今天我们来看一下Android中有关绘图的技巧，这里我们引用李阳老师非常经典的一个绘图案例，只做了一些小小改动
先上主要的绘图类：
/**
*
*/
package com.qq.canvas;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.LinearGradient;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.RectF;
import android.graphics.Shader;
import android.util.AttributeSet;
import android.view.View;
/**
* 这个类主要负责绘图我们常用继承View来完成它，当然也可以用SurfaceView,其主要运用动的绘图
*/
public class MyView extends View
{
Bitmap bitmap;
public MyView(Context context, AttributeSet set)
{
super(context, set);
bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.background);
}
@Override
// 重写该方法，进行绘图
protected void onDraw(Canvas canvas)
{
super.onDraw(canvas);
// 把整张画布绘制成白色
canvas.drawColor(Color.WHITE);
Paint paint = new Paint();
// 去锯齿
paint.setAntiAlias(true);
paint.setColor(Color.BLUE);
//画笔风格
paint.setStyle(Paint.Style.STROKE);
//画笔大小
paint.setStrokeWidth(3);
//画背景图片,由于画图片的时候会导致绘画的效果不明显，所以先注释掉
//paint.setAlpha(10);//设置图片透明度
//canvas.drawBitmap(bitmap, 0, 0, null);
//paint.setAlpha(255);//还原透明度
// 绘制圆形
canvas.drawCircle(40, 40, 30, paint);
// 绘制正方形
canvas.drawRect(10, 80, 70, 140, paint);
// 绘制矩形
canvas.drawRect(10, 150, 70, 190, paint);
RectF re1 = new RectF(10, 200, 70, 230);
// 绘制圆角矩形
canvas.drawRoundRect(re1, 15, 15, paint);
RectF re11 = new RectF(10, 240, 70, 270);
// 绘制椭圆
canvas.drawOval(re11, paint);
// 定义一个Path对象，封闭成一个三角形。
Path path1 = new Path();
path1.moveTo(10, 340);
path1.lineTo(70, 340);
path1.lineTo(40, 290);
path1.close();
// 根据Path进行绘制，绘制三角形
canvas.drawPath(path1, paint);
// 定义一个Path对象，封闭成一个五角形。每一个To都是一个点，五个点连起来刚好是一个五角星
Path path2 = new Path();
path2.moveTo(26, 360);
path2.lineTo(54, 360);
path2.lineTo(70, 392);
path2.lineTo(40, 420);
path2.lineTo(10, 392);
path2.close();
// 根据Path进行绘制，绘制五角形
canvas.drawPath(path2, paint);
// ----------设置填充风格后绘制----------
paint.setStyle(Paint.Style.FILL);
paint.setColor(Color.RED);
canvas.drawCircle(120, 40, 30, paint);
//绘制正方形
canvas.drawRect(90, 80, 150, 140, paint);
//绘制矩形
canvas.drawRect(90, 150, 150, 190, paint);
RectF re2 = new RectF(90, 200, 150, 230);
//绘制圆角矩形
canvas.drawRoundRect(re2, 15, 15, paint);
RectF re21 = new RectF(90, 240, 150, 270);
// 绘制椭圆
canvas.drawOval(re21, paint);
Path path3 = new Path();
path3.moveTo(90, 340);
path3.lineTo(150, 340);
path3.lineTo(120, 290);
path3.close();
//绘制三角形
canvas.drawPath(path3, paint);
Path path4 = new Path();
path4.moveTo(106, 360);
path4.lineTo(134, 360);
path4.lineTo(150, 392);
path4.lineTo(120, 420);
path4.lineTo(90, 392);
path4.close();
//绘制五角形
canvas.drawPath(path4, paint);
// ----------设置渐变器后绘制----------
// 为Paint设置渐变器
Shader mShader = new LinearGradient(0, 0, 40, 60
, new int[] {
Color.RED, Color.GREEN, Color.BLUE, Color.YELLOW }
, null , Shader.TileMode.REPEAT);
paint.setShader(mShader);
//设置阴影
paint.setShadowLayer(45 , 10 , 10 , Color.GRAY);
// 绘制圆形
canvas.drawCircle(200, 40, 30, paint);
// 绘制正方形
canvas.drawRect(170, 80, 230, 140, paint);
// 绘制矩形
canvas.drawRect(170, 150, 230, 190, paint);
RectF re3 = new RectF(170, 200, 230, 230);
// 绘制圆角矩形
canvas.drawRoundRect(re3, 15, 15, paint);
RectF re31 = new RectF(170, 240, 230, 270);
// 绘制椭圆
canvas.drawOval(re31, paint);
Path path5 = new Path();
path5.moveTo(170, 340);
path5.lineTo(230, 340);
path5.lineTo(200, 290);
path5.close();
// 根据Path进行绘制，绘制三角形
canvas.drawPath(path5, paint);
Path path6 = new Path();
path6.moveTo(186, 360);
path6.lineTo(214, 360);
path6.lineTo(230, 392);
path6.lineTo(200, 420);
path6.lineTo(170, 392);
path6.close();
// 根据Path进行绘制，绘制五角形
canvas.drawPath(path6, paint);
// ----------设置字符大小后绘制----------
paint.setTextSize(24);
paint.setShader(null);
// 绘制7个字符串
canvas.drawText(getResources().getString(R.string.circle), 240, 50,
paint);
canvas.drawText(getResources().getString(R.string.square), 240, 120,
paint);
canvas.drawText(getResources().getString(R.string.rect), 240, 175,
paint);
canvas.drawText(getResources().getString(R.string.round_rect), 230,
220, paint);
canvas.drawText(getResources().getString(R.string.oval), 240,
260, paint);
canvas.drawText(getResources().getString(R.string.triangle), 240, 325,
paint);
canvas.drawText(getResources().getString(R.string.pentagon), 240, 390,
paint);
}
}