What is Android?

Google's figure shows that android is a big package!

With an eye-catching look, I got 5 big blocks! From the application to the underlying operating system kernel, this is really complicated !!!

Take a closer look, the first layer is skipped! You can find an Android phone after it is turned on.

As a result:

Now it's easy!

Look at the bottom Linux kernel. What's so advanced cannot be seen! Besides, the operating system should be similar, with a bunch of driver packages! Kill!

This is basically dry! It should have been studied!

Let's continue to look at the heap in the lower-left corner, the appearance manager, multimedia framework, and SQLite (actually integrated with the database ?), OpenGL ES !), FreeType bitmap, vector font rendering, WebKit (it is said that it is a good browser kernel), SGL (when it comes to GL), SSL (I guess it is a security protocol and so on) as to the inconspicuous libc, it is said that C/C ++ has a special liking for them. They can use them to build linux kernels and drive what they drive. It's just a fantasy for me !!!

It is said that these are all using C/C ++ class library APIs. They have never been able to play with these two languages. Stay away!

So, I will cut it again !!!

 

Although the graph is a little ugly, I finally removed the useless ones. I can study this residual graph with my mind. I hope I can find the mysterious path to the treasure from this graph !!!!

 

There are only two major blocks. Application Framework + application program running environment!

 

Now, from the beginning, Android is a miscellaneous package. There is an operating system in it, and some application software commonly used by mobile terminals is attached to the operating system. If you are a master, it is estimated that you can replace these software by yourself.

 

Of course, just like Java, They optimized a virtual machine and reduced Java's JVM, because there is no big computer on the mobile terminal. The main reason is that they optimized the memory usage to the minimum and changed to the Dalvik virtual machine, I don't know why this name is called? Can this small virtual machine be instantiated? Can I run multiple?

 

Java Virtual Machine (JVM). I have heard of it, never used it, and I don't know what it is like? Does JVM have executable files?

Dalvik says it has a symbolic suffix. PEX, which says it can run classes written in Java, but it needs to be compiled using the Java compiler and converted using dx. Not clear!

 

In any case, it is still not supported by the Linux kernel, such as the underlying memory management and thread management.

 

What does it do?

It also has a core libraries, which is a color that corresponds to components in the application framework. It indicates that all components are developed in Java. Of course, people say that Dalvik is an executable file, it's none of my business.

 

Each application has its own process and corresponding Dalvik VM instance !!!! --- Is that true?

 

Can Dalvik be instantiated at will? Further research is required!

At present, it is understood that an android application will have a separate process and a Dalvik VM instance dedicated to it to serve it.

 

Core libraries core class library, introduced in the android runtime environment, is the interface class library that has just been torn up by libraries in the android runtime environment packaged by Java.

 

Let's look at the application framework. I rely on seven officers !!! There is another service provider. view has become an independent system !!!

These seven managers are all managed! Provider provider, which is engaged in service! Is the view independent? Self-built system!

 

It is said that this is a component unit specially encapsulated by Android to enable developers to develop applications.

Do developers rely on these officials and providers to write applications? By the way, there is another guy who claims to be a system !!!

Let's take a look at the contacts, phone, browser... all the applications that were sitting on them. It should be like this!

 

They are all blue and should all be written in Java. It is said that android has basically covered all the core class libraries in Java, hoping not to blow them.

 

Ah, no, it's too late to go to bed!