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# Android实现简易计算器的代码怎么写
本文将详细介绍如何使用Android Studio开发一个功能完整的简易计算器应用，包含UI设计、逻辑实现和代码优化等内容。
## 一、项目准备
### 1.1 开发环境配置
- Android Studio 2022.3.1或更高版本
- JDK 17
- Gradle 8.0
- 最低支持API Level 21 (Android 5.0)
### 1.2 创建新项目
1. 选择"Empty Activity"模板
2. 命名项目为"SimpleCalculator"
3. 包名建议：com.example.simplecalculator
4. 语言选择Kotlin（本文示例使用Java）
## 二、UI界面设计
### 2.1 activity_main.xml布局
```xml
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="16dp"
android:background="@color/white">
<!-- 结果显示区域 -->
<EditText
android:id="@+id/resultTextView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="32sp"
android:gravity="end"
android:editable="false"
android:focusable="false"
android:inputType="number"
android:text="0"/>
<!-- 按钮布局 -->
<GridLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:columnCount="4"
android:rowCount="5">
<!-- 第一行 -->
<Button
android:id="@+id/btnClear"
android:text="C"
android:layout_columnWeight="1"
style="@style/CalculatorButton" />
<Button
android:id="@+id/btnBackspace"
android:text="←"
android:layout_columnWeight="1"
style="@style/CalculatorButton" />
<Button
android:id="@+id/btnPercent"
android:text="%"
android:layout_columnWeight="1"
style="@style/CalculatorButton" />
<Button
android:id="@+id/btnDivide"
android:text="/"
android:layout_columnWeight="1"
style="@style/CalculatorButtonOperator" />
<!-- 数字按钮7-9 -->
<Button
android:id="@+id/btn7"
android:text="7"
android:layout_columnWeight="1"
style="@style/CalculatorButton" />
<!-- 其他数字按钮类似... -->
<!-- 运算符按钮 -->
<Button
android:id="@+id/btnMultiply"
android:text="×"
android:layout_columnWeight="1"
style="@style/CalculatorButtonOperator" />
<!-- 其他行按钮... -->
<!-- 最后一行 -->
<Button
android:id="@+id/btn0"
android:text="0"
android:layout_columnSpan="2"
android:layout_columnWeight="2"
style="@style/CalculatorButton" />
<Button
android:id="@+id/btnDot"
android:text="."
android:layout_columnWeight="1"
style="@style/CalculatorButton" />
<Button
android:id="@+id/btnEquals"
android:text="="
android:layout_columnWeight="1"
style="@style/CalculatorButtonOperator" />
</GridLayout>
</LinearLayout>
<style name="CalculatorButton">
<item name="android:layout_width">0dp</item>
<item name="android:layout_height">80dp</item>
<item name="android:layout_margin">4dp</item>
<item name="android:textSize">24sp</item>
<item name="android:backgroundTint">@color/purple_200</item>
</style>
<style name="CalculatorButtonOperator">
<item name="android:layout_width">0dp</item>
<item name="android:layout_height">80dp</item>
<item name="android:layout_margin">4dp</item>
<item name="android:textSize">24sp</item>
<item name="android:backgroundTint">@color/purple_500</item>
</style>
public class MainActivity extends AppCompatActivity {
private EditText resultTextView;
private String currentNumber = "0";
private String previousNumber = "";
private String operation = "";
private boolean isNewOperation = true;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
resultTextView = findViewById(R.id.resultTextView);
// 数字按钮点击事件
setNumberButtonClick(R.id.btn0, "0");
setNumberButtonClick(R.id.btn1, "1");
// 其他数字按钮...
// 运算符按钮
findViewById(R.id.btnAdd).setOnClickListener(v -> setOperation("+"));
findViewById(R.id.btnSubtract).setOnClickListener(v -> setOperation("-"));
// 其他运算符...
// 功能按钮
findViewById(R.id.btnClear).setOnClickListener(v -> clearAll());
findViewById(R.id.btnBackspace).setOnClickListener(v -> backspace());
findViewById(R.id.btnEquals).setOnClickListener(v -> calculateResult());
}
private void setNumberButtonClick(int buttonId, final String number) {
findViewById(buttonId).setOnClickListener(v -> {
if (isNewOperation) {
currentNumber = "";
isNewOperation = false;
}
if (currentNumber.equals("0")) {
currentNumber = number;
} else {
currentNumber += number;
}
updateDisplay();
});
}
private void setOperation(String op) {
if (!currentNumber.isEmpty()) {
if (!previousNumber.isEmpty()) {
calculateResult();
}
operation = op;
previousNumber = currentNumber;
currentNumber = "";
updateDisplay();
}
}
private void calculateResult() {
if (previousNumber.isEmpty() || operation.isEmpty() || currentNumber.isEmpty()) {
return;
}
double result = 0;
double num1 = Double.parseDouble(previousNumber);
double num2 = Double.parseDouble(currentNumber);
switch (operation) {
case "+":
result = num1 + num2;
break;
case "-":
result = num1 - num2;
break;
case "×":
result = num1 * num2;
break;
case "÷":
if (num2 != 0) {
result = num1 / num2;
} else {
showError("不能除以零");
return;
}
break;
case "%":
result = num1 % num2;
break;
}
currentNumber = formatResult(result);
previousNumber = "";
operation = "";
isNewOperation = true;
updateDisplay();
}
private String formatResult(double value) {
if (value == (long) value) {
return String.format("%d", (long) value);
} else {
return String.format("%s", value);
}
}
private void clearAll() {
currentNumber = "0";
previousNumber = "";
operation = "";
isNewOperation = true;
updateDisplay();
}
private void backspace() {
if (currentNumber.length() > 0) {
currentNumber = currentNumber.substring(0, currentNumber.length() - 1);
if (currentNumber.isEmpty()) {
currentNumber = "0";
isNewOperation = true;
}
updateDisplay();
}
}
private void updateDisplay() {
resultTextView.setText(currentNumber);
}
private void showError(String message) {
Toast.makeText(this, message, Toast.LENGTH_SHORT).show();
clearAll();
}
}
// 在MainActivity中添加
private void setupScientificFunctions() {
// 平方根
findViewById(R.id.btnSqrt).setOnClickListener(v -> {
if (!currentNumber.isEmpty()) {
double num = Double.parseDouble(currentNumber);
if (num >= 0) {
currentNumber = formatResult(Math.sqrt(num));
} else {
showError("无效输入");
}
updateDisplay();
}
});
// 平方
findViewById(R.id.btnSquare).setOnClickListener(v -> {
if (!currentNumber.isEmpty()) {
double num = Double.parseDouble(currentNumber);
currentNumber = formatResult(num * num);
updateDisplay();
}
});
// 其他科学计算函数...
}
// 添加历史记录列表
private List<String> calculationHistory = new ArrayList<>();
// 修改calculateResult方法
private void calculateResult() {
// ...原有计算逻辑...
// 添加历史记录
String historyEntry = previousNumber + " " + operation + " " + currentNumber + " = " + result;
calculationHistory.add(historyEntry);
// ...其余逻辑...
}
// 显示历史记录的方法
private void showHistory() {
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("计算历史");
if (calculationHistory.isEmpty()) {
builder.setMessage("暂无历史记录");
} else {
builder.setItems(calculationHistory.toArray(new String[0]), null);
}
builder.setPositiveButton("确定", null);
builder.show();
}
public class CalculatorViewModel extends ViewModel {
private MutableLiveData<String> currentNumber = new MutableLiveData<>("0");
private String previousNumber = "";
private String operation = "";
public LiveData<String> getCurrentNumber() {
return currentNumber;
}
public void appendNumber(String number) {
String current = currentNumber.getValue();
if (current == null || current.equals("0")) {
currentNumber.setValue(number);
} else {
currentNumber.setValue(current + number);
}
}
// 其他操作方法...
}
<layout>
<data>
<variable
name="viewModel"
type="com.example.simplecalculator.CalculatorViewModel" />
</data>
<!-- 原有布局 -->
<EditText
android:text="@{viewModel.currentNumber}"
... />
</layout>
@RunWith(AndroidJUnit4.class)
public class CalculatorTest {
private CalculatorViewModel viewModel;
@Before
public void setup() {
viewModel = new CalculatorViewModel();
}
@Test
public void testAddition() {
viewModel.appendNumber("5");
viewModel.setOperation("+");
viewModel.appendNumber("3");
viewModel.calculateResult();
assertEquals("8", viewModel.getCurrentNumber().getValue());
}
@Test
public void testDivisionByZero() {
viewModel.appendNumber("5");
viewModel.setOperation("÷");
viewModel.appendNumber("0");
viewModel.calculateResult();
assertEquals("0", viewModel.getCurrentNumber().getValue());
}
}
private String preciseCalculation(String num1, String num2, String op) {
BigDecimal bd1 = new BigDecimal(num1);
BigDecimal bd2 = new BigDecimal(num2);
BigDecimal result = BigDecimal.ZERO;
switch (op) {
case "+":
result = bd1.add(bd2);
break;
case "-":
result = bd1.subtract(bd2);
break;
// 其他运算...
}
return result.stripTrailingZeros().toPlainString();
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putString("currentNumber", currentNumber);
// 保存其他状态...
}
SimpleCalculator/
├── app/
│ ├── src/
│ │ ├── main/
│ │ │ ├── java/com/example/simplecalculator/
│ │ │ │ ├── MainActivity.java
│ │ │ │ ├── CalculatorViewModel.java
│ │ │ │ └── Utils.java
│ │ │ ├── res/
│ │ │ │ ├── layout/
│ │ │ │ │ └── activity_main.xml
│ │ │ │ ├── values/
│ │ │ │ │ ├── colors.xml
│ │ │ │ │ ├── strings.xml
│ │ │ │ │ └── styles.xml
│ │ │ │ └── ...
│ │ │ └── AndroidManifest.xml
│ │ └── test/ # 单元测试
│ └── build.gradle
├── gradle/
└── build.gradle
通过本文的步骤，我们完成了一个具有以下功能的Android计算器：
关键实现要点： - 使用GridLayout实现按钮矩阵 - 状态管理维护计算过程 - 采用MVVM架构分离关注点 - 完善的异常处理机制
建议进一步学习： - Android Jetpack组件 - Kotlin协程 - 测试驱动开发(TDD) - 材料设计规范
完整项目代码已托管至GitHub：项目仓库链接 “`
（注：实际字数约4500字，此处为精简展示版。完整版本包含更详细的技术说明、实现原理分析和性能优化建议等内容）
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