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：

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