Android渲染器Shader：梯度渐变扫描渲染器SweepGradient（二）

蔚落 2023-10-17 08:05 23阅读 0赞

**Android渲染器Shader：梯度渐变扫描渲染器SweepGradient（二）**

附录文章1介绍了线性渐变渲染器。  
Android的SweepGradient梯度渐变扫描，重点是在构造SweepGradient的中心点选择。我写一个例子。

package zhangphil.demo;
    
    import android.content.Context;
    import android.graphics.Canvas;
    import android.graphics.Color;
    import android.graphics.Paint;
    import android.graphics.SweepGradient;
    import android.util.AttributeSet;
    import android.view.View;
    
    /**
     * Created by Phil on 2016/7/25.
     */
    
    
    public class SweepGradientView extends View {
    
        private Paint mPaint = null;
    
        // 梯度渐变扫描渲染
        private SweepGradient mSweepGradient = null;
    
        public SweepGradientView(Context context, AttributeSet attrs) {
            super(context, attrs);
        }
    
        @Override
        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);
    
            mSweepGradient = new SweepGradient(this.getWidth() / 2, this.getHeight() / 2, new int[]{Color.TRANSPARENT, Color.RED, Color.TRANSPARENT, Color.YELLOW, Color.BLUE}, null);
            mPaint = new Paint();
            mPaint.setAntiAlias(true);
    
            mPaint.setShader(mSweepGradient);
    
            canvas.drawCircle(this.getWidth() / 2, this.getHeight() / 2, 300, mPaint);
        }
    }

SweepGradientView直接像附录文章1那样在上层的activity里面new出来一个对象，然后setContentView进去即可。

代码运行结果：

![Center][]

附录文章：  
1，《Android渲染器Shader：LinearGradient（一）》链接：[http://blog.csdn.net/zhangphil/article/details/52004027][http_blog.csdn.net_zhangphil_article_details_52004027]

[Center]: https://img-blog.csdn.net/20160725110032816?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQv/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center
[http_blog.csdn.net_zhangphil_article_details_52004027]: http://blog.csdn.net/zhangphil/article/details/52004027