Android 颜色渲染(八) SweepGradient扫描/梯度渲染 .

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Android 颜色处理(八) SweepGradient 扫描/梯度渲染

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:

[java]
view plaincopyprint?

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; } }

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:

[java]
view plaincopyprint?

<PRE class=java name="code">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);
}
}</PRE><PRE></PRE><PRE></PRE><PRE></PRE>