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Mobile application development has been popular for ten years , Most schools still don't open special courses .

Most of the current market  Android  Most development engineers are self-taught or trained , Use it for a while  Android  Develop skills （ best-selling author  Josh Kaufman  Put forward , After mastering the correct method , You can use any skill in a short time  ）, Then enter a company or take over a project to cultivate practical ability 、 Accumulate practical experience .

And then ,Android  How to improve after the initial stage of development ？

How can we call mastery ？ Where is the direction ？

Usually ,Android  The engineer  1-3  I should be able to rise from junior to senior engineer in five years , This stage is mainly the promotion of technology and the accumulation of experience .

after  1-3  Continue to be a senior engineer , This position requires that the whole module can be completed independently , Have a deep understanding of the project architecture , Be able to design the program scheme of complex modules .

At the same time, it needs a certain management ability , Be able to lead new colleagues to start projects quickly , So at this time, I usually also act as the main process or  Team Leader, Part of the project management .

（ One ） java Basic interview knowledge

• java in == and equals and hashCode The difference between

• int、char、long How many bytes do each take up

• int And integer The difference between

• Talk about right java The understanding of polymorphism

• String、StringBuffer、StringBuilder difference

• What is an inner class ？ The role of inner classes

• The difference between abstract classes and interfaces is the same

• The meaning of abstract class

• Application scenarios of abstract classes and interfaces

• Whether abstract classes can have no methods and properties ？

• The meaning of the interface

• In the generic extends and super The difference between

• Whether the static method of the parent class can be overridden by the child class

• Difference between process and thread

• final,finally,finalize The difference between

• Serialization method

• Serializable  and Parcelable  The difference between

• Whether static properties and static methods can be inherited ？ Can it be rewritten ？ And why ？

• Static inner class design intent

• Member inner class 、 Static inner class 、 Understanding of local inner class and anonymous inner class , And the application in the project

• Talk about right kotlin The understanding of the

• The difference between closures and local inner classes

• string  convert to  integer How and how

（ Two ） java In depth source level interview questions （ Difficult ）

• In which cases the objects will be disposed by the garbage collection mechanism ？

• Let's talk about the common coding methods ？

• utf-8 Chinese in the code takes a few bytes ;int Type a few bytes ？

• The difference between static agent and dynamic agent , What scenarios to use ？

• Java Abnormal system of

• Talk about your understanding of parsing and distribution .

• Modify object A Of equals Method signature , So use HashMap When the object instance is stored , Which will be called equals Method ？

• Java What is the mechanism of realizing polymorphism in ？

• How to put a Java Object serialization into a file ？

• Tell me about your right Java Reflexive understanding

• Tell me about your right Java The understanding of annotation

• Talk about your understanding of dependency injection

• Let's talk about generic principles , And give an example

• Java in String Understanding

• String Why is it designed to be immutable ？

• Object Class equal and hashCode Method rewriting , Why? ？

（ 3、 ... and ）  data structure

• Introduction to common data structures

• What do concurrent collections know about ？

• list java Sets of and inheritance relationships between sets

• Collection classes and collection frameworks

• Introduction to container classes and the differences between them （ Container class is estimated that many people haven't heard the word ,Java Containers can be mainly divided into 4 Parts of ：List list 、Set aggregate 、Map mapping 、 Tool class （Iterator iterator 、Enumeration Enumeration class 、Arrays and Collections））

• List,Set,Map The difference between

• List and Map How to realize and store

• HashMap Implementation principle of

• HashMap data structure ？

• HashMap Source code understanding

• HashMap how put data （ from HashMap Explanation of source code ）？

• HashMap How to write ？

• ConcurrentHashMap Implementation principle of

• ArrayMap and HashMap Comparison of

• HashTable Realization principle

• TreeMap Concrete realization

• HashMap and HashTable The difference between

• HashMap And HashSet The difference between

• HashSet And HashMap How to judge the repetition of set elements ？

• aggregate Set Realization Hash How to prevent collision

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   ArrayList and LinkedList The difference between , And application scenarios

• The difference between arrays and linked lists

• The concrete implementation of depth first traversal and breadth first traversal of binary tree

• The structure of the pile

• The difference between heap and tree

• What's the difference between heap and stack in memory ( Answer tips ： It can be answered from two aspects: data structure and actual implementation )？

• What is deep copy and shallow copy

• Handwritten list reverse order code

• Talk about trees ,B+ Understanding of trees

• Let's talk about the understanding of graphs

• Judge whether the single linked list is looped or not ？

• List flip （ namely ： Flip a single Necklace Watch ）

• Merge multiple single ordered linked lists （ Let's assume it's all incremental ）

（ Four ）  Threads 、 Multithreading and thread pooling

• Three ways to start a thread ？

• The difference between threads and processes ？

• Why have threads , Instead of just using processes ？

• run() and start() Method difference

• How to control the number of concurrent access threads allowed by a method ？

• stay Java in wait and seelp Different methods ;

• Talk about wait/notify Keyword understanding

• What causes threads to block ？

• How does the thread close ？

• Let's talk about java The method of synchronization in

• How to ensure data consistency ？

• How to ensure thread safety ？

• How to realize thread synchronization ？

• Both processes require writing or reading at the same time , Can we achieve ？ How to prevent process synchronization ？

• Operation between threads List

• Java The life cycle of the object in

• Synchronized usage

• synchronize Principle

• Talk about right Synchronized keyword , Kind of lock , Method lock , The understanding of reentry lock

• static synchronized  The multithreaded access and function of the

• Two of the same class synchronized Method , The problem of two threads accessing at the same time

• volatile Principle

• Talk about volatile Keyword usage

• Talk about volatile The role of keywords

• Talk about NIO The understanding of the

• synchronized  and volatile  The difference between keywords

• synchronized And Lock The difference between

• ReentrantLock 、synchronized and volatile Compare

• ReentrantLock Internal implementation

• lock principle

• Four necessary conditions for deadlock ？

• How to avoid deadlock ？

• Do object locks and class locks affect each other ？

• What is a thread pool , How to use ?

• Java Concurrent 、 Multithreading 、 Threading model

• Talk about the understanding of multithreading

• What should we pay attention to in multithreading ？

• Talk about your understanding of concurrent programming and give examples

• Talk about your understanding of multithreading synchronization mechanism ？

• How to ensure the security of multi thread reading and writing files ？

• The principle of multi thread breakpoint continuous transmission

• Implementation of breakpoint continuous transmission

One ）Android Basic knowledge points

• What are the four components

• The life cycle and simple usage of the four components

• Activity The way of communication between

• Activity Life cycle in all cases

• When the horizontal and vertical screens are switched ,Activity  Life cycle in all cases

• Activity And Fragment Life cycle comparison between

• Activity There are Dialog When you press Home The life cycle of the bond

• Two Activity  Which methods will be executed when jumping between ？

• Switch from the front to the back , And then back to the front desk ,Activity Lifecycle callback methods . eject Dialog, Lifecycle callback method .

• Activity Comparison of four startup modes of

• Activity The state is preserved in recovery

• fragment Life cycle in all cases

• Fragment State of preservation startActivityForResult What kind of method is it , Under what circumstances ？

• How to achieve Fragment The slide of ？

• fragment How to transfer data between ？

• Activity  How and Service  binding ？

• How the Activity  Start the corresponding Service？

• service and activity How to interact data ？

• Service How to open it

• Please describe Service  Life cycle of

• Talk to you about ContentProvider The understanding of the

• say something ContentProvider、ContentResolver、ContentObserver  The relationship between

• Please describe the broadcast BroadcastReceiver The understanding of the

• Classification of broadcasting

• The way the broadcast is used and the scene

• stay manifest  And how to register and use BroadcastReceiver?

• What's the difference between local broadcasting and global broadcasting ？

• BroadcastReceiver,LocalBroadcastReceiver  difference

• AlertDialog,popupWindow,Activity difference

• Application  and  Activity  Of  Context  The difference between objects

• Android Property animation features

• How to import an external database ?

• LinearLayout、RelativeLayout、FrameLayout The characteristics and comparison of , And introduce the usage scenarios .

• Talk about the understanding of interface and callback

• The principle of callback

• Write a callback demo

• introduce SurfView

• RecycleView Use

• The function of serialization , as well as Android The difference between the two serialization

• Differentiator

• Estimator

• Android How to store data in

（ Two ）Android Source code correlation analysis

• Android Animation framework implementation principle

• Android Versions API The difference between

• Requestlayout,onlayout,onDraw,DrawChild Differences and connections

• invalidate and postInvalidate The difference and use of

• Activity-Window-View The difference between the three

• Talk about right Volley The understanding of the

• How to optimize customization View

• Low version SDK How to implement higher version api？

• Describe the flow of a network request

• HttpUrlConnection  and  okhttp Relationship

• Bitmap Understanding of the object

• looper framework

• ActivityThread,AMS,WMS How it works

• Customize View How to consider model adaptation

• Customize View Events

• AstncTask+HttpClient  And  AsyncHttpClient What's the difference? ？

• LaunchMode Application scenarios

• AsyncTask  How to use ?

• SpareArray principle

• Please introduce ContentProvider  How to realize data sharing ？

• AndroidService And Activity There are several ways to communicate with each other

• IntentService What are the principles and functions of ？

• say something Activity、Intent、Service  What's the relationship

• ApplicationContext and ActivityContext The difference between

• SP Is it process synchronization ? What's the way to synchronize ？

• On Multithreading in Android The use of

• The process and  Application  Life cycle of

• encapsulation View How do you know view Size

• RecycleView principle

• AndroidManifest The role and understanding of

（ 3、 ... and ） Some common principle problems

• Handler Mechanism and underlying implementation

• Handler、Thread and HandlerThread The difference between

• handler Send message to child thread ,looper How to start ？

• About Handler, anywhere new Handler  Under what thread ?

• ThreadLocal principle , Implementation and how to guarantee Local attribute ？

• Please explain in the single thread model Message、Handler、Message Queue、Looper The relationship between

• Please describe View Event delivery and distribution mechanism

• Touch Event delivery process

• In event distribution onTouch  and onTouchEvent  What's the difference? , How to use ？

• View and ViewGroup There are callback methods related to event distribution

• View Refresh mechanism

• View Drawing process

• Principle of custom control

• Customize View How to provide access to View Interface to properties ？

• Android In the code WAP The Internet

• AsyncTask Mechanism

• AsyncTask Principles and shortcomings

• How to cancel AsyncTask？

• Why can't I update in a child thread UI？

• ANR What is the cause of this ？

• ANR Positioning and correction

• oom What is it? ？

• What causes oom？

• What is the solution to avoid OOM？

• Oom  Whether it can be or not? try catch？ Why? ？

• What is a memory leak ？

• What causes a memory leak ？

• How to prevent thread memory leakage ？

• Solution to memory leak field

• The difference between memory leak and memory overflow ？

• LruCache Default cache size

• ContentProvider Authority management ( answer ： Read / write separation , Access control - Accurate to the table level ,URL control )

• How to intercept and abort A text message ？

• Whether the broadcast can request the network ？

• Broadcast induced anr What's the time limit of ？

• Calculate a view Nesting level of

• Activity Stack

• Android There is no upper limit for threads ？

• There is no upper limit on thread pool ？

• ListView What is reused ？

• Android Why introduce Parcelable？

• Have you tried to simplify Parcelable Use ？

（ Four ） Some common problems in development

• ListView  How is the problem of image dislocation in Chinese ?

• Do you understand hybrid development ？

• Know what hybrid development methods ？ Tell their advantages and disadvantages and their respective use scenarios ？（ answer ： such as :RN,weex,H5, Applet ,WPA etc. . do Android Understand some front-end js It's good to wait );

• What are the processing skills of screen adaptation ?

• The server only provides data receiving interface , In the case of multithreading or multiprocessing , How to ensure the orderly arrival of data ？

• Understanding of dynamic layout

• How to remove duplicate code ？

• Draw  Android  The general structure of

• Recycleview and ListView The difference between

• ListView The principle and solution of image loading disorder

• Dynamic permission adaptation scheme , The concept of permission group

• Android Why is the system designed ContentProvider？

• Does the drop-down status bar affect activity Life cycle of

• If in onStop When I made a network request ,onResume How to recover when ？

• Bitmap  What to pay attention to when using ？

• Bitmap Of recycler()

• Android The main steps to turn on the camera in

• ViewPager Use details , How to set to initialize only the current Fragment, The others are not initialized ？

• Click event is blocked , But I want to pass it down View, How to operate ？

• Implementation of wechat homepage

• The principle of small red dots on wechat

• CAS Introduce

3、 ... and 、 Mixed development interview questions

In addition to technical depth, big factories , It also requires you to have some breadth of knowledge , For example, you need to know front-end knowledge , Mixed development , At least one scripting language ,C c++ Let alone , It's inevitable .

• Hybrid Have you ever done ？

• Hybrid What is the principle of communication , Did you do any research ？

• react native How much do you know ？ Let's talk about the principle .

• weex Understand? ？ How to implement similar technologies by yourself ？

• flutter Understand? ？ How does the internal implement cross platform ？

• Dart Is language research expensive ？

• Come on, you know ？ What are the advantages and disadvantages compared with other methods ？

• Tell me about the hybrid development technologies you've used ？ What are the advantages and disadvantages of each ？

• Python Will it? ？

• Will the PHP？

• Gradle To understand how much ？groovy Do you know grammar ？

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