android.graphics类绘制2D图形
注：来自豆豆网
本范例将运用Paint对象（绘笔）的设置值不同，在Cavas(画布）上绘制空心、实习及渐变色的多种几何多形。先看下效果图：
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范例：主程序中继承自Android.view.View的 MyView类，重写 MyView的onDraw（）方法，一开始就会运行绘制的工作，在onDraw（）中以Paint将几何图形绘制在Canvas上，以 paint.setColor() 改变图形颜色、以 paint.setStyle()的设置来控制画出的的图形是空心还是实心。程序的最后一段，就是直接在Canvas写上文字，随着Paint对象里的属性设置，也会有不同的外观模式。
package com.graphices; import android.app.Activity;import android.os.Bundle;import android.view.View;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.RectF;import android.graphics.Path;import android.graphics.Shader;import android.graphics.LinearGradient;public class GraphicesActivity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); /*设置ContentView为自定义的MyVieW*/ MyView myView=new MyView(this); setContentView(myView); } /* 自定义继承View 的MyView*/ private class MyView extends View{ public MyView(Context context){ super(context) ; } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); /*设置背景为白色*/ canvas.drawColor(Color.WHITE); Paint paint=new Paint(); /*去锯齿*/ paint.setAntiAlias(true); /*设置paint的颜色*/ paint.setColor(Color.RED); /*设置paint的 style 为STROKE：空心*/ paint.setStyle(Paint.Style.STROKE); /*设置paint的外框宽度*/ paint.setStrokeWidth(3); /*画一个空心圆形*/ canvas.drawCircle(40, 40, 30, paint); /*画一个空心正方形*/ canvas.drawRect(10, 90, 70, 150, paint); /*画一个空心长方形*/ canvas.drawRect(10, 170, 70,200, paint); /*画一个空心椭圆形*/ RectF re=new RectF(10,220,70,250); canvas.drawOval(re, paint); /*画一个空心三角形*/ Path path=new Path(); path.moveTo(10, 330); path.lineTo(70,330); path.lineTo(40,270); path.close(); canvas.drawPath(path, paint); /*画一个空心梯形*/ Path path1=new Path(); path1.moveTo(10, 410); path1.lineTo(70,410); path1.lineTo(55,350); path1.lineTo(25, 350); path1.close(); canvas.drawPath(path1, paint); /*设置paint 的style为 FILL：实心*/ paint.setStyle(Paint.Style.FILL); /*设置paint的颜色*/ paint.setColor(Color.BLUE); /*画一个实心圆*/ canvas.drawCircle(120,40,30, paint); /*画一个实心正方形*/ canvas.drawRect(90, 90, 150, 150, paint); /*画一个实心长方形*/ canvas.drawRect(90, 170, 150,200, paint); /*画一个实心椭圆*/ RectF re2=new RectF(90,220,150,250); canvas.drawOval(re2, paint); /*画一个实心三角形*/ Path path2=new Path(); path2.moveTo(90, 330); path2.lineTo(150,330); path2.lineTo(120,270); path2.close();// If the current point is not equal to the first point of the contour, a line segment is automatically added.看来还挺智能的 canvas.drawPath(path2, paint); /*画一个实心梯形*/ Path path3=new Path(); path3.moveTo(90, 410); path3.lineTo(150,410); path3.lineTo(135,350); path3.lineTo(105, 350); path3.close(); canvas.drawPath(path3, paint); /*设置渐变色*/ Shader mShader=new LinearGradient(0,0,100,100, new int[]{Color.RED,Color.GREEN,Color.BLUE,Color.YELLOW}, null,Shader.TileMode.REPEAT); paint.setShader(mShader); /*画一个渐变色圆*/ canvas.drawCircle(200,40,30, paint); /*画一个渐变色正方形*/ canvas.drawRect(170, 90, 230, 150, paint); /*画一个渐变色长方形*/ canvas.drawRect(170, 170, 230,200, paint); /*画一个渐变色椭圆*/ RectF re3=new RectF(170,220,230,250); canvas.drawOval(re3, paint); /*画一个渐变色三角形*/ Path path4=new Path(); path4.moveTo(170,330); path4.lineTo(230,330); path4.lineTo(200,270); path4.close(); canvas.drawPath(path4, paint); /*画一个渐变色梯形*/ Path path5=new Path(); path5.moveTo(170, 410); path5.lineTo(230,410); path5.lineTo(215,350); path5.lineTo(185, 350); path5.close(); canvas.drawPath(path5, paint); /*写字*/ paint.setTextSize(24); canvas.drawText(getResources().getString(R.string.str_text1), 240, 50, paint); canvas.drawText(getResources().getString(R.string.str_text2), 240, 120, paint); canvas.drawText(getResources().getString(R.string.str_text3), 240, 190, paint); canvas.drawText(getResources().getString(R.string.str_text4), 240, 250, paint); canvas.drawText(getResources().getString(R.string.str_text5), 240, 320, paint); canvas.drawText(getResources().getString(R.string.str_text6), 240, 390, paint); }}}