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9419 page analysis of the latest first-line Internet Android interview questions

2022-04-23 13:10:00 【InfoQ】

  • 1.8 Android Medium Context, Activity,Appliction What's the difference? ？

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[](()2.Service


[](()2.1Service Whether in main thread In the implementation of , service Whether it can perform time-consuming operations ?

By default , If no finger is shown servic Running process , Service and activity Is running in the current app In the process of main thread(UI The main thread ) Inside .

service It can't perform time-consuming operations ( Network request , Copy database , A large file  )

A special case  , Can be configured in the manifest file  service  Process of execution  , Give Way service Execute... In another process .

<service

android:name=&quot;com.baidu.location.f&quot;

android:enabled=&quot;true&quot;

android:process=&quot;:remote&quot; >

</service>

[](()2.2Activity How and Service binding , How the Activity Start the corresponding Service？

Activity adopt bindService(Intent service, ServiceConnection conn, int flags) Follow Service Binding , When the binding succeeds Service The proxy object is passed to... As a callback conn, So we get Service Service proxy object provided .

stay Activity Through startService and bindService Method start up Service. In general, if you want to get Service The service object of must pass bindService（） Method , Like a music player , Third party payment, etc . If you just want to open a background task, you can use startService（） Method .

[](()2.3 say something Activity、Intent、Service What's the relationship

They are all Android The most frequently used class in development . among Activity and Service All are Android One of the four components . They are both Context Subclasses of classes ContextWrapper Subclasses of , So they are brothers . But the two brothers have their own skills ,Activity Responsible for the display and interaction of user interface ,Service Responsible for background task processing .Activity and Service You can go through Intent To transfer data , So we can Intent As a messenger of communication .

  • 2.4 Service and Activity In the same thread ？
  • 2.5 Service What are the starting methods , What's the difference? , How to stop Service？
  • 2.6  What is? IntentService？ What are the advantages of ？
  • 2.7  Please describe Service Life cycle of
  • 2.8 Service The boot process

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[](()3. ListView


[](()3.1ListView How to improve its efficiency ？

When convertView It's empty time , use setTag() Method for each View Bind a control's ViewHolder object . When convertView Not empty , Reuse what has been created view When , Use getTag() Method to get the bound ViewHolder object , This avoids findViewById Layer by layer query on the control , It's about quickly navigating to the control .

①  Reuse ConvertView, Use historical view, Improve efficiency 200%

②  Custom static class ViewHolder, Reduce findViewById The number of times . Improve efficiency 50%

③  Load data asynchronously , Page load data .

④  Use WeakRefrence quote ImageView object .

[](()3.2ListView How to achieve paging loading

①  Set up ListView The scrolling monitor of ：setOnScrollListener(new OnScrollListener{….})

There are two ways in the listener ：  How to change the rolling state (onScrollStateChanged) and listView Method called when scrolling (onScroll)

②  In the way the scrolling state changes , There are three states ：

The state in which the fingers are pressed and moved ：SCROLL_STATE_TOUCH_SCROLL: //  Touch slide

Inertia roll （ Gliding （flgin） state ）：SCROLL_STATE_FLING: //  Gliding

Stationary state ： SCROLL_STATE_IDLE: //  static

Dealing with different states ：

Load data in batches , Only care about the rest of the State ： Care about the last visible item , If the last visible entry is the data adapter （ aggregate ） The last one in , More data can be loaded at this time . Every time you load , Calculate the number of rolls , When the number of scrolls is greater than or equal to the total number , The user can be prompted that there is no more data .

[](()3.3ListView Can I display multiple types of items

Of course it can ,ListView Each entry shown is passed through the baseAdapter Of getView(int position, View convertView, ViewGroup parent) To show. , In theory, we can make every item a different type view.

such as ： Take back an identifier from the server as id=1, So when id=1 When , We just load the type one entry , When id=2 When , Loading entries of type 2 . Common layout can be seen in the information client .

besides adapter It also provides getViewTypeCount（） and getItemViewType(int position) Two methods . stay getView In the method, we can according to different viewtype Load different layout files .

  • 3.4 When ListView After the dataset changes , How to update ListView
  • 3.5ListView How to locate the specified location
  • 3.6 How to be in ScrollView How to embed ListView
  • 3.7ListView How to optimize pictures in
  • 3.8ListView How is the problem of image dislocation in Chinese

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[](()4.Fragment



  • What is? Fragment ？
  • Fragment Life cycle of
  • Fragment How to use
  • Fragment  Life cycle and  Activity  contrast
  • What is? Fragment Back stack of ？
  • Fragment Overlapping problems

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[](()5.Android  performance optimization



  • How to Android Application for performance analysis
  • When will it cause memory leaks
  • How to avoid OOM abnormal
  • Android How to catch uncaught exceptions in
  • ANR What is it? ？ How to avoid and solve ANR

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[](()6.Handler



  • Handler Looper Message  What is the relationship ？
  • Messagequeue  What is the data structure of ？ Why use this data structure ？
  • Handler post  Methods the principle ？
  • How to create  Handler?

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[](()7.Flutter Relevant interview questions



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