How to stand out in Android interviews, analysis of high-frequency Android interview questions, help you get Offer quickly

Android interview on "tips"

• Know your skill level: Before your interview, make sure you have a good understanding of the skill requirements of the position you are interviewing for and check that your skill level matches those requirements.
• Familiarize yourself with the interview process: Understand the questions you may encounter during the interview and prepare answers to each question.
• Learn more about the company: Before the interview, learn about the culture, values ​​and products of the company you are interviewing for. This can help you present yourself better in interviews and answer questions about the company accurately.
• Practice interviews: Practice interviews with a friend or colleague so you can answer questions more confidently and calmly during the interview.
• Prepare some questions in advance: Prepare some questions before the interview to ask the interviewer at the end of the interview. Not only will this show your interest in the company, but it will also give you a better understanding of the company's culture and team.
• Pay attention to interview etiquette: dress appropriately, arrive at the interview location on time, and maintain a good facial expression and posture.
• Demonstrate your skills: During the interview process, demonstrate your skills and experience. Provide practical examples and project experience to demonstrate your abilities and achievements.
• Keep calm: If you don't know how to answer a question, keep calm and answer honestly. You can tell the interviewer that you don't know the answer, but can offer a solution to the problem.
• Thank the interviewer: After the interview, don’t forget to thank the interviewer. Not only does this show your courtesy and humility, it also strengthens the bond between you and the interviewer.

Android2023 common interview questions

Talk about the four major components of Android, what are their functions?

The four major components refer to the Activity, Service, Broadcast Receiver and Content Provider in the Android application, and they respectively assume different roles and functions. Among them, Activity is the displayer of the user interface, Service is used for processing background tasks, Broadcast Receiver is used for receiving and processing broadcast information, and Content Provider is used for data sharing and access between different applications.

What is the Activity life cycle, can you explain it in detail?

Activity life cycle refers to the whole process from creation to destruction of Activity, including onCreate, onStart, onResume, onPause, onStop, onDestroy and other life cycle methods. When the Activity changes from the invisible state to the visible state, the system will execute these methods in a certain order of life cycle method calls, and when the Activity is destroyed, it will also execute these methods in a certain order of life cycle method calls.

What is the function of Handler in Android? What is the relationship between it and threads?

Handler is a mechanism for implementing inter-thread communication in Android. It is mainly used to implement asynchronous message processing. Handler is used in combination with MessageQueue to send messages to the message queue, and then process these messages in the specified thread. Since the UI thread in Android can only be handled by one thread, the relationship between the Handler and the UI thread is very close, and can be used to implement operations such as UI update and background task processing.

What is Context and what does it do?

Context is a very important concept in Android. It represents the information of the application environment, including the context information of the application's resources, Activity, Service, Broadcast Receiver and other objects. Context can be used to obtain system resources, start Activity, send Broadcast Receiver and other operations.

What is Application, and what is the difference between Activity?

Application is a global singleton object in Android, which represents the context information of the entire application. Unlike Activity, the Application object has a long life cycle and can be shared and accessed throughout the application. Activity is the user interface displayer in the application, which only exists during the interaction between the user and the application.

Talk about the message mechanism in Android, what are the different message types?

The message mechanism in Android mainly includes objects such as Message, Handler, MessageQueue, and Looper, which are respectively used to realize the sending and processing of asynchronous messages. The message mechanism can be used for operations such as UI update and background task processing, and message types include ordinary messages, delayed messages, and cyclic messages.

What are Fragments? What lifecycle methods does it have?

Fragment is a UI component in Android, which can be nested in Activity to display and switch dynamic interfaces. Fragment has its own life cycle methods, including onAttach, onCreate, onCreateView, onStart, onResume, onPause, onStop, onDestroyView, onDestroy, and onDetach.

What is Intent in Android? What are the different types?

Intent is an important component in Android, which is used to perform various operations in the application or start other application components. It can be used to start Activity, Service, BroadcastReceiver or other components in the application. Intent can transmit and process data by specifying information such as action, category, data, and extras. Common Intent types include:

• Explicit Intent: It is used to start the components inside the application, and the complete component name needs to be specified.
• Implicit Intent: It is used to start components outside the application, and information such as action and category need to be specified.
• Service Intent: Used to start the Service component.
• Broadcast Intent: used to send broadcast messages, which can be sent by sendBroadcast(), sendOrderedBroadcast(), sendStickyBroadcast() and other methods.

What is Service? What are the different ways to start?

A Service is a component that performs long-running operations in the background, performing tasks without user interaction. It is a thread that runs in the background to perform long-running operations such as downloading files, playing music, uploading data, etc. Services can be started, bound, stopped and destroyed by other components. In Android, Service has two startup methods:

• Started Service: Start the Service through the startService() method, and you can perform some time-consuming operations in the Service.
• Bound Service: Start the Service through the bindService() method, and you can interact with the Service, such as calling methods in the Service, obtaining data returned by the Service, and so on.

What is the View drawing process in Android?

The View drawing process in Android mainly includes three stages:

• Measurement phase (Measure): Measure the width and height of the View.
• Layout phase (Layout): Determine the position and size of the View in the parent container.
• Drawing phase (Draw): Draw the View to the screen.

During the drawing process of View, the system will call View's onMeasure(), onLayout() and onDraw() methods to complete the measurement, layout and drawing operations. In the measurement phase, View will calculate its own width and height according to the MeasureSpec parameter passed by the parent container. In the layout phase, View calculates its position and size in the parent container based on the size of the parent container and its own size. During the drawing phase, View will call its own onDraw() method to draw itself to the screen.

What are ANRs? How to avoid ANR?

ANR means that the Android application is unresponsive on the main thread, that is, the application cannot respond to user input events or other system events within the specified time, causing the application to stop responding, a "Program Not Responding" dialog box, and finally blocked. A case where the system is forced to shut down.

There are mainly the following methods to avoid ANR:

1. Avoid time-consuming operations in the main thread, and put time-consuming operations in sub-threads for execution.
2. Reasonable use of asynchronous processing mechanisms, such as using AsyncTask, Handler, etc.
3. Avoid blocking the main thread. If you must block the main thread, you can use android.os.SystemClock.sleep() instead of Java's Thread.sleep().
4. Avoid too much initialization work in the onCreate() and onResume() methods, and try to perform asynchronous initialization in the onResume() method.
5. Optimize the code of the application to reduce useless operations, such as using static variables instead of dynamic variables as much as possible, avoiding frequent memory allocation and recycling in loops, etc.
6. Minimize the use of BroadcastReceiver, because BroadcastReceiver will be executed in the main thread, if the processing logic is too complicated, it will cause ANR.
7. For specific business scenarios, such as music players, you can start an independent process to perform corresponding operations to avoid affecting the response of the main process.

Advanced Android technology

Interview questions are a bridge between jobs, and the most important thing is to improve technology, which plays a core role in development, and is the top priority for job-hopping and salary increase. Here are some aspects of lifting techniques:

• In-depth understanding of the Android Framework: understand the architecture and principles of the Android Framework, learn the implementation principles of each module in the Android Framework, such as Activity, Service, Broadcast, Content Provider, etc., and how to interact with the underlying system to improve the overall understanding of the Android system.
• Learn Android performance optimization: master how to locate and solve performance problems of Android applications, such as UI freeze, slow startup, power consumption, memory leaks, etc., and understand the principles and methods of performance optimization, such as layout optimization, memory optimization, network optimization, power consumption optimization etc.
• In-depth understanding of Android development tools: Master the advanced usage skills of Android Studio, such as Gradle configuration and optimization, the use of Android Studio plug-ins, the use of code analysis tools, etc., and be able to use various tools to solve problems encountered in development.
• Master new technologies and frameworks: Understand the usage methods and principles of new Android technologies and frameworks, such as Kotlin, Jetpack components, ARCore, Flutter, etc., keep up with the technological development of Android, and broaden your technical horizons.
• Learn general skills of mobile development: Understand general skills of mobile development, such as design patterns, data structures, algorithms, network protocols, etc. These skills are not only useful in Android development, but also very important in other mobile development fields.
• Participate in open source projects and community activities: Actively participate in open source projects and community activities, communicate and learn with other developers, improve your technical level and ability, and learn about industry trends and latest developments.

Based on the above, it is not only necessary to brush up on a wide range of Android interview questions, but also to advance its own technology; for relevant information, refer to more than 30 core technology sections in "Android Core Technology + Answers to Interview Questions" , involving Are there more than 20 interview questions? It can be used as a very important information for Android programmers who want to get promoted and raise their salary.

Summarize

As an Android developer preparing for an interview, you need to prepare and summarize the following aspects:

1. Mastery of theoretical knowledge: To understand the role and life cycle of the four major components of Android, the relationship between the role of Handler and threads, the role of Context and Application, the message mechanism, and the theoretical knowledge of View drawing process, etc., and be able to use these knowledge proficiently Knowledge.
2. Accumulation of practical experience: Practice more in the usual development process, accumulate practical experience, be familiar with the use of various Android development frameworks and third-party libraries, and be familiar with commonly used development tools and techniques, such as debugging tools and performance analysis tools.
3. Mastery of interview skills: You must have a certain self-introduction and resume preparation, understand the interview process and common interview questions, and have enough self-confidence and expressive ability to clearly express your thoughts and ideas.
4. Improvement of comprehensive quality: In addition to technical ability, we must also pay attention to our own comprehensive quality, including communication skills, teamwork skills, and problem-solving skills.

In short, Android developers who are well-prepared, have solid knowledge, rich practical experience, confident expression, and excellent overall quality can stand out in the interview.