Android绘图Canvas、Paint类基本用法

这些用法都是英文的字面意思，所以解释部分就放在代码的注释那里了，要画图，就要继承View类重写onDraw方法，要注意的是构造方法也重写一下吧，话不多说直接上代码~~~

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.LinearGradient;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.RectF;
import android.graphics.Shader;
import android.util.AttributeSet;
import android.view.View;

public class MyView extends View {
  public MyView(Context context, AttributeSet set) {
    super(context, set);
  }

  @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);
    //设置画笔颜色
    paint.setColor(Color.BLUE);
    //设置画笔风格
    paint.setStyle(Paint.Style.STROKE);
    //设置画笔大小
    paint.setStrokeWidth(3);
    //绘制圆形，这里cx,cy参数是指圆心的坐标，更JavaSE的不一样
    canvas.drawCircle(40, 40, 30, paint);
    //绘制正方形(左上 、右下)
    canvas.drawRect(10, 80, 70, 140, paint);
    //绘制矩形
    canvas.drawRect(10, 150, 70, 190, paint);
    //绘制圆角矩形
    RectF re1 = new RectF(10, 200, 70, 230);
    //下面方法参数解释
    //rx The x-radius of the oval used to round the corners
    //ry The y-radius of the oval used to round the corners
    canvas.drawRoundRect(re1, 15, 15, paint);
    //绘制椭圆
    RectF re11 = new RectF(10, 240, 70, 270);
    canvas.drawOval(re11, paint);
    //绘制三角形--需要定义一个Path对象来绘制路径
    Path path1 = new Path();
    path1.moveTo(10, 340);
    path1.lineTo(70, 340);
    path1.lineTo(40, 290);
    path1.close();
    canvas.drawPath(path1, paint);
    //绘制五边形--需要定义一个Path对象来绘制路径
    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();
    canvas.drawPath(path2, paint);
    //改变风格再绘制
    paint.setStyle(Paint.Style.FILL);
    paint.setColor(Color.RED);
    //绘制圆形
    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);
    //绘制圆角矩形
    RectF re2 = new RectF(90, 200, 150, 230);
    canvas.drawRoundRect(re2, 15, 15, paint);
    //绘制椭圆
    RectF re21 = new RectF(90, 240, 150, 270);
    canvas.drawOval(re21, paint);
    //绘制三角形
    Path path3 = new Path();
    path3.moveTo(90, 340);
    path3.lineTo(150, 340);
    path3.lineTo(120, 290);
    path3.close();
    canvas.drawPath(path3, paint);
    //绘制五角形
    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();
    canvas.drawPath(path4, paint);
    //改变样式--设置渐变
    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);
    //绘制圆角矩形
    RectF re3 = new RectF();
    canvas.drawRoundRect(re3, 15, 15, paint);
    //绘制椭圆
    RectF re31 = new RectF(170, 240, 230, 270);
    canvas.drawOval(re31, paint);
    //绘制三角形
    Path path5 = new Path();
    path5.moveTo(170, 340);
    path5.lineTo(230, 340);
    path5.lineTo(200, 290);
    path5.close();
    canvas.drawPath(path5, paint);
    //绘制五边形
    Path path6 = new Path();
    path6.moveTo(186, 360);
    path6.moveTo(214, 360);
    path6.moveTo(230, 392);
    path6.moveTo(200, 420);
    path6.moveTo(170, 392);
    path6.close();
    canvas.drawPath(path6, paint);
    //改变风格，绘制字体
    paint.setTextSize(10);
    paint.setShader(null);
//    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);
  }

}