Android计算器
GitHub地址
先上图
UI
采用百分比布局，在app\build.gradle的dependencies里面加上
implementation 'com.android.support:percent:28.0.0-alpha3'
后面对应SDK版本，我的是28.0.0-alpha3
两个TextView用于显示我的APP名称和用户输入的计算式
其他均为按钮
version="1.0" encoding="utf-8"?>
"http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#FAFFF0">
id="@+id/app_name"
android:layout_width="wrap_content"
android:layout_height="58dp"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:gravity="center"
android:text="CalculatorByLPD"
android:textColor="#292421"
android:textSize="35sp" />
id="@+id/view_input"
android:layout_width="match_parent"
android:layout_height="117dp"
android:layout_above="@+id/button_AC"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:layout_marginBottom="-3dp"
android:layout_marginLeft="0dp"
android:layout_marginStart="0dp"
android:layout_marginTop="98dp"
android:gravity="left|top"
android:text=""
android:textColor="#292421"
android:textSize="30sp" />
按钮点击事件的处理或逻辑判断
这个我先写完了基本的功能，就是保证正确的输入，然后会得到正确的结果，最后一步一步的测问题，改代码，禁止用户一些错误的输入，和处理一些能出现问题的操作。方法的调用和输入的判断我已经在代码里面注释好了，还有什么疑问还可以可以评论留言
package com.example.calculator;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private TextView view_input;
private StringBuilder sb = new StringBuilder(); //把所有的输入放在这个StringBuilder里面
private int FLAG = 0; //这个是用于二次计算的标记
private int FLAG2 = 0; //这个是检测括号输入的标记 输入一个左括号+1 输入一个右括号-1
//要注意的就是要是有删除、清空、计算结果时要改变这个的值
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ActionBar actionBar = getSupportActionBar();
if (actionBar != null) { //隐藏自带标题
actionBar.hide();
}
view_input = (TextView) findViewById(R.id.view_input);
Button button_1 = (Button) findViewById(R.id.button_1);
Button button_0 = (Button) findViewById(R.id.button_0);
Button button_2 = (Button) findViewById(R.id.button_2);
Button button_3 = (Button) findViewById(R.id.button_3);
Button button_4 = (Button) findViewById(R.id.button_4);
Button button_5 = (Button) findViewById(R.id.button_5);
Button button_6 = (Button) findViewById(R.id.button_6);
Button button_7 = (Button) findViewById(R.id.button_7);
Button button_8 = (Button) findViewById(R.id.button_8);
Button button_9 = (Button) findViewById(R.id.button_9);
Button button_point = (Button) findViewById(R.id.button_point);
Button button_divi = (Button) findViewById(R.id.button_divi);
Button button_end = (Button) findViewById(R.id.button_end);
Button button_mul = (Button) findViewById(R.id.button_mul);
Button button_brac = (Button) findViewById(R.id.button_brac);
Button button_brac2 = (Button) findViewById(R.id.button_brac2);
Button button_exit = (Button) findViewById(R.id.button_exit);
Button button_add = (Button) findViewById(R.id.button_add);
Button button_sub = (Button) findViewById(R.id.button_sub);
Button button_del = (Button) findViewById(R.id.button_del);
Button button_AC = (Button) findViewById(R.id.button_AC);
button_0.setOnClickListener(this);
button_1.setOnClickListener(this);
button_2.setOnClickListener(this);
button_3.setOnClickListener(this);
button_4.setOnClickListener(this);
button_5.setOnClickListener(this);
button_6.setOnClickListener(this);
button_7.setOnClickListener(this);
button_8.setOnClickListener(this);
button_9.setOnClickListener(this);
button_point.setOnClickListener(this);
button_divi.setOnClickListener(this);
button_end.setOnClickListener(this);
button_mul.setOnClickListener(this);
button_brac.setOnClickListener(this);
button_brac2.setOnClickListener(this);
button_exit.setOnClickListener(this);
button_add.setOnClickListener(this);
button_sub.setOnClickListener(this);
button_del.setOnClickListener(this);
button_AC.setOnClickListener(this);
view_input.setOnClickListener(this);
}
@Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.button_0:
if (!inScope()) { //检测输入字符串的总长度，下同
Toast.makeText(getBaseContext(),
"Out of scope", Toast.LENGTH_SHORT).show(); // 提示长度超限，下同
break;
}
if (haveBrac()) break;// 数字不能加在右括号后面，下同
changeFlag(); //更改二次计算用的标记，下同
if (sb.length() == 0) {
view_input.setText("0"); //这个是用于处理不断输入0的时候屏幕上会一直显示0的问题
} else {
sb.append("0"); //如果长度不为零那么就显示0 并加在sb后面
view_input.setText(sb.toString());
}
break;
case R.id.button_1:
if (!inScope()) {
Toast.makeText(getBaseContext(), "Out of scope", Toast.LENGTH_SHORT).show();
break;
}
if (haveBrac()) break;
changeFlag();
sb.append("1");
view_input.setText(sb.toString());
break;
case R.id.button_2:
if (!inScope()) {
Toast.makeText(getBaseContext(), "Out of scope", Toast.LENGTH_SHORT).show();
break;
}
if (haveBrac()) break;
changeFlag();
sb.append("2");
view_input.setText(sb.toString());
break;
case R.id.button_3:
if (!inScope()) {
Toast.makeText(getBaseContext(), "Out of scope", Toast.LENGTH_SHORT).show();
break;
}
if (haveBrac()) break;
changeFlag();
sb.append("3");
view_input.setText(sb.toString());
break;
case R.id.button_4:
if (!inScope()) {
Toast.makeText(getBaseContext(), "Out of scope", Toast.LENGTH_SHORT).show();
break;
}
if (haveBrac()) break;
changeFlag();
sb.append("4");
view_input.setText(sb.toString());
break;
case R.id.button_5:
if (!inScope()) {
Toast.makeText(getBaseContext(), "Out of scope", Toast.LENGTH_SHORT).show();
break;
}
if (haveBrac()) break;
changeFlag();
sb.append("5");
view_input.setText(sb.toString());
break;
case R.id.button_6:
if (!inScope()) {
Toast.makeText(getBaseContext(), "Out of scope", Toast.LENGTH_SHORT).show();
break;
}
if (haveBrac()) break;
changeFlag();
sb.append("6");
view_input.setText(sb.toString());
break;
case R.id.button_7:
if (!inScope()) {
Toast.makeText(getBaseContext(), "Out of scope", Toast.LENGTH_SHORT).show();
break;
}
if (haveBrac()) break;
changeFlag();
sb.append("7");
view_input.setText(sb.toString());
break;
case R.id.button_8:
if (!inScope()) {
Toast.makeText(getBaseContext(), "Out of scope", Toast.LENGTH_SHORT).show();
break;
}
if (haveBrac()) break;
changeFlag();
sb.append("8");
view_input.setText(sb.toString());
break;
case R.id.button_9:
if (!inScope()) {
Toast.makeText(getBaseContext(), "Out of scope", Toast.LENGTH_SHORT).show();
break;
}
if (haveBrac()) break;
changeFlag();
sb.append("9");
view_input.setText(sb.toString());
break;
case R.id.button_add:
if (!inScope()) {
Toast.makeText(getBaseContext(), "Out of scope", Toast.LENGTH_SHORT).show();
break;
}
changeFlagByMethod(); //计算完一次后 会改变FLAG的值
// 当再次输入运算符号时会改变这个标记的值
//效果就是计算玩一次后 若输入运算符号会直接在上次的结果上进行运算 若输入数字表示重新进行其他的运算
// 其他运算符调用这个函数的作用相同下同
if (sb.length() == 0) //等于零不会显示加号
break;
String s = sb.substring(sb.length() - 1, sb.length());
if (s.equals("(")) //加号不能加在左括号后面
break;
if (couldAdd(s)) { // 还是用于能否输入这个加号的
// 如果不能那就替换原本的运算符号为+
// 其他运算符调用这个函数的作用相同下同
// 具体实现看下面的函数
sb.delete(sb.length() - 1, sb.length());
}
sb.append("+");
view_input.setText(sb.toString());
break;
case R.id.button_sub:
if (!inScope()) {
Toast.makeText(getBaseContext(), "Out of scope", Toast.LENGTH_SHORT).show();
break;
}
changeFlagByMethod();
if (sb.length() == 0)
break;
s = sb.substring(sb.length() - 1, sb.length());
if (s.equals("("))
break;
if (couldAdd(s)) {
sb.delete(sb.length() - 1, sb.length());
}
sb.append("-");
view_input.setText(sb.toString());
break;
case R.id.button_mul:
if (!inScope()) {
Toast.makeText(getBaseContext(), "Out of scope", Toast.LENGTH_SHORT).show();
break;
}
changeFlagByMethod();
if (sb.length() == 0)
break;
s = sb.substring(sb.length() - 1, sb.length());
if (s.equals("("))
break;
if (couldAdd(s)) {
sb.delete(sb.length() - 1, sb.length());
}
sb.append("×");
view_input.setText(sb.toString());
break;
case R.id.button_divi:
if (!inScope()) {
Toast.makeText(getBaseContext(), "Out of scope", Toast.LENGTH_SHORT).show();
break;
}
changeFlagByMethod();
if (sb.length() == 0)
break;
s = sb.substring(sb.length() - 1, sb.length());
if (s.equals("("))
break;
if (couldAdd(s)) {
sb.delete(sb.length() - 1, sb.length());
}
sb.append("/");
view_input.setText(sb.toString());
break;
case R.id.button_point:
if (!inScope()) {
Toast.makeText(getBaseContext(), "Out of scope", Toast.LENGTH_SHORT).show();
break;
}
if (sb.length() == 0) { //如果这个长度为0 而且还直接输入了. 那么就直接变为0.
sb.append("0.");
view_input.setText(sb.toString());
break;
}
s = sb.substring(sb.length() - 1, sb.length());
if (s.equals("("))
break;
if (s.equals(")"))
break;
if (couldAdd(s)) { //还是检测能不能添加这个 小数点
sb.delete(sb.length() - 1, sb.length());
}
if (havePoint()) //这个是检测如果输入了一个小数 那么就不能再输入小数点了
break;
sb.append(".");
view_input.setText(sb.toString());
break;
case R.id.button_brac:
if (!inScope()) {
Toast.makeText(getBaseContext(), "Out of scope", Toast.LENGTH_SHORT).show();
break;
}
if (bracAddLeft()) { //这个也是检测能不能把左括号加在这里
sb.append("(");
view_input.setText(sb.toString());
FLAG2++; //如果加了 那么就给这个标记+1 表示目前有一个左括号没有被匹配
}
break;
case R.id.button_brac2:
if (FLAG2 == 0) break; // 如果是0 说明没有未匹配的左括号
if (bracAddRight() && bracAddFromLeft()) { //检测能否加这个括号
sb.append(")");
view_input.setText(sb.toString());
FLAG2--; //加了以后就会减少一个未被匹配的左括号数
}
break;
case R.id.button_end:
try {//抛一个最大的异常 直接提示Error
dealBrac();//这个是比较重要的一个方法，作用是补全没有输上的')'
//比如输入((9+1 他会根据FLAG2的值进行补输 变成((9+1))
FLAG2 = 0; //计算完后应该恢复这个检测括号的标记
FLAG = 1; //这个这个是用于下次计算的标记
String end = InfixInToDuffix.dealEquation(InfixInToDuffix.toSuffix(sb));
//这个是将中缀表达式转为后缀表达式 并求值
sb.delete(0, sb.length()); //清空字符串缓冲
sb.append(end); //把结果添加到字符串缓冲
view_input.setText(end);
} catch (Exception e) {
sb.delete(0, sb.length());
sb.append("Error");
view_input.setText(sb.toString());
sb.delete(0, sb.length());
}
break;
case R.id.button_AC:
sb.delete(0, sb.length());
view_input.setText(sb.toString());
FLAG2 = 0; //这里注意 不仅要清空字符串缓冲区
// 还要改变用于检测括号匹配的标记
break;
case R.id.button_del:
if (sb.length() >= 1) {
char c = sb.charAt(sb.length() - 1);
if (c == ')') FLAG2++; //这里要注意 如果遇到删除左右括号要改变标记的值
if (c == '(') FLAG2--;
sb.delete(sb.length() - 1, sb.length());
view_input.setText(sb.toString());
}
break;
case R.id.button_exit:
AlertDialog.Builder dialog = new AlertDialog.Builder(MainActivity.this);
dialog.setTitle("Dialog"); // 弹出一个会话框 询问知否退出
dialog.setMessage("Are you sure to exit?");
dialog.setCancelable(true);
dialog.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
finish();
}
});
dialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
}
});
dialog.show();
break;
default:
break;
}
}
// 下面的函数在上面的调用时 已经介绍过作用
// 不过多解释了 都是一些用于判断的函数
private void dealBrac() {
if (FLAG2 == 0) {
return;
}
for (int i = 0; i < FLAG2; i++) {
sb.append(")");
}
}
private boolean haveBrac() {
char[] c = sb.toString().toCharArray();
boolean b = false;
if (c.length == 0)
return b;
if (c[c.length - 1] == ')')
b = true;
return b;
}
private boolean inScope() {
boolean b = true;
if (sb.length() == 90)
b = false;
return b;
}
private boolean havePoint() {
boolean b = false;
int i;
char[] c = sb.toString().toCharArray();
for (i = c.length - 1; i >= 0 && (c[i] >= '0' && c[i] <= '9'); i--) {
}
if (i != -1) {
if (c[i] == '.')
b = true;
}
return b;
}
private void changeFlag() {
if (FLAG == 1) {
sb.delete(0, sb.length());
FLAG = 0;
}
}
private void changeFlagByMethod() {
if (FLAG == 1) {
FLAG = 0;
}
}
private boolean couldAdd(String s) {
boolean b = false;
if (s.equals("+")) b = true;
if (s.equals("-")) b = true;
if (s.equals("×")) b = true;
if (s.equals("/")) b = true;
if (s.equals(".")) b = true;
if (s.equals("(")) b = true;
return b;
}
private boolean bracAddFromLeft() {
int i = sb.length();
boolean b = false;
if (sb.indexOf("(") >= 0) {
b = true;
}
return b;
}
private boolean bracAddLeft() {
boolean b = false;
if (sb.length() == 0) {
b = true;
return b;
}
String s = sb.substring(sb.length() - 1, sb.length());
if (s.equals("+")) b = true;
if (s.equals("-")) b = true;
if (s.equals("×")) b = true;
if (s.equals("/")) b = true;
if (s.equals("(")) b = true;
return b;
}
private boolean bracAddRight() {
Boolean b = true;
if (sb.length() == 0) {
b = false;
return b;
}
String s = sb.substring(sb.length() - 1, sb.length());
if (s.equals("+")) b = false;
if (s.equals("-")) b = false;
if (s.equals("×")) b = false;
if (s.equals("/")) b = false;
if (s.equals(".")) b = false;
if (s.equals("(")) b = false;
return b;
}
}
计算
通过上面的逻辑处理，最终得到的sb就是一个正确的中缀表达式，计算的思路就是将中缀表达式转换成后缀表达式，然后进行计算得到结果，具体算法我不过多阐述，代码是借用别人的，我附上中缀表达式和后缀表达式的介绍和转换计算的代码，新建一个类
public static String toSuffix(StringBuilder infix)方法是将中缀表达式转为后缀表达式
public static String dealEquation(String equation)方法是计算后缀表达式的值并返回
将中缀表达式转化为后缀表达式
图解后缀表达式的计算过程
package com.example.calculator;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class InfixInToDuffix {
private static final Map basic = new HashMap();
static {
basic.put('-', 1);
basic.put('+', 1);
basic.put('×', 2);
basic.put('/', 2);
basic.put('(', 0);
}
public static String toSuffix(StringBuilder infix) {
List queue = new ArrayList();
List stack = new ArrayList();
char[] charArr = infix.substring(0, infix.length()).trim().toCharArray();
String standard = "×/+-()";
char ch = '&';
int len = 0;
for (int i = 0; i < charArr.length; i++) {
int last = 0;
if (i > 0) {
last = charArr[i - 1];
}
ch = charArr[i];
if (Character.isDigit(ch)) {
len++;
} else if (ch == '.') {
len++;
} else if (ch == '-' && (last == '×' || last == '/' || i == 0)) {
len++;
continue;
} else if (standard.indexOf(ch) != -1) {
if (len > 0) {
queue.add(String.valueOf(Arrays.copyOfRange(charArr, i - len, i)));
len = 0;
}
if (ch == '(') {
stack.add(ch);
continue;
}
if (!stack.isEmpty()) {
int size = stack.size() - 1;
boolean flag = false;
while (size >= 0 && ch == ')' && stack.get(size) != '(') {
queue.add(String.valueOf(stack.remove(size)));
size--;
flag = true;
}
if (ch == ')' && stack.get(size) == '(') {
flag = true;
}
while (size >= 0 && !flag && basic.get(stack.get(size)) >= basic.get(ch)) {
queue.add(String.valueOf(stack.remove(size)));
size--;
}
}
if (ch != ')') {
stack.add(ch);
} else {
stack.remove(stack.size() - 1);
}
}
if (i == charArr.length - 1) {
if (len > 0) {
queue.add(String.valueOf(Arrays.copyOfRange(charArr, i - len + 1, i + 1)));
}
int size = stack.size() - 1;
while (size >= 0) {
queue.add(String.valueOf(stack.remove(size)));
size--;
}
}
}
String a = queue.toString();
return a.substring(1, a.length() - 1);
}
public static String dealEquation(String equation) {
String[] arr = equation.split(", ");
List list = new ArrayList();
for (int i = 0; i < arr.length; i++) {
int size = list.size();
switch (arr[i]) {
case "+":
double a = Double.parseDouble(list.remove(size - 2)) + Double.parseDouble(list.remove(size - 2));
list.add(String.valueOf(a));
break;
case "-":
double b = Double.parseDouble(list.remove(size - 2)) - Double.parseDouble(list.remove(size - 2));
list.add(String.valueOf(b));
break;
case "×":
double c = Double.parseDouble(list.remove(size - 2)) * Double.parseDouble(list.remove(size - 2));
list.add(String.valueOf(c));
break;
case "/":
double d = Double.parseDouble(list.remove(size - 2)) / Double.parseDouble(list.remove(size - 2));
list.add(String.valueOf(d));
break;
default:
list.add(arr[i]);
break;
}
}
return list.size() == 1 ? list.get(0) : "运算失败";
}
}