SweepGradient梯度渲染旋转_sweepgradient 旋转-优快云博客

本文链接：https://blog.youkuaiyun.com/yegucheng2618/article/details/38042789

本文详细介绍了如何使用APIDemo的代码进行学习，包括创建自定义视图类、设置渐变色背景以及实现旋转动画效果。通过实例代码演示了如何在Android应用中运用这些技术，提供了一个实用的学习指南。

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此代码主要是学习APIDemo的代码：

package com.example.demo;

import android.os.Bundle;
import android.view.View;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Shader;
import android.graphics.SweepGradient;

public class MainActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(new myView(this));
	}
	
	private static class myView extends View {
		float x = 250;
		float y = 400;
		private Paint mPaint = new Paint();
		private Shader mShader;
		private float mRotate;
		private Matrix mMatrix = new Matrix();

		public myView(Context context) {
			super(context);			
			mShader = new SweepGradient(x, y, new int[] {Color.GREEN,
														 Color.RED,
														 Color.BLUE,
														 Color.GREEN}, null);
			mPaint.setShader(mShader);
		}
		
		@Override
		protected void onDraw(Canvas canvas) {
			// TODO Auto-generated method stub
			super.onDraw(canvas);
			canvas.drawColor(Color.WHITE);
			mMatrix.setRotate(mRotate, x, y);//旋转mRotate度,圆心为(x,y)
            mShader.setLocalMatrix(mMatrix);
            
            mRotate += 30;//mRotate增加30度
            if (mRotate >= 360) {
                mRotate = 0;
            }
            invalidate();
            
            canvas.drawCircle(x, y, 180, mPaint);
		}
	}
}

运行结果如下：