1 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  2     xmlns:tools="http://schemas.android.com/tools"
  3     android:layout_width="match_parent"
  4     android:layout_height="match_parent"
  5     android:paddingBottom="@dimen/activity_vertical_margin"
  6     android:paddingLeft="@dimen/activity_horizontal_margin"
  7     android:paddingRight="@dimen/activity_horizontal_margin"
  8     android:paddingTop="@dimen/activity_vertical_margin"
  9     tools:context="com.example.aaa.MainActivity" >
 10 
 11        <TextView
 12            android:id="@+id/tv2"
 13            android:layout_width="wrap_content"
 14            android:layout_height="wrap_content"
 15            android:layout_alignLeft="@+id/et2"
 16            android:layout_centerVertical="true"
 17            android:gravity="center"
 18            android:text="显示计算结果"
 19            android:textStyle="italic" />
 20 
 21        <EditText
 22            android:id="@+id/et2"
 23            android:layout_width="fill_parent"
 24            android:layout_height="wrap_content"
 25            android:layout_above="@+id/tv2"
 26            android:layout_alignLeft="@+id/et1"
 27            android:ems="10" >
 28 
 29            <requestFocus />
 30        </EditText>
 31 
 32        <EditText
 33            android:id="@+id/et1"
 34            android:layout_width="fill_parent"
 35            android:layout_height="wrap_content"
 36            android:layout_above="@+id/et2"
 37            android:layout_alignLeft="@+id/tv1"
 38            android:ems="10" />
 39 
 40        <Button
 41            android:id="@+id/btn3"
 42            android:layout_width="wrap_content"
 43            android:layout_height="wrap_content"
 44            android:layout_below="@+id/btn1"
 45            android:layout_marginTop="16dp"
 46            android:layout_toRightOf="@+id/tv1"
 47            android:gravity="center"
 48            android:onClick="click"
 49            android:text="*"
 50            android:textColor="#FFF79E38"
 51            android:textSize="25sp"
 52            android:textStyle="italic" />
 53 
 54        <Button
 55            android:id="@+id/btn4"
 56            android:layout_width="wrap_content"
 57            android:layout_height="wrap_content"
 58            android:layout_alignBaseline="@+id/btn3"
 59            android:layout_alignBottom="@+id/btn3"
 60            android:layout_toRightOf="@+id/btn3"
 61            android:gravity="center"
 62            android:onClick="click"
 63            android:text="÷"
 64            android:textColor="#FFF79E38"
 65            android:textSize="25sp"
 66            android:textStyle="italic" />
 67 
 68        <TextView
 69            android:id="@+id/tv1"
 70            android:layout_width="wrap_content"
 71            android:layout_height="wrap_content"
 72            android:layout_alignBottom="@+id/btn1"
 73            android:layout_alignParentLeft="true"
 74            android:gravity="center"
 75            android:text="计算器"
 76            android:textColor="#FFF79E38"
 77            android:textSize="25sp"
 78            android:textStyle="italic" />
 79 
 80        <Button
 81            android:id="@+id/btn2"
 82            android:layout_width="wrap_content"
 83            android:layout_height="wrap_content"
 84            android:layout_above="@+id/btn3"
 85            android:layout_alignLeft="@+id/btn4"
 86            android:gravity="center"
 87            android:onClick="click"
 88            android:text="-"
 89            android:textColor="#FFF79E38"
 90            android:textSize="25sp"
 91            android:textStyle="italic" />
 92 
 93        <Button
 94            android:id="@+id/btn1"
 95            android:layout_width="wrap_content"
 96            android:layout_height="wrap_content"
 97            android:layout_alignParentTop="true"
 98            android:layout_marginTop="20dp"
 99            android:layout_toLeftOf="@+id/btn2"
100            android:gravity="center"
101            android:onClick="click"
102            android:text="+"
103            android:textColor="#FFF79E38"
104            android:textSize="25sp"
105            android:textStyle="italic" />
106 
107 </RelativeLayout>

 1 package com.example.bbb;
 2 
 3 import android.os.Bundle;
 4 import android.app.Activity;
 5 import android.view.Menu;
 6 import android.view.View;
 7 import android.view.View.OnClickListener;
 8 import android.widget.Button;
 9 import android.widget.EditText;
10 import android.widget.TextView;
11 import android.widget.Toast;
12 
13 public class MainActivity extends Activity {
14 
15     @Override
16     protected void onCreate(Bundle savedInstanceState) {
17         super.onCreate(savedInstanceState);
18         setContentView(R.layout.activity_main);
19     }
20 
21     public void click(View v) {
22         TextView tv2 = (TextView) findViewById(R.id.tv2);
23         EditText et1 = (EditText) findViewById(R.id.et1);
24         EditText et2 = (EditText) findViewById(R.id.et2);
25         
26         int num1,num2,result=0;
27         num1=Integer.parseInt(et1.getText().toString());
28         num2=Integer.parseInt(et2.getText().toString());
29         
30         switch (v.getId()) {
31         case R.id.btn1:
32             result=num1+num2;
33             break;
34         case R.id.btn2:
35             result=num1-num2;
36             break;
37         case R.id.btn3:
38             result=num1*num2;
39             break;
40         case R.id.btn4:
41             result=num1/num2;
42             break;
43         }
44         tv2.setText(result+"");
45     }
46 
47 }