Android interview questions (6)-important

59. Why does Android introduce the broadcast mechanism?

A: From the Perspective of MVC (in applications), you can also ask why android has the four major components, the current mobile development model is basically a copy of the web-based MVC Architecture, but it only changes the dowry. The four components of android are essentially designed to implement the MVC Architecture on mobile devices or embedded devices. They are sometimes interdependent and complementary, the broadcast mechanism can be introduced to facilitate information and data interaction between several components.

B: intercommunication between programs (for example, listening for system calls in your own applications)

C: efficiency (refer to the convenience of UDP broadcast protocol in LAN)

D: Design Pattern (an application of reverse control, similar to the listener pattern)

 

60. The process of Android dvm and the process of Linux, whether the process of the application is the same concept DVM refers to the Virtual Machine of dalivk. Every Android application runs in its own process and has an independent Dalvik Virtual Machine instance. Every DVM is a process in Linux, so it can be considered the same concept.

61. what is the role of EF files on the sim card? The sim card's file system has its own specifications mainly for communication with mobile phones. The sim itself can have its own operating system, EF is 62 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.

63. 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 handle external events or data as quickly as possible, 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 in an embedded operating system for consistent operation. It is mainly used for industrial control, military equipment, aviation, and other fields that have demanding system response time requirements. This requires real-time systems. It can be divided into soft real-time and hard real-time, while android is based on the linux kernel, so it is soft real-time.

64. How many bytes does the longest Short Message count? 70 Chinese characters (including punctuation marks), 160,160 English bytes.

65. What are the features and differences of animations in android? Two types: Tween animation and Frame animation. Tween animation, which allows view components to move, zoom in, zoom out, and change transparency. Another Frame Animation, the traditional animation method, it is achieved through sequential playback of arranged images, similar to movies.

66. handler mechanism principle andriod provides Handler and logoff to satisfy the communication between threads. Handler first-in-first-out principle. The logoff class is used to manage Message Exchange between objects in a specific thread ). 1) loue: A thread can generate a loue object to manage the Message Queue (Message Queue) in this thread ).

2) Handler: You can construct a Handler object to communicate with logoff so as to push new messages to the Message Queue or receive messages sent by logoff from the Message Queue.

3) Message Queue: used to store messages placed by threads.

4) thread: The thread is usually the main thread, and a Message UI and Queue will be created for the Android Startup Program.

 

67. Let's talk about the principles of the mvc model. It uses MVC (Model_view_contraller) in android to "model _ view_controller ". MVC applications are always grouped by these three parts. Event causes the Controller to change the Model or View, or change both. As long as the Controller changes the data or attributes of Models, all dependent views are automatically updated. Similarly, as long as Contro

68. What is the difference between DDMS and TraceView? DDMS is a program execution viewer where information such as threads and stacks can be seen. TraceView is a Program Performance Analyzer.

69. How to reference the local language in java can use the JNI (java native interface java Local interface) interface.

70. Let's talk about the Android IPC (inter-process communication) mechanism. IPC is short for internal process communication and is a resource sharing "named Pipeline. The IPC Mechanism in Android is used to allow interaction between Activity and Service at any time. Therefore, in Android, this mechanism is only applicable to communication between Activity and Service, similar to remote method calls, similar to access in C/S mode. Define the IPC interface by defining the AIDL interface file. The Servier side implements the IPC interface, and the Client side calls the IPC interface as a local proxy. 71. what is NDK? NDK is a collection of column tools. NDK provides a series of tools to help developers quickly develop C/C ++ dynamic libraries, and can automatically compress the so and java applications into an apk package. NDK integrates with the cross compiler and provides the corresponding mk file and isolates the differences between cpu and platform. Developers only need to modify the mk file to create the so