<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/tv1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal
 
="true"
        android:gravity="center"
        android:text="計算器"
        android:textColor="#FF2196F3"
        android:textSize="25sp"
        android:textStyle="italic" />
   
        <TextView
        android:id="@+id/tv_number"
        android:layout_width="wrap_content"
        android:layout_height
 
="wrap_content"
        android:layout_below="@+id/tv1"
        android:layout_marginTop="34dp"
        android:padding="10dp"
        android:text="數值1:"
        android:textColor="#000"
        android:textSize="20sp" />
 <TextView
        android:id="@+id/tv_number2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/et2"
        android:layout_alignLeft="@+id/l1_number"
        android:padding="10dp"
        android:text="數值2:"
        android:textColor="#000"
        android:textSize="20sp" />
 
 
    <EditText
        android:id="@+id/et1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/tv_number"
        android:layout_alignParentRight="true"
        android:layout_toRightOf="@+id/tv_number"
        android:ems="10" 
        />

      

    <EditText
        android:id="@+id/et2"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/et1"
        android:layout_below="@+id/et1"
        android:layout_marginTop="24dp"
        android:ems="10" 
        />

     <TextView
         android:id="@+id/tv2"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignLeft="@+id/tv_number2"
         android:layout_below="@+id/tv_number2"
         android:layout_marginTop="116dp"
         android:gravity="center"
         android:text="顯示計算結果"
         android:textSize="20sp"
         android:textStyle="italic" />

     <Button
         android:id="@+id/btn4"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignRight="@+id/et2"
         android:layout_below="@+id/et2"
         android:layout_marginTop="29dp"
         android:gravity="center"
         android:onClick="click"
         android:text="-"
         android:textColor="#FFF79E38"
         android:textSize="25sp"
         android:textStyle="italic" />

     <Button
         android:id="@+id/btn2"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignBaseline="@+id/btn3"
         android:layout_alignBottom="@+id/btn3"
         android:layout_toRightOf="@+id/tv_number2"
         android:gravity="center"
         android:onClick="click"
         android:text="+"
         android:textColor="#FFE91E63"
         android:textSize="25sp"
         android:textStyle="italic" />

     <Button
         android:id="@+id/btn1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignBaseline="@+id/btn2"
         android:layout_alignBottom="@+id/btn2"
         android:layout_alignLeft="@+id/tv_number2"
         android:gravity="center"
         android:onClick="click"
         android:text="/"
         android:textColor="#FFF44336"
         android:textSize="25sp"
         android:textStyle="italic" />

     <Button
         android:id="@+id/btn3"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignBaseline="@+id/btn4"
         android:layout_alignBottom="@+id/btn4"
         android:layout_toLeftOf="@+id/btn4"
         android:gravity="center"
         android:onClick="click"
         android:text="*"
         android:textColor="#FFF79E38"
         android:textSize="25sp"
         android:textStyle="italic" />

    </RelativeLayout>



package com.example.text;

    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 tv1 = (TextView) findViewById(R.id.tv1);
            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.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+"");
        }

    }

、