基于Java的Android计算器设计与实现

基于Java的Android计算器设计与实现
目录
一、设计分析 1
1.1 题目重述 1
1.2 设计思路 1
二、程序结构 2
三、各模块的功能及程序说明 4
3.1 计算器界面设计 4
3.2 界面各模块功能 8
3.3 ScienceCalculator接口 27
3.4 BaseCalculator 接口 32
四、操作流程 37
4.1 操作流程图 37
4.2 操作流程步骤 37
五、测试 38
5.1 弧度角度运算 38
5.2 数学表达式 40
5.3 包含科学计算的数学表达式 40
5.4 保留相应小数位数 41
5.5 处理异常 42
5.6 保存运算过程到文件 43
六、实验心得 45
一、设计分析
1.1 题目重述
本次实验为了实现一个保存计算过程的计算器，主要有以下三个要求：
1.仿照真实的计算器实现其功能。
2.在左上方的文本框中显示当前的计算过程，在右边的文本区中显示以往的计算过程。
3.单击“保存”按钮可以将文本区中的全部计算过程保存到文件；单击“复制”按钮可以将文本区中选中的文本复制到剪贴本；单击“清除”按钮可以清除文本区的全部内容。
1.2 设计思路
考虑到计算器的美观和易用性，我决定把计算器做在 Android 端，Android 系统的 App 的底层功能由 Java 实现，所以工作主要分为两部分：
1.设计计算器界面 (activity_main.xml) 计算器界面用xml文件编写，包括手机竖屏和横屏两个布局文件： 竖屏：activity_main.xml 布局为 portrait 横屏：activity_main_land.xml 布局为 landscape 竖屏模式可以完成基本的四则运算，不涉及科学计算 横屏模式除了完成基本的四则运算，还添加了科学运算
2.编写计算接口 (ScienceCalculator.java) ScienceCalculator 可以完成包含科学运算函数的 math，先实现可以完成基本四则运算的 BaseCalculator，在此基础上，实现 ScienceCalculator。 运算的思路是先通过 ScienceCalculator 完成math中需要科学计算函数的部分，本文转载自http://www.biyezuopin.vip/onews.asp?id=16770再用这些部分计算的结果替换原 math 中的这些部分，使包含科学计算函数的 math 转变成可用 BaseCalculator 计算的 math。
4.2 操作流程步骤
1.程序开始；
2.在手机上点击计算器APP，进入默认的计算器竖屏界面，通过点击按钮输入math表达式，按钮设置了响应事件的场景，避免了一些math 表达式的格式错误，最后完成math 表达式的输入；
3.点击 = 按钮进行计算，如果运算过程中出现除以0的情况或者格式错误的math表达式，输出Math Error，正常情况下完成math计算，输出计算结果；
4.此时用户有5个选择：
o继续输入math表达式计算
o点击保存按钮将文本区中的全部计算过程保存到文件
o点击复制按钮将文本区中选中的文本复制到剪贴本
o点击清除按钮将文本区的全部内容清除
o点击系统返回键退出计算器
5.用户在完成(3)中的1，2，3，4任意一个之后均可以点击系统返回键退出计算器；
6.用户将手机横屏，App切换到科学计算器的界面，同样完成(1)，(2)，(3)，(4)操作；
7.程序结束。

package com.example.eric.mycal;

import android.content.ClipboardManager;
import android.content.Context;
import android.content.Intent;
import android.content.res.Configuration;
import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.text.method.ScrollingMovementMethod;
import android.view.View;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import java.io.FileOutputStream;

import butterknife.BindView;
import butterknife.ButterKnife;

public class MainActivity extends AppCompatActivity {

//tvNow,tvPast显示运算过程
@BindView(R.id.tv_past)
TextView tvPast;
@BindView(R.id.tv_now)
AutoScaleTextView tvNow; //继承TextView自适应屏幕宽度设置字体大小

//保存，复制，清空tvPast中的运算过程
@BindView(R.id.btn_save)
Button btnSave;
@BindView(R.id.btn_copy)
Button btnCopy;
@BindView(R.id.btn_clear)
Button btnClear;

//数字btns
@BindView(R.id.btn_7)
Button btn7;
@BindView(R.id.btn_8)
Button btn8;
@BindView(R.id.btn_9)
Button btn9;
@BindView(R.id.btn_4)
Button btn4;
@BindView(R.id.btn_5)
Button btn5;
@BindView(R.id.btn_6)
Button btn6;
@BindView(R.id.btn_1)
Button btn1;
@BindView(R.id.btn_2)
Button btn2;
@BindView(R.id.btn_3)
Button btn3;
@BindView(R.id.btn_0)
Button btn0;
@BindView(R.id.btn_dot)
Button btnDot;

//基本运算符: + - × / ( ) =
@BindView(R.id.btn_add)
Button btnAdd;
@BindView(R.id.btn_sub)
Button btnSub;
@BindView(R.id.btn_mul)
Button btnMul;
@BindView(R.id.btn_div)
Button btnDiv;
@BindView(R.id.btn_bracket)
Button btnBracket;
@BindView(R.id.btn_equal)
Button btnEqual;

//基本计算器功能：删除一个字符，清空当前math
@BindView(R.id.btn_del)
Button btnDel;
@BindView(R.id.btn_clc)
Button btnClc;

//存储过去和当前的math
private String mathPast = "";
private String mathNow = "";
private int precision = 6;
private int equal_flag = 0; //设置flag值判断是否需要清空mathNow进行新的运算
private ScienceCalculator scienceCalculator = new ScienceCalculator(); //一个科学计算器


//监听设备当前朝向
@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);

    //如果为landscape，切换activity
    if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
        Intent intent = new Intent(MainActivity.this, LandActivity.class);
        intent.putExtra("main", tvPast.getText().toString()); //把当前的tvPast中的运算过程传递给LandActivity
        startActivity(intent);
        finish(); //退出当前的activity
    }
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    //隐藏状态栏 manifest的application中要设置appTheme为NoActionBar
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
    setContentView(R.layout.activity_main);
    ButterKnife.bind(this); //初始化控件

    //设置控件属性
    initTvPast();
    initNumBtns();
    initBaseOpers();
    initThreeFunctions();
    initBaseCalculatorFunction();
}

//初始化tvPast
public void initTvPast() {

    //设置tvPast一些属性
    tvPast.setMovementMethod(ScrollingMovementMethod.getInstance()); //内容自动滚动到最新的一行
    tvPast.setTextIsSelectable(true); //长按复制

    //获取界面切换的tvPast的内容
    Intent intent = this.getIntent();
    String tvPastContent = intent.getStringExtra("land");

    //如果当前的界面是启动界面，不是从MainActivity切换来的，上面的mathPast就为null了，要处理这种异常
    if (tvPastContent == null) {
        tvPast.setText("");
    } else {
        String[] maths = tvPastContent.split("n");
        int i;
        for (i = 0; i < maths.length - 1; i++) {
            tvPast.append(maths[i] + "n");
        }
        tvPast.append(maths[i]); //最后一个math不用加换行
    }

}


//初始化数字btns
public void initNumBtns() {

    btn0.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            //如果flag=1，表示要输入新的运算式，清空mathNow并设置flag=0
            if (equal_flag == 1) {
                mathNow = "";
                equal_flag = 0;
            }

            if (mathNow.length() == 0) {                    //1.mathNow为空，+0
                mathNow += "0";
            } else if (mathNow.length() == 1) {             //2.mathNow 长度为1

                if (mathNow.charAt(0) == '0') {                 //2.1 如果该字符为0，不加
                    mathNow += "";
                } else if (isNum(mathNow.charAt(0))) {          //2.2 如果该字符为1-9，+0
                    mathNow += "0";
                }

            } else if (!isNum(mathNow.charAt(mathNow.length() - 2)) && mathNow.charAt(mathNow.length() - 1) == '0') {
                mathNow += "";                              //3.属于2.1的一般情况，在math中间出现 比如：×0 +0
            } else {                                        //4.除此之外，+0
                mathNow += "0";
            }
            tvNow.setText(mathNow);
        }
    });

    //btn 1-9 输入条件相同
    btn1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            if (equal_flag == 1) {
                mathNow = "";
                equal_flag = 0;
            }

            if (mathNow.length() == 0) {
                mathNow += "1";
            } else {

                //math的最后一个字符是：1-9, oper, (, .
                char ch = mathNow.charAt(mathNow.length() - 1);
                if (isNum(ch) || isOper(ch) || ch == '(' || ch == '.')
                    mathNow += "1";
            }
            tvNow.setText(mathNow);
        }
    });

    btn2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (equal_flag == 1) {
                mathNow = "";
                equal_flag = 0;
            }
            if (mathNow.length() == 0) {
                mathNow += "2";
            } else {
                char ch = mathNow.charAt(mathNow.length() - 1);
                if (isNum(ch) || isOper(ch) || ch == '(' || ch == '.')
                    mathNow += "2";
            }
            tvNow.setText(mathNow);
        }
    });

    btn3.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (equal_flag == 1) {
                mathNow = "";
                equal_flag = 0;
            }
            if (mathNow.length() == 0) {
                mathNow += "3";
            } else {
                char ch = mathNow.charAt(mathNow.length() - 1);
                if (isNum(ch) || isOper(ch) || ch == '(' || ch == '.')
                    mathNow += "3";
            }
            tvNow.setText(mathNow);
        }
    });

    btn4.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (equal_flag == 1) {
                mathNow = "";
                equal_flag = 0;
            }
            if (mathNow.length() == 0) {
                mathNow += "4";
            } else {
                char ch = mathNow.charAt(mathNow.length() - 1);
                if (isNum(ch) || isOper(ch) || ch == '(' || ch == '.')
                    mathNow += "4";
            }
            tvNow.setText(mathNow);
        }
    });

    btn5.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (equal_flag == 1) {
                mathNow = "";
                equal_flag = 0;
            }
            if (mathNow.length() == 0) {
                mathNow += "5";
            } else {
                char ch = mathNow.charAt(mathNow.length() - 1);
                if (isNum(ch) || isOper(ch) || ch == '(' || ch == '.')
                    mathNow += "5";
            }
            tvNow.setText(mathNow);
        }
    });

    btn6.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (equal_flag == 1) {
                mathNow = "";
                equal_flag = 0;
            }
            if (mathNow.length() == 0) {
                mathNow += "6";
            } else {
                char ch = mathNow.charAt(mathNow.length() - 1);
                if (isNum(ch) || isOper(ch) || ch == '(' || ch == '.')
                    mathNow += "6";
            }
            tvNow.setText(mathNow);
        }
    });

    btn7.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (equal_flag == 1) {
                mathNow = "";
                equal_flag = 0;
            }
            if (mathNow.length() == 0) {
                mathNow += "7";
            } else {
                char ch = mathNow.charAt(mathNow.length() - 1);
                if (isNum(ch) || isOper(ch) || ch == '(' || ch == '.')
                    mathNow += "7";
            }
            tvNow.setText(mathNow);
        }
    });

    btn8.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (equal_flag == 1) {
                mathNow = "";
                equal_flag = 0;
            }
            if (mathNow.length() == 0) {
                mathNow += "8";
            } else {
                char ch = mathNow.charAt(mathNow.length() - 1);
                if (isNum(ch) || isOper(ch) || ch == '(' || ch == '.')
                    mathNow += "8";
            }
            tvNow.setText(mathNow);
        }
    });

    btn9.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (equal_flag == 1) {
                mathNow = "";
                equal_flag = 0;
            }
            if (mathNow.length() == 0) {
                mathNow += "9";
            } else {
                char ch = mathNow.charAt(mathNow.length() - 1);
                if (isNum(ch) || isOper(ch) || ch == '(' || ch == '.')
                    mathNow += "9";
            }
            tvNow.setText(mathNow);
        }
    });

    btnDot.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (equal_flag == 1) {
                mathNow = "";
                equal_flag = 0;
            }
            if (mathNow.length() == 0) {                                //1.mathNow为空，+0.
                mathNow += "0.";
            } else if (isOper(mathNow.charAt(mathNow.length() - 1))) {  //2.mathNow的最后一个字符为oper，+0.
                mathNow += "0.";
            } else if (isNum(mathNow.charAt(mathNow.length() - 1))) {   //3.mathNow的最后一个字符为num，+.
                mathNow += ".";
            } else {                                                    //4.除此之外，不加
                mathNow += "";
            }
            tvNow.setText(mathNow);
        }
    });
}

//初始化基本的运算符
public void initBaseOpers() {

    btnAdd.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (mathNow.length() == 0) {
                mathNow += "+";
            } else {
                if (isNum(mathNow.charAt(mathNow.length() - 1))
                        || mathNow.charAt(mathNow.length() - 1) == ')'
                        || mathNow.charAt(mathNow.length() - 1) == '('
                        || mathNow.charAt(mathNow.length() - 1) == 'π'
                        || mathNow.charAt(mathNow.length() - 1) == 'e')
                    mathNow += "+";
            }
            tvNow.setText(mathNow);
            equal_flag = 0; //可能用运算结果直接运算，flag直接设0
        }
    });

    btnSub.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (mathNow.length() == 0) {
                mathNow += "-";
            } else {
                if (isNum(mathNow.charAt(mathNow.length() - 1))
                        || mathNow.charAt(mathNow.length() - 1) == ')'
                        || mathNow.charAt(mathNow.length() - 1) == '('
                        || mathNow.charAt(mathNow.length() - 1) == 'π'
                        || mathNow.charAt(mathNow.length() - 1) == 'e')
                    mathNow += "-";
            }
            tvNow.setText(mathNow);
            equal_flag = 0;
        }
    });

    btnMul.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (mathNow.length() != 0) {
                if (isNum(mathNow.charAt(mathNow.length() - 1))
                        || mathNow.charAt(mathNow.length() - 1) == ')'
                        || mathNow.charAt(mathNow.length() - 1) == 'π'
                        || mathNow.charAt(mathNow.length() - 1) == 'e')
                    mathNow += "×";
            }
            tvNow.setText(mathNow);
            equal_flag = 0;
        }
    });

    btnDiv.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (mathNow.length() != 0) {
                if (isNum(mathNow.charAt(mathNow.length() - 1))
                        || mathNow.charAt(mathNow.length() - 1) == ')'
                        || mathNow.charAt(mathNow.length() - 1) == 'π'
                        || mathNow.charAt(mathNow.length() - 1) == 'e')
                    mathNow += "/";
            }
            tvNow.setText(mathNow);
            equal_flag = 0;
        }
    });


    btnBracket.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (equal_flag == 1) {
                mathNow = "";
                equal_flag = 0;
            }
            if (mathNow.length() == 0) {                                //1.mathNow为空，+(
                mathNow += "(";
            } else if (isOper(mathNow.charAt(mathNow.length() - 1))) {  //2.mathNow最后一个字符是oper，+(
                mathNow += "(";
            } else if (isNum(mathNow.charAt(mathNow.length() - 1))      //3.mathNow最后一个字符是num, π, e
                    || mathNow.charAt(mathNow.length() - 1) == 'π'
                    || mathNow.charAt(mathNow.length() - 1) == 'e') {
                if (!hasLeftBracket(mathNow))                               //3.1 没有(, 加 ×(
                    mathNow += "×(";
                else                                                        //3.2 已有(, 加 )
                    mathNow += ")";
            } else if (mathNow.charAt(mathNow.length() - 1) == ')') {   //4.mathNow最后一个字符是)，说明用户是在补全右括号，+)
                mathNow += ')';
            }
            tvNow.setText(mathNow);
        }
    });


    btnEqual.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            //右括号自动补全
            int leftNum = 0;
            int rightNum = 0;
            for (int i = 0; i < mathNow.length(); i++) {
                if (mathNow.charAt(i) == '(')
                    leftNum++;
                if (mathNow.charAt(i) == ')')
                    rightNum++;
            }
            int missingNum = leftNum - rightNum; //缺失的 ) 数量
            while (missingNum > 0) {
                mathNow += ')';
                missingNum--;
            }
            tvNow.setText(mathNow);

            mathPast = "n" + mathNow; //使得呈现的mathPast自动换行

            double result = scienceCalculator.cal(mathNow, precision, 0); //调用科学计算器

            if (result == Double.MAX_VALUE)
                mathNow = "Math Error";
            else {
                mathNow = String.valueOf(result);
                if (mathNow.charAt(mathNow.length() - 2) == '.' && mathNow.charAt(mathNow.length() - 1) == '0') {
                    mathNow = mathNow.substring(0, mathNow.length() - 2);
                }
            }

            mathPast = mathPast + "=" + mathNow;

            //用tvPast.set(mathPast)不能实现自动滚动到最新运算过程
            tvPast.append(mathPast); //添加新的运算过程

            //tvPast滚动到最新的运算过程
            int offset = tvPast.getLineCount() * tvPast.getLineHeight();
            if (offset > tvPast.getHeight()) {
                tvPast.scrollTo(0, offset - tvPast.getHeight());
            }
            tvNow.setText(mathNow);

            equal_flag = 1; //设置flag=1
        }
    });
}

//保存，复制，清空
public void initThreeFunctions() {
    //保存
    btnSave.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            //保存文件到sd卡 manifest文件中也要添加2个permission
            if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
                String path = Environment.getExternalStorageDirectory().getPath() + "/math.txt"; //设置保存路径和文件名
                try {
                    FileOutputStream outputStream = new FileOutputStream(path);
                    outputStream.write(tvPast.getText().toString().getBytes()); //写字节
                    outputStream.close(); //关闭输出流
                } catch (Exception e) {
                    e.printStackTrace();
                }
                Toast.makeText(MainActivity.this, "保存到" + path, Toast.LENGTH_SHORT).show();
            }
        }
    });

    //复制
    btnCopy.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            ClipboardManager cm = (ClipboardManager) getSystemService(Context.CLIPBOARD_SERVICE); //采用ClipboardManager类
            cm.setText(tvPast.getText());
            Toast.makeText(MainActivity.this, "已复制到剪切板", Toast.LENGTH_SHORT).show();
        }
    });

    //清空
    btnClear.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            mathPast = "";
            tvPast.setText(mathPast);
            Toast.makeText(MainActivity.this, "计算过程已经清除", Toast.LENGTH_SHORT).show();
        }
    });
}

//初始化计算器基本Button
public void initBaseCalculatorFunction() {
    btnClc.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            mathNow = "";
            tvNow.setText(mathNow);
        }
    });

    btnDel.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (mathNow.length() != 0) {
                mathNow = mathNow.substring(0, mathNow.length() - 1);
                tvNow.setText(mathNow);
            }
        }
    });
}

//判断当前字符是否为数字
private boolean isNum(char c) {
    char num[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};
    int i = 0;
    for (; i < num.length; i++) {
        if (num[i] == c)
            break;
    }
    return i != num.length;
}

//判断当前字符是否为运算符
private boolean isOper(char c) {
    char oper[] = {'+', '-', '×', '/'};
    int i = 0;
    for (; i < oper.length; i++) {
        if (oper[i] == c)
            break;
    }
    return i != oper.length;
}

//判断当前math是否有')'
private boolean hasLeftBracket(String s) {
    int i = 0;
    for (; i < s.length(); i++) {
        if (s.charAt(i) == '(')
            break;
    }
    return i != s.length();
}

}

文章转自：基于Java的Android计算器设计与实现_Java-答学网

作者：答学网，转载请注明原文链接：http://www.dxzl8.com/