绘制几何图形——使用android.graphics类

范例说明

“如何在和机上绘制2D图形呢？”这是许多android游戏开发都是常提到的问题，在android SDK 当中，并没有Java Graphics2D的函数可以使用，而是使用android.graphics底下的类来绘制2D向量图。这个package提供了许多在手机上绘制图形的类与方法，其中Canvas上，而Paint（Android.graphics.Paint)类则像是彩色铅笔，给予不同的调协，即可绘制不同颜色、不同种类效果的向量图形。

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。

运行结果如果



范例程序

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 {

/** Called when the activity is first created. */

@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) ;

}

/*重写onDraw（）*/

@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();

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);

}

}

}