<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    //加载背景图片
    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:background="@drawable/jsq"
    />
    <Button
        android:id="@+id/bt1"
        android:text="+"
        android:textSize="25dp"
        android:textColor="#ffffff"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="200dp"
        android:layout_marginRight="20dp"
        android:onClick="click_bt1"
        tools:ignore="OnClick">
    </Button>

    <Button
        android:id="@+id/bt2"
        android:text="-"
        android:textSize="25dp"
        android:textColor="#ffffff"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/bt1"
        android:layout_alignTop="@id/bt1"
        android:layout_marginRight="20dp"
        android:onClick="click_bt2"
        />

    <Button
        android:id="@+id/bt3"
        android:text="×"
        android:textSize="25dp"
        android:textColor="#ffffff"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/bt2"
        android:layout_alignTop="@id/bt2"
        android:layout_marginRight="20dp"
        android:onClick="click_bt3"
        tools:ignore="OnClick" />

    <Button
        android:id="@+id/bt4"
        android:text="÷"
        android:textSize="25dp"
        android:textColor="#ffffff"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/bt3"
        android:layout_alignTop="@id/bt3"
        android:onClick="click_bt4"
        tools:ignore="OnClick" />

    <EditText
        android:id="@+id/et1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:hint="输入第一个数"

        android:layout_centerHorizontal="true"
        android:layout_marginTop="44dp"
        />
    <EditText
        android:id="@+id/et2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:hint="输入第一个数"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="110dp"
        />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="结果："
        android:textSize="35dp"
        android:layout_marginTop="280dp"
        />
    <TextView
        android:id="@+id/tv1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:textSize="35dp"
        android:layout_marginLeft="120dp"
        android:layout_marginTop="280dp"
        />
</RelativeLayout>

package com.example.myapplication;

import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import org.w3c.dom.Text;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private Button bt1;
    private Button bt2;
    private Button bt3;
    private Button bt4;
    private EditText et1, et2;
    private TextView tv1;
    private double d1, d2, sum = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bt1 = (Button) findViewById(R.id.bt1);
        bt2 =(Button)  findViewById(R.id.bt1);
        bt3 = (Button) findViewById(R.id.bt1);
        bt4 = (Button) findViewById(R.id.bt1);
        et1 =(EditText) findViewById(R.id.et1);
        et2 =(EditText) findViewById(R.id.et2);
        tv1 = (TextView) findViewById(R.id.tv1);
        bt1.setOnClickListener(this);
        bt2.setOnClickListener(this);
        bt3.setOnClickListener(this);
        bt4.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        d1=Integer.parseInt(et1.getText().toString());
        d2=Integer.parseInt(et2.getText().toString());

        sum=d1+d2;
        String q = String.valueOf(sum);


        tv1.setText(d1+"+"+d2+"="+q);
    }

    public void click_bt2(View view) {
        d1=Integer.parseInt(et1.getText().toString());
        d2=Integer.parseInt(et2.getText().toString());
        sum=d1-d2;
        String q = String.valueOf(sum);
        tv1.setText(d1+"—"+d2+"="+q);
    }
    public void click_bt3(View view) {
        d1=Integer.parseInt(et1.getText().toString());
        d2=Integer.parseInt(et2.getText().toString());
        sum=d1*d2;
        String q = String.valueOf(sum);
        tv1.setText(d1+"×"+d2+"="+q);
    }

    public void click_bt4(View view) {
        d1=Integer.parseInt(et1.getText().toString());
        d2=Integer.parseInt(et2.getText().toString());
        sum=d1/d2;
        String q = String.valueOf(sum);
        tv1.setText(d1+"÷"+d2+"="+q);
    }
}