Android "Basic article"

A communication technology

1 G: Communication standard: Analog format can only voice calls, cannot send SMS

2 G: Communication standard: Digital format: GSM and CDMA send and receive SMS and mail

2.5G: Communication standard: Gprs,edge Access WAP network data (images, wallpapers, text messages)

3g: Communication standards: WCDMA (Unicom), CDMA2000 (Telecom), TD-SCDMA (MOBILE) Hair micro Bo, on QQ, view high-definition pictures, movies (see the movie is not mature)

3.5G: Communication standard: WCDMA extension technology: hsdpa,hsdpa+

4G: Communication standard: Td-lte, download speed: 50mb/s upload speed: 10mb/s

"Jokes about the 4G."

I wrapped 300M traffic, 4G claimed to be hundred trillion megabytes per second, that is not 3 seconds of traffic ran out, in fact, almost 50mb/s, upload the speed of almost 10mb/s, need to note is, 50mb/s! = S. Because the lowercase b is bit, the uppercase B is byte,1byte=8bit, so 50mb/s=6.25mb/s.

Two Android architectures

　　

Linux Kernel: Most of the storage is hardware-driven driver, implemented in C.

The function library of libraries:android system's important function is implemented by c,c++.

Application framework: Application framework layer, the API that Android provides to us

Applications: mobile app.

Call Example: There is an alarm app under applications, and you want to respond by invoking some APIs from the application framework that actually call libraries's media framwork. Then call the driver for the sound card in the Linux kernel. The final horn will ring up.

Android Runtime: Runs in the Dalvik VM and requires the support of the core libraries.

Comparison of 2.2 Dalvik vn with JVM

JVM: preferred to compile the. java file, then load the. class into memory and then hit multiple. class files into jar packages, which are then executed by the JVM, and the JVM schema is the stack. The specific process is as follows

DVM: first to compile the. java file, where DVM cannot load. class files, you must use the Dx.bat command to change the. dex file to. The DVM will then be able to interpret the. dex file as running, the schema is a register (a cache on the CPU), and the important information is placed on the register.

Process comparison:

Jvm	. jar, jar, Javac, Java---
Dvm	. Dex, Dx.bat, Java-Javac.

2.3. jar files differ from. dex Files

　　

Three Android development Environment building

There were a lot of things to download before, so now download an SDK kit.

The toolkit includes the following:

1.adt Plug-in

2.android SDK

3.Android Plateform-tooll

4. The latest Android development platform Plateforms

5. Latest Simulator image

3.1 Some of the settings before downloading

Open the SDK Manager.exe under the folder. Pop up a

　　

The development version of Android is managed by Google and Google is a foreign site, so the SDK manager does some special processing by clicking option under Tools. Tick force https://under others .... This option means that the HTTPS request is changed to an HTTP request.

　　

Then modify C:\Windows\System32\drivers\etc\ to add some content to the Hosts file

74.125.113.121 developer.android.com
203.208.46.146 dl.google.com
203.208.46.146 dl-ssl.google.com

Once this is set up, you can download the SDK in China.

-------------------------the split line--------------------------------

This thought that the SDK manager can be updated normally, but the network is really poor to the pole, searching for half a day, found an excellent solution, is the East soft to provide us with the image

　　

This way, the SDK manager can start

　　

Android "Basic article"