<?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
 
        <TextView
            android:id="@+id/tv1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:gravity="center"
            android:text="计算器"
            android:textColor="#FF2196F3"
            android:textSize="25sp"
            android:textStyle="italic" />
 
        <LinearLayout
            android:id="@+id/l1_number"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_below="@+id/tv1"
            android:layout_centerVertical="true"
            android:layout_marginLeft="10dp"
            android:layout_marginTop="15dp"
            android:layout_marginRight="10dp"
            android:layout_marginBottom="5dp"
            android:background="#FFFFFF">
 
            <TextView
                android:id="@+id/tv_number"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:padding="10dp"
                android:text="数值1:"
                android:textColor="#000"
                android:textSize="20sp" />
 
            <EditText
                android:id="@+id/et1"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:layout_below="@id/tv1" />
        </LinearLayout>
 
        <LinearLayout
            android:id="@+id/l2_number"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_below="@+id/l1_number"
            android:layout_centerVertical="true"
            android:layout_marginLeft="10dp"
            android:layout_marginTop="15dp"
            android:layout_marginRight="10dp"
            android:layout_marginBottom="5dp"
            android:background="#FFFFFF">
 
            <TextView
                android:id="@+id/tv_number2"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:padding="10dp"
                android:text="数值2:"
                android:textColor="#000"
                android:textSize="20sp" />
 
            <EditText
                android:id="@+id/et2"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:layout_below="@id/tv2" />
        </LinearLayout>
 
 
        <TextView
            android:id="@+id/tv2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@id/l2_number"
            android:layout_centerHorizontal="true"
            android:layout_marginLeft="10dp"
            android:layout_marginTop="50dp"
            android:layout_marginRight="10dp"
            android:layout_marginBottom="50dp"
            android:gravity="center"
            android:text="显示计算结果"
            android:textSize="20sp"
            android:textStyle="italic" />
 
        <Button
            android:id="@+id/btn1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@id/tv2"
            android:gravity="center"
            android:onClick="click"
            android:text="+"
            android:textColor="#FFF44336"
            android:textSize="25sp"
            android:textStyle="italic" />
 
        <Button
            android:id="@+id/btn2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@id/tv2"
            android:layout_toRightOf="@id/btn1"
            android:gravity="center"
            android:onClick="click"
            android:text="-"
            android:textColor="#FFE91E63"
            android:textSize="25sp"
            android:textStyle="italic" />
 
        <Button
            android:id="@+id/btn3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@id/tv2"
            android:layout_toRightOf="@id/btn2"
            android:gravity="center"
            android:onClick="click"
            android:text="*"
            android:textColor="#FFF79E38"
            android:textSize="25sp"
            android:textStyle="italic" />
 
        <Button
            android:id="@+id/btn4"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@id/tv2"
            android:layout_toRightOf="@id/btn3"
            android:gravity="center"
            android:onClick="click"
            android:text="/"
            android:textColor="#FFF79E38"
            android:textSize="25sp"
            android:textStyle="italic" />
 
 
    </RelativeLayout>

package com.example.calculator;
 
import androidx.appcompat.app.AppCompatActivity;
 
import android.os.Bundle;
import android.app.Activity;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
 
 
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+"");
    }
 
}

 

 

<?xml version="1.0" encoding="utf-8"?>     <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"         android:layout_width="match_parent"         android:layout_height="match_parent">           <TextView             android:id="@+id/tv1"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:layout_centerHorizontal="true"             android:gravity="center"             android:text="计算器"             android:textColor="#FF2196F3"             android:textSize="25sp"             android:textStyle="italic" />           <LinearLayout             android:id="@+id/l1_number"             android:layout_width="match_parent"             android:layout_height="wrap_content"             android:layout_below="@+id/tv1"             android:layout_centerVertical="true"             android:layout_marginLeft="10dp"             android:layout_marginTop="15dp"             android:layout_marginRight="10dp"             android:layout_marginBottom="5dp"             android:background="#FFFFFF">               <TextView                 android:id="@+id/tv_number"                 android:layout_width="wrap_content"                 android:layout_height="wrap_content"                 android:padding="10dp"                 android:text="数值1:"                 android:textColor="#000"                 android:textSize="20sp" />               <EditText                 android:id="@+id/et1"                 android:layout_width="fill_parent"                 android:layout_height="wrap_content"                 android:layout_below="@id/tv1" />         </LinearLayout>           <LinearLayout             android:id="@+id/l2_number"             android:layout_width="match_parent"             android:layout_height="wrap_content"             android:layout_below="@+id/l1_number"             android:layout_centerVertical="true"             android:layout_marginLeft="10dp"             android:layout_marginTop="15dp"             android:layout_marginRight="10dp"             android:layout_marginBottom="5dp"             android:background="#FFFFFF">               <TextView                 android:id="@+id/tv_number2"                 android:layout_width="wrap_content"                 android:layout_height="wrap_content"                 android:padding="10dp"                 android:text="数值2:"                 android:textColor="#000"                 android:textSize="20sp" />               <EditText                 android:id="@+id/et2"                 android:layout_width="fill_parent"                 android:layout_height="wrap_content"                 android:layout_below="@id/tv2" />         </LinearLayout>             <TextView             android:id="@+id/tv2"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:layout_below="@id/l2_number"             android:layout_centerHorizontal="true"             android:layout_marginLeft="10dp"             android:layout_marginTop="50dp"             android:layout_marginRight="10dp"             android:layout_marginBottom="50dp"             android:gravity="center"             android:text="显示计算结果"             android:textSize="20sp"             android:textStyle="italic" />           <Button             android:id="@+id/btn1"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:layout_below="@id/tv2"             android:gravity="center"             android:onClick="click"             android:text="+"             android:textColor="#FFF44336"             android:textSize="25sp"             android:textStyle="italic" />           <Button             android:id="@+id/btn2"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:layout_below="@id/tv2"             android:layout_toRightOf="@id/btn1"             android:gravity="center"             android:onClick="click"             android:text="-"             android:textColor="#FFE91E63"             android:textSize="25sp"             android:textStyle="italic" />           <Button             android:id="@+id/btn3"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:layout_below="@id/tv2"             android:layout_toRightOf="@id/btn2"             android:gravity="center"             android:onClick="click"             android:text="*"             android:textColor="#FFF79E38"             android:textSize="25sp"             android:textStyle="italic" />           <Button             android:id="@+id/btn4"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:layout_below="@id/tv2"             android:layout_toRightOf="@id/btn3"             android:gravity="center"             android:onClick="click"             android:text="/"             android:textColor="#FFF79E38"             android:textSize="25sp"             android:textStyle="italic" />         </RelativeLayout>