Master this set of refined Android advanced interview questions analysis, oppoandroid interview questions

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Everybody knows , It's hard to get a high salary when looking for a job , Most people can take  30k  Of  offer  Pretty good . As far as I know, 90% of Android Development is all about 30k following ！?

But there is a classmate in my group , I usually like to study the source code and framework , Then after a month's question brushing , Jump to the headlines , Got it  50k  Monthly salary , I think it's great , Envy, jealousy, hate .??

Then I talked to him , I found that his skill is really good , During the question brushing , Besides algorithms , He also put his  Android  Take out the notes , It's all his usual accumulation , comprehensive , Depth also has , Plug in 、 Dependency injection , And all kinds of architecture knowledge .??

Sure enough , As long as the technology is good , I'm not afraid to go anywhere . When we are studying , Besides reading books and blogs , It's best to find a systematic , And have enough in-depth learning video learning , Build your own knowledge framework .??

Android Develop several parts of the interview

1、 Basic knowledge of

The basics include several parts ：Java（JDK、JVM）、Android、 Data structures and algorithms 、 Fundamentals of computer 、 Design patterns , Some will ask Flutter.

Java part

：

I don't recommend this part. Just read the blog , Because many blogs are not systematic or complete , It is recommended to read it completely 《 In depth understanding of Java virtual machine 》 This book , Basically, it covers JVM All relevant interview questions , Including memory partitions 、GC Mechanism 、 Memory model 、 lock 、 Bytecode 、 Class loading, etc .JDK The part will be more miscellaneous , Basically, it can be classified into several ： Containers （ Must ask HashMap、CurrentHashMap、ArrayList etc. ）、 Thread pool （ Must ask ）、 annotation 、 Synchronization tool 、 A dynamic proxy 、notify/wait/sleep. This part can be seen from some JDK Sort it out in relevant articles .

Android part ：

What must be asked in this part is Handler Mechanism 、 Touch event delivery 、 Four components start process 、View Drawing process 、Binder Mechanism 、 Life cycle

. Classic questions such as ：

• The touch event must be passed to Activity Then pass it on to View The? ？

• If you want to in Application Of onCreate Execute some logic before the lifecycle , Where can I put it ？

• draw、onDraw、dispatchDraw What is the order of execution ？

• View The real display is in onResume Before or after ？

• Activity There is a nested Fragment,startActivity after ,Activity and Fragment What is the life cycle sequence of ？

Data structure and algorithm ：

The proportion of this part will be smaller in client development , However, many companies attach great importance to handwritten code . Frequently encountered problems are binary tree traversal 、 Ordered two-dimensional array lookup , Sort, etc , Basically with 《 The finger of the sword offer》 perhaps 《 The beauty of programming 》 That's fine .

Fundamentals of computer ：

This part covers more miscellaneous , For example, computer network （7 Layer network model 、Http and Https）、git Workflows and commands 、 Computer cache policy 、UML、 Information security, etc .

Design patterns ：

In your own project, you must summarize and use more design patterns , When the interviewer asks what design patterns you have used , If you can answer, such as state mode 、 Responsibility chain 、 Decoration, etc , It will certainly add a lot of points . If you just answer the singleton and builder mode , That would be much worse . This part is recommended to see 《 Grinding design mode 》.

Open source project ：

This is also one of the necessary questions , It is recommended to start with the open source projects used in your own projects , Follow the code , Draw a flow chart and architecture diagram , Carefully understand the advantages and disadvantages of this design .

such as OkHttp、LeakCanery wait , These are all fine . Open source projects vary according to the interviewer's personal experience , The depth of the question is also different , At this time, you need some personal guidance skills , For example, the interviewer may not be very familiar with this framework , At this time, you can actively express some details of the design , It can also leave a good impression on the interviewer .

Never write a framework that has only been used but has not seen the source code on your resume .

Key project experience

Projects in small factories often pursue rapid iterative business on-line , Relatively tolerant of some technical difficulties , But these

Technical difficulties are often those that can reflect a person's technical ability

. So if you're in a small factory , You can't get too involved in the business , We must jump out and find some bright technical points , Do a good job . These technical points are the capital for a programmer to settle down , Otherwise the company's business will be in trouble , Your value will no longer exist . In how to prepare for an interview, this part of the project , Xiaobian has some experience ：

Divided into three parts ：

• Why do you do this ,

• What factors are considered and how are they done ,

• What effect has been achieved （ For example, the starting speed is from 1000ms drop to 200ms, This specific data ）

You can string a few dots together , This can be more systematic and comprehensive , For example, the combination of code optimization and performance optimization .

Some optimization points of small factories can only do the most cost-effective part , At this time, we can also talk about what better solutions there are in the industry

You'd better prepare again “ If you don't quit, what are the deficiencies and areas that can be optimized in the project ？”（ The author has encountered such problems several times during the interview ）

** Small factories jump to big factories , The technical foundation can be well prepared , But the project is definitely a weakness .** A big factory App There may be dozens or hundreds of people doing , Many so-called optimization in small factories may have been done by interviewers in large factories for a long time , At this time, what the project itself has done is not too important , It needs to focus on your idea of solving problems and that you are a aspiring programmer , At least you should be able to achieve the average level of the industry , In order to have a chance to pass the interview .

Beyond technology

The part other than technology is also a very important part in the interview of large factories , This part is mostly some soft skills :

Self drive and pursuit

This part mainly focuses on some self driven learning and independent pursuit of some technical abilities in daily work , Not just  

《Android Summary of learning notes + Latest mobile architecture video + Big Android interview questions + Project actual combat source code handout 》 Free open source Hui Xin search official account 【 Advanced programming 】

  It is enough to complete the requirements , In this way, you can reflect your personal growth and potential .

Communication and collaboration

This section will assess your future integration into the team and your ability to collaborate and communicate with the team across teams . For example, whether you can correctly view and solve some cross departmental communication problems at work .

My face to face summary

It is mainly divided into four aspects ：

Android

• Android Features of each version （ for example 6.0, Dynamic permissions ）

• ANR Why

• Android The way and comparison of inter process communication in

• AsyncTask Implementation principle, advantages and disadvantages of

• Handler Mechanism

• Customize view Trilogy , technological process （ Or the actual scene , For example, implement a dial , How do you do it? ）

• FrameWork hierarchy

• Activity Life cycle （A Jump to B,A and B The execution sequence of the life cycle in ）

• Dvlik、ART、JVM The difference between the three virtual machines

• Can you be in Africa UI Thread update UI

• Service and IntentService The difference between

• Thread and HandlerThread The difference between

• Touch Event distribution mechanism

• How do you know a Activity Whether there was a leak

• Click on a from APP What happened to the icon

• Activity Start process （ Look at the source code , Just say it roughly ）

• Activity Boot mode （ Four kinds of ）

• Intent start-up Activity The way

• onStart and onResume The difference between

• LruCache And how it works

• Android Medium MVC、MVP、MVVM The difference and connection

• Parcelable and Serializable The difference between

• Service Life cycle

• Service Startup mode and difference of

• Binder Mechanism

• onSaveInstanceState and onRestoreInstanceState When to call （ You need to understand , There is usually a scene for you to judge ）

• onNewIntent When to call （ ditto ）

• Android Performance optimization and memory optimization in

• RxJava The way （ Common operators , Back pressure , Thread switching principle , The practical application ）

• RxAndroid The way

• EventBus principle

• Volley principle

• OkHttp principle

• Retrofit principle

• RxJava and Retrofit combination

• Dagger2 principle

• Let's introduce componentization （ Why there should be componentization , How to resolve merge conflicts ）

• Quickly introduce

• Common methods of screen adaptation

• Service、 Process keeping alive

• Glide principle

• AsyncTask principle

• SurfaceView And the general View The difference between

• Implementation principle of dependency injection framework

• Git project management

• What is L3 cache

Java

• Common design patterns （ Master common about 10 Plant on Ok）

• ThreadLoal Function and principle of

• Implementation mode and principle of thread

• State of thread , How to create threads , Transition between thread states （ For example, when a thread changes from running to blocking ）

• State of process

• transient The role of keywords

• sleep() and wait() The difference between

• hashcode() The role of methods

• == and equals() Method difference （ Why rewrite equals() Methods have to be rewritten hashcode Method ）

• Java Three characteristics of

• The difference between interface and abstract class

• Difference between process and thread

• Meaning of thread pool parameters , And four common thread pool application scenarios

• Characteristics, principles and application scenarios of blocking queue

• yield() The role of methods

• The type of multithreaded lock ,ReentrantLock,Lock,synchrnoized Keywords, etc

• volatile The role of keywords （ Role in single case ）

• The concept of closures

• Generic （ What is type erasure , Why generics ）

• Lock optimization method （ spinlocks 、 Adaptive spin 、 Lock elimination 、 Lock coarsening 、 Biased locking ）

• Class execution order

• StringBuffer and StringBuilder The difference between

• HashMap Implementation principle of （ It is best to 1.8 Before and 1.8 After that, you should know ）

• ConcurrentHashMap Implementation principle of （ Same as 1.8 Know before and after ）

• ArrayList and LinkedList The difference between

• Java Memory area （ The difference between heap and stack , What is a runtime constant pool ）

• Packing and unpacking

• OOM abnormal

• GC Mechanism （GC Area , How to judge whether an object can be recycled ,GC Algorithm ,GC Strategy ）

• Class loading mechanism （ Class loading process parent delegation model ）

• Java Memory model （ Main memory and working memory ）

• Atomicity （AtomicInteger principle ）、 visibility （volatile keyword ）、 Orderliness , How to ensure

• Antecedent principle （happens-before principle ）

• Thread safe implementation method

• The type of lock （ Pessimistic locking , Optimism lock CAS Algorithm , Fair lock , How to realize unfair lock ）

• StringBuffer and StringBuilder difference

• annotation （ Custom annotation ）

• The concepts and differences of four kinds of references

computer network

• HTTP agreement （ Head structure , Several request methods , Caching mechanisms , The difference between the versions ）

• HTTPS agreement , and HTTP The difference between agreements , The process of key agreement ,SSL Mechanism

• Symmetric and asymmetric encryption

• TCP and UDP The difference between

• TCP Three handshakes of 、 Four waves （ Including status code , And why wait after four waves 2*TIME_WAIT）

• TCP congestion control mechanism

• TCP Sliding window mechanism

• TCP Timeout retransmission mechanism

• DNS agreement

• Five layer network model （ The physical layer , Data link layer , The network layer , Transport layer , application layer ）

• IP Head

• Enter a web address in the browser address , What happened?

Data structure and algorithm

• Linked list （ One way linked list , Double linked list ）

• Array （ Rotated array ）

• queue （ deque , Blocking queues ）

• Stack

• Pile up （ Big root pile 、 Heap ）

• Binary tree （ Perfect binary tree 、 Full binary tree 、 Binary sort tree 、 Balanced binary trees , Red and black trees ）（ Depth traversal , Sequence traversal ）

• chart （ Focus on the depth first traversal and breadth first traversal of the graph ）

• Seven sorting algorithms （ Bubbling , choice , Insert , Merge sort , Quick sort , Heap sort , Shell Sort ）

• The finger of the sword offer Algorithm problem on （ Be able to compare directories , Look at the title , Can have ideas , Just ok）

• Two points search

• Two stacks implement a queue , Two queues implement a stack

• Massive data sorting

• topK problem , Yes 1 Tens of millions , How to quickly find the biggest 100 individual

• Merge two ordered arrays , Merge two ordered lists

• Young's matrix （ Horizontal increment , Increasing vertically ） How to find the specified number in

• Flip a sentence , for example I am 3 years old, After flipping ,old years 3 am I

• Yes 10 Billion data , Now only 200M Memory , How to find this 10 The most frequent of 100 million data 100 Data

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