Journey of APK from compilation to installation

Transcript

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2. Destination:
   

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3. - “Sometimes its the journey that teaches you a lot about your
   destination.”
   Destination:
   

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4. Bon Voyage!!
   • Aim: To compile your Android Code.
   • Material required: Java files, AndroidManifest.xml, resources,
   assets(optional)
   • Procedure:
   Step 1: Your .java files or .kt files gets converted to .class files that
   is the ByteCode through “javac” or “kotlinc” command.
   

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5. MainActivity.java File:
   MainActivity.class
   ByteCode:
   

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6. ByteCode Execution of: c = 2 * (a+b)
   • iConst 2
   
   • iLoad a
   
   • iLoad b
   
   • iAdd
   
   • iMul
   
   • iStore c
   a
   b
   42
   7
   C 0 2
   

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7. ByteCode Execution of: c = 2 * (a+b)
   • iConst 2
   
   • iLoad a
   
   • iLoad b
   
   • iAdd
   
   • iMul
   
   • iStore c
   a
   b
   42
   7
   C 0 2
   42
   

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8. ByteCode Execution of: c = 2 * (a+b)
   • iConst 2
   
   • iLoad a
   
   • iLoad b
   
   • iAdd
   
   • iMul
   
   • iStore c
   a
   b
   42
   7
   C 0 2
   42
   7
   

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9. ByteCode Execution of: c = 2 * (a+b)
   • iConst 2
   
   • iLoad a
   
   • iLoad b
   
   • iAdd
   
   • iMul
   
   • iStore c
   a
   b
   42
   7
   C 0 2
   49
   

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10. ByteCode Execution of: c = 2 * (a+b)
    • iConst 2
    
    • iLoad a
    
    • iLoad b
    
    • iAdd
    
    • iMul
    
    • iStore c
    a
    b
    42
    7
    C 0 98
    

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11. ByteCode Execution of: c = 2 * (a+b)
    • iConst 2
    
    • iLoad a
    
    • iLoad b
    
    • iAdd
    
    • iMul
    
    • iStore c
    a
    b
    42
    7
    C 98
    

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12. • Android does not use this .class file directly. Android has its own
    byte code format and its own virtual machine that is Dalvik Virtual
    Machine.
    • Multiple .class files or class files from any .jar file gets converted to
    a single classes.dex file.
    • Dx tool from the build platform tools inside Android SDK converts
    multiple .class files into single classes.dex .
    

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13. MainActivity.dex
    MainActivity.java
    Dx:
    --dex --output MainActivity.dex
    

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14. Dalvik code of int foo = 1+2
    const-1 r0 1
    foo
    Dest Arg0 Arg1
    

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15. Dalvik code of int foo = 1+2
    const-1 r0 1
    add-int/lit8 r1
    Foo
    Arg1
    Arg0
    Dest
    

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16. Dalvik code of int foo = 1+2
    const-1 r0 1
    add-int/lit8 r1
    Foo
    r0 2
    Dest Arg0 Arg1
    

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17. Dalvik code of int foo = 1+2
    const-1 r0 1
    add-int/lit8 r1
    Foo
    r0 2
    1
    Dest Arg0 Arg1
    

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18. Dalvik code of int foo = 1+2
    const-1 r0 1
    add-int/lit8 r1
    Foo
    r0 2
    1 1+2
    Dest Arg0 Arg1
    

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19. Building a story from Why?
    - “The art and science of asking questions is the source of all
    knowledge. The more you ask the more you know”
    • Why does Android not use .class files?
    • Why does Android not use JVM?
    

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20. Types of Virtual Machine
    • Virtual machine is a software environment that can be an
    emulator, an operating system or complete hardware
    virtualization, that has implementation of resources without the
    actual hardware.
    • Two types of VM on basis of architecture: Stack Based
    architecture and Register Based Architecture.
    

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21. Types of Virtual Machine
    • Virtual machine is a software environment that can be an emulator,
    an operating system or complete hardware virtualization, that has
    implementation of resources without the actual hardware.
    • Two types of VM on basis of architecture: Stack Based architecture
    and Register Based Architecture.
    • And yes, from previous examples you guessed right:
    JVM: Stack Based Architecture
    DVM: Register Based Architecture
    

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22. Let’s look numbers
    • Study on different VM shows that register based architecture requires an 47% less
    executed VM instructions than stack based.
    • Register based code is 25% larger in code size than the corresponding stack based
    code but this overall effects around 1.05% on load of VM.
    • So overall performance is that Dalvik VM is taking 32.3 % less time to execute
    standard benchmarks.
    • Licensing issues from Sun side which also led to have conflicts and thus Android
    took another VM.
    • Used because of memory limitations, reduce system overhead, redundancies and
    bringing optimization to .class files.
    - And you will have the answer to WHY?
    1
    2 3
    Dalvik VM
    JVM
    

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23. .class
    .
    .
    .
    .
    .
    .
    .
    .
    .class
    .class
    .class
    .
    .
    

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24. .class
    .
    .
    .
    .
    .
    .
    .
    .
    .class
    .class
    .class
    .
    .
    classes.dex
    

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25. Step 2: Resources Prepared
    • Drawables (all dpis: xxhdpi, mdpi, xhdpi, hdpi)
    
    • Layout files
    
    • Menu files (optional)
    
    • Anim folder
    
    • raw
    
    • Color
    
    • Styles
    

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26. Putting it all together
    • Material 3: Android asset Packaging Tool.
    • It allows to create, update zip compatible archive (apk,
    zip, jar). It can also compile resources into binary assets.
    • Printing permissions, printing resources, print
    configurations supported.
    • Step 3: aapt zip classes.dex, resources and
    AndroidManifest.xml into a zip archive called APK.
    

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27. The Final picture to the APK
    

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28. Installation
    Dalvik ART
    ???
    

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29. Dalvik
    • Based on JIT (Just in Time) Compilation
    • Every time your app runs, part of code important for its execution is going to be
    translated to machine code at that moment. Further caching while app is running.
    • DEX to ODEX conversion and copy to dalvik-cache.
    • Optimizations:
    • Replace method index with vtable index
    • Replace field index with byte offset
    • Replacement with inline calls
    • Cut Empty methods
    

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30. ART: The next level
    • Based on AOT (Ahead of time) compilation.
    • Perform dex2oat to have a elf file.
    • Solved garbage collection issues.
    • Improved battery performance as power to interpret line
    by line is saved.
    

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31. Installation Picture
    

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32. Thank you !
    

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