Interview experience: An Android interview question compiled by an interviewer from a major BAT factory, and finally got an offer after five rounds of interviews!

It’s ten gold, nine silver and ten. Recently, many friends around me have quit naked, but found that the job is not as easy to find as I imagined. My friend Xiao A only wanted to enter a big factory to interview for Android, so he interviewed Alibaba, Meituan, Didi, etc., and finally got an offer after five rounds of interviews in a big factory. Today I have sorted out the Android interview questions he interviewed with a big factory, hoping to help everyone!

Alibaba

• LRUCache principle
• Image loading principle
• Modular implementation (benefits, reasons)
• JVM
• Video encryption transmission
• Statistics start time, standard
• How to maintain the stability of the application
• ThreadLocal principle
• Talk about classloader
• Dynamic layout
• Hot repair, plug-in
• HashMap source code, SpareArray principle
• Performance optimization, how to ensure that the application startup does not freeze
• How to remove duplicate code
• Is the SP process synchronized? Is there any way to synchronize
• Introduce SurfView
• HashMap realization principle, ConcurrentHashMap realization principle
• BroadcastReceiver, LocalBroadcastReceiver classification
• Bundle mechanism
• Handler mechanism
• android event delivery mechanism
• List of operations between threads
• App startup process starts from clicking on the desktop
• Dynamic loading
• Class loader
• OSGI
• Https request slow solution, DNS, carry data, direct access to IP
• GC recovery strategy
• Draw the general architecture diagram of Android
• Describe what happens after you click the build button of Android Studio, and roughly explain what happens when an application is installed on the phone;
• Have a basic understanding of Dalvik and ART virtual machine;
• How does Inter-Process-Communication on Android work when communicating across processes;
• How is the App sandboxed and why should it be done;
• Authority management system (how the underlying authority is granted)
• The life cycle of the process and Application;
• System startup process Zygote process -> SystemServer process -> various system services -> application process
• The difference between recycleview listview, performance
• Sort, the realization of quick sort
• Tree: Introduction to B-tree
• Figure: Explanation of directed acyclic graph
• The difference between TCP/UDP
• The difference between synchronized and Lock
• volatile
• Java thread pool
• The life cycle of objects in Java
• Class loading mechanism
• Parent Delegation Model
• Android event distribution mechanism
• MVP mode
• RxJava
• The difference between abstract class and interface
• How to prevent collision by implementing Hash in Set
• Which memory is affected by threads in the JVM memory area
• Garbage collection mechanism object creation, new generation and old generation
• Binary tree depth traversal and breadth traversal
• B tree, B tree
• Message mechanism
• Process scheduling
• Process and thread
• Deadlock
• Process status
• JVM memory model
• What do concurrent collections know about
• ConCurrentHashMap implementation
• Introduction to CAS
• Three ways to start threads, the difference between run() and start() methods
• Thread Pool
• Introduction to common data structures
• Judgment ring (guess it should be a linked list ring)
• Sort, heap sort implementation
• Linked list inversion
• Dynamic permission adaptation scheme, the concept of permission groups
• Network request cache processing, how okhttp handles network cache
• Related to the image loading library, how bitmap handles large images, such as a 30M large image, and how to pre-prevent OOM
• Process keep alive
• The principle and solution of listview picture loading disorder
• https related, how to verify the legitimacy of the certificate, where is symmetric encryption used in https, where is asymmetric encryption, do you have any understanding of encryption algorithms (such as RSA), etc.

Meituan

• Multi-threaded access and function of static synchronized method, two synchronized methods in the same class, two threads access at the same time
• Inner classes and static inner classes and anonymous inner classes, and applications in the project
• The handler sends a message to the child thread, how to start the looper
• View event delivery
• activity stack
• How to know the size of the view when encapsulating the view
• The difference between arraylist and linkedlist, and application scenarios
• How to start the service, how to exchange data between service and activity
• Does the pull-down status bar affect the life cycle of the activity? If you make a * network request during onStop, how to resume during onResume
• view rendering

Today's headlines

• The concept of heap in data structure, heap sort
• The concept of deadlock, how to avoid deadlock
• ReentrantLock 、synchronized和volatile（n面）
• HashMap
• singleTask startup mode
• Some open source frameworks used, introduce an internal implementation process that has seen the source code.
• Message mechanism implementation
• Internal implementation of ReentrantLock
• App startup crash exception capture
• Introduction to event delivery mechanism
• Optimization of ListView
• Binary tree, given the root node and target node, find the path from the root node to the target node
• Pattern MVP, MVC introduction
• Realization of Resumable Transmission
• Collection interface and specific implementation class, introduction
• TreeMap implementation
• synchronized与ReentrantLock
• Handwritten producer/consumer model
• Logical address and physical address, why use logical address
• An unordered, non-repeating array, outputs N elements, so that the sum of N elements is M, and * gives time complexity and space complexity. Handwriting algorithm
• .Android process classification
• The foreground switches to the background, and then back to the foreground, the Activity life cycle callback method. Pop up Dialog, life value cycle callback method.
• Activity start mode

IQIYI

• The function and principle of RxJava
• The use of RecycleView, principle, RecycleView optimization
• Reasons for ANR
• Four major components
• How to open the service
• The way Activity communicates with Service
• Communication between activities
• The realization of HashMap, the difference with HashSet
• JVM memory model, memory area
• Keyword used synchronously in Java, deadlock
• MVP mode
• Java design pattern, observer pattern
• Life cycle comparison between Activity and Fragment
• Broadcast usage scenarios

Baidu

• What should I pay attention to when using Bitmap?
• Can Oom try catch?
• How does a memory leak occur?
• What are the similarities and differences between adapter mode, decorator mode, and appearance mode?
• How is ANR generated?
• What is the difference between String buffer and string builder?
• How to ensure thread safety?
• java four references
• Has Jni used it?
• Have you ever met a multi-process scene?
• Regarding the handler, what thread is the new handler everywhere?
• SQLite upgrade, increase the field statement
• bitmap recycler related
• If a strong reference is set to null, will it be recycled?
• What cache does glide use?
• How to control the size of Glide memory cache?
• How to ensure the safety of multithreading to read and write files?

Ctrip

• Activity start mode
• How to use the broadcast, the scene
• How to wake up other processes in App
• The role and understanding of AndroidManifest
• The difference between List, Set, Map
• How do HashSet and HashMap judge the duplicate of set elements
• Memory area and garbage collection mechanism in Java
• EventBus function, implementation method, instead of EventBus method
• The main steps to turn on the camera in Android

NetEase

• concurrenthashmap
• volatile
• synchronized与Lock
• Java thread pool
• wait/notify
• NIO
• Garbage collector
• Activity life cycle
• AlertDialog, popupWindow, Activity difference

Xiaomi

• Why should String be designed to be immutable?
• Fragment life cycle in various situations
• The life cycle when the home button is pressed when there is a Dialog on the Activity
• When switching between horizontal and vertical screens, the life cycle of Activity in various situations
• The difference between Application and Activity context objects
• The role of serialization, and the difference between the two types of serialization in Android.
• Implementation and storage of List and Map.
• The design intent of the static inner class.
• How to close the thread, and how to prevent thread memory leaks

The above are the Android interview questions he encountered when interviewing big factories. I hope to help everyone. Finally, I would like to ask everyone: "In a real interview, especially in a big company, there is no established questioning method. Only the strength is serious. win".

End of sentence

That’s all for today’s interview sharing. It’s the same sentence. There are some things you must not only understand, but also express them well, so that the interviewer can recognize your understanding, such as the Handler mechanism. This is a must-question in the interview. . There are some obscure points, maybe it only lives in the interview, you will not use it at all in actual work, but you have to know what it is.

Finally, to help you a deep understanding of the principles of Android-related knowledge as well as knowledge of the interview , I was put here to collect finishing 2019-2020BAT interview Zhenti resolve , I interview the manufacturers often asked technical points finish became a PDF, package Knowledge context + many details.

Save everyone's time to search for information on the Internet to learn, and you can also share with friends around you to learn together.

"960 The most complete Android development notes in the entire network"

"379-page Android Development Interview Collection"

Took six months, we've put together the most comprehensive on the market this Android interview questions resolved Daquan
includes Tencent, Baidu, millet, Ali, TV Plus, the US group, 58, cheetahs, 360, Sina, Sohu and other Internet companies first-line interview asked The topic. Familiarity with the knowledge points listed in this article will greatly increase the chance of passing the first two rounds of technical interviews.

How to use it?

1. You can directly browse the required knowledge points through the catalog index to check the missing points.
2. The number of five-pointed stars indicates the frequency of interviews and represents an important recommendation index

"507 pages of Android development related source code analysis"

As long as it is a programmer, whether it is Java or Android, if you do not read the source code and only look at the API documentation, it will just stay on the skin. This is not good for the establishment and completeness of our knowledge system and the improvement of actual combat technology.

The one who can really exercise the most ability is to read the source code directly, not only reading the source code of major systems, but also including various excellent open source libraries.

Analysis of Real Questions in 2019-2020 Interviews of BAT Companies such as Tencent, ByteDance, Ali, Baidu

There are too many materials, and all the display will affect the length. For the time being, I will list some of these screenshots first, and you can click here to get them yourself.