Android interview question 1

DVM
RefersDalivk
. Every android application runs in its own process and has an independentDalvik
Virtual Machine instance. And everyDVM
All in Linux
So it can be considered the same concept.

1. What is the role of the SIM card EF file?


 
SIM card file systems have their own specifications, mainly to communicate with mobile phones, Sim itself can have its own operating system, EF is used for storage and communication with mobile phones

Which types of memory management are available for Embedded Operating Systems? What are the features of page type, segment type, segment page? technologies such as MMU and virtual space are used.

2. What is an embedded real-time operating system? Does the Android operating system belong to a real-time operating system?



An embedded real-time operating system can accept and process external events or data at a high speed, the processing result can control the production process or quickly respond to the processing system within the specified time, and control all real-time tasks to coordinate and operate in an embedded operating system. Mainly used for industrial control,
Military equipment,
Aerospace and other fields have strict requirements on the system response time, which requires the use of real-time systems. It can be divided into soft real-time and hard real-time. Android is based on the Linux kernel, so it is soft real-time.

 
3. How many bytes does the longest Short Message count?



70 Chinese characters (including punctuation marks), 160,160 English bytes.

4. What are the features and differences of animations in Android?

Either isTween
Animation, there is alsoFrame
Animation.Tween
Animation, which allows the view component to move, zoom in, zoom out, and change the transparency.Frame
Animation, a traditional animation method, is achieved through sequential playback of arranged images, similar to movies.

5. Handler mechanism Principle

Andriod
ProvidedHandler
AndLogoff

To enable inter-thread communication.Handler

First-in-first-out principle.Logoff
Class is used to manage the message exchange between objects in a specific thread (Message
Exchange
).

1)Logoff
:
A thread can generateLogoff
Object To manageMessage
Queue
(Message Queue ).
2)Handler
:
You can constructHandler
ObjectLogoff
Communication to facilitatePush
New messageMessage
Queue
Or receiveLogoff
SlaveMessage
Queue
) The sent message.
3)Message
Queue
(Message Queue): used to store messages placed by threads.
4) threads:Ui thread

UsuallyMain
Thread
, AndAndroid
When you start a program,Message
Queue