初学Android,图形图像之使用Shader填充图像(三十三)

Shader本身是一个抽象类，它提供了如下实现类

BitmapShader 　　使用位图平铺的渲染效果

LinearGradient 使用线性渐变来填充图形

RadialGradient 使用圆形渐变来填充图形

SweepGradient 使用角度渐变来填充图形

ComposeShader 使用组合渲染来填充图形

下面的例子有５个按钮，分别调用５个效果

下面是定义的xml及代码

string.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
  <string name="hello">Hello World, ShaderTest!</string> 
  <string name="app_name">渲染测试</string> 
  <string name="bitmap">位图</string> 
  <string name="line">线性渐变</string> 
  <string name="radial">圆形渐变</string> 
  <string name="sweep">角度渐变</string> 
  <string name="composite">混合</string> 
</resources>

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent">
   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="horizontal" android:layout_width="wrap_content" android:layout_height="wrap_content">
	    <Button android:id="@+id/bn1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/bitmap" /> 
	    <Button android:id="@+id/bn2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/line" /> 
	    <Button android:id="@+id/bn3" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/radial" /> 
	    <Button android:id="@+id/bn4" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/sweep" /> 
	    <Button android:id="@+id/bn5" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/composite" /> 
    </LinearLayout>
    <WangLi.Graphics.ShaderTest.MyView android:id="@+id/my_view" 
        android:layout_width="wrap_content" android:layout_height="wrap_content" />
</LinearLayout>

package WangLi.Graphics.ShaderTest;

import android.app.Activity;
import android.view.View.OnClickListener;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapShader;
import android.graphics.Color;
import android.graphics.ComposeShader;
import android.graphics.LinearGradient;
import android.graphics.PorterDuff;
import android.graphics.RadialGradient;
import android.graphics.Shader;
import android.graphics.Shader.TileMode;
import android.graphics.SweepGradient;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class ShaderTest extends Activity
       implements OnClickListener
{
	// 声明位图渲染对象
	private Shader[] shaders = new Shader[5];
	// 声明颜色数组
	private int[] colors;	
	MyView myView;
	// 自定义视图类
	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		myView = (MyView)findViewById(R.id.my_view);
		// 获得Bitmap实例
		Bitmap bm = BitmapFactory.decodeResource(getResources()
			, R.drawable.water);
		// 设置渐变的颜色组，也就是按红、绿、蓝的方式渐变
		colors = new int[] { Color.RED, Color.GREEN, Color.BLUE };
		// 实例化BitmapShader,x坐标方向重复图形，y坐标方向镜像图形
		shaders[0] = new BitmapShader(bm, TileMode.REPEAT,
			TileMode.MIRROR);
		// 实例化LinearGradient
		shaders[1] = new LinearGradient(0, 0, 100, 100
			, colors, null, TileMode.REPEAT);
		// 实例化RadialGradient
		shaders[2] = new RadialGradient(100, 100, 80, colors, null,
			TileMode.REPEAT);
		// 实例化SweepGradient
		shaders[3] = new SweepGradient(160, 160, colors, null);
		// 实例化ComposeShader
			shaders[4] = new ComposeShader(shaders[1], shaders[2],
				PorterDuff.Mode.DARKEN);
			Button bn1 = (Button)findViewById(R.id.bn1);
			Button bn2 = (Button)findViewById(R.id.bn2);
			Button bn3 = (Button)findViewById(R.id.bn3);
			Button bn4 = (Button)findViewById(R.id.bn4);
			Button bn5 = (Button)findViewById(R.id.bn5);
			bn1.setOnClickListener(this);
			bn2.setOnClickListener(this);
			bn3.setOnClickListener(this);
			bn4.setOnClickListener(this);
			bn5.setOnClickListener(this);
		}
	    @Override
		public void onClick(View source)
		{
			switch(source.getId())
			{
				case R.id.bn1:
					myView.paint.setShader(shaders[0]);
					break;
				case R.id.bn2:
					myView.paint.setShader(shaders[1]);
					break;
				case R.id.bn3:
					myView.paint.setShader(shaders[2]);
					break;
				case R.id.bn4:
					myView.paint.setShader(shaders[3]);
					break;
				case R.id.bn5:
					myView.paint.setShader(shaders[4]);
					break;
			}
			// 重绘界面
			myView.invalidate();
		}
}