放射渐变RadialGradient

   public RadialGradient(float centerX, float centerY, float radius, int[] colors, float[] stops, TileMode tileMode) {
        throw new RuntimeException("Stub!");
    }

    public RadialGradient(float centerX, float centerY, float radius, int centerColor, int edgeColor, TileMode tileMode) {
        throw new RuntimeException("Stub!");
    }

具体用法:

package com.loaderman.customviewdemo;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.RadialGradient;
import android.graphics.Shader;
import android.util.AttributeSet;
import android.view.View;

public class RadialGradientView extends View {
    private Paint mPaint;
    private RadialGradient mRadialGradient;
    private int mRadius;

    public RadialGradientView(Context context, AttributeSet attrs) {
        super(context, attrs);
        setLayerType(LAYER_TYPE_SOFTWARE, null);
        mPaint = new Paint();
    }

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

    /**
     * 两色渐变
     */
    if (mRadialGradient == null){
        mRadius = getWidth()/6;
        mRadialGradient = new RadialGradient(getWidth()/2,getHeight()/2,mRadius,0xffff0000,0xff00ff00, Shader.TileMode.CLAMP);
        mPaint.setShader(mRadialGradient);
    }

    /**
     * 多色渐变
     */
//        if (mRadialGradient == null) {
//            mRadius = getWidth() / 2;
//            int[] colors = new int[]{0xffff0000, 0xff00ff00, 0xff0000ff, 0xffffff00};
//            float[] stops = new float[]{0f, 0.2f, 0.5f, 1f};
//            mRadialGradient = new RadialGradient(getWidth() / 2, getHeight() / 2, mRadius, colors, stops, Shader.TileMode.REPEAT);
//            mPaint.setShader(mRadialGradient);
//        }

    canvas.drawRect(0,0,getWidth(),getHeight(),mPaint);
}
}

package com.loaderman.customviewdemo;

import android.animation.Animator;
import android.animation.ObjectAnimator;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.RadialGradient;
import android.graphics.Shader;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.animation.AccelerateInterpolator;
import android.widget.Button;

public class RippleView extends Button {
    private int mX, mY;
    private ObjectAnimator mAnimator;
    private int DEFAULT_RADIUS = 50;
    private int mCurRadius = 0;
    private RadialGradient mRadialGradient;
    private Paint mPaint;

    public RippleView(Context context, AttributeSet attrs) {
        super(context, attrs);
        setLayerType(LAYER_TYPE_SOFTWARE,null);
        mPaint = new Paint();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {

        if (mX != event.getX() || mY != mY) {
            mX = (int) event.getX();
            mY = (int) event.getY();

            setRadius(DEFAULT_RADIUS);
        }

        if (event.getAction() == MotionEvent.ACTION_DOWN) {

            return true;
        } else if (event.getAction() == MotionEvent.ACTION_UP) {

            if (mAnimator != null && mAnimator.isRunning()) {
                mAnimator.cancel();
            }

            if (mAnimator == null) {
                mAnimator = ObjectAnimator.ofInt(this,"radius",DEFAULT_RADIUS, getWidth());
            }

            mAnimator.setInterpolator(new AccelerateInterpolator());
            mAnimator.addListener(new Animator.AnimatorListener() {
                public void onAnimationStart(Animator animation) {

                }
                public void onAnimationEnd(Animator animation) {
                    setRadius(0);
                }

                public void onAnimationCancel(Animator animation) {

                }

                public void onAnimationRepeat(Animator animation) {

                }
            });
            mAnimator.start();
        }

        return super.onTouchEvent(event);
    }

    public void setRadius(final int radius) {
        mCurRadius = radius;
        if (mCurRadius > 0) {
            mRadialGradient = new RadialGradient(mX, mY, mCurRadius, 0x00FFFFFF, 0xFF58FAAC, Shader.TileMode.CLAMP);
            mPaint.setShader(mRadialGradient);
        }
        postInvalidate();
    }

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

        canvas.drawCircle(mX, mY, mCurRadius, mPaint);
    }
}

效果图: