Precautions for developing Android source code using eclipse

Source: Internet
Author: User


1. What is the structure of the android file system? Where are the installed programs?
After the android source code is compiled, some files in out/target/product/generic:
Ramdisk. IMG, system. IMG, userdata. IMG, system, data, root
Here, system. IMG is packaged and compressed by system, and userdata. IMG is packaged and compressed by data.

Ramdisk. IMG is the file system of the simulator. After extracting ramdisk. IMG, you can see that the files in ramdisk. IMG are basically the same as those in the root folder.
The simulator loads ramdisk. IMG and decompress it To the memory. Then, the system. IMG and userdata. IMG are mounted to the system and data directories under ramdisk respectively. The compiled application is stored in system/app. The programs installed by the user are stored in data/app.

2. What tools does the android SDK and Android Source Code provide for us?
The android SDK provides many tools, such as ADB, ddms, emulator, and aapt. It also provides kernel-qemu, ramdisk. IMG, system. IMG, and userdata. IMG. Therefore, with the android SDK, we can run Android on the simulator.
Android source code can compile Android SDK, ADB, and other tools, Android file systems, and ADT plug-ins. That is to say, we can compile all Android-related things from Android source code.

3. Many tools and Android file systems (system. IMG, etc.), and we can use the "make SDK" to generate the android SDK. The Android SDK also includes tools and the android File System (system. IMG), and Android is also installed during the original installation.
SDK, which tools and Android file system should we use during development?
This question will be answered later.

4. We officially recommend using eclipse + ADT to develop applications. Our helloactivity program is also developed here. When we import the project under the android source code/packages/apps/into eclipse, the error that cannot find the package usually occurs. So how can we modify, compile, and debug the android source code? What kind of work does Google use?
For Android development?
This question will be answered later.

The following describes how to establish an android development environment and how to use development tools.

I. Installation of Android SDK and eclipse and establishment of Android Development Environment
Android tool chain is relatively complete and requires fewer external tools. For more information about the installation process, see the official documentation or <Android simulator installation in ubuntu8.10> and <Android source code compilation>.
Note that when "make" is used to compile the android source code, JDK 5 or JDK 6 can be used. When "make SDK" is used to compile the code, javadoc is used to generate the document, javadoc of JDK 5 must be used; otherwise, the compilation will fail. Therefore, we can install jdk5 and jdk6, and then point javadocand javadoc.1.gz to corresponding tools of jdk5. other tools still use jdk6. Of course, we can only install JDK 5
Or use only JDK 5. For more information, see <Android source code compilation>

2. Use eclipse to develop Android source code
For more information, see the official documentation.

Next, we will summarize from the official documents how to use eclipse to develop the android source code.

1. Establish a basic Android Development Environment
Please refer to the official documentation or <Android simulator installation in ubuntu8.10>

2. Compile the android source code
Use make to compile the android source code in the root directory. Pay attention to some configurations. For more information, see <Android source code compilation>

3. Copy the Eclipse project configuration file to the root directory of the android source code.
CP development/IDE/Eclipse/. classpath ./
Chmod U + W. classpath # Make the copy writable
4. modify the configuration of the eclipse Program
1) Increase eclipse memory settings
Change the three values of eclipse. ini (under the eclipse installation directory) to the following values:
-XX: maxpermsize = 256 m
2), the Android-formatting.xml and Android. importorder into eclipse (optional)
The Android-formatting.xml,. classpath, and Android. importorder are all placed in the development/IDE/Eclipse/
Android-formatting.xml is used to configure the code style of the eclipse editor; Android. importorder is used to configure the order and structure of the eclipse import.
Import Android-formatting.xml in window-> preferences-> JAVA-> code style-> formatter
Import Android. importorder to WINDOW> preferences> JAVA> code style> organize imports.
3) install the anyedit plug-in (optional)
Download and import data to eclipseat at

5. Import the android source code as a project into eclipse
Check Before importing. whether the files in classpath have corresponding files (folders) in the android source code; otherwise, the android source code will be damaged (usually multiple files/folders are added ),. the redundant paths in classpath can be deleted.
Create a Java Project (not an android project; otherwise, the android source code will be damaged). Select to import the existing project. The project name is arbitrary and complete.
It is slow to build a project in eclipse during import. After the import, there are generally no errors.
4th questions are answered here

6. debug the android program on Eclipse.
To prevent other versions of Android tools and Android file systems from affecting compilation and debugging, you need to remove the paths of Android tools and Android file systems from the environment variables:
Vim ~ /. Bashrc
Check whether the path of the android tool and Android file system is added to the PATH variable. If yes, comment it out. In the following method, we do not need to add the path of the android tool and the android File System to. bashrc.
Android source code directory
. Build/envsetup. Sh # After the environment variable is set, mmm and other commands will be added. You can enter help to view
Lunch 1 # maps emulator and other tools with the paths of files such as ramdisk. IMG, you can directly call emulator and other tools, and solve 3rd Problems
Emulator &
Ddms &
Note: first start ddms and then start eclipse, so that there will be no port conflict in eclipse.
Configure the debugging type and port in Eclipse:
Double-click Run-> debug deployments-> remote Java application and set "Host:" to localhost and "port:" To 8800, "connection type" is standard (socket attach)
Then "Apply"
Note: The port set above must be the same as the port set in ddms. The ADT plug-in uses port 8700, so the port set above is 8800. If the VM cannot be connected, note that you must select a process (corresponding to an application) in ddms before executing debug in eclipse.
During eclipse debugging, you can set breakpoints and perform one-step debugging. It is estimated that the Google team developed and debugged Android applications in this way.

7. Compile the android source code
Android source code directory
. Build/envsetup. Sh
Then there will be more commands such as mm/mmm. mm/Mmm is used to compile modules (including C, C ++, and Java programs ). We can also directly
Run "make Module name" in the root directory of the android source code to compile the module (the module name can be found in the. mk file ). After the module is compiled, it will generate a corresponding .apk package under out/target/product/generic/system/app. However, the. APK compiled with mm/mmmwill not be packaged into the system. in IMG, We need to manually package the system folder as system through make Snod. IMG, but you have to re-run the simulator, which is also very troublesome. For our developers, we can do this:
1. Remove the modified versions (such as alarmclock.apk) from/system/app, and then make snod,system.imghas no alarmclock.apk.
2) run the simulator and you will not be able to see alarmclock.
3) modify the source code of alarmclock and compile it with mm/mmm. Then, generate alarmclock.apk under/system/app.
4. Install alarmclock.apk to the android file system through adb. there are two installation methods:
A. Run ADB install xxx/alarmclock.apk
B. Push xxx/alarmclock.apk/data/APP through ADB
You can install alarmclock under/data/app. androidwill automatically display the lock in the main menu (only alarmclock.apk contains an activity package containing android. intent. category. launcher attribute), but method A generates in/data/app, and method B is
Alarmclock.apk. When using method A, if alarmclock has been installed, you must first ADB uninstall it, and method B does not need. The B method is recommended. Similarly, you can use ADB uninstall or ADB shell RM xxx/xxx.apk to uninstall the SDK. We recommend that you delete the SDK.

8. How to develop your own projects
The previous section mainly describes how to develop the original Android project on Eclipse. For our own projects, we can do this:
1) Create an android project.
The advantage of building an android project is that you can make full use of the ADT function.
2) import the required package
3) Compile, run, and debug
4) Add the app to the corresponding Android source code Directory, which is usually stored in packages/apps.
When we observe the original project of packages/apps, we will find that their code is "clean", without folders such as assets and bin automatically generated by ADT and R. java, of course not. classpath and. project
5) write the makefile XXX. mk.
The dedicated makefile XXX. mk provided by the android source code is in a simple format.
6) Add the newly added project to the android project of eclipse
You can add a path in eclipse or in. classpath. For example, add the following content to. classpath:
<Classpathentry kind = "src" Path = "packages/apps/helloworld/src"/>
R. Java is automatically generated during compilation. In fact, all projects that use "Resources" will use R. java. These R. java files are placed under out/target/common/R. During makefull code under the source code root directory, modules that have been compiled and generated with .apk files will not be compiled for each worker. Therefore, if the newly added project has been compiled (using mm/mmm), we need to change the "resource" of the project first (the "resource" must be changed because R. java is generated by a "resource"), and then make, you will see the r of your project in the package path corresponding to out/target/common/R. java. Refresh out/target/common/R in eclipse
Child project, and then add its package where you use the r class, such
Import com. Android. example. Test. Inside. helloworld. R.
In fact, this error has no effect on us, because we compile it in shell.
7) Compile the newly added project in the android source code directory.
You can use the mm/Mmm Or make Module name.
8) Use a version control tool (SVN, git, or other) to upload the project to the server.

From the official documents and practices, we can summarize the following points:
1. You can use eclipse to edit Java programs and check for errors (mainly including class library inclusion and syntax). However, you cannot compile and run the android source code on Eclipse, still make (or mm or MMM) in Shell)
2. Some eclipse configuration files are provided in the android source code folder,
. Claapath: the configuration file of the eclipse project, so that we can directly import the file and Java package corresponding to the android source code to the project.
Android-formatting.xml and Android. importorder: This is very important, mainly used to regulate our encoding style, it is easier to make our code style consistent
3. When importing the android source code as a project into eclipse, pay attention to the following two points:
1) the newly created project must be a Java project, not an android project. Otherwise, the android source code will be damaged (generally multiple files/folders are added)
2) check whether the file in. classpath has a corresponding file (folder) in the android source code before import. Otherwise, the android source code will be damaged (generally add more files/folders)

In general:
1. Use eclipse to edit code and check for errors
2. If you do not compile or run the android source code program on Eclipse, you can only compile the android source code through make (or mm or MMM) on the command line.
3. You can debug the android source code program on Eclipse (Principle: Eclipse uses the ddms server to debug on emulator), and can debug and breakpoint in one step.
4. The program to be debugged removes it from/system/APP/and installs it under data/app, which is more convenient.
5. It is easier to install and uninstall programs by using ADB push and ADB shell RM.


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