在之前通过Circle画了一个奥运五环，这次通过RectF来画矩形，常规的就是长方形正方形之类的。
还是新建一个自定义View,CustomViewRectF，然后继承View,实现里面的两个基本的构造方法，这样就可以在布局中显示了，自定义View代码如下：
package com.llw.paintdemo; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.RectF; import android.util.AttributeSet; import android.view.View; import androidx.annotation.Nullable; public class CustomViewRectF extends View { public CustomViewRectF(Context context) { super(context); } public CustomViewRectF(Context context, @Nullable AttributeSet attrs) { super(context, attrs); } private Paint customPaint(int color) { Paint paint = new Paint(); paint.setColor(color);//画笔颜色 paint.setStyle(Paint.Style.FILL);//实心 paint.setStrokeWidth(6);//画笔宽度 paint.setAntiAlias(true);//光滑 return paint; } /** * 在纸上画矩形 * @param canvas 纸 */ @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); /** * 画矩形 以两个点来画，起点和终点，通常是左上为起点，右下为终点 以下面这个图来看 * 参数一：起点的Y轴坐标 * 参数二：起点的X轴坐标 * 参数三：终点的Y轴坐标 * 参数四：终点的Y轴坐标 * * * * * * * top * **************** * * * * left * * right * * * * * * * ****************** * bottom * * * * * * 可以看到，左和上无限延长就会在一个点，右和下也是如此，这样应该理解了吧 * */ RectF rectF = new RectF(10,10,200,200); canvas.drawRect(rectF, customPaint(Color.BLUE)); } }
运行一下：
这个看到就是这样的。
然后改一下
paint.setStyle(Paint.Style.STROKE);//空心
可以看到左边有一部分被遮挡住了
再画长方形
RectF rectF = new RectF(10,10,100,200);//长方形
然后运行
再多画几个长方形
RectF rectF2 = new RectF(120,10,210,200);//长方形2 canvas.drawRect(rectF2, customPaint(Color.BLUE)); RectF rectF3 = new RectF(240,10,330,200);//长方形3 canvas.drawRect(rectF3, customPaint(Color.BLUE)); RectF rectF4 = new RectF(360,10,450,200);//长方形4 canvas.drawRect(rectF4, customPaint(Color.BLUE));
再改一下
RectF rectF = new RectF(10,10,100,200);//长方形 canvas.drawRect(rectF, customPaint(Color.GREEN)); RectF rectF2 = new RectF(100,10,190,200);//长方形2 canvas.drawRect(rectF2, customPaint(Color.YELLOW)); RectF rectF3 = new RectF(190,10,280,200);//长方形3 canvas.drawRect(rectF3, customPaint(Color.BLUE)); RectF rectF4 = new RectF(280,10,370,200);//长方形4 canvas.drawRect(rectF4, customPaint(Color.RED));
再通过改边top的位置，形成从低到高
RectF rectF = new RectF(10,160,100,200);//长方形 canvas.drawRect(rectF, customPaint(Color.GREEN)); RectF rectF2 = new RectF(100,120,190,200);//长方形2 canvas.drawRect(rectF2, customPaint(Color.YELLOW)); RectF rectF3 = new RectF(190,80,280,200);//长方形3 canvas.drawRect(rectF3, customPaint(Color.BLUE)); RectF rectF4 = new RectF(280,40,370,200);//长方形4 canvas.drawRect(rectF4, customPaint(Color.RED));
运行一下
再整体改一下形成旋转的效果。
RectF rectF = new RectF(10,10,300,100);//长方形 canvas.drawRect(rectF, customPaint(Color.GREEN)); RectF rectF2 = new RectF(300,10,390,300);//长方形2 canvas.drawRect(rectF2, customPaint(Color.YELLOW)); RectF rectF3 = new RectF(100,300,390,390);//长方形3 canvas.drawRect(rectF3, customPaint(Color.BLUE)); RectF rectF4 = new RectF(10,100,100,390);//长方形4 canvas.drawRect(rectF4, customPaint(Color.RED));
运行一下
再改一下：
RectF rectF = new RectF(10,100,300,190);//长方形 canvas.drawRect(rectF, customPaint(Color.GREEN)); RectF rectF2 = new RectF(300,10,390,300);//长方形2 canvas.drawRect(rectF2, customPaint(Color.YELLOW)); RectF rectF3 = new RectF(190,300,480,390);//长方形3 canvas.drawRect(rectF3, customPaint(Color.BLUE)); RectF rectF4 = new RectF(100,190,190,480);//长方形4 canvas.drawRect(rectF4, customPaint(Color.RED));
画矩形记住一点，bottom - top等于矩形的高度，right - left 等于矩形的宽度就可以了。相信你的理解已经很深了吧。
