Android ipm 20110409
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The document discusses inter-process method invocation in Android using Binder and AIDL. It describes how Binder allows processes to communicate across memory spaces using a kernel driver. The document outlines how AIDL generates proxy and stub classes to allow a caller process to invoke methods on a callee process via an interface. It provides an example of how the ActivityManager uses Binder to schedule pausing an Activity running in another process.
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Android ipm 20110409
- 1. Inter-process method invocation in Android 2011.4.9 Tetsuyuki Kobayashi 1
- 2. Who am I? 20+ years involved in embedded systems 10 years in real time OS, such as iTRON 10 years in embedded Java Virtual Machine Now GCC, Linux, QEMU, Android, … Blogs http://d.hatena.ne.jp/embedded/ (Personal) http://blog.kmckk.com/ (Corporate) Twitter @tetsu_koba 2
- 3. Today's topic inter process communications in Android Inter process method invocation using Binder AIDL Example of inter process method invocation 3
- 4. Inter Process Communication Activity Activity Window Alarm Manager Manager Manager Kernel 4
- 5. Abstraction of Inter Process Communication More abstract Intent AIDL Binder No need to use Binder directly. AIDL requires multi-thread programming 5 In most case Intent is easy and powerful enough.
- 6. Invoking method via interface caller callee In the same process 6
- 7. Inter-process invocation caller interface caller interface How? callee interface callee 7
- 8. Inter-process invocation caller interface Proxy caller interface Binder in kernel Binder Thread callee Stub interface callee 8
- 9. android.os.Parcel Delivering arguments of method ”flatten” ”unflatten” transmit 9
- 10. Describing in UML ... <<interface>> Proxy Stub 10
- 11. Describing in UML ... caller <<interface>> calls implements Proxy Stub extends callee 11
- 12. AIDL Auto generated from .aidl file caller <<interface>> Proxy Stub callee 12
- 13. Use case: Who calls ”onPause” in Activity? 2:Send message Activity by Handler 3:”onPause” is called queue Looper in main thread Activity Manager Main Main Binder Thread Thread Binder Thread #1 Thread #1 Kernel 1:Call ”schedulePauseActivity” across process 13
- 14. Binder /etc/binder Not for general purpose. Tuned for specific transaction. Multi-thread aware Have internal data per thead (CF. Socket have internal data per fd.) Not use ”write” and ”read”. Write and read at once by ”ioctl”. 14
- 15. Transaction of Binder Process A and B have different memory space. They can not see each other. Kernel Process B Process A Binder Copy memory by copy_from _user Then, wake up process B Kernel Process B Binder Process A Copy memory by copy_to_user 15
- 16. See also rd 3 session of Yokohama Android Platform club http://www.yokohama.android-pf.org/study/dai-san-kai-benkyou-kai 1st session of Android SDK work group http://www.android-group.jp/index.php?%CA%D9%B6%AF%B2%F1%2FAndr KMC blog http://blog.kmckk.com/archives/3611344.html http://blog.kmckk.com/archives/3613707.html http://blog.kmckk.com/archives/3627888.html http://blog.kmckk.com/archives/3645070.html http://blog.kmckk.com/archives/3647635.html http://blog.kmckk.com/archives/3617229.html 16
- 17. Q&A Thank you for listening! Any comments to blogs are welcome. 17