【Android】简易计算器_android开发一个简易的计算器

作者：从前慢现在也慢 | 2024-03-12 08:35:33

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android开发一个简易的计算器

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Android简易计算器

前言
一、Kotlin版本
- 1. activity_main.xml
- 2. MainActivity.kt
二、Java版本
- 1. activity_main.xml
- 2. MainActivity.java
总结

前言

提示：Kotlin版本＋Java版本

这学期学习了Android开发，写的第一个小项目就是简易计算器。原本只写了kotlin版本，放假后加了Java版本，在此记录下。

计算器的功能包括【加减乘除、求余】，功能比较简单，所以是简易计算器。

计算器效果如图：

简易计算器

一、Kotlin版本

示例：pandas 是基于NumPy 的一种工具，该工具是为了解决数据分析任务而创建的。

1. activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    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:id="@+id/main_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#1a1c21"
    tools:context=".MainActivity">

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guideline1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_begin="167dp" />


    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guideline2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_begin="261dp" />


    <TextView
        android:id="@+id/process_text_view"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginStart="20dp"
        android:layout_marginEnd="20dp"
        android:gravity="bottom|end"
        android:letterSpacing="0.1"
        android:text="16x16"
        android:textColor="#f4f0f2"
        android:textSize="25sp"
        app:layout_constraintBottom_toTopOf="@+id/guideline1"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.0" />

    <TextView
        android:id="@+id/result_text_view"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginStart="20dp"
        android:layout_marginEnd="20dp"
        android:gravity="end|center_vertical"
        android:letterSpacing="0.1"
        android:text="196"
        android:textColor="@color/white"
        android:textSize="30sp"
        app:layout_constraintBottom_toTopOf="@+id/guideline2"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/guideline1" />

    <TextView
        android:id="@+id/btn_view"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:background="@drawable/top_round_shape"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/result_text_view"
        app:layout_constraintVertical_bias="0.0" />

    <TextView
        android:id="@+id/mod_view"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="operatorButtonClicked"
        android:text="@string/percent"
        android:textColor="#d74b51"
        android:textSize="25sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/div_view"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/view_M"
        app:layout_constraintTop_toBottomOf="@+id/result_text_view" />

    <TextView
        android:id="@+id/view_M"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="mButtonClicked"
        android:text="@string/M"
        android:textColor="#29d1b2"
        android:textSize="22sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/view_9"
        app:layout_constraintEnd_toStartOf="@+id/mod_view"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/del_view"
        app:layout_constraintTop_toBottomOf="@+id/result_text_view" />

    <TextView
        android:id="@+id/view_7"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="numberButtonClicked"
        android:text="@string/num_7"
        android:textColor="@color/white"
        android:textSize="22sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/view_4"
        app:layout_constraintEnd_toStartOf="@+id/view_8"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/ac_view" />

    <TextView
        android:id="@+id/view_8"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="numberButtonClicked"
        android:text="@string/num_8"
        android:textColor="@color/white"
        android:textSize="22sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/view_5"
        app:layout_constraintEnd_toStartOf="@+id/view_9"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/view_7"
        app:layout_constraintTop_toBottomOf="@+id/del_view" />

    <TextView
        android:id="@+id/view_4"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="numberButtonClicked"
        android:text="@string/num_4"
        android:textColor="@color/white"
        android:textSize="22sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/view_1"
        app:layout_constraintEnd_toStartOf="@+id/view_5"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/view_7" />

    <TextView
        android:id="@+id/view_1"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="numberButtonClicked"
        android:text="@string/num_1"
        android:textColor="@color/white"
        android:textSize="22sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/view_0"
        app:layout_constraintEnd_toStartOf="@+id/view_2"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/view_4" />

    <TextView
        android:id="@+id/view_0"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="numberButtonClicked"
        android:text="@string/num_0"
        android:textColor="@color/white"
        android:textSize="22sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/dot_view"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/view_1" />

    <TextView
        android:id="@+id/view_3"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="numberButtonClicked"
        android:text="@string/num_3"
        android:textColor="@color/white"
        android:textSize="22sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/equal_view"
        app:layout_constraintEnd_toStartOf="@+id/add_view"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/view_2"
        app:layout_constraintTop_toBottomOf="@+id/view_6" />

    <TextView
        android:id="@+id/view_5"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="numberButtonClicked"
        android:text="@string/num_5"
        android:textColor="@color/white"
        android:textSize="22sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/view_2"
        app:layout_constraintEnd_toStartOf="@+id/view_6"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/view_4"
        app:layout_constraintTop_toBottomOf="@+id/view_8" />

    <TextView
        android:id="@+id/equal_view"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="equalButtonClicked"
        android:text="@string/equal"
        android:textColor="#ffff00"
        android:textSize="30sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/sub_view"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/dot_view"
        app:layout_constraintTop_toBottomOf="@+id/view_3" />

    <TextView
        android:id="@+id/dot_view"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="dotButtonClicked"
        android:text="@string/dot"
        android:textColor="@color/white"
        android:textSize="30sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/equal_view"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/view_0"
        app:layout_constraintTop_toBottomOf="@+id/view_2" />

    <TextView
        android:id="@+id/add_view"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="operatorButtonClicked"
        android:text="@string/add"
        android:textColor="#d74b51"
        android:textSize="35sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/sub_view"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/view_3"
        app:layout_constraintTop_toBottomOf="@+id/mul_view" />

    <TextView
        android:id="@+id/sub_view"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="operatorButtonClicked"
        android:text="@string/sub"
        android:textColor="#d74b51"
        android:textSize="35sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/equal_view"
        app:layout_constraintTop_toBottomOf="@+id/add_view" />

    <TextView
        android:id="@+id/view_2"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="numberButtonClicked"
        android:text="@string/num_2"
        android:textColor="@color/white"
        android:textSize="22sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/dot_view"
        app:layout_constraintEnd_toStartOf="@+id/view_3"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/view_1"
        app:layout_constraintTop_toBottomOf="@+id/view_5" />

    <TextView
        android:id="@+id/mul_view"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="operatorButtonClicked"
        android:text="@string/mul"
        android:textColor="#d74b51"
        android:textSize="35sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/add_view"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/view_6"
        app:layout_constraintTop_toBottomOf="@+id/div_view" />

    <TextView
        android:id="@+id/view_6"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="numberButtonClicked"
        android:text="@string/num_6"
        android:textColor="@color/white"
        android:textSize="22sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/view_3"
        app:layout_constraintEnd_toStartOf="@+id/mul_view"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/view_5"
        app:layout_constraintTop_toBottomOf="@+id/view_9" />

    <TextView
        android:id="@+id/ac_view"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="clearButtonClicked"
        android:text="@string/AC"
        android:textColor="#29d1b2"
        android:textSize="22sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/view_7"
        app:layout_constraintEnd_toStartOf="@+id/del_view"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/result_text_view" />

    <TextView
        android:id="@+id/view_9"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="numberButtonClicked"
        android:text="@string/num_9"
        android:textColor="@color/white"
        android:textSize="22sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/view_6"
        app:layout_constraintEnd_toStartOf="@+id/div_view"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/view_8"
        app:layout_constraintTop_toBottomOf="@+id/view_M" />

    <TextView
        android:id="@+id/div_view"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="operatorButtonClicked"
        android:text="@string/div"
        android:textColor="#d74b51"
        android:textSize="35sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/mul_view"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/view_9"
        app:layout_constraintTop_toBottomOf="@+id/mod_view" />

    <TextView
        android:id="@+id/del_view"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:background="@drawable/round_shape"
        android:gravity="center"
        android:onClick="delButtonClicked"
        android:text="@string/Del"
        android:textColor="#29d1b2"
        android:textSize="22sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/view_8"
        app:layout_constraintEnd_toStartOf="@+id/view_M"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/ac_view"
        app:layout_constraintTop_toBottomOf="@+id/result_text_view" />

    <ImageView
        android:id="@+id/lightMode"
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:layout_marginTop="5dp"
        android:layout_marginEnd="5dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@drawable/mode_ic" />
</androidx.constraintlayout.widget.ConstraintLayout>
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2. MainActivity.kt

package com.example.my_counter

import android.os.Bundle
import android.util.Log
import android.view.View
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import com.example.my_counter.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {
    private val currentInputNumString = StringBuilder()
    private val numbersList = mutableListOf<Double>()
    private val operatorsList = mutableListOf<String>()
    private val dotsList = mutableListOf(false)
    private var isNumStart = true

    private lateinit var processTextView: TextView
    private lateinit var resultTextView: TextView

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        processTextView = binding.processTextView
        resultTextView = binding.resultTextView
    }

    fun numberButtonClicked(view: View) {
        val tv = view as TextView
        if (currentInputNumString.toString() == "0") {
            currentInputNumString.clear()
        }
        // 更新text view内容
        currentInputNumString.append(tv.text)
        processTextView.text = currentInputNumString.toString()

        if (isNumStart) {
            isNumStart = false
        }
    }

    fun operatorButtonClicked(view: View) {
        val tv = view as TextView
        val myOperators = listOf('+', '-', '×', '÷', '%')
        val digits = listOf('0', '1', '2', '3', '4', '5', '6', '7', '8', '9')
        // 如果前一个符号为运算符，则更换运算符
        when {
            currentInputNumString[currentInputNumString.length - 1] in myOperators -> {
                currentInputNumString.deleteCharAt(currentInputNumString.length - 1)
                currentInputNumString.append(tv.text)
            }
            currentInputNumString[currentInputNumString.length - 1] in digits -> {
                // 如果前一个符号为数字
                currentInputNumString.append(tv.text.toString())
                processTextView.text = currentInputNumString.toString()
                isNumStart = true
                dotsList.add(false)
            }
            else -> {
                Toast.makeText(this, "此刻不能添加${tv.text}!", Toast.LENGTH_SHORT).show()
            }
        }
        processTextView.text = currentInputNumString.toString()
        Log.v("myTag", "$operatorsList")
    }


    fun clearButtonClicked(view: View) {
        currentInputNumString.clear()
        currentInputNumString.append("0")
        processTextView.text = currentInputNumString.toString()
        // 重置列表、参数
        isNumStart = true
        dotsList.clear()
        dotsList.add(false)
    }

    fun delButtonClicked(view: View) {
        val myOperators = listOf('+', '-', '×', '÷', '%')
        // 若输入串为NULL，则不进行操作
        if (currentInputNumString.isNotEmpty()) {
            if (currentInputNumString[currentInputNumString.length - 1] in myOperators) {
                isNumStart = false
                dotsList.removeLast()
            } else if (currentInputNumString[currentInputNumString.length - 1] == '.') {
                dotsList[dotsList.size - 1] = false
            } else {
                if (currentInputNumString.length >= 2 && currentInputNumString[currentInputNumString.length - 2] in myOperators) {
                    isNumStart = true
                    //dotsList.removeLast()
                } else if(currentInputNumString.length == 1){
                    isNumStart = true
                }
            }
            currentInputNumString.deleteCharAt(currentInputNumString.length - 1)
            processTextView.text = currentInputNumString.toString()
        }
    }

    fun dotButtonClicked(view: View) {
        if (!dotsList[dotsList.size - 1]) {
            val tv = view as TextView
            if (currentInputNumString.isEmpty()) {
                currentInputNumString.append("0")
            }
            currentInputNumString.append(tv.text.toString())
            processTextView.text = currentInputNumString.toString()
            dotsList[dotsList.size - 1] = true
        }
    }

    fun equalButtonClicked(view: View) {
        if (currentInputNumString.isEmpty()) {
            resultTextView.text = "0"
            return
        }
        var resNum = 0.0
        var i = 0
        var temp = 0.0
        val numStr = StringBuilder()
        val firstOperators = listOf("×", "÷", "%")
        val operators = listOf('×', '÷', '%', '+', '-')
        // 构造numbersList、operatorsList
        numbersList.clear()
        operatorsList.clear()
        while (i < currentInputNumString.length) {
            if (currentInputNumString[i] in operators) {
                numbersList.add(numStr.toString().toDouble())
                operatorsList.add(currentInputNumString[i].toString())
                numStr.clear()
            } else {
                numStr.append(currentInputNumString[i])
            }
            i++
        }
        if (numStr.isNotEmpty()) {
            numbersList.add(numStr.toString().toDouble())
        } else {
            operatorsList.removeLast()
        }
        // 进行乘除运算
        i = 0
        while (i < operatorsList.size) {
            if (operatorsList[i] in firstOperators) {
                when (operatorsList[i]) {
                    "×" -> temp = numbersList[i] * numbersList[i + 1]
                    "÷" -> temp = numbersList[i] / numbersList[i + 1]
                    "%" -> temp = numbersList[i] % numbersList[i + 1]
                }
                operatorsList.removeAt(i)
                numbersList[i + 1] = temp
                numbersList.removeAt(i)
            } else {
                i++
            }
        }
        // 进行加减运算
        i = 0
        resNum = numbersList[i]
        numbersList.removeAt(0)
        while (i < operatorsList.size) {
            if (operatorsList[i] == "+") {
                resNum += numbersList[i]
            } else {
                resNum -= numbersList[i]
            }
            i++
        }
        // 显示结果
        val resStr = resNum.toString()
        val ii = resStr.indexOf('.')
        var flagInt = true
        for (a in ii + 1 until resStr.length) {
            if (resStr[a] != '0') {
                flagInt = false
                break
            }
        }
        if (flagInt) {    // 显示整数
            resultTextView.text = resNum.toInt().toString()
        } else {  // 显示浮点数
            resultTextView.text = resNum.toString()
        }
        Log.v("myTag", "$numbersList")
        Log.v("myTag", "$operatorsList")
    }

    fun mButtonClicked(view: View) {
        // 更新显示
        processTextView.text = resultTextView.text
        // 更新字符串
        currentInputNumString.clear()
        currentInputNumString.append(resultTextView.text.toString())
        // 重置dotsList列表
        dotsList.clear()
        dotsList.add(false)
        // 标记是否数字开头
        isNumStart = false
        // 判断是否为小数
        val numStr = resultTextView.text.toString()
        val i = numStr.indexOf('.')
        if (i > 0) {
            dotsList[0] = true
        }
    }
}
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二、Java版本

1. activity_main.xml

提示：其实两个版本的布局文件都差不多，只是颜色和背景有区别而已。直接用Kotlin版本的activity_main.xml，再修改下颜色、背景即可。

2. MainActivity.java

代码如下：

package com.example.zhangskin;

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

import com.zhy.changeskin.SkinManager;

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


public class MainActivity extends com.zhy.changeskin.base.BaseSkinActivity implements View.OnClickListener {

    private int signal = 0;
    private final StringBuilder currentInputNumString = new StringBuilder();
    private final ArrayList<Double> numbersList = new ArrayList<>();
    private final ArrayList<String> operatorsList = new ArrayList<>();
    private final ArrayList<Boolean> dotsList = new ArrayList<>();
    private Boolean isNumStart = true;

    private TextView processTextView;
    private TextView resultTextView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // 换肤第三方库注册，可直接注释掉
        SkinManager.getInstance().init(this);

        dotsList.add(false);

        processTextView = findViewById(R.id.process_text_view);
        resultTextView = findViewById(R.id.result_text_view);

        // 绑定监听事件
        findViewById(R.id.view_0).setOnClickListener(this);
        findViewById(R.id.view_1).setOnClickListener(this);
        findViewById(R.id.view_2).setOnClickListener(this);
        findViewById(R.id.view_3).setOnClickListener(this);
        findViewById(R.id.view_4).setOnClickListener(this);
        findViewById(R.id.view_5).setOnClickListener(this);
        findViewById(R.id.view_6).setOnClickListener(this);
        findViewById(R.id.view_7).setOnClickListener(this);
        findViewById(R.id.view_8).setOnClickListener(this);
        findViewById(R.id.view_9).setOnClickListener(this);
        findViewById(R.id.view_M).setOnClickListener(this);
        findViewById(R.id.ac_view).setOnClickListener(this);
        findViewById(R.id.del_view).setOnClickListener(this);
        findViewById(R.id.add_view).setOnClickListener(this);
        findViewById(R.id.sub_view).setOnClickListener(this);
        findViewById(R.id.mul_view).setOnClickListener(this);
        findViewById(R.id.div_view).setOnClickListener(this);
        findViewById(R.id.mod_view).setOnClickListener(this);
        findViewById(R.id.dot_view).setOnClickListener(this);
        findViewById(R.id.equal_view).setOnClickListener(this);

        // bringToFront()让控件始终在最顶层，不被覆盖                     
        findViewById(R.id.lightMode).bringToFront();
        // 换肤操作，可直接注释掉
        findViewById(R.id.lightMode).setOnClickListener(view -> {
            if(signal == 0){
                signal = 1;
                SkinManager.getInstance().changeSkin("night");
            }else{
                signal = 0;
                SkinManager.getInstance().removeAnySkin();
            }
        });
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.view_0:
            case R.id.view_1:
            case R.id.view_2:
            case R.id.view_3:
            case R.id.view_4:
            case R.id.view_5:
            case R.id.view_6:
            case R.id.view_7:
            case R.id.view_8:
            case R.id.view_9:
                numberButtonClicked(view);break;
            case R.id.add_view:
            case R.id.sub_view:
            case R.id.mul_view:
            case R.id.div_view:
            case R.id.mod_view:
                operatorButtonClicked(view);break;
            case R.id.ac_view:
                clearButtonClicked(view);break;
            case R.id.del_view:
                delButtonClicked(view);break;
            case R.id.view_M:
                mButtonClicked(view);break;
            case R.id.dot_view:
                dotButtonClicked(view);break;
            case R.id.equal_view:
                equalButtonClicked(view);break;
            default:break;
        }
    }

    public void numberButtonClicked(View v){
        TextView tv = (TextView) v;
        if (currentInputNumString.toString().equals("0")) {
            currentInputNumString.delete(0,currentInputNumString.length());
        }
        // 更新text view内容
        currentInputNumString.append(tv.getText());
        processTextView.setText(currentInputNumString.toString());
        if (isNumStart) {
            isNumStart = false;
        }
    }
    public void operatorButtonClicked(View view) {
        TextView tv = (TextView) view;
        List<Character> myOperators = Arrays.asList('+', '-', '×', '÷', '%');
        List<Character> digits = Arrays.asList('0', '1', '2', '3', '4', '5', '6', '7', '8', '9');
        // 如果前一个符号为运算符，则更换运算符
        if(myOperators.contains(currentInputNumString.charAt(currentInputNumString.length() - 1))) {
                currentInputNumString.deleteCharAt(currentInputNumString.length() - 1);
                currentInputNumString.append(tv.getText());
        }else if(digits.contains(currentInputNumString.charAt(currentInputNumString.length() - 1))){
            // 如果前一个符号为数字
            currentInputNumString.append(tv.getText().toString());
            processTextView.setText(currentInputNumString.toString());
            isNumStart = true;
            dotsList.add(false);
        }else {
            Toast.makeText(this, "此刻不能添加${tv.getText()}!", Toast.LENGTH_SHORT).show();
        }
        processTextView.setText(currentInputNumString.toString());
    }


    public void clearButtonClicked(View view) {
        currentInputNumString.delete(0,currentInputNumString.length());
        currentInputNumString.append("0");
        processTextView.setText(currentInputNumString.toString());
        // 重置列表、参数
        isNumStart = true;
        dotsList.clear();
        dotsList.add(false);
    }

    public void delButtonClicked(View view) {
        List<Character> myOperators = Arrays.asList('+', '-', '×', '÷', '%');
        // 若输入串为NULL，则不进行操作
        if (currentInputNumString.length()>0) {
            char temp = currentInputNumString.charAt(currentInputNumString.length() - 1);
            if (myOperators.contains(temp)) {
                isNumStart = false;
                dotsList.remove(dotsList.size()-1);
                //dotsList.removeLast();
            } else if ('.' == currentInputNumString.charAt(currentInputNumString.length() - 1)) {
                dotsList.set(dotsList.size() - 1, false);
            } else {
                if (currentInputNumString.length() >= 2 &&
                        myOperators.contains(currentInputNumString.charAt(currentInputNumString.length() - 2))) {
                    isNumStart = true;
                } else if(currentInputNumString.length() == 1){
                    isNumStart = true;
                }
            }
            currentInputNumString.deleteCharAt(currentInputNumString.length() - 1);
            processTextView.setText(currentInputNumString.toString());
        }
    }

    public void dotButtonClicked(View view) {
        if (!dotsList.get(dotsList.size() - 1)) {
            TextView tv = (TextView) view;
            if (currentInputNumString.length() == 0) {
                currentInputNumString.append("0");
            }
            currentInputNumString.append(".");
            processTextView.setText(currentInputNumString.toString());
            dotsList.set(dotsList.size() - 1, true);
        }
    }

    public void mButtonClicked(View view) {
        // 更新显示
        processTextView.setText(resultTextView.getText());
        // 更新字符串
        currentInputNumString.delete(0,currentInputNumString.length());
        currentInputNumString.append(resultTextView.getText().toString());
        // 重置dotsList列表
        dotsList.clear();
        dotsList.add(false);
        // 标记是否数字开头
        isNumStart = false;
        // 判断是否为小数
        String numStr = resultTextView.getText().toString();
        int i = numStr.indexOf('.');
        if (i > 0) {
            dotsList.set(0, true);
        }
    }

    public void equalButtonClicked(View view) {
        if (currentInputNumString.length() == 0 ) {
            resultTextView.setText("0");
            return;
        }
        double resNum = 0.0;
        int i = 0;
        double temp = 0.0;
        StringBuilder numStr = new StringBuilder();
        List<String> firstOperators = Arrays.asList("×", "÷", "%");
        List<Character> operators = Arrays.asList('×', '÷', '%', '+', '-');
        // 构造numbersList、operatorsList
        numbersList.clear();
        operatorsList.clear();
        while (i < currentInputNumString.length()) {
            if (operators.contains(currentInputNumString.charAt(i))) {
                numbersList.add(Double.parseDouble(numStr.toString()));
                operatorsList.add(Character.toString(currentInputNumString.charAt(i)));
                numStr.delete(0,numStr.length());
            } else {
                numStr.append(currentInputNumString.charAt(i));
            }
            i++;
        }
        if (numStr.length()>0) {
            numbersList.add(Double.parseDouble(numStr.toString()));
        } else {
            operatorsList.remove(operatorsList.size()-1);
        }
        // 进行乘除运算
        i = 0;
        while (i < operatorsList.size()) {
            if (firstOperators.contains(operatorsList.get(i))){
                switch (operatorsList.get(i)) {
                    case "×":
                        temp = numbersList.get(i) * numbersList.get(i + 1);break;
                    case "÷":
                        temp = numbersList.get(i) / numbersList.get(i + 1);break;
                    case "%":
                        temp = numbersList.get(i) % numbersList.get(i + 1);break;
                }
                operatorsList.remove(i);
                numbersList.set(i+1,temp);
                numbersList.remove(i);
            } else {
                i++;
            }
        }
        // 进行加减运算
        i = 0;
        resNum = numbersList.get(i);
        numbersList.remove(0);
        while (i < operatorsList.size()) {
            if (operatorsList.get(i).equals("+")) {
                resNum += numbersList.get(i);
            } else {
                resNum -= numbersList.get(i);
            }
            i++;
        }
        // 显示结果
        String resStr = Double.toString(resNum);
        int ii = resStr.indexOf('.');
        boolean flagInt = true;
        for (int a = ii + 1;a < resStr.length();a++) {
            if (resStr.charAt(a) != '0') {
                flagInt = false;
                break;
            }
        }
        if (flagInt) {    // 显示整数
            resultTextView.setText(String.valueOf((int)resNum));
        } else {  // 显示浮点数
            resultTextView.setText(String.valueOf(resNum));
        }
    }
}
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总结

计算器的界面，是我参照B站上一个up主的讲解视频完成的，至于逻辑完成的代码，原本也是照着up主来，后来发现效果不是我想要的，就自己改了。

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