Do you want to create a calculator app for Android? Look no further!
In this tutorial, we will guide you through the step-by-step process of building your very own calculator app. Let’s get started!
Setting Up the Project
Before we dive into coding, let’s set up our project. To create an Android app, we need to have Android Studio installed on our computer. If you haven’t installed it yet, head over to the official Android Studio website and download the latest version for your operating system.
Create a New Project
Open Android Studio and click on “Start a new Android Studio project” or go to File > New > New Project. Fill in the required details like “Application name”, “Company domain”, and choose a project location. Once done, click on “Next”.
Selecting the Target Devices
In this step, you can choose the devices you want your app to run on. You can select either “Phone and Tablet” or “Wear OS” or both depending on your preference. After selecting, click on “Next”.
Designing the Calculator Layout
The next step is designing the layout of our calculator app. Open the layout file called “activity_main.xml”. This file is located in the “res > layout” directory of your project.
To create a basic calculator layout, we can use a combination of LinearLayouts, TextViews, and Buttons.
Create TextViews for Displaying Input and Result
To display user input and calculation results, add two TextView elements inside a LinearLayout:
<LinearLayout
..
android:orientation="vertical">
<TextView
.
android:id="@+id/inputTextView" />
<TextView
.
android:id="@+id/resultTextView" />
</LinearLayout>
Create Buttons for Digits and Operators
Next, let’s add buttons for digits (0-9) and operators (+, -, *, /). We can use a GridLayout to display the buttons in a grid-like structure.
<GridLayout
.
android:rowCount="4"
android:columnCount="4">
<Button
.
android:text="1" />
<Button
.
android:text="2" />
.
</GridLayout>
Repeat this process for all the digit and operator buttons.
Handling User Input and Performing Calculations
Now that our layout is ready, let’s move on to handling user input and performing calculations. Open the Java file called “MainActivity.java”. This file is located in the “java > com.example.yourappname” directory of your project.
Binding Views
We need to bind the TextViews and Buttons from our layout file to variables in our Java code. Add the following code inside the onCreate() method:
TextView inputTextView = findViewById(R.id.inputTextView); TextView resultTextView = findViewById(R.resultTextView); Button button1 = findViewById(R.button1); Button button2 = findViewById(R.button2);
Implementing Button Click Listeners
To handle button clicks, we need to set click listeners for all the buttons. Inside the onCreate() method, add the following code:
button1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
inputTextView.append("1");
}
});
button2.append("2");
}
});
Performing Calculations
To perform calculations, we can use the built-in eval() function from the Expression class provided by the "androidx.expressions" library. Add the following code inside a method called calculateResult():
String userInput = inputTextView.getText().toString();
Expression expression = new Expression(userInput);
BigDecimal result = expression.eval();
resultTextView.setText(result.toString());
Testing Your Calculator App
Now that we have implemented the basic functionality of our calculator app, it's time to test it on an Android device or emulator. Connect your device or start an emulator and click on the "Run" button in Android Studio.
- If you're using a device, make sure USB debugging is enabled in your device's developer options.
- If you're using an emulator, make sure it is running before clicking on "Run".
Congratulations! You have successfully created a calculator app for Android. Feel free to customize and enhance it further with additional features like parentheses, decimal points, and more advanced operations.
I hope you found this tutorial helpful in creating your own calculator app. Happy coding!