安卓开发入门：手把手教你打造简易计算器App

安卓App开发实例：简单计算器应用

1. 项目概述

本项目是一个简单的安卓计算器应用，用户可以通过点击按钮输入数字和运算符，进行基本的加减乘除运算。应用界面简洁，功能明确，适合初学者学习安卓开发。

2. 开发环境

• 操作系统：Windows 10
• 开发工具：Android Studio 4.2
• 编程语言：Java
• 最低API级别：API 21 (Android 5.0 Lollipop)

3. 项目结构

CalculatorApp/
├── app/
│   ├── src/
│   │   ├── main/
│   │   │   ├── java/
│   │   │   │   └── com/
│   │   │   │       └── example/
│   │   │   │           └── calculatorapp/
│   │   │   │               ├── MainActivity.java
│   │   │   ├── res/
│   │   │   │   ├── layout/
│   │   │   │   │   ├── activity_main.xml
│   │   │   │   ├── values/
│   │   │   │   │   ├── strings.xml
│   │   │   │   │   ├── colors.xml
│   │   │   │   │   ├── dimens.xml
│   │   │   ├── AndroidManifest.xml
│   ├── build.gradle
│   ├── proguard-rules.pro
├── build.gradle
├── settings.gradle

4. 界面设计

4.1 activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp">

    <EditText
        android:id="@+id/et_display"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="0"
        android:textSize="24sp"
        android:gravity="right"
        android:editable="false"
        android:background="@null" />

    <GridLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:columnCount="4"
        android:rowCount="5">

        <Button
            android:id="@+id/btn_7"
            android:text="7"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

        <Button
            android:id="@+id/btn_8"
            android:text="8"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

        <Button
            android:id="@+id/btn_9"
            android:text="9"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

        <Button
            android:id="@+id/btn_divide"
            android:text="/"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

        <Button
            android:id="@+id/btn_4"
            android:text="4"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

        <Button
            android:id="@+id/btn_5"
            android:text="5"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

        <Button
            android:id="@+id/btn_6"
            android:text="6"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

        <Button
            android:id="@+id/btn_multiply"
            android:text="*"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

        <Button
            android:id="@+id/btn_1"
            android:text="1"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

        <Button
            android:id="@+id/btn_2"
            android:text="2"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

        <Button
            android:id="@+id/btn_3"
            android:text="3"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

        <Button
            android:id="@+id/btn_subtract"
            android:text="-"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

        <Button
            android:id="@+id/btn_0"
            android:text="0"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

        <Button
            android:id="@+id/btn_dot"
            android:text="."
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

        <Button
            android:id="@+id/btn_equals"
            android:text="="
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

        <Button
            android:id="@+id/btn_add"
            android:text="+"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1" />

    </GridLayout>
</LinearLayout>

4.2 strings.xml

<resources>
    <string name="app_name">Calculator</string>
</resources>

4.3 colors.xml

<resources>
    <color name="colorPrimary">#3F51B5</color>
    <color name="colorPrimaryDark">#303F9F</color>
    <color name="colorAccent">#FF4081</color>
</resources>

4.4 dimens.xml

<resources>
    <dimen name="activity_horizontal_margin">16dp</dimen>
    <dimen name="activity_vertical_margin">16dp</dimen>
</resources>

5. 功能实现

5.1 MainActivity.java

package com.example.calculatorapp;

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

public class MainActivity extends AppCompatActivity {

    private EditText etDisplay;
    private String currentNumber = "";
    private String operator = "";
    private double result = 0.0;

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

        etDisplay = findViewById(R.id.et_display);

        setupButtons();
    }

    private void setupButtons() {
        int[] buttonIds = {
                R.id.btn_0, R.id.btn_1, R.id.btn_2, R.id.btn_3, R.id.btn_4,
                R.id.btn_5, R.id.btn_6, R.id.btn_7, R.id.btn_8, R.id.btn_9,
                R.id.btn_dot, R.id.btn_add, R.id.btn_subtract, R.id.btn_multiply,
                R.id.btn_divide, R.id.btn_equals
        };

        for (int id : buttonIds) {
            findViewById(id).setOnClickListener(this::onButtonClick);
        }
    }

    private void onButtonClick(View view) {
        Button button = (Button) view;
        String buttonText = button.getText().toString();

        switch (buttonText) {
            case "0":
            case "1":
            case "2":
            case "3":
            case "4":
            case "