Android实现自带横线的EditText

package com.ayqy.app_test;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.widget.EditText;

public class myEditText extends EditText{
	
	private int lineColor;//横线颜色
	private float lineWidth;//横线宽度

	public myEditText(Context context) {
		super(context);
		
		//设置默认颜色和横线宽度
		lineColor = Color.BLUE;//默认蓝色线
		lineWidth = 2f;//宽度为2
	}
	
	public myEditText(Context context,int color,float width) {
		super(context);
		
		//设置颜色和横线宽度
		this.lineColor = color;
		this.lineWidth = width;
	}

	@Override
	protected void onDraw(Canvas canvas) {
		// TODO Auto-generated method stub
		super.onDraw(canvas);
		
		//创建画笔
		Paint mPaint = new Paint();
		mPaint.setStrokeWidth(lineWidth);
		mPaint.setStyle(Paint.Style.FILL);
		mPaint.setColor(lineColor);
		
		//获取参数
		int w = this.getWidth();//获取控件宽度
		int h = this.getHeight();//获取控件高度
		int padB = this.getPaddingBottom();//获取底部留白
		int padL = this.getPaddingLeft();//获取左边留白
		int padR = this.getPaddingRight();//获取右边留白
		float size = this.getTextSize() * 7 / 6;//获取横栏间距（TextSize的默认值为18）
		/*设置size的值是一个核心问题，size的值要适应不同的字体大小（不同大小字体的行距也不同）
		 *经过多次尝试发现以字体大小的7/6倍作为横栏间距最合适
		 * */
		int lines = (int)(h / size);//获取行数
		
		//从下向上画线
		for(int i = 0;i < lines;i++)
			canvas.drawLine(padL//startX
					, this.getHeight() - padB - size * i//startY
					, this.getWidth() - padR//endX
					, this.getHeight() - padB - size * i//endY
					, mPaint);
	}
	
	public int getLineColor() {
		return lineColor;
	}

	public void setLineColor(int color) {
		this.lineColor = color;
	}

	public float getLineWidth() {
		return lineWidth;
	}

	public void setLineWidth(float width) {
		this.lineWidth = width;
	}

}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android: 
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity" >

</LinearLayout>

package com.ayqy.app_test;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.widget.LinearLayout;

public class MainActivity extends Activity {
	
	LinearLayout root;//声明根布局

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		root = (LinearLayout) findViewById(R.id.root);//获取根布局
		//创建自定义EditText控件对象
		myEditText txt = new myEditText(this);
		//设置多行文本
		txt.setText("这是一个很长很长很长很长很长很长很长很长很长很长很长很长很长很长很长很长的测试内容");
		//用来测试是否能够适应不同大小的字体
		//txt.setTextSize(48);
		//txt.setTextSize(24);
		root.addView(txt);//添加控件
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

}