android继承TextView的高度宽度计算问题

      当需要扩展android原生TextView的时候，比如需要给TextView默认加上10像素的颜色边框时，当设置宽高为wrap_content时，高度并不好处理。网上大部分人云亦云的说设置一个默认值，然后根据测量模式，取 MeasureSpec.getSize(widthMeasureSpec)和默认值中的较小值，我想说就是扯淡。比如说我需要的宽度是200px,默认值是50px，此时宽度肯定不够。先看如下代码

package com.example.customview.view;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View.MeasureSpec;
import android.view.WindowManager;
import android.widget.TextView;

public class CustomTextView extends TextView {

    private Paint paint1;
    private Paint paint2;

    public CustomTextView(Context context) {
        super(context, null);
    }

    public CustomTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initView(context, attrs);
        // TODO Auto-generated constructor stub
    }

    private void initView(Context context, AttributeSet attrs) {
        paint1 = new Paint();
        paint1.setColor(getResources().getColor(android.R.color.holo_blue_dark));
        paint1.setStyle(Paint.Style.FILL);
        paint2 = new Paint();
        paint2.setStyle(Paint.Style.FILL);
        paint2.setColor(Color.GREEN);

    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // // TODO Auto-generated method stub
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        if(heightMode == MeasureSpec.AT_MOST&&widthMode == MeasureSpec.AT_MOST){
            //高度宽度为wrap_content时
            setMeasuredDimension(getMeasuredWidth()+20, getMeasuredHeight()+20);
        }

    }

    @Override
    protected void onDraw(Canvas canvas) {
        Log.e("CustomTextView", "widthSize" + getMeasuredWidth() + "heightSize"
                + getMeasuredHeight());
        canvas.drawRect(0, 0, getMeasuredWidth(), getMeasuredWidth(), paint1);
        canvas.drawRect(10, 10, getMeasuredWidth() - 10,
                getMeasuredHeight() - 10, paint2);
        canvas.translate(10, 10);
        super.onDraw(canvas);
    }
}

注意：

　　

if(heightMode == MeasureSpec.AT_MOST&&widthMode == MeasureSpec.AT_MOST){
            //高度宽度为wrap_content时
            setMeasuredDimension(getMeasuredWidth()+20, getMeasuredHeight()+20);
        }

通过调用TextView的getMeasuredWidth()，getMeasuredHeight()的方法获取获取不加边框时的宽高，在加上适当的偏移量，就能实现了。

用法如下：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:orientation="vertical" >

    <com.example.customview.view.CustomTextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="参与人数"/>

</LinearLayout>

运行结果如下：