Introduction

In general, developing a mobile application is a complex and challenging task. There are many frameworks available to develop a mobile application. Android provides a native framework based on Java language and iOS provides a native framework based on Objective-C / Swift language.

However, to develop an application supporting both the OSs, we need to code in two different languages using two different frameworks. To help overcome this complexity, there exists mobile frameworks supporting both OS. These frameworks range from simple HTML based hybrid mobile application framework (which uses HTML for User Interface and JavaScript for application logic) to complex language specific framework (which do the heavy lifting of converting code to native code). Irrespective of their simplicity or complexity, these frameworks always have many disadvantages, one of the main drawback being their slow performance.

In this scenario, Flutter – a simple and high performance framework based on Dart language, provides high performance by rendering the UI directly in the operating system’s canvas rather than through native framework.

Flutter also offers many ready to use widgets (UI) to create a modern application. These widgets are optimized for mobile environment and designing the application using widgets is as simple as designing HTML.

Master advanced Flutter concepts with clarity and confidence through this curated collection of insightful questions and detailed answers, designed to sharpen your skills and enhance your expertise in the world of mobile app development.

Advanced Flutter Interview Questions

It’s difficult to decide which framework to choose as they both are exceptionally good and loved by companies and developers. However, you can pick one based on your particular needs.

Here’s why you would need two different directories for Android and iOS files in Flutter:

Android Folder: You need an Android folder to keep files of an Android project. When any Flutter framework creates the code, the compiler converts the Flutter code into native code that is then imported to Android projects creating a native Android app.

iOS: This stores all the files for Mac projects. If you’re creating a project for the iOS platform, the iOS folder will be used. iOS apps can only be developed using the Xcode IDE and macOS in Flutter, which is why you’d need the iOS folder.

Flutter’s navigation system allows you to create a multi-level navigation hierarchy by using the Navigator widget to manage a stack of pages. You can push new pages onto the stack using the Navigator.push method and remove them using the Navigator.pop method

Flutter’s gesture recognition system provides a set of pre-defined gestures, such as tap, drag, and scale, that allow you to detect user input and react to it. You can use the GestureDetector widget to listen for gestures and the GestureDetector.onTap method to handle taps. You can also create custom gestures by subclassing the GestureRecognizer class.

To create a custom widget in Flutter, you need to create a new class that extends either StatefulWidget or StatelessWidget, depending on whether your widget needs to be stateful or not. The benefits of creating custom widgets include reusability, encapsulation of complex logic, and improved code organization.

Example code:

 

In Flutter, Hot Reload is the easiest and quickest way to make any changes, create UIs, fix bugs, and add features to the app. A Hot Reload performs all these changes rapidly and makes changes in the UI without disturbing the entire app.

Here’s how to perform Hot Reload:

  • Run the Flutter editor using command prompt or editor.
  • Once the project is created, you can use debug mode and perform hot reload
  • In windows, use “ctrl+\” to perform hot reload or using the button. For Mac devices, you can use “cmd+s” to perform hot reload. If you’re using the command prompt enter ‘r’ to run.

A Hot Restart is different from Hot Reload as it demolishes the preserved states of the app and compiles the code from scratch. Hot Restart takes more time as compared to Hot Reload but takes less time than restart function.
Here’s how to perform Hot Restart:

  • Run the editor using command prompt
  • Make some changes and run the hot restart
  • To start hot restart use the hot reload button or press ctrl+shift+.

The Flutter animations API provides a set of classes and widgets that allow you to create custom animations, such as tween animations or physics-based animations. You can use the AnimationController class to manage the animation’s state, and the Tween class to define the animation’s values over time.

Some of the most popular Flutter IDEs include the following:

  • IntelliJ IDEA is feature-rich, boasts extensive support for many languages, and provides smart coding assistance. Most beginner developers would probably get by with the free Community Edition, but the paid Ultimate Edition is required to access additional features.
  • Android Studio works like IntelliJ IDEA but for Android only. Unlike the latter, though, Android studio is free and open-source. With smart coding assistance and a built-in debugger, it seems the best choice when programming for Android devices.
  • Visual Studio code, or simply VS Code, is a free tool backed by Microsoft. It speeds up development and lowers development time. It works with Windows, macOS, and Linux.

As this is one of the most critical Flutter interview questions to guage a developer’s knowledge, you can also ask what their favorite IDE is and their justification for picking one.

 

To implement a custom transition between screens, you can use the PageRouteBuilder class and provide a custom transitionBuilder function.

For example, to create a fade transition:

Then, to use the custom transition, you can simply push the new route:

Navigator.of(context).push(FadeRoute(page: MyNewPage()));

To implement a draggable widget in Flutter, you can use the Draggable and DragTarget widgets. For example, to create a draggable widget that can be dropped onto a specific target:

To implement a custom animation curve in Flutter, you can create a class that extends the Curve class and provide a custom implementation of the transform method. Here is an example of how to create a bounce-in curve:

In the transform method, you can use any mathematical formula to create a custom curve. In this example, we’re using a mathematical formula that simulates a bounce-in effect.

Then, to use the custom curve in an animation, you can simply pass it to the curve property of the Tween class:

In this example, we’re using the BounceInCurve as the curve property of the CurvedAnimation widget, which is then passed to the parent property of the Tween widget. This will create an animation with the bounce-in effect.

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