怎么让Android buttton按钮美化?请大家帮帮小弟我

package com.demo.android.bmi;import java.text.DecimalFormat;import android.app.Activity;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.view.View.OnTouchListener;import android.widget.Button;import android.widget.EditText;import android.widget.TextView;public class Bmi extends Activity {    /** Called when the activity is first created.      * @param <calcBMI>*/    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);                //Listen for button clicks        Button button = (Button)findViewById(R.id.submit);        button.setOnClickListener(calcBMI);    }        private OnClickListener calcBMI = new OnClickListener(){    public void onClick(View v){        DecimalFormat nf =new DecimalFormat("0.00");        EditText fieldheight = (EditText)findViewById(R.id.height);        EditText fieldweight = (EditText)findViewById(R.id.weight);        double height = Double.parseDouble(fieldheight.getText().toString())/100;        double weight = Double.parseDouble(fieldweight.getText().toString());        double BMI = weight / (height * height);                TextView result = (TextView)findViewById(R.id.result);        result.setText("Your BMI is "+nf.format(BMI));                //Give health advice        TextView fieldsuggest = (TextView)findViewById(R.id.suggest);        if(BMI>25){            fieldsuggest.setText(R.string.advice_heavy);        } else if(BMI<20){            fieldsuggest.setText(R.string.advice_light);        } else {            fieldsuggest.setText(R.string.advice_average);        }    }    };    }