实现简单的Android计算器
目录
设置UI
实现计算器的代码
按钮点击的实现
处理输入的表达式
中缀转后缀的函数
计算函数
效果图
设置UI
首先，让我们先来设置UI。
在res资源找到values文件夹，右键设置style.xlm文件，即为按钮的样式
其次，让我们在res下的drawable文件夹下新建一个select文件 ，里面是关于按钮的一些的形状、背景颜色、以及点击时变色的设置
注意：颜色可以按照自己选择的背景图来设置，而不是照搬
-
-
让我们重新回到activity_main.xlm,这里，我使用的是表格布局嵌套线性布局
实现计算器的代码
按钮点击的实现
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
public static EditText editText;
public static String string = "";
public static int left = 0;
public static int right = 0;
public static boolean pointFlat = true;
public static boolean isResult = false;
public static Button tempButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button1 = (Button) findViewById(R.id.button_1);
Button button2 = (Button) findViewById(R.id.button_2);
Button button3 = (Button) findViewById(R.id.button_3);
Button button4 = (Button) findViewById(R.id.button_4);
Button button5 = (Button) findViewById(R.id.button_5);
Button button6 = (Button) findViewById(R.id.button_6);
Button button7 = (Button) findViewById(R.id.button_7);
Button button8 = (Button) findViewById(R.id.button_8);
Button button9 = (Button) findViewById(R.id.button_9);
Button button0 = (Button) findViewById(R.id.button_0);
Button add = (Button) findViewById(R.id.button_add);
Button subtract = (Button) findViewById(R.id.button_subtract);
Button multiply = (Button) findViewById(R.id.button_multiply);
Button divide = (Button) findViewById(R.id.button_divide);
Button ac = (Button) findViewById(R.id.button_ac);
Button delete = (Button) findViewById(R.id.button_delete);
Button equal = (Button) findViewById(R.id.button_equal);
Button button_left = (Button) findViewById(R.id.button_brackets_left);
Button button_right = (Button) findViewById(R.id.button_brackets_right);
Button point = (Button) findViewById(R.id.button_point);
editText = (EditText) findViewById(R.id.edit);
button1.setOnClickListener(this);
button2.setOnClickListener(this);
button3.setOnClickListener(this);
button4.setOnClickListener(this);
button5.setOnClickListener(this);
button6.setOnClickListener(this);
button7.setOnClickListener(this);
button8.setOnClickListener(this);
button9.setOnClickListener(this);
button0.setOnClickListener(this);
add.setOnClickListener(this);
subtract.setOnClickListener(this);
multiply.setOnClickListener(this);
divide.setOnClickListener(this);
ac.setOnClickListener(this);
delete.setOnClickListener(this);
button_left.setOnClickListener(this);
button_right.setOnClickListener(this);
equal.setOnClickListener(this);
point.setOnClickListener(this);
}
@Override
public void onClick(View view) {
if (isResult){
String tempbutton;
tempButton = (Button) findViewById(view.getId());
// tempButton.setOnClickListener(this);
tempbutton = String.valueOf(tempButton.getText());
if (tempbutton.matches("[\\+\\-\\*\\/]")){
isResult = false;
}else if(tempbutton.equals("=")){
} else if (tempbutton.equals("del")) {
isResult = false;
} else {
string = "";
editText.setText(string);
isResult = false;
}
}
if (view.getId() == R.id.button_1) {
string += "1";
editText.setText(string);
}
if (view.getId() == R.id.button_2) {
string += "2";
editText.setText(string);
}
if (view.getId() == R.id.button_3) {
string += "3";
editText.setText(string);
}
if (view.getId() == R.id.button_4) {
string += "4";
editText.setText(string);
}
if (view.getId() == R.id.button_5) {
string += "5";
editText.setText(string);
}
if (view.getId() == R.id.button_6) {
string += "6";
editText.setText(string);
}
if (view.getId() == R.id.button_7) {
string += "7";
editText.setText(string);
}
if (view.getId() == R.id.button_8) {
string += "8";
editText.setText(string);
}
if (view.getId() == R.id.button_9) {
string += "9";
editText.setText(string);
}
if (view.getId() == R.id.button_0) {
int length_0 = string.length();
if (length_0 > 0 && String.valueOf(string.charAt(length_0 - 1)).equals("/")) {
editText.setText(string + "0" + " tip : 0不能作为除数");
} else {
string += "0";
editText.setText(string);
}
}
if (view.getId() == R.id.button_add) {
int length_add = string.length();
if (length_add == 0){
string = "+";
}else if (String.valueOf(string.charAt(length_add - 1)).equals(".")) {
string += "0+";
} else if (String.valueOf(string.charAt(length_add - 1)).matches("[\\-\\*\\/\\+]")) {
string = string.substring(0,length_add - 1);
string += "+";
} else {
string += "+";
}
editText.setText(string);
pointFlat = true;
}
if (view.getId() == R.id.button_subtract) {
int length_sub = string.length();
if (length_sub == 0) {
string += "-";
} else if (String.valueOf(string.charAt(length_sub - 1)).matches("[\\+\\-\\*\\/]{1}")) {
string += "(0-";
left++;
}//减号前有运算符的情况
else if (String.valueOf(string.charAt(length_sub - 1)).equals(".")) {
string += "0-";
} else {
string += "-";
}
editText.setText(string);
pointFlat = true;
}
if (view.getId() == R.id.button_multiply) {
int length_mul = string.length();
if (length_mul == 0){
string = "*";
} else if (String.valueOf(string.charAt(length_mul - 1)).equals(".")) {
string += "0*";
} else if (String.valueOf(string.charAt(length_mul - 1)).matches("[\\-\\+\\/\\*]")) {
string = string.substring(0,length_mul - 1);
string += "*";
} else {
string += "*";
}
editText.setText(string);
pointFlat = true;
}
if (view.getId() == R.id.button_divide) {
int length_divide = string.length();
if (length_divide == 0){
string = "/";
}else if (String.valueOf(string.charAt(length_divide - 1)).equals(".")) {
string += "0/";
} else if (String.valueOf(string.charAt(length_divide - 1)).matches("[\\+\\*\\-\\/]")) {
string = string.substring(0,length_divide - 1);
string += "/";
} else {
string += "/";
}
editText.setText(string);
pointFlat = true;
}
if (view.getId() == R.id.button_ac) {
string = "";
left = right = 0;
pointFlat = true;
editText.setText(string);
}
if (view.getId() == R.id.button_delete) {
int length_del = string.length();
if (length_del > 0){
String temp = String.valueOf(string.charAt(length_del - 1));
if (temp.equals(".")) {
pointFlat = true;
} else if (temp.equals("(")) {
left--;
} else if (temp.equals(")")) {
right--;
}
string = string.substring(0, length_del - 1);
editText.setText(string);
if (string.equals("")) {
left = right = 0;
pointFlat = true;
isResult = false;
}
}
}
if (view.getId() == R.id.button_brackets_left) {
string += "(";
left++;
editText.setText(string);
}
if (view.getId() == R.id.button_brackets_right) {
int length_right = string.length();
if (string.charAt(length_right - 1) == '.'){
string += "0)";
right++;
editText.setText(string);
}else {
string += ")";
right++;
editText.setText(string);
}
}
if (view.getId() == R.id.button_point) {
if (pointFlat) {
int length_point = string.length();
if (length_point == 0 || (length_point > 0
&& String.valueOf(string.charAt(length_point - 1)).matches("[\\+\\-\\*\\/\\(]{1}"))) {
string += "0.";
editText.setText(string);
pointFlat = false;
} else {
string += ".";
editText.setText(string);
pointFlat = false;
}
}
}
if (view.getId() == R.id.button_equal) {
String temp;
if(string.equals("")){
}else {
isResult = true;
string = temp = Equal(string);
if (string.equals("Error")) {
editText.setText("Error");
left = right = 0;
pointFlat = true;
}else if (string.matches("^[+-]?[1-9]\\d*$") || string.matches("^[+-]?\\d+(\\.\\d+)$")
|| string.equals("0")){
editText.setText(temp + "\n" + "= " + string);
pointFlat = true;
left = right = 0;
} else {
string = Deal(string);//中缀表达式转后缀表达式
string = Calculate(string);
editText.setText(temp + "\n" + "= " + string);
left = right = 0;
isResult = true;
pointFlat = true;
}
}
}
}处理输入的表达式
这个函数是处理一些不完整的输入比如少括号、小数点后没有数值、表达式前后是计算符号等等，以提高该计算器的鲁棒性
public String Equal(String string){
int length_equ = string.length();
if(length_equ == 1 && (string.equals("(") || string.equals(")"))){
string = "Error";
return string;
}else if (String.valueOf(string.charAt(0)).equals(")")){
string = "Error";
return string;
}
if (length_equ == 2 && string.equals("()")){
string = "Error";
return string;
}
if (length_equ - 1 >= 0 && String.valueOf(string.charAt(length_equ - 1)).matches("[\\*\\/]{1}")){
string += "1";
} else if (length_equ - 1 >= 0 && String.valueOf(string.charAt(length_equ - 1)).matches("[\\+\\-\\.]{1}")) {
string += "0";
}//结尾是运算符的情况
if (String.valueOf(string.charAt(0)).matches("[\\+\\-\\*\\/]{1}")){
string = "0" + string;
} //开头是运算符的情况
while(left != right){
if (left > right){
right++;
string += ")";
}else if(left < right){
string = "Error";
return string;
}
}//括号不匹配的情况
for (int i = 0; i < string.length(); i++) {
String temp = String.valueOf(string.charAt(i));
if (temp.equals("(") && i + 1 < string.length()
&& String.valueOf(string.charAt(i + 1)).matches("[\\+\\*\\/\\)]{1}")) {
string = "Error";
break;
} else if (temp.equals(")") && i - 1 >= 0 &&
String.valueOf(string.charAt(i - 1)).matches("[\\+\\-\\*\\/\\(]{1}")) {
string = "Error";
break;
} //出现(+*/ 或者 +-*/)的情况
if (temp.equals("(") && i - 1 > 0
&& String.valueOf(string.charAt(i - 1)).matches("[0-9\\.\\)]{1}")) {
string = "Error";
break;
} else if (temp.equals(")") && i + 1 < string.length()
&& String.valueOf(string.charAt(i + 1)).matches("[0-9\\(\\.\\(]{1}")) {
string = "Error";
break;
}//防止出现[0-9]( 和 )[0-9]的情况
}
if (string.length() >= 2 && string.charAt(0) == '(' && string.charAt(string.length() - 1) == ')'){
String temp = string.substring(1,string.length() - 1);
if (temp.matches("^[+-]?[1-9]\\d*$") || temp.matches("^[+-]?\\d+(\\.\\d+)$")
|| temp.equals("0")){
return temp;
}
}
return string;
}中缀转后缀的函数
中缀转后缀是实现该计算器的核心算法，没学过的建议先去补一下该方面的知识
中缀表达式转后缀表达式
public String Deal(String infix){
Stack stack = new Stack<>();
StringBuilder postfix = new StringBuilder();
int length = infix.length();
for (int i = 0; i < length; i++){
String temp;
String charAt = String.valueOf(infix.charAt(i));
if (charAt.equals("(")){
stack.push(String.valueOf(charAt));
} else if (charAt.equals("+") || charAt.equals("-")) {
while (!stack.isEmpty()){
temp = stack.peek();
if (temp.equals("(")){
break;
}
postfix.append(" ").append(stack.pop());
}
stack.push(charAt);
} else if (charAt.equals("*") || charAt.equals("/")) {
while (!stack.isEmpty()){
temp = stack.pop();
if (temp.equals("(") || temp.equals("+") || temp.equals("-")){
stack.push(temp);
break;
}
postfix.append(" ").append(temp);
}
stack.push(charAt);
} else if (charAt.equals(")")) {
while (!stack.isEmpty()){
temp = stack.pop();
if (!temp.equals("(")){
postfix.append(" ").append(temp);
}else {
break;
}
}
} else if (charAt.matches("[0-9]|\\.")){
postfix.append(" ").append(charAt);
if (i < length - 1){
int j = i + 1;
String nextNumber = String.valueOf(infix.charAt(j));
while (j < length && nextNumber.matches("[0-9]|\\.")){
postfix.append(nextNumber);
if (++j < length)
nextNumber = String.valueOf(infix.charAt(j));
}
i = j - 1;
}
}
}
while (!stack.isEmpty()){
postfix.append(" ").append(stack.pop());
}
return postfix.toString().trim();
} 计算函数
处理完输入的字符串接下来就是计算了，这里全程使用Bigdecimal，在除法处使用了double，因为Bigdecimal精度是十分准确的，在计算无限小数时无法输出会报错，除非设置四舍五入，但是精度的话无法控制得很好，所以我结合两者一起使用
public String Calculate(@NonNull String s){
String[] nums = s.split(" ");
Stack stack = new Stack<>();
BigDecimal big1,big2,big;
String result = "";
for(String str : nums){
if (str.matches("^[+-]?[1-9]\\d*$") || str.matches("^[+-]?\\d+(\\.\\d+)$") || str.equals("0")){
stack.push(str);
} else if (str.equals("+")){
big1 = new BigDecimal(stack.pop());
big2 = new BigDecimal(stack.pop());
big = big2.add(big1);
result = big + "";
stack.push(result);
} else if (str.equals("-")) {
big1 = new BigDecimal(stack.pop());
big2 = new BigDecimal(stack.pop());
big = big2.subtract(big1);
result = big + "";
stack.push(result);
} else if (str.equals("*")) {
big1 = new BigDecimal(stack.pop());
big2 = new BigDecimal(stack.pop());
big = big2.multiply(big1);
result = big + "";
stack.push(result);
} else if (str.equals("/")) {
String temp1 = stack.pop();
String temp2 = stack.pop();
big1 = new BigDecimal(temp1);
big2 = new BigDecimal(temp2);
double b1 = Double.valueOf(temp1);
double b2 = Double.valueOf(temp2);
if (big1.compareTo(BigDecimal.ZERO) == 0){
return "Error : 除数不能为0";
}
if (temp1.length() <= 20 && temp2.length() <= 20){
double b = b2 / b1;
result = b + "";
}else {
big = big2.divide(big1,BigDecimal.ROUND_HALF_UP);
result = new BigDecimal(big + "").setScale(12, RoundingMode.HALF_UP) + "";
}
stack.push(result);
} else {
return "Error : " + str + "不是数字";
}
}
return result;
} 效果图
