android13/frameworks/base/startop/view_compiler

View Compiler

This directory contains an experimental compiler for layout files.

It will take a layout XML file and produce a CompiledLayout.java file with a specialized layout inflation function.

To use it, let's assume you had a layout in my_layout.xml and your app was in the Java language package com.example.myapp. Run the following command:

viewcompiler my_layout.xml --package com.example.myapp --out CompiledView.java

This will produce a CompiledView.java, which can then be compiled into your Android app. Then to use it, in places where you would have inflated R.layouts.my_layout, instead call CompiledView.inflate.

Precompiling views like this generally improves the time needed to inflate them.

This tool is still in its early stages and has a number of limitations.

• Currently only one layout can be compiled at a time.
• merge and include nodes are not supported.
• View compilation is a manual process that requires code changes in the application.
• This only works for apps that do not use a custom layout inflater.
• Other limitations yet to be discovered.

DexBuilder Tests

The DexBuilder has several low-level end to end tests to verify generated DEX code validates, runs, and has the correct behavior. There are, unfortunately, a number of pieces that must be added to generate new tests. Here are the components:

• dex_testcase_generator - Written in C++ using DexBuilder. This runs as a build step produce the DEX files that will be tested on device. See the genrule named generate_dex_testcases in Android.bp. These files are then copied over to the device by TradeFed when running tests.
• DexBuilderTest - This is a Java Language test harness that loads the generated DEX files and exercises methods in the file.

To add a new DEX file test, follow these steps:

1. Modify dex_testcase_generator to produce the DEX file.
2. Add the filename to the out list of the generate_dex_testcases rule in Android.bp.
3. Add a new push option to AndroidTest.xml to copy the DEX file to the device.
4. Modify DexBuilderTest.java to load and exercise the new test.

In each case, you should be able to cargo-cult the existing test cases.

In general, you can probably get by without adding a new generated DEX file, and instead add more methods to the files that are already generated. In this case, you can skip all of steps 2 and 3 above, and simplify steps 1 and 4.