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/et3"
           android:layout_width="fill_parent"
           android:layout_height="wrap_content"
           android:layout_below="@+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_below="@+id/et3"
           android:layout_alignLeft="@+id/tv1"
           android:hint="请输入数值"
           android:ems="10" />
           <EditText
           android:id="@+id/et2"
           android:layout_width="fill_parent"
           android:layout_height="wrap_content"
           android:layout_below="@+id/et1"
           android:layout_alignLeft="@+id/tv1"
           android:hint="请输入数值"
           android:ems="10" />
     <Button
            android:id="@+id/sum"
            android:layout_width="152dp"
            android:layout_height="wrap_content"
            android:editable="false"
            android:text="+" />

        <Button
            android:id="@+id/reduce"
            android:layout_width="152dp"
            android:layout_height="wrap_content"
            android:layout_toRightOf="@+id/sum"
            android:text="-"
            android:textSize="20sp" />
        <Button
            android:id="@+id/ride"
            android:layout_width="152dp"
            android:layout_height="wrap_content"
            android:layout_below="@+id/sum"
            android:text="X" />

        <Button
            android:id="@+id/except"
            android:layout_width="152dp"
            android:layout_height="wrap_content"
            android:layout_below="@+id/reduce"
            android:layout_toRightOf="@+id/ride"
            android:text="/" />
        
</RelativeLayout>

package com.example.aaaa;
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);

        int num1,num2,result=0;
        num1=Integer.parseInt(et1.getText().toString());
        num2=Integer.parseInt(et2.getText().toString());

        switch (v.getId()) {
        case R.id.sum:
            result=num1+num2;
            break;
        case R.id.reduce:
            result=num1-num2;
            break;
        case R.id.ride:
            result=num1*num2;
            break;
        case R.id.except:
            result=num1/num2;
            break;
        }
        tv2.setText(result+"");
    }

}