil drawable = new Builder()
                .setBgColor(shapeColor)
                .setShapeRadius(shapeRadius)
                .setShadowColor(shadowColor)
                .setShadowRadius(shadowRadius)
                .builder();
        view.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        ViewCompat.setBackground(view, drawable);
    }

    public static void setShadowDrawable(View view, int shape, TypeEnum type, String shapeColor, int shapeRadius, String shadowColor, int shadowRadius) {
        ShadowDrawableUtil drawable = new Builder()
                .setBgColor(shapeColor)
                .setShapeRadius(shapeRadius)
                .setShadowColor(shadowColor)
                .setShadowRadius(shadowRadius)
                .setShape(shape)
                .setType(type)
                .builder();
        view.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        ViewCompat.setBackground(view, drawable);
    }

    public static void setShadowDrawable(View view, int shape, TypeEnum type, String[] shapeColor, int shapeRadius, String shadowColor, int shadowRadius) {
        ShadowDrawableUtil drawable = new Builder()
                .setBgColor(shapeColor)
                .setShapeRadius(shapeRadius)
                .setShadowColor(shadowColor)
                .setShadowRadius(shadowRadius)
                .setShape(shape)
                .setType(type)
                .builder();
        view.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        ViewCompat.setBackground(view, drawable);
    }


    private static class Builder {
        private int mShape;
        private int mShapeRadius;
        private int mShadowColor;
        private int mShadowRadius;
        private int[] mBgColor;
        private TypeEnum type;

        private Builder() {
            mShape = SHAPE_ROUND;
            type = TypeEnum.All;
            mShapeRadius = 17;
            mShadowColor = Color.parseColor("#FF0000");
            mShadowRadius = 4;
            mBgColor = new int[1];
            mBgColor[0] = Color.GREEN;
        }

        private Builder setShape(int mShape) {
            this.mShape = mShape;
            return this;
        }

        private Builder setShapeRadius(int ShapeRadius) {
            this.mShapeRadius = ShapeRadius;
            return this;
        }

        private Builder setShadowColor(String shadowColor) {

            this.mShadowColor = Color.parseColor(shadowColor);
            return this;
        }

        private Builder setShadowRadius(int shadowRadius) {
            this.mShadowRadius = shadowRadius;
            return this;
        }

        private Builder setBgColor(String bgColor) {
            this.mBgColor[0] = Color.parseColor(bgColor);
            return this;
        }

        private Builder setType(TypeEnum type) {
            this.type = type;
            return this;
        }


        private Builder setBgColor(String[] bgColors) {
            if (bgColors != null && bgColors.length > 0) {
                int[] b = new int[bgColors.length];
                for (int i = 0; i < bgColors.length; i++) {
                    b[i] = Color.parseColor(bgColors[i]);
                }
                this.mBgColor = b;
            }

            return this;
        }

        private ShadowDrawableUtil builder() {
            return new ShadowDrawableUtil(mShape, type, mBgColor, dp2px(mShapeRadius), mShadowColor, dp2px(mShadowRadius));
        }
    }

    private static int dp2px(float dpVal) {
        return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dpVal, ShadowApplication.getApplication().getResources().getDisplayMetrics());
    }
}

如有意见和建议，及时沟通。

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