Android interview question 4

16th. What is the difference between Dalvik and JVM in Android?

Stack Based on registers. Register-based virtual machines take less time to compile larger programs.

Responsible for process isolation and thread management. Each application corresponds to an independent virtual machine instance at the underlying layer, which is specially optimized for running multiple virtual machines efficiently at the same time, the code can be executed under the explanation of the virtual machine.

They do not comply with the specifications and are not compatible with the two. It runs bytecode (File) and its proprietary () file. The file format can reduce the overall file size and improve the Class search speed of operations. The Dalvik virtual machine has its own bytecode instead of using Java bytecode.

This is a common method to implement serialization using interfaces.

Implementation interface, the partial classification here, such as the class, has been implemented, and data exchange is also very common.

Application entry point?

This package is the real entry point, but most developers do not need to rewrite this class. Its inheritance relationship is as follows:

? Android. content. Context
? Android. content. ContextWrapper
? Android. app. Application

Class contains a public Method

Void onCreate () // here is the real entry point.
Void onTerminate ()

The entry point is yes. You can see the inclusion relationship clearly, which is not required by every application.

Are you familiar with all the Resolvers?

There are three main parsing methods ,,,.

, The difference has been introduced in.

Similarly, it is a processing program written by the developer based on the stream () operation file and then callback based on the node event. Because it is stream-based processing, it saves both memory resources and does not display all nodes in the memory as an oak tree. But it is more concise and does not need to scan the entire stream.

As a lightweight database, it is relatively small, but supports statement queries. To improve performance, you can consider using the original optimized query statement method.

Different from?

: Stores static files that need to be packaged into the application for deployment to the device. The difference is that sub-directories in any depth are supported. These files do not generate any resources, and must use the relative path name of the beginning (excluding it.

: Resources used to store applications (such as labels and la s) will be packaged into compiled resources. Deep subdirectories are not supported;

: Stores the menu Description Based on;

: Stores common files. files in this folder will not be compiled into binary files and copied to the device as they are;

: Stores string and size values.

Store common files.

?

An advantages:

The platform is developed first. The platform allows any mobile terminal vendor to join the Android alliance. Significant openness allows more developers. as users and applications become increasingly diversified, a new platform will soon become mature. Development is conducive to accumulating popularity for the development of Android. The popularity here includes consumers and manufacturers. for consumers, the biggest benefit is the rich software resources. Open platforms will also bring greater competition, so that consumers can purchase their desired mobile phones at a lower price.

Listed on the market, users can connect to the network more conveniently, and the operator's restrictions are reduced. Android terminals promoted by Internet giant Google are inherently networked and will bring users closer to the Internet.

The openness of the platform is related. Due to the openness of Android, many manufacturers and Chambers of Commerce have released a variety of unique features.

One of the challenges.

Application:Over the past 10 years, from search giants to comprehensive Internet penetration, Google services such as maps, emails, and searches have become an important link connecting users and the Internet, android mobile phones are seamlessly integrated with these excellent Google services.

Disadvantages:

This giant is always standing behind you and wearing everything. Therefore, the depth of the Internet will bring about a new round of privacy crisis.

Mobile phones are not the largest carriers:On the 23th, the first Android mobile phone G1 was released in New York, USA. However, in the North American market, the two largest carriers are AT&T and Verizon. Currently, only T-Mobile and Sprint are known to have the right to sell Android Mobile phones, among them, T-Mobile's 3G network is inferior to the other three. Therefore, users can purchase G1. whether they can experience the best 3G network service is another matter!

Mobile phone:Sprint, another mobile phone sales operator, will build its mobile phone store program in its model.

Because of the diversified manufacturers and product types of platform mobile phones, fewer and fewer users use the same model, and lack of program enhancement for unified models. For example, there are few discussions and groups dedicated to a specific model of a stockade, because of the proliferation and variety of devices in the stockade area, in addition to which features are eye-catching and popular models.

When using Windows XP, a browser program such as Microsoft Windows Media Player is built in. You can choose a more diverse Player, such as Realplay or storm. However, starting to use the default program can also meet diverse needs. In the Android platform, because of its openness, the software is more dependent on third-party vendors. For example, the Android SDK does not have a built-in music player, and all depends on third-party development, which lacks product uniformity.

All files in the card are organized by treeMain FileEach card has only one primary file. All other files are its children and grandchildren. Only the file header stores the control and management information of the entire card.
Private filesThere is only one file header, which stores the management and control information of the entire directory. A dedicated file is equivalent to the root of a directory.Basic FileThere are both file headers and file headers to store the location of the file and control information. The file body stores real data. In the whole card, only basic files have file bodies and only basic files are used to store data.