Android Studio 制作简易计算器

 activity_main.xml代码

<?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">

    <EditText
        android:id="@+id/editTextNumber"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="输入数字"
        android:inputType="numberDecimal"
        android:textSize="24sp"
        android:layout_margin="16dp"/>

    <GridLayout
        android:layout_below="@id/editTextNumber"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:rowCount="5"
        android:columnCount="4">

        <Button android:id="@+id/button1" android:text="1" />
        <Button android:id="@+id/button2" android:text="2" />
        <Button android:id="@+id/button3" android:text="3" />
        <Button android:id="@+id/buttonPlus" android:text="+" />

        <Button android:id="@+id/button4" android:text="4" />
        <Button android:id="@+id/button5" android:text="5" />
        <Button android:id="@+id/button6" android:text="6" />
        <Button android:id="@+id/buttonMinus" android:text="-" />

        <Button android:id="@+id/button7" android:text="7" />
        <Button android:id="@+id/button8" android:text="8" />
        <Button android:id="@+id/button9" android:text="9" />
        <Button android:id="@+id/buttonMultiply" android:text="*" />

        <Button android:id="@+id/buttonC" android:text="C" />
        <Button android:id="@+id/button0" android:text="0" />
        <Button android:id="@+id/buttonEquals" android:text="=" />
        <Button android:id="@+id/buttonDivide" android:text="/" />
    </GridLayout>
</RelativeLayout>

MainActivity代码

package com.example.myapplication;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import androidx.appcompat.app.AppCompatActivity;

import com.example.myapplication.R;

public class MainActivity extends AppCompatActivity {

    private EditText editTextNumber;
    private String operator = "";
    private double firstValue = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        editTextNumber = findViewById(R.id.editTextNumber);

        int[] buttonIds = {
                R.id.button1, R.id.button2, R.id.button3, R.id.buttonPlus,
                R.id.button4, R.id.button5, R.id.button6, R.id.buttonMinus,
                R.id.button7, R.id.button8, R.id.button9, R.id.buttonMultiply,
                R.id.buttonC, R.id.button0, R.id.buttonEquals, R.id.buttonDivide
        };

        for (int id : buttonIds) {
            Button button = findViewById(id);
            button.setOnClickListener(new ButtonClickListener());
        }
    }

    private class ButtonClickListener implements View.OnClickListener {
        @Override
        public void onClick(View v) {
            Button button = (Button) v;
            String buttonText = button.getText().toString();

            switch (buttonText) {
                case "C":
                    editTextNumber.setText("");
                    firstValue = 0;
                    operator = "";
                    break;
                case "=":
                    double secondValue = Double.parseDouble(editTextNumber.getText().toString());
                    double result = calculate(firstValue, secondValue, operator);
                    editTextNumber.setText(String.valueOf(result));
                    operator = "";
                    break;
                case "+":
                case "-":
                case "*":
                case "/":
                    firstValue = Double.parseDouble(editTextNumber.getText().toString());
                    operator = buttonText;
                    editTextNumber.setText("");
                    break;
                default:
                    editTextNumber.append(buttonText);
                    break;
            }
        }
    }

    private double calculate(double firstValue, double secondValue, String operator) {
        switch (operator) {
            case "+":
                return firstValue + secondValue;
            case "-":
                return firstValue - secondValue;
            case "*":
                return firstValue * secondValue;
            case "/":
                return secondValue != 0 ? firstValue / secondValue : 0;
            default:
                return 0;
        }
    }
}