计算器——第一个Android小项目
16lz
2021-01-23
Android计算器
目录
这是我第一个Android小项目，相信这也是大多数人的第一个小项目。
这个项目非常的简单，只有一个Activity。
首先是布局文件，这里我用的是线性布局。
计算器的布局
这个布局文件中的按钮（Button）比较多。
首先是一个TextView，然后是一堆按钮。
<?xml version="1.0" encoding="utf-8"?>"http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent" > id="@+id/text_view" android:layout_width="match_parent" android:layout_height="0dp" android:layout_weight="2" > id="@+id/text_edit" android:layout_width="match_parent" android:layout_height="match_parent" android:background="#ffffff" android:textColor="#e51c23" android:gravity="bottom|right" android:textSize="30sp" /> id="@+id/button_1line" android:layout_width="match_parent" android:layout_height="0dp" android:layout_weight="1" android:orientation="horizontal"> id="@+id/button_2line" android:layout_width="match_parent" android:layout_height="0dp" android:layout_weight="1" android:orientation="horizontal" > id="@+id/button_3line" android:layout_width="match_parent" android:layout_height="0dp" android:layout_weight="1" android:orientation="horizontal" > id="@+id/button_4line" android:layout_width="match_parent" android:layout_height="0dp" android:layout_weight="1" android:orientation="horizontal" > id="@+id/button_5line" android:layout_width="match_parent" android:layout_height="0dp" android:layout_weight="1" android:orientation="horizontal" > 接下来就是ManActivity中的代码了，当然其中主要就是一个按钮的监听，也没有什么难度。
MainActivity中的代码
package com.example.calculatortest;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.Button;import android.widget.TextView;public class MainActivity extends AppCompatActivity implements View.OnClickListener{ StringBuffer sb = new StringBuffer(); private TextView text = null; // 用于显示输入和输出 @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.simple_1); getSupportActionBar().hide(); text = (TextView) findViewById(R.id.text_edit); // 数字按钮 Button button0 = (Button)findViewById(R.id.button_0); 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); // 功能按钮 // 四则运算 Button button_div = (Button)findViewById(R.id.button_div); Button button_mul = (Button)findViewById(R.id.button_mul); Button button_add = (Button)findViewById(R.id.button_add); Button button_minus = (Button) findViewById(R.id.button_minus); Button button_back = (Button)findViewById(R.id.button_back); Button button_clear = (Button) findViewById(R.id.button_clear); Button button_point = (Button) findViewById(R.id.button_point); Button button_equals = (Button) findViewById(R.id.button_equals); // 左右括号 Button button_left = (Button) findViewById(R.id.button_left); Button button_right = (Button) findViewById(R.id.button_right); button0.setOnClickListener(this); 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); button_add.setOnClickListener(this); button_minus.setOnClickListener(this); button_mul.setOnClickListener(this); button_div.setOnClickListener(this); button_back.setOnClickListener(this); button_clear.setOnClickListener(this); button_point.setOnClickListener(this); button_equals.setOnClickListener(this); button_left.setOnClickListener(this); button_right.setOnClickListener(this); } private String sign = "+-*/"; @Override public void onClick(View view) { switch (view.getId()) { case R.id.button_1: sb.append("1"); text.setText(sb); break; case R.id.button_2: sb.append("2"); text.setText(sb); break; case R.id.button_3: sb.append("3"); text.setText(sb); break; case R.id.button_4: sb.append("4"); text.setText(sb); break; case R.id.button_5: sb.append("5"); text.setText(sb); break; case R.id.button_6: sb.append("6"); text.setText(sb); break; case R.id.button_7: sb.append("7"); text.setText(sb); break; case R.id.button_8: sb.append("8"); text.setText(sb.toString()); break; case R.id.button_9: sb.append("9"); text.setText(sb); break; case R.id.button_0: sb.append("0"); text.setText(sb); break; case R.id.button_back: if(sb.length() > 0) { sb.deleteCharAt(sb.length() - 1); text.setText(sb); } break; case R.id.button_clear: sb.setLength(0); text.setText(sb); break; case R.id.button_add: if(sb.length() > 0 && sign.indexOf(sb.charAt(sb.length() - 1)) == -1) { sb.append("+"); } text.setText(sb); break; case R.id.button_minus: if(sb.length() == 0 || sb.length() > 0 && sign.indexOf(sb.charAt(sb.length() - 1)) == -1) { sb.append("-"); } text.setText(sb); break; case R.id.button_mul: if(sb.length() > 0 && sign.indexOf(sb.charAt(sb.length() - 1)) == -1) { sb.append("×"); } text.setText(sb); break; case R.id.button_div: if(sb.length() > 0 && sign.indexOf(sb.charAt(sb.length() - 1)) == -1) { sb.append("÷"); } text.setText(sb); break; case R.id.button_point: if(sb.length() == 0 ||!Character.isDigit(sb.charAt(sb.length() - 1))) { sb.append("0."); } else { sb.append("."); } text.setText(sb); break; case R.id.button_left: sb.append("("); text.setText(sb); break; case R.id.button_right: if (sb.indexOf("(") != -1) { sb.append(")"); } text.setText(sb); break; case R.id.button_equals: String s = sb.toString().replace("×", "*").replace("÷", "/"); try { s = Calculator.toSuffix(s); } catch (Exception ex) { s = "出错"; } text.setText(sb + "\n"+"=" + s); if (s != "出错") { sb = new StringBuffer(s); }else { sb.delete(0, sb.length()); } break; } }}当然还有一个Calculator类，这个就是计算的核心代码了，这个类中用的是中缀转后缀来计算的，当然如果看不懂，可以看我的这个博客：
package com.example.calculatortest;import java.math.BigDecimal;import java.math.BigInteger;import java.math.MathContext;import java.math.RoundingMode;import java.util.ArrayDeque;public class Calculator { public static String toSuffix(String input) { int len = input.length(); char c, tempChar; ArrayDeque s1 = new ArrayDeque(); ArrayDeque s2 = new ArrayDeque<>(); int lastIndex = -1; for (int i = 0; i < len; ++i) { c = input.charAt(i); if (Character.isDigit(c) || c == '.') { lastIndex = readDouble(input, i); if (lastIndex == -10) return "出错"; BigDecimal number = new BigDecimal(input.substring(i, lastIndex)); s2.push(number); i = lastIndex - 1; }else if (c == '-' && i == 0) { lastIndex = readDouble(input, i + 1); if (lastIndex == -10) return "出错"; BigDecimal number = new BigDecimal(input.substring(i, lastIndex)); s2.push(number); i = lastIndex - 1; }else if (i > 0 && c == '-' && (input.charAt(i-1) == '(' || isOperator(input.charAt(i-1)))) { lastIndex = readDouble(input, i + 1); if (lastIndex == -10) return "出错"; BigDecimal number = new BigDecimal(input.substring(i, lastIndex)); s2.push(number); i = lastIndex - 1; } else if (isOperator(c)) { while (!s1.isEmpty() && s1.peek() != '(' && priorityCompare(c, s1.peek()) <= 0) {// double num1 = s2.pop();// double num2 = s2.pop(); BigDecimal num1 = s2.pop(); BigDecimal num2 = s2.pop(); s2.push(calc(num2, num1, s1.pop())); } s1.push(c); } else if (c == '(') { s1.push(c); } else if (c == ')') { while ((tempChar = s1.pop()) != '(') {// double num1 = s2.pop();// double num2 = s2.pop(); BigDecimal num1 = s2.pop(); BigDecimal num2 = s2.pop(); s2.push(calc(num2, num1, tempChar)); if (s1.isEmpty()) { return "出错"; } } } else if (c == ' ') { // ignore } else { return "出错"; } } while (!s1.isEmpty()) { tempChar = s1.pop();// double num1 = s2.pop();// double num2 = s2.pop(); BigDecimal num1 = s2.pop(); BigDecimal num2 = s2.pop(); s2.push(calc(num2, num1, tempChar)); } BigDecimal result = s2.pop(); if (!s2.isEmpty()) return "出错"; if (result.toString().length() < 20) return result.stripTrailingZeros().toPlainString(); else return result.round(new MathContext(6, RoundingMode.HALF_UP)).toEngineeringString(); } /** * 获取是double值得最后一位索引 */ public static int readDouble(String str, int start) throws IllegalArgumentException{ int len = str.length(); int dotIndex = -1; char ch; for (int i = start; i < len ; i++) { ch = str.charAt(i); if(ch == '.') { if(dotIndex != -1) return -10; else if(i == len - 1) return -10; else dotIndex = i; } else if(!Character.isDigit(ch)) { if (dotIndex == -1 || i - dotIndex > 1) return i; else throw new IllegalArgumentException("不是数字，不能作为数字的一部分"); } else if(i == len - 1) { return len; } } return -10; } /** * 判断优先级 */ private static int priorityCompare (char op1, char op2) { if(op1 == '+' || op1 == '-') return (op2 == '*' || op2 == '/' ? -1 : 0); if (op1 == '*' || op1 == '/') { return (op2 == '+' || op2 == '-' ? 1 : 0); } return 1; } /** * 这个函数能够判断是否是操作运算符 */ private static boolean isOperator (char ch) { return (ch == '+' || ch == '-' || ch == '*' || ch == '/'); } /** * 计算两个数的结果 * 并返回 */ private static BigDecimal calc (BigDecimal num1, BigDecimal num2, char op) throws IllegalArgumentException{ switch (op) { case '+': return num1.add(num2); case '-': return num1.subtract(num2); case '*': return num1.multiply(num2); case '/': if (num2.equals(0)) throw new IllegalArgumentException("除数不能为0"); return num1.divide(num2, 8, RoundingMode.HALF_UP); default: return new BigDecimal(0); } }} 更多相关文章
- android 多个按钮中一个高亮
- Android自适应屏幕大小和layout布局
- Android之布局
- android在使用RecyclerView布局里的androidstudio的模拟器虚拟键
- Android布局——Linearlayout线性布局
- Android中包含多个Activity的应用退出按钮实现
- Android 布局深度优化(减少布局层次)