【Android】控件与布局入门 - 简易计算器

目录

[1. 基础开发环境](#1. 基础开发环境)

[2. 计算器的布局和相关按钮](#2. 计算器的布局和相关按钮)

[3. 计算器的主要运算逻辑](#3. 计算器的主要运算逻辑)

[4. APK 文件](#4. APK 文件)

[5. 项目源码](#5. 项目源码)

---

1. 基础开发环境

JDK：JDK17

Android Studio：Android Studio Giraffe | 2022.3.1

Android SDK：Android API 34

Gradle: gradle-8.0-bin.zip

2. 计算器的布局和相关按钮

使用 LinearLayout 和 GridLayout 实现计算器的交互前端。

layout 文件如下

<?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:background="#EEEEEE"
    android:orientation="vertical"
    android:padding="5dp">

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">

            <TextView
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:gravity="center"
                android:text="@string/simple_calculator"
                android:textColor="@color/black"
                android:textSize="20sp"/>

            <TextView
                android:id="@+id/tv_result"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:background="@color/white"
                android:lines="3"
                android:text="@string/filler"
                android:gravity="end|bottom"
                android:textColor="@color/black"
                android:textSize="25sp"/>

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

                <Button
                    android:id="@+id/btn_clear_entry"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/cancel"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_divide"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/divide"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_multiply"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/multiply"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_clear"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/delete"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_seven"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/seven"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_eight"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/eight"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_nine"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/nine"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_plus"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/plus"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_four"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/four"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_five"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/five"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_six"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/six"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_minus"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/minus"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_one"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/one"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_two"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/two"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_three"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/three"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_sqrt"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/sqrt"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_reciprocal"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/reciprocal"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_zero"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/zero"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_dot"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/dot"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_equal"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/equal"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

            </GridLayout>

        </LinearLayout>

    </ScrollView>


</LinearLayout>

相关 values 如下：

• strings.xml

  <resources> <string name="app_name">calculator</string> <string name="simple_calculator">计算器</string> <string name="filler">0</string> <string name="cancel">CE</string> <string name="divide">÷</string> <string name="multiply">×</string> <string name="plus">+</string> <string name="minus">-</string> <string name="delete">C</string> <string name="zero">0</string> <string name="one">1</string> <string name="two">2</string> <string name="three">3</string> <string name="four">4</string> <string name="five">5</string> <string name="six">6</string> <string name="seven">7</string> <string name="eight">8</string> <string name="nine">9</string> <string name="sqrt">√</string> <string name="dot">.</string> <string name="equal">=</string> <string name="reciprocal">1/X</string> </resources>

• dimens.xml

  <?xml version="1.0" encoding="utf-8"?> <resources> <dimen name="button_font_size">30sp</dimen> <dimen name="button_height">75dp</dimen> </resources>

实际效果：

3. 计算器的主要运算逻辑

package com.example.calculator;

import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;

import java.util.Arrays;
import java.util.List;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private TextView tvResult;

    private String firstNum = "";
    private String secondNum = "";
    private String operator = "";
    private String result = "";
    private String showText = "";

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

        // 从布局文件中获取文本视图
        tvResult = findViewById(R.id.tv_result);

        // 为所有按钮注册点击监听器
        findViewById(R.id.btn_clear_entry).setOnClickListener(this);
        findViewById(R.id.btn_divide).setOnClickListener(this);
        findViewById(R.id.btn_multiply).setOnClickListener(this);
        findViewById(R.id.btn_clear).setOnClickListener(this);
        findViewById(R.id.btn_seven).setOnClickListener(this);
        findViewById(R.id.btn_eight).setOnClickListener(this);
        findViewById(R.id.btn_nine).setOnClickListener(this);
        findViewById(R.id.btn_plus).setOnClickListener(this);
        findViewById(R.id.btn_four).setOnClickListener(this);
        findViewById(R.id.btn_five).setOnClickListener(this);
        findViewById(R.id.btn_six).setOnClickListener(this);
        findViewById(R.id.btn_minus).setOnClickListener(this);
        findViewById(R.id.btn_one).setOnClickListener(this);
        findViewById(R.id.btn_two).setOnClickListener(this);
        findViewById(R.id.btn_three).setOnClickListener(this);
        findViewById(R.id.btn_sqrt).setOnClickListener(this);
        findViewById(R.id.btn_reciprocal).setOnClickListener(this);
        findViewById(R.id.btn_zero).setOnClickListener(this);
        findViewById(R.id.btn_dot).setOnClickListener(this);
        findViewById(R.id.btn_equal).setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        String inputText = ((TextView) view).getText().toString();

        List<Integer> fourOperations = Arrays.asList(R.id.btn_plus, R.id.btn_minus, R.id.btn_multiply, R.id.btn_divide);
        int id = view.getId();

        if (id == R.id.btn_clear) {
            // 清除
            clear();
        } else if (id == R.id.btn_clear_entry) {
            // 清除输入
            clearEntryOperate();
        } else if (fourOperations.contains(id)) {
            operator = inputText;
            refreshShowText(showText + operator);
            // 四则运算
        } else if (id == R.id.btn_equal) {
            // 等号
            if (!secondNum.equals("")) {
                double calculateResult = calculateFour();
                refreshOperateResult(String.valueOf(calculateResult));
                refreshShowText(result);
            }
        } else if (id == R.id.btn_sqrt) {
            // 根号
            double sqrtResult = Math.sqrt(Double.parseDouble(firstNum));
            refreshOperateResult(String.valueOf(sqrtResult));
            refreshShowText(result);
        } else if (id == R.id.btn_reciprocal) {
            // 倒数
            double reciprocalResult = 1.0 / Double.parseDouble(firstNum);
            refreshOperateResult(String.valueOf(reciprocalResult));
            refreshShowText(result);
        } else {
            // 其它
            if (result.length() > 0 && operator.equals("")) {
                clear();
            }

            if (operator.equals("")) {
                firstNum += inputText;
            } else {
                secondNum += inputText;
            }
            if (showText.equals("0") && !inputText.equals(".")) {
                refreshShowText(inputText);
            } else {
                refreshShowText(showText + inputText);
            }

        }
    }

    private double calculateFour() {
        switch (operator) {
            case "+":
                return Double.parseDouble(firstNum) + Double.parseDouble(secondNum);
            case "-":
                return Double.parseDouble(firstNum) - Double.parseDouble(secondNum);
            case "×":
                return Double.parseDouble(firstNum) * Double.parseDouble(secondNum);
            default:
                return Double.parseDouble(firstNum) / Double.parseDouble(secondNum);
        }
    }

    private void clear() {
        refreshOperateResult("");
        refreshShowText("0");
    }

    private void refreshOperateResult(String newResult) {
        result = newResult;
        firstNum = result;
        secondNum = "";
        operator = "";

    }

    private void clearEntryOperate() {
        String tmp = showText.substring(0, showText.length() - 1);
        if (tmp.equals("")) {
            tmp = "0";
        }
        refreshShowText(tmp);
    }

    // 刷新显示文本
    private void refreshShowText(String text) {
        showText = text;
        integerRemoveDot();
        tvResult.setText(showText);
    }

    private void integerRemoveDot() {
        int start = showText.indexOf(".");
        if (start != -1) {
            int end = showText.length();
            String value = showText.substring(start + 1, end);
            if (Double.parseDouble(value) == 0.0) {
                showText = showText.substring(0, start);
            }
        }
    }
}

4. APK 文件

构建好的 APK 文件见文件开头，可直接下载安装。

5. 项目源码

https://gitee.com/hl0929/calculator