计算器

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >
    
    <TextView
        android:id="@+id/tv2"       
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/et2"
        android:layout_centerVertical="true"
        android:gravity="center"
        android:text="显示计算结果"
        android:textStyle="italic" />
    
    <EditText
         android:id="@+id/et2"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:layout_above="@+id/tv2"
         android:layout_alignLeft="@+id/et1"
         android:ems="10" >
          <requestFocus />
          
          </EditText>
          
        
    <EditText
        android:id="@+id/et1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_above="@+id/et2"
        android:layout_alignLeft="@+id/tv1"
        android:ems="10" />
  
    <Button
        android:id="@+id/btn3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/btn1"
        android:layout_marginTop="16dp"
        android:layout_toRightOf="@+id/tv1"
        android:gravity="center"
        android:onClick="click"
        android:text="*"
        android:textColor="#000000"
        android:textSize="25sp"
        android:textStyle="italic" />
 
    <Button
        android:id="@+id/btn4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/btn3"
        android:layout_alignBottom="@+id/btn3"
        android:layout_toRightOf="@+id/btn3"
        android:gravity="center"
        android:onClick="click"
        android:text="÷"
        android:textColor="#000000"
        android:textSize="25sp"
        android:textStyle="italic" />
    
    <TextView
            android:id="@+id/tv1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignBottom="@+id/btn1"
            android:layout_alignParentLeft="true"
            android:gravity="center"
            android:text="计算器"
            android:textColor="#000000"
            android:textSize="25sp"
            android:textStyle="italic" />
 
       
        <Button
            android:id="@+id/btn2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_above="@+id/btn3"
            android:layout_alignLeft="@+id/btn4"
            android:gravity="center"
            android:onClick="click"
            android:text="-"
            android:textColor="#000000"
            android:textSize="25sp"
            android:textStyle="italic" />
 
        <Button
            android:id="@+id/btn1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:layout_marginTop="20dp"
            android:layout_toLeftOf="@+id/btn2"
            android:gravity="center"
            android:onClick="click"
            android:text="+"
            android:textColor="#000000"
            android:textSize="25sp"
            android:textStyle="italic" />
 
        
</RelativeLayout>

package com.example.s;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    
    public void click(View v) {
        TextView tv2 = (TextView) findViewById(R.id.tv2);
        EditText et1 = (EditText) findViewById(R.id.et1);
        EditText et2 = (EditText) findViewById(R.id.et2);
        double num1,num2,result=0;
        num1=Integer.parseInt(et1.getText().toString());
        num2=Integer.parseInt(et2.getText().toString());

        switch (v.getId()) {
            case R.id.btn1:
                result=num1+num2;
                break;
            case R.id.btn2:
                result=num1-num2;
                break;
            case R.id.btn3:
                result=num1*num2;
                break;
            case R.id.btn4:
                result=num1/num2;
                break;
        }
        tv2.setText(result+"");
    }
}