Android学习之Shader渲染

Shader有几个直接子类：

BitmapShader : 图像渲染

LinearGradient : 线性渐变

RadialGradient : 环形渐变

SweepGradient : 扫描渐变---围绕一个中心点扫描渐变就像电影里那种雷达扫描

ComposeShader : 组合渲染

先看效果图：



先保存好你要在BitmapShader中显示的图片.

看代码(代码中带有注释)：

我采用的还是SurefaceView框架,

[java]
view plaincopy

package com.ldj.helloshader;

import android.content.Context;

import android.graphics.*;

import android.graphics.Shader.TileMode;

import android.graphics.drawable.BitmapDrawable;

import android.graphics.drawable.ShapeDrawable;

import android.graphics.drawable.shapes.OvalShape;

import android.view.*;

public class ShaderView extends SurfaceView implements SurfaceHolder.Callback,Runnable{

//声明渐变的颜色数组

private int[] color =

new int[]{Color.GREEN,Color.GRAY,Color.MAGENTA,Color.RED,Color.WHITE};

private boolean loop = false;

private SurfaceHolder surfaceHolder;

private Bitmap bitPic = null;

int bitPicWidth = 0;

int bitPicHeight = 0;

//声明一个图片渲染

BitmapShader bitmapShader = null;

//声明一个线性渐变

LinearGradient linearGradient = null;

//声明一个环形渐变

RadialGradient radialGradient = null;

//声明一个扫描渐变

//-围绕一个中心点扫描渐变就像电影里那种雷达扫描

SweepGradient sweepGradient = null;

//声明一个组合渲染

ComposeShader composeShader = null;

//定义画笔

Paint paint = null;

//利用这个类也可以实现绘制图像的功能

ShapeDrawable shapeDrawable = null;

public ShaderView(Context context) {

super(context);

surfaceHolder = this.getHolder();

//增加回调

surfaceHolder.addCallback(this);

loop = true;

paint = new Paint();

//获取图像资源

bitPic =

((BitmapDrawable)this.getResources().getDrawable(R.drawable.screenshot))

.getBitmap();

//将图片的长和高的值赋给变量

bitPicWidth = bitPic.getWidth();

bitPicHeight = bitPic.getHeight();

/*

* ~~~BitmapShader(Bitmap,TileMode,TileMode)~~~

*/

bitmapShader = new BitmapShader(bitPic, TileMode.REPEAT, TileMode.MIRROR);

/*

* ~~~LinearGradient(x0,y0,x1,y1,int[Color],float[],TileMode)~~~

*/

linearGradient = new LinearGradient(0,0,100,100,color,null,TileMode.REPEAT);

/*

* ~~~RadialGradient~~~

*/

radialGradient = new RadialGradient(160,240,66,color,null,TileMode.MIRROR);

/*

* ~~~SweepGradient~~~

*/

sweepGradient = new SweepGradient(100,350,color,null);

//~~~ComposeShader（shaderA,shaderB,Mode）~~~

//组合线性和环形两种渐变,当然其他的也可以的

composeShader

= new ComposeShader(linearGradient,radialGradient,PorterDuff.Mode.DARKEN);

}

@Override

public void run() {

while(loop) {

draw();

try {

Thread.sleep(100);

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

@Override

public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {

}

@Override

public void surfaceCreated(SurfaceHolder arg0) {

new Thread(this).start();

}

@Override

public void surfaceDestroyed(SurfaceHolder arg0) {

loop = false;

}

private void draw() {

Canvas canvas = surfaceHolder.lockCanvas();

/*

* ~~~BitmapShader

*/

//构造形状为椭圆的shapeDrawable对象

shapeDrawable = new ShapeDrawable(new OvalShape());

//设置显示的图片

shapeDrawable.getPaint().setShader(bitmapShader);

//设置显示的长和高

shapeDrawable.setBounds(0, 0, bitPicWidth, bitPicHeight);

//绘制图像

shapeDrawable.draw(canvas);

//~~~LinearGradient~~~

//设置画笔的渲染类型

paint.setShader(linearGradient);

canvas.drawRect(0, bitPicHeight, 320, 150, paint);

//~~~RadialGradient~~~

paint.setShader(radialGradient);

canvas.drawCircle(160, 240, 66, paint);

//~~~SweepGradient

paint.setShader(sweepGradient);

canvas.drawCircle(100, 350, 66, paint);

//~~~ComposeShader~~~

paint.setShader(composeShader);

canvas.drawRect(bitPicWidth, 320, 320, 480, paint);

surfaceHolder.unlockCanvasAndPost(canvas);

}

}