Java实现表达式的运算-Android简易计算器

计算一个正确的字符串形式运算式(若要实现计算器，还需对表达式的合法性进行判断)

运算代码CalculatorMathUtil.java

import java.math.BigDecimal;import java.math.MathContext;import java.util.Stack;/**  * 计算一个正确的字符串形式运算式 * @author HLP * */public class CalculatorMathUtil {/** * 数据栈 */Stack<BigDecimal> number;/** * 符号栈 */Stack<Character> operator;/** * 计算除法时，设置的结果标度 */int length;public CalculatorMathUtil(int length) {this.length = length;}/** * 获得计算结果的字符串表示形式 * @param exp * @return */public String getResult(String exp) {this.number = new Stack<BigDecimal>();this.operator = new Stack<Character>();calculate(exp);return this.number.peek().toString();}/** * 对运算式exp进行解析，并计算 * @param exp */public void calculate(String exp) {int index = 0;int sign = 0;while (index < exp.length()) {char op = exp.charAt(index);if ((op <= '9' && op >= '0') || op == '.') {index++;} else {if (index > 0) {char opp = exp.charAt(index-1);if (op == '-' && !((opp <= '9' && opp >= '0') || opp == '.')) {index++;continue;}}if (sign != index) {String numStr = exp.substring(sign, index);BigDecimal num = new BigDecimal(numStr);number.push(num);}analysis(op);sign = ++index;}}}/** * 对得到的数据和符号进行分析处理 * @param op * @param num */public void analysis(char op) {if (operator.empty() || comparePriority(op, operator.peek())) {operator.push(op);} else {makeNum(op);}}/** * 计算 * @param op * @param num */private void makeNum(char op) {BigDecimal result = null;while (!operator.empty() && !comparePriority(op, operator.peek())) {char op2 = operator.pop();if (op == ')' && op2 == '(') {return;}BigDecimal num1 = null;BigDecimal num2 = number.pop();if (number.empty()) {num1 = new BigDecimal(0);} else {num1 = number.pop();}switch (op2) {case '+':result = num1.add(num2);break;case '-':result = num1.subtract(num2);break;case '*':result = num1.multiply(num2);break;case '/':result = num1.divide(num2, new MathContext(length));break;default:operator.pop();break;}number.push(result);}if (op != ')') {operator.push(op);}}/** * 判断优先级：true(c1优先级高于c2)、false(c1优先级低于c2) * @param c1 * @param c2 * @return */public boolean comparePriority(char c1, char c2) {if (c1 == '=') {return false;} else if (c1 == ')') {return false;} else if (c1 == '(') {return true;} else if (c2 == '(') {return true;} else if ((c1 == '*' || c1 == '/') && (c2 == '-' || c2 == '+')) {return true;} else {return false;}}}

Android简易计算器

CalculatorMainActivity.java

在输入的同时来保证表达式的合法性

import com.anjoyo.lifelittlehelper.R;import android.os.Bundle;import android.app.Activity;import android.view.View;import android.widget.Button;import android.widget.TextView;import android.widget.Toast;public class CalculatorMainActivity extends Activity {private TextView mShowTextView = null;private StringBuffer mExpressBuffer = new StringBuffer();private String mResult = "";private static CalculatorMathUtil mCalculatorMathUtil = new CalculatorMathUtil(20);@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_calculator_main);mShowTextView = (TextView) findViewById(R.id.tv_calculator_result);}public void clickMe(View v) {if (mResult.length() > 0 && mExpressBuffer.toString().contains("=")) {mExpressBuffer = new StringBuffer();}Button btn = (Button) v;switch (btn.getId()) {case R.id.btn_calculator_num_0:if (mExpressBuffer.length() != 0 && mExpressBuffer.charAt(mExpressBuffer.length() - 1) == ')') {break;}mExpressBuffer.append(0);break;case R.id.btn_calculator_num_1:if (mExpressBuffer.length() != 0 && mExpressBuffer.charAt(mExpressBuffer.length() - 1) == ')') {break;}mExpressBuffer.append(1);break;case R.id.btn_calculator_num_2:if (mExpressBuffer.length() != 0 && mExpressBuffer.charAt(mExpressBuffer.length() - 1) == ')') {break;}mExpressBuffer.append(2);break;case R.id.btn_calculator_num_3:if (mExpressBuffer.length() != 0 && mExpressBuffer.charAt(mExpressBuffer.length() - 1) == ')') {break;}mExpressBuffer.append(3);break;case R.id.btn_calculator_num_4:if (mExpressBuffer.length() != 0 && mExpressBuffer.charAt(mExpressBuffer.length() - 1) == ')') {break;}mExpressBuffer.append(4);break;case R.id.btn_calculator_num_5:if (mExpressBuffer.length() != 0 && mExpressBuffer.charAt(mExpressBuffer.length() - 1) == ')') {break;}mExpressBuffer.append(5);break;case R.id.btn_calculator_num_6:if (mExpressBuffer.length() != 0 && mExpressBuffer.charAt(mExpressBuffer.length() - 1) == ')') {break;}mExpressBuffer.append(6);break;case R.id.btn_calculator_num_7:if (mExpressBuffer.length() != 0 && mExpressBuffer.charAt(mExpressBuffer.length() - 1) == ')') {break;}mExpressBuffer.append(7);break;case R.id.btn_calculator_num_8:if (mExpressBuffer.length() != 0 && mExpressBuffer.charAt(mExpressBuffer.length() - 1) == ')') {break;}mExpressBuffer.append(8);break;case R.id.btn_calculator_num_9:if (mExpressBuffer.length() != 0 && mExpressBuffer.charAt(mExpressBuffer.length() - 1) == ')') {break;}mExpressBuffer.append(9);break;case R.id.btn_calculator_num_point:if (mExpressBuffer.length() != 0) {char c = mExpressBuffer.charAt(mExpressBuffer.length() - 1);if (c >= '0' && c <= '9') {mExpressBuffer.append(".");}}break;case R.id.btn_calculator_brackets_left:if (mExpressBuffer.length() == 0) {mExpressBuffer.append("(");} else {char c = mExpressBuffer.charAt(mExpressBuffer.length() - 1);if (c == '+' || c == '-' || c == '*' || c == '/' || c == '(') {mExpressBuffer.append("(");}}break;case R.id.btn_calculator_brackets_right:if (mExpressBuffer.length() != 0) {char c = '\0';int n1 = 0;// '('的个数int n2 = 0;// ')'的个数for (int i = 0; i < mExpressBuffer.length(); i++) {c = mExpressBuffer.charAt(i);if (c == '(') {n1++;} else if (c == ')') {n2++;}}if (n2 < n1 && (c >= '0' && c <= '9' || c == ')')) {mExpressBuffer.append(")");}}break;case R.id.btn_calculator_back_space:if (mExpressBuffer.length() != 0) {mExpressBuffer.deleteCharAt(mExpressBuffer.length() - 1);}break;case R.id.btn_calculator_operator_0:mExpressBuffer = new StringBuffer();mResult = "";break;case R.id.btn_calculator_operator_1:if (mResult.length() != 0) {mExpressBuffer.append(mResult);mResult = "";}if (mExpressBuffer.length() == 0) {mExpressBuffer.append("+");} else {char c = mExpressBuffer.charAt(mExpressBuffer.length() - 1);if (c >= '0' && c <= '9' || c == ')') {mExpressBuffer.append("+");}}break;case R.id.btn_calculator_operator_2:if (mResult.length() != 0) {mExpressBuffer.append(mResult);mResult = "";}if (mExpressBuffer.length() == 0) {mExpressBuffer.append("-");} else {int len = mExpressBuffer.length();char c = mExpressBuffer.charAt(len - 1);if (c >= '0' && c <= '9' || c == '(' || c == ')') {mExpressBuffer.append("-");} else if (len >= 2) {c = mExpressBuffer.charAt(len - 2);if (c >= '0' && c <= '9' || c == '(' || c == ')') {mExpressBuffer.append("-");}}}break;case R.id.btn_calculator_operator_3:if (mResult.length() != 0) {mExpressBuffer.append(mResult);mResult = "";}if (mExpressBuffer.length() != 0) {char c = mExpressBuffer.charAt(mExpressBuffer.length() - 1);if (c >= '0' && c <= '9' || c == ')') {mExpressBuffer.append("*");}}break;case R.id.btn_calculator_operator_4:if (mResult.length() != 0) {mExpressBuffer.append(mResult);mResult = "";}if (mExpressBuffer.length() != 0) {char c = mExpressBuffer.charAt(mExpressBuffer.length() - 1);if (c >= '0' && c <= '9' || c == ')') {mExpressBuffer.append("/");}}break;case R.id.btn_calculator_operator_5:if (mExpressBuffer.length() != 0) {char c = '\0';int n1 = 0;// '('的个数int n2 = 0;// ')'的个数for (int i = 0; i < mExpressBuffer.length(); i++) {c = mExpressBuffer.charAt(i);if (c == '(') {n1++;} else if (c == ')') {n2++;}}if (n1 == n2 && (c >= '0' && c <= '9' || c == ')')) {mExpressBuffer.append("=");try {mResult = mCalculatorMathUtil.getResult(mExpressBuffer.toString());mExpressBuffer.append(mResult);} catch (Exception e1) {//mExpressBuffer.append("  IS ERROR");mExpressBuffer.deleteCharAt(mExpressBuffer.length() - 1);Toast.makeText(this, "表达式错误", Toast.LENGTH_LONG).show();}}}break;default:break;}mShowTextView.setText(mExpressBuffer.toString());}}

布局

<?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="#ff000000"    android:orientation="vertical" >        <TextView        android:id="@+id/tv_calculator_result"        android:layout_width="match_parent"        android:layout_height="100dp"        android:background="#cccccccc"        android:textSize="26sp"        android:gravity="bottom|right"        android:layout_margin="10dp"        android:paddingBottom="10dp"        android:paddingLeft="5dp"        android:paddingRight="5dp"        />    <TableLayout         android:id="@+id/tl_calculator_keys_layout"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:stretchColumns="0,1,2,3"        android:layout_marginTop="10dp"        android:layout_marginLeft="5dp"        android:layout_marginRight="5dp"        >        <TableRow >            <Button                 android:id="@+id/btn_calculator_brackets_left"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/brackets0"                android:onClick="clickMe"                />            <Button                 android:id="@+id/btn_calculator_brackets_right"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/brackets1"                android:onClick="clickMe"                />            <Button                 android:id="@+id/btn_calculator_operator_0"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/operator0"                android:background="@drawable/calculator_button_background_2"                android:onClick="clickMe"                />            <Button                android:id="@+id/btn_calculator_back_space"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/operatorC"                 android:background="@drawable/calculator_button_background_2"                android:onClick="clickMe"                />        </TableRow>                <TableRow >            <Button                 android:id="@+id/btn_calculator_operator_1"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/operator1"                android:onClick="clickMe"                />            <Button                 android:id="@+id/btn_calculator_num_7"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/num7"                android:onClick="clickMe"                />            <Button                 android:id="@+id/btn_calculator_num_8"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/num8"                android:onClick="clickMe"                />            <Button                android:id="@+id/btn_calculator_num_9"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/num9"                 android:onClick="clickMe"                />        </TableRow>                <TableRow >            <Button                 android:id="@+id/btn_calculator_operator_2"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/operator2"                android:onClick="clickMe"                />            <Button                 android:id="@+id/btn_calculator_num_4"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/num4"                android:onClick="clickMe"                />            <Button                 android:id="@+id/btn_calculator_num_5"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/num5"                android:onClick="clickMe"                />            <Button                android:id="@+id/btn_calculator_num_6"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/num6"                 android:onClick="clickMe"                />        </TableRow>                <TableRow >            <Button                 android:id="@+id/btn_calculator_operator_3"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/operator3"                android:onClick="clickMe"                />            <Button                 android:id="@+id/btn_calculator_num_1"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/num1"                android:onClick="clickMe"                />            <Button                 android:id="@+id/btn_calculator_num_2"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/num2"                android:onClick="clickMe"                />            <Button                android:id="@+id/btn_calculator_num_3"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/num3"                 android:onClick="clickMe"                />        </TableRow>                <TableRow >            <Button                 android:id="@+id/btn_calculator_operator_4"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/operator4"                android:onClick="clickMe"                />            <Button                 android:id="@+id/btn_calculator_num_point"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/point"                android:onClick="clickMe"                />            <Button                 android:id="@+id/btn_calculator_num_0"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/num0"                android:onClick="clickMe"                />            <Button                android:id="@+id/btn_calculator_operator_5"                style="@style/calculator_button_style"                android:layout_margin="1dp"                android:layout_weight="0.25"                android:text="@string/operator5"                 android:background="@drawable/calculator_button_background_2"                android:onClick="clickMe"                />        </TableRow>            </TableLayout></LinearLayout>

样式

<style name="calculator_button_style">        <item name="android:layout_width">68dp</item>        <item name="android:layout_height">50dp</item>        <item name="android:gravity">center</item>        <item name="android:textSize">18sp</item>        <item name="android:textColor">#ffffffff</item>        <item name="android:textStyle">bold</item>        <item name="android:background">@drawable/calculator_button_background</item></style>

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