android学习笔记42——图形图像处理2——绘图

绘图

android的绘图应该继承View组件，并重写onDraw(Canvas canvas)方法即可。

重写onDraw(Canvas canvas)方法时涉及一个绘图API:Canvas，Canvas代表了“依附”于指定View的画布，其提供了如下图所示的方法——用于绘制各种图像：

注意：在Canvas提供的绘制方法中还用到了一个API:Path,Path代表任意多条直线连接而成的任意图形，当Canvas根据Path绘制时，可以绘制出任意的形状。

实例如下：

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布局文件==》
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity" >
 
    <com.example.mycanvas.MyView
        android:id="@+id/myView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
   
</LinearLayout>
 
代码实现==》
package com.example.mycanvas;
 
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
    protected void onDraw(Canvas canvas)
    {
        super.onDraw(canvas);
        // 把整张布绘制成白色
        canvas.drawColor(Color.WHITE);
        Paint p = new Paint();
        // 去除锯齿
        p.setAntiAlias(true);
        p.setColor(Color.BLUE);
        p.setStyle(Paint.Style.STROKE);
        p.setStrokeWidth(3);
        // 绘制圆形
        canvas.drawCircle(40, 40, 30, p);
        // 绘制正方形
        canvas.drawRect(10, 80, 70, 140, p);
        // 绘制矩形
        canvas.drawRect(10, 150, 70, 190, p);
        RectF rect = new RectF(10, 200, 70, 230);
        // 绘制圆角矩形
        canvas.drawRoundRect(rect, 15, 15, p);
        RectF rect1 = new RectF(10, 240, 70, 270);
        // 绘制椭圆
        canvas.drawOval(rect1, p);
 
        paintTriangle(canvas, p);
        paintFivePointStar(canvas, p);
        paintGraph(canvas, p);
        paintGraph2(canvas, p);
        paintGraph3(canvas, p);
    }
 
    /* 设置字符大小后绘制 */
    private void paintGraph3(Canvas canvas, Paint paint)
    {
        paint.setTextSize(26);
        paint.setShader(null);
        // 绘制字符串
        canvas.drawText("圆形", 260, 50, paint);
        // canvas.drawText("方形", 260, 120, paint);
        // canvas.drawText("长方形", 240, 170, paint);
        // canvas.drawText("圆角矩形", 230, 220, paint);
        // canvas.drawText("圆形", 240, 260, paint);
        // canvas.drawText("三角形", 240, 325, paint);
        // canvas.drawText("五角形", 240, 390, paint);
    }
 
    private void paintGraph2(Canvas canvas, Paint paint)
    {
        // 设置渐变器后绘制
        Shader shader = new LinearGradient(0, 0, 40, 60, new int[] { Color.RED, Color.GREEN,
                Color.BLUE, Color.YELLOW }, null, Shader.TileMode.REPEAT);
        paint.setShader(shader);
        // 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);
        // 绘制圆角矩形
        RectF r = new RectF(170, 200, 230, 230);
        canvas.drawRect(r, paint);
 
        // 绘制椭圆
        RectF rel2 = new RectF(170, 240, 230, 270);
        canvas.drawOval(rel2, paint);
 
        // 绘制三角形
        Path path = new Path();
        path.moveTo(170, 340);
        path.lineTo(230, 340);
        path.lineTo(200, 290);
        path.close();
        // 根据Path进行绘制，绘制三角形
        canvas.drawPath(path, paint);
 
        // 定义一个Path对象，封闭成一个三角形
        Path p1 = new Path();
        p1.moveTo(186, 360);
        p1.lineTo(214, 360);
        p1.lineTo(230, 392);
        p1.lineTo(200, 420);
        p1.lineTo(170, 392);
        p1.close();
        // 根据Path进行绘制，绘制三角形
        canvas.drawPath(p1, paint);
    }
 
    private void paintGraph(Canvas canvas, Paint p)
    {
        // 设置填充风格后绘制
        p.setStyle(Paint.Style.FILL);
        p.setColor(Color.RED);
        canvas.drawCircle(120, 40, 30, p);
        // 绘制正方形
        canvas.drawRect(90, 80, 150, 140, p);
        // 绘制矩形
        canvas.drawRect(90, 150, 150, 190, p);
        RectF re2 = new RectF(90, 200, 150, 230);
        // 绘制圆角矩形
        canvas.drawRoundRect(re2, 15, 15, p);
 
        RectF rel2 = new RectF(90, 240, 150, 270);
        // 绘制椭圆
        canvas.drawOval(rel2, p);
 
        // 绘制三角形
        Path path = new Path();
        path.moveTo(90, 340);
        path.lineTo(150, 340);
        path.lineTo(120, 290);
        path.close();
        // 根据Path进行绘制，绘制三角形
        canvas.drawPath(path, p);
 
        // 定义一个Path对象，封闭成一个三角形
        Path p1 = new Path();
        p1.moveTo(106, 360);
        p1.lineTo(134, 360);
        p1.lineTo(150, 390);
        p1.lineTo(120, 420);
        p1.lineTo(90, 392);
        p1.close();
        // 根据Path进行绘制，绘制三角形
        canvas.drawPath(p1, p);
    }
 
    private void paintFivePointStar(Canvas canvas, Paint p)
    {
        // 定义一个Path对象，封闭成一个五角星
        Path p2 = new Path();
        p2.moveTo(26, 360);
        p2.lineTo(54, 360);
        p2.lineTo(70, 392);
        p2.lineTo(40, 420);
        p2.lineTo(10, 392);
        p2.close();
        // 根据Path进行绘制，绘制五角形
        canvas.drawPath(p2, p);
    }
 
    private void paintTriangle(Canvas canvas, Paint p)
    {
        // 定义一个Path对象，封闭成一个三角形
        Path p1 = new Path();
        p1.moveTo(10, 340);
        p1.lineTo(70, 340);
        p1.lineTo(40, 290);
        p1.close();
        // 根据Path进行绘制，绘制三角形
        canvas.drawPath(p1, p);
    }
 
}