//请在这里添加您的包名import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.util.AttributeSet;import android.widget.EditText;public class LineEditText extends EditText {    private Paint mPaint;    /**     * @param context     * @param attrs     */    public LineEditText(Context context, AttributeSet attrs) {        super(context, attrs);        // TODO Auto-generated constructor stub        mPaint = new Paint();                mPaint.setStyle(Paint.Style.STROKE);        mPaint.setColor(Color.BLUE);    }        @Override    public void onDraw(Canvas canvas)    {        super.onDraw(canvas);        //        画底线        canvas.drawLine(0,this.getHeight()-1,  this.getWidth()-1, this.getHeight()-1, mPaint);    }}

import android.app.Activity;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Rect;import android.os.Bundle;import android.text.InputFilter;import android.util.AttributeSet;import android.widget.EditText;public class LineEditTextTest extends Activity {    /** Called when the activity is first created. */    private EditText mEdit;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);                mEdit=(LineEditText)findViewById(R.id.myEdit);        mEdit.setHint("从这里开始输入...");        mEdit.setSingleLine();        mEdit.setFilters(new InputFilter[]{
   new InputFilter.LengthFilter(20)});    }    }