自定义控件之--继承控件（圆形TextView）

师从郭大，自学于心，继承控件无疑就是继承自现有控件，保持继承的控件的属性并进行必要的扩展。

比如下面这个自定义控件，它就保持了TextView的属性，并对TextView的外观进行必要的修改该来适应自己的项目，主要实现的是一个圆形的TextView的功能。

三个构造方法：

onMesure():onMeasure()方法顾名思义就是用于测量视图的大小的,确定视图的宽度和高度的规格和大小;

draw():视图绘制，canvas.drawCircle(getWidth()/2, getHeight()/2,Math.max(getWidth(), getHeight())/2, mBgPaint);绘制圆形。

给Canvas加上抗锯齿标志:

PaintFlagsDrawFilter pfd =newPaintFlagsDrawFilter(0,Paint.ANTI_ALIAS_FLAG|Paint.FILTER_BITMAP_FLAG);

canvas.setDrawFilter(pfd);

绘制圆形的TextView:

canvas.drawCircle(getWidth()/2, getHeight()/2,Math.max(getWidth(), getHeight())/2, mBgPaint);

设置回调方法，然后控制组件的内容和背景：

setBackgroundColor

setNotifiText

 1 package com.example.circletextview;
 2 import android.content.Context;
 3 import android.graphics.Canvas;
 4 import android.graphics.Color;
 5 import android.graphics.Paint;
 6 import android.graphics.PaintFlagsDrawFilter;
 7 import android.util.AttributeSet;
 8 import android.widget.TextView;
 9 public class CircleView extends TextView {
10     private Paint mBgPaint = new Paint();
11     PaintFlagsDrawFilter pfd = new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG|Paint.FILTER_BITMAP_FLAG); 
12     public CircleView(Context context, AttributeSet attrs, int defStyle) {
13         super(context, attrs, defStyle);
14     }
15     public CircleView(Context context, AttributeSet attrs) {
16         super(context, attrs);
17         mBgPaint.setColor(Color.WHITE);
18         mBgPaint.setAntiAlias(true);
19     }
20     public CircleView(Context context) {
21         super(context);
22         mBgPaint.setColor(Color.WHITE);
23         mBgPaint.setAntiAlias(true);
24     }
25     @Override
26     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
27         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
28         int measuredWidth = getMeasuredWidth();
29         int measuredHeight = getMeasuredHeight();
30         int max = Math.max(measuredWidth, measuredHeight);
31         setMeasuredDimension(max, max);
32     }
33     @Override
34     public void setBackgroundColor(int color) {
35         mBgPaint.setColor(color);
36     }
37     /**
38      * 设置通知个数显示
39      * @param text
40      */
41     public void setNotifiText(int text){
42         setText(text+"");
43     }
44     @Override
45     public void draw(Canvas canvas) {
46         canvas.setDrawFilter(pfd);//给Canvas加上抗锯齿标志
47         canvas.drawCircle(getWidth()/2, getHeight()/2, Math.max(getWidth(), getHeight())/2, mBgPaint);
48         super.draw(canvas);
49     }
50 }

github:

https://github.com/soyoungboy/MyCircleTextView