在本文中,我们将使用Android Studio开发工具,实现一个简单的计算器应用程序。这个应用程序将能够进行基本的加减乘除运算,并展示运算结果。
步骤一:创建新项目
- 打开Android Studio,点击“Create New Project”来创建一个新的Android项目。
- 在弹出的窗口中,输入应用程序名称(例如:SimpleCalculator),选择保存位置,然后点击“Next”。
- 在选择设备类型和最低SDK版本时,选择“Phone and Tablet”并选择一个合适的最低SDK版本,然后点击“Next”。
- 在“Add an Activity to Mobile”界面上,选择“Empty Activity”,然后点击“Next”。
- 在“Configure Activity”界面上,保持默认设置,点击“Finish”完成项目创建。
步骤二:设计用户界面
- 打开res/layout/activity_main.xml文件,使用XML布局设计计算器界面。以下是一个简单的示例:
<?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="#eeeeee"
android:orientation="vertical"
android:padding="5dp">
<ScrollView
android:layout_width="match_parent"
android:layout_height="wrap_content">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:text="@string/simple_calculator"
android:textColor="@color/black"
android:textSize="20sp" />
<TextView
android:id="@+id/tv_result"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/white"
android:gravity="right|bottom"
android:lines="3"
android:text="0"
android:textColor="@color/black"
android:textSize="25sp" />
<GridLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:columnCount="4"
android:rowCount="5">
<Button
android:id="@+id/btn_cancel"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/cancel"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_divide"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/divide"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_multiply"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/multiply"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_clear"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/clear"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_seven"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/seven"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_eight"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/eight"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_nine"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/nine"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_plus"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/plus"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_four"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/four"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_five"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/five"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_six"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/six"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_minus"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/minus"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_one"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/one"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_two"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/two"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_three"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/three"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_sqrt"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/sqrt"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<!-- <ImageButton-->
<!-- android:id="@+id/btn_sqrt"-->
<!-- android:layout_width="0dp"-->
<!-- android:layout_height="@dimen/button_height"-->
<!-- android:layout_columnWeight="1"-->
<!-- android:scaleType="centerInside"-->
<!-- android:src="@drawable/ic_launcher_background"-->
<!-- />-->
<Button
android:id="@+id/btn_reciprocal"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/reciprocal"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_zero"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/zero"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_dot"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/dot"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
<Button
android:id="@+id/btn_equal"
android:layout_columnWeight="1"
android:width="0dp"
android:height="@dimen/button_height"
android:gravity="center"
android:text="@string/equal"
android:textColor="@color/black"
android:textSize="@dimen/button_font_size" />
</GridLayout>
</LinearLayout>
</ScrollView>
</LinearLayout>
- 在res/values下创建一个用来定义尺寸的资源文件dimens.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<dimen name="button_font_size">30sp</dimen>
<dimen name="button_height">75dp</dimen>
</resources>
- 修改res/values下的字符串资源文件strings.xml
<resources>
<string name="app_name">simpleCalculator</string>
<string name="simple_calculator">简单计算器</string>
<string name="cancel">CE</string>
<string name="divide">/</string>
<string name="multiply">x</string>
<string name="clear">C</string>
<string name="seven">7</string>
<string name="eight">8</string>
<string name="nine">9</string>
<string name="plus">+</string>
<string name="four">4</string>
<string name="five">5</string>
<string name="six">6</string>
<string name="minus">-</string>
<string name="one">1</string>
<string name="two">2</string>
<string name="three">3</string>
<string name="sqrt">√</string>
<string name="reciprocal">1/x</string>
<string name="zero">0</string>
<string name="dot">.</string>
<string name="equal">=</string>
</resources>
步骤三:实现逻辑代码
- 打开MainActivity.java文件,实现计算器的逻辑功能。以下是代码:
package com.example.simplecalculator;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private TextView tv_result;
private String firstNum = "";
private String operator = "";
private String secondNum = "";
private String result = "";
private String showText = "";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tv_result = findViewById(R.id.tv_result);
findViewById(R.id.btn_cancel).setOnClickListener(this);
findViewById(R.id.btn_divide).setOnClickListener(this);
findViewById(R.id.btn_multiply).setOnClickListener(this);
findViewById(R.id.btn_clear).setOnClickListener(this);
findViewById(R.id.btn_seven).setOnClickListener(this);
findViewById(R.id.btn_eight).setOnClickListener(this);
findViewById(R.id.btn_nine).setOnClickListener(this);
findViewById(R.id.btn_plus).setOnClickListener(this);
findViewById(R.id.btn_four).setOnClickListener(this);
findViewById(R.id.btn_five).setOnClickListener(this);
findViewById(R.id.btn_six).setOnClickListener(this);
findViewById(R.id.btn_minus).setOnClickListener(this);
findViewById(R.id.btn_one).setOnClickListener(this);
findViewById(R.id.btn_two).setOnClickListener(this);
findViewById(R.id.btn_three).setOnClickListener(this);
findViewById(R.id.btn_reciprocal).setOnClickListener(this);
findViewById(R.id.btn_zero).setOnClickListener(this);
findViewById(R.id.btn_dot).setOnClickListener(this);
findViewById(R.id.btn_equal).setOnClickListener(this);
findViewById(R.id.btn_sqrt).setOnClickListener(this);
}
@Override
public void onClick(View view) {
String inputText;
if (view.getId() == R.id.btn_sqrt) {
inputText = "√";
} else {
inputText = ((TextView) view).getText().toString();
}
if (view.getId() == R.id.btn_clear) {
clear();
} else if (view.getId() == R.id.btn_cancel) {
}
//加减乘除
else if (view.getId() == R.id.btn_plus) {
//加
operator = inputText;
refreshText(showText + operator);
} else if (view.getId() == R.id.btn_minus) {
//减
operator = inputText;
refreshText(showText + operator);
} else if (view.getId() == R.id.btn_multiply) {
//乘
operator = inputText;
refreshText(showText + operator);
} else if (view.getId() == R.id.btn_divide) {
//除
operator = inputText;
refreshText(showText + operator);
}
//等于
else if (view.getId() == R.id.btn_equal) {
//等于
double calculate_result = calculateFour();
refreshOperate(String.valueOf(calculate_result));
refreshText(showText + "=" + result);
// if (!result.isEmpty() && operator.isEmpty()){
// clear();
// }
}
else if (view.getId() == R.id.btn_sqrt) {
//开平方
double sqrt_result = Math.sqrt(Double.parseDouble(firstNum));
refreshOperate(String.valueOf(sqrt_result));
refreshText(showText + "√=" + result);
}
else if (view.getId() == R.id.btn_reciprocal) {
//倒数
double reciprocal_result =1.0/Double.parseDouble(firstNum);
refreshOperate(String.valueOf(reciprocal_result));
refreshText(showText + "/=" + result);
}
else {
//点击其他按钮 包括数字和小数点
if (operator.equals("")) {
//无运算符,则继续拼接第一个操作数
firstNum = firstNum + inputText;
} else {
//有运算符,则拼接第二个操作数
secondNum = secondNum + inputText;
}
//整数不需要拼接0
if (showText.equals("0") && !inputText.equals(".")) {
refreshText(inputText);
} else {
refreshText(showText + inputText);
}
}
}
//四则运算
private double calculateFour() {
switch (operator) {
case "+":
return Double.parseDouble(firstNum) + Double.parseDouble(secondNum);
case "-":
return Double.parseDouble(firstNum) - Double.parseDouble(secondNum);
case "x":
return Double.parseDouble(firstNum) * Double.parseDouble(secondNum);
case "/":
return Double.parseDouble(firstNum) / Double.parseDouble(secondNum);
}
return 0;
}
//清空文本框
private void clear() {
refreshOperate("");
refreshText("");
}
//刷新运算结果
private void refreshOperate(String new_result) {
result = new_result;
firstNum = result;
secondNum = "";
operator = "";
}
//刷新文本框
private void refreshText(String text) {
showText = text;
tv_result.setText(showText);
}
}
步骤四:运行和测试
- 连接你的Android设备或启动模拟器,确保Android Studio正确配置。接着,点击Android Studio中的运行按钮来安装和启动你的应用程序。
- 应用程序启动后,你将看到一个简单的计算器界面,包括数字按钮(0-9)、运算符按钮(+、-、*、/)、清除按钮(C)、小数点按钮(.)和等号按钮(=)。
- 输入数字和运算符来执行计算。例如,输入数字和运算符后,点击等号按钮进行计算,结果将显示在顶部文本框中。
- 点击清除按钮可以清除当前输入和计算结果,重新开始新的计算。
- 效果预览: