Android SweepGradient扫描梯度渲染

时间:2022-06-28 时之沙人气:0

扫描渲染

为什么什么叫扫描渲染呢? 相信大家都看过雷达扫描的效果，尤其是在安全软件中.

public SweepGradient(float cx, float cy, int[] colors, float[] positions)

Parameters:

cx	渲染中心点x 坐标
cy	渲染中心y 点坐标
colors	围绕中心渲染的颜色数组，至少要有两种颜色值
positions	相对位置的颜色数组,可为null, 若为null,可为null,颜色沿渐变线均匀分布

public SweepGradient(float cx, float cy, int color0, int color1)

Parameters:

cx	渲染中心点x 坐标
cy	渲染中心点y 坐标
color0	起始渲染颜色
color1	结束渲染颜色

效果图:

代码：

MainActivity:

package com.tony.testshader;
import android.os.Bundle;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.view.Menu;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
public class MainActivity extends Activity  implements OnSeekBarChangeListener{
    private SweepGradientView sweepGradientView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        sweepGradientView = new SweepGradientView(MainActivity.this);
        setContentView(sweepGradientView);
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
}

SweepGradientView:

package com.tony.testshader;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Shader;
import android.graphics.SweepGradient;
import android.util.AttributeSet;
import android.view.View;
public class SweepGradientView extends View {
    Paint mPaint = null;  
    // 梯度渲染  
    Shader mSweepGradient = null;  
    public SweepGradientView(Context context) {
        super(context);
         // 创建SweepGradient对象  
        // 第一个,第二个参数中心坐标  
        // 后面的参数与线性渲染相同  
        mSweepGradient = new SweepGradient(240, 360, new int[] {Color.CYAN,Color.DKGRAY,Color.GRAY,Color.LTGRAY,Color.MAGENTA,  
                Color.GREEN,Color.TRANSPARENT, Color.BLUE }, null);  
        mPaint = new Paint();  
    }
    public SweepGradientView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
         // 绘制梯度渐变  
        mPaint.setShader(mSweepGradient);  
        canvas.drawCircle(240, 360, 200, mPaint);
    }
}

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