Android Build Tools dx

Android_Tools

java class 转 dex 文件
adb shell 执行java

在\Sdk\build-tools\25.0.0\dx.bat，跟随SDK版本

usage:
  dx --dex [--debug] [--verbose] [--positions=<style>] [--no-locals]
  [--no-optimize] [--statistics] [--[no-]optimize-list=<file>] [--no-strict]
  [--keep-classes] [--output=<file>] [--dump-to=<file>] [--dump-width=<n>]
  [--dump-method=<name>[*]] [--verbose-dump] [--no-files] [--core-library]
  [--num-threads=<n>] [--incremental] [--force-jumbo] [--no-warning]
  [--multi-dex [--main-dex-list=<file> [--minimal-main-dex]]
  [--input-list=<file>]
  [<file>.class | <file>.{zip,jar,apk} | <directory>] ...
    Convert a set of classfiles into a dex file, optionally embedded in a
    jar/zip. Output name must end with one of: .dex .jar .zip .apk or be a dir
tory.
    Positions options: none, important, lines.
    --multi-dex: allows to generate several dex files if needed. This option i
    exclusive with --incremental, causes --num-threads to be ignored and only
    supports folder or archive output.
    --main-dex-list=<file>: <file> is a list of class file names, classes defi
d by
    those class files are put in classes.dex.
    --minimal-main-dex: only classes selected by --main-dex-list are to be put
n
    the main dex.
    --input-list: <file> is a list of inputs.
    Each line in <file> must end with one of: .class .jar .zip .apk or be a di
ctory.
  dx --annotool --annotation=<class> [--element=<element types>]
  [--print=<print types>]
  dx --dump [--debug] [--strict] [--bytes] [--optimize]
  [--basic-blocks | --rop-blocks | --ssa-blocks | --dot] [--ssa-step=<step>]
  [--width=<n>] [<file>.class | <file>.txt] ...
    Dump classfiles, or transformations thereof, in a human-oriented format.
  dx --find-usages <file.dex> <declaring type> <member>
    Find references and declarations to a field or method.
    declaring type: a class name in internal form, like Ljava/lang/Object;
    member: a field or method name, like hashCode
  dx -J<option> ... <arguments, in one of the above forms>
    Pass VM-specific options to the virtual machine that runs dx.
  dx --version
    Print the version of this tool (1.12).
  dx --help
    Print this message.

常规JVM执行环境

编写一个java文件，

public class JavaTest {
    public static void main(String[] args) {
        System.out.println("This is java class main method");
        System.out.println("print main method arguments");
        for (int i = 0; i < args.length; i++) {
            System.out.println("args[" + i + "] = " + args[i]);
        }
    }
}

编译java文件,未指定编译版本和兼容版本（本地安装JDK8）

javac JavaTest.java

本地运行

java JavaTest

带参数运行：

java JavaTest 0 1 2 3

输出结果：

This is java class main method
print main method arguments
args[0] = 0
args[1] = 1
args[2] = 2
args[3] = 3

转换为Android VM可执行的Dex文件

执行dx命令，把class文件转为dex文件

~\Android\Sdk\build-tools\25.0.0\dx.bat --dex --output=TestDex.dex JavaTest.class
PARSE ERROR:
unsupported class file version 52.0
...while parsing JavaTest.class
1 error; aborting

说明是JDK8直接编译的在这里还不能完全兼容使用，所以需要对JDK编译时做兼容

javac -target 1.7 -source 1.7 JavaTest.java

这里指定JDK编译兼容1.7（Java 7）
再次使用dx命令即可生成TestDex.dex文件

将dex文件push到手机任意地方

adb push TestDex.dex /sdcard 

执行adb shell命令

adb shell app_process -Djava.class.path=/sdcard/TestDex.dex /sdcard JavaTest

app_process也就AppRuntime,对应的源码在
~/platform/framework/base/cmds/app_process/app_main.cpp

static void app_usage()
{
    fprintf(stderr,
        "Usage: app_process [java-options] cmd-dir start-class-name [options]\n");
}

可参考pm命令的使用

base=/system
export CLASSPATH=$base/framework/pm.jar
exec app_process $base/bin com.android.commands.pm.Pm "$@"