修改aapt和自定义资源ID

源码查看

aapt的源码在所在的目录：Android/frameworks/base/tools/aapt/。

Main.cpp位置：android-6.0.0_r1/frameworks/base/tools/aapt/Main.cpp
首先查看Main.cpp的main方法:

int main(int argc, char* const argv[])
{char *prog = argv[0];Bundle bundle;bool wantUsage = false;int result = 1;    // pessimistically assume an error....//进行资源打包的参数p或packageelse if (argv[1][0] == 'p')bundle.setCommand(kCommandPackage);.../** Pull out flags.  We support "-fv" and "-f -v".*/while (argc && argv[0][0] == '-') {/* flag(s) found */const char* cp = argv[0] +1;while (*cp != '\0') {...//收集appt命令输入的参数，这些参数以"-"开头case '-':if (strcmp(cp, "-debug-mode") == 0) {bundle.setDebugMode(true);} ...break;default:fprintf(stderr, "ERROR: Unknown flag '-%c'\n", *cp);wantUsage = true;goto bail;}cp++;}argc--;argv++;}/** We're past the flags. The rest all goes straight in.*/bundle.setFileSpec(argv, argc);//根据bundle收集的参数进行资源处理result = handleCommand(&bundle);//输入参数错误时会跳转到此
bail:if (wantUsage) {usage();result = 2;}return result;
}

在main函数内，首先创建一个Bundle对象，这个对象用来存储输入的操作类型和相关的参数。argv相当于java中的字符串数组。取该数组的第2个字符串的第一个char值。因为是执行资源打包，所以它是’p’。bundle记录执行类型为kCommandPackage，即资源打包。while循环处理剩余的char数组（即字符串数组），将参数按照类型设置到bundle中。参数解析完毕，则会执行handleCommand(&bundle)。如果在解析输入的参数时出现了错误，便使用goto跳转到bail代码块。在bail代码块中可能会执行usage();，这个方法会打印出aapt所有的命令类型和相关的参数。

先看看usage()函数，省略了与资源打包无关的信息。

void usage(void)
{...fprintf(stderr," %s p[ackage] [-d][-f][-m][-u][-v][-x][-z][-M AndroidManifest.xml] \\\n"" [-0 extension [-0 extension ...]] [-g tolerance] [-j jarfile] \\\n"" [--debug-mode] [--min-sdk-version VAL] [--target-sdk-version VAL] \\\n"" [--app-version VAL] [--app-version-name TEXT] [--custom-package VAL] \\\n"" [--rename-manifest-package PACKAGE] \\\n"" [--rename-instrumentation-target-package PACKAGE] \\\n"" [--utf16] [--auto-add-overlay] \\\n"" [--max-res-version VAL] \\\n"" [-I base-package [-I base-package ...]] \\\n"" [-A asset-source-dir] [-G class-list-file] [-P public-definitions-file] \\\n"" [-S resource-sources [-S resource-sources ...]] \\\n"" [-F apk-file] [-J R-file-dir] \\\n"" [--product product1,product2,...] \\\n"" [-c CONFIGS] [--preferred-density DENSITY] \\\n"" [--split CONFIGS [--split CONFIGS]] \\\n"" [--feature-of package [--feature-after package]] \\\n"" [raw-files-dir [raw-files-dir] ...] \\\n"" [--output-text-symbols DIR]\n"" [--apk-module moduleName]\n""\n"" Package the android resources. It will read assets and resources that are\n"" supplied with the -M -A -S or raw-files-dir arguments. The -J -P -F and -R\n"" options control which files are output.\n\n", gProgName);...
}

打印appt执行的操作类型和对应的参数。

先看看handleCommand()函数，

int handleCommand(Bundle* bundle)
{switch (bundle->getCommand()) {case kCommandVersion:      return doVersion(bundle);...case kCommandPackage:      return doPackage(bundle);...default:fprintf(stderr, "%s: requested command not yet supported\n", gProgName);return 1;}
}

在main函数中bundle设置的cmmand类型为kCommandPackage，所以会执行doPackage(bundle)代码。使用操作系统自带的搜索，检索aapt目录内的文件内容’doPackage’。会查找到doPackage()是Command.cpp中的函数。

Command.cpp位置：android-6.0.0_r1/frameworks/base/tools/aapt/Command.cpp
doPackage()函数中处理资源相关的代码：

int doPackage(Bundle* bundle)
{...// If they asked for any fileAs that need to be compiled, do so.if (bundle->getResourceSourceDirs().size() || bundle->getAndroidManifestFile()) {err = buildResources(bundle, assets, builder);if (err != 0) {goto bail;}}...
}

继续搜索buildResources()函数所在的文件，查找到Resource.cpp。

Resource.cpp位置：android-6.0.0_r1/frameworks/base/tools/aapt/Resource.cpp
buildResources()函数中创建资源表相关的代码：

status_t buildResources(Bundle* bundle, const sp<AaptAssets>& assets, sp<ApkBuilder>& builder)
{...//设置资源类型ResourceTable::PackageType packageType = ResourceTable::App;if (bundle->getBuildSharedLibrary()) {packageType = ResourceTable::SharedLibrary;} else if (bundle->getExtending()) {packageType = ResourceTable::System;} else if (!bundle->getFeatureOfPackage().isEmpty()) {packageType = ResourceTable::AppFeature;}//创建资源表ResourceTable table(bundle, String16(assets->getPackage()), packageType);...
}

继续查看ResourceTable.cpp的构造函数。

ResourceTable.cpp位置：android-6.0.0_r1/frameworks/base/tools/aapt/ResourceTable.cpp
ResourceTable构造函数

ResourceTable::ResourceTable(Bundle* bundle, const String16& assetsPackage, ResourceTable::PackageType type): mAssetsPackage(assetsPackage), mPackageType(type), mTypeIdOffset(0), mNumLocal(0), mBundle(bundle)
{ssize_t packageId = -1;switch (mPackageType) {case App:case AppFeature:packageId = 0x7f;break;case System:packageId = 0x01;break;case SharedLibrary:packageId = 0x00;break;default:assert(0);break;}sp<Package> package = new Package(mAssetsPackage, packageId);mPackages.add(assetsPackage, package);mOrderedPackages.add(package);// Every resource table always has one first entry, the bag attributes.const SourcePos unknown(String8("????"), 0);getType(mAssetsPackage, String16("attr"), unknown);
}

应用的资源id从0x7f开始，系统的资源id从0x01开始，共享类库的从0x00开始。如果我们想要自定义应用的资源id的起始值，则需要在switch结束后重新设置packageId值。这个自定义值可以Main.cpp的main函数中解析获取，并存放到bundle中。

修改源码

1，修改Bundle.h文件。
Bundle.h位置：android-6.0.0_r1/frameworks/base/tools/aapt/Bundle.h

添加如下代码：

class Bundle {
public:...//添加的获取和设置自定义id的函数const android::String8& getApkModule() const {return mApkModule;}void setApkModule(const char* str) { mApkModule=str;}...private:/* commands & modifiers */...//自定义idandroid::String8 mApkModule;...
}

2，修改Main.cpp的main函数，添加解析自定义id的参数并设置到bundle。
代码如下：

int main(int argc, char* const argv[])
{...while (argc && argv[0][0] == '-') {...while (*cp != '\0') {...case '-':...//添加解析-apk-module参数信息} else if(strcmp(cp, "-apk-module") == 0){argc--;argv++;if (!argc) {fprintf(stderr, "ERROR: No argument supplied for '--apk-model' option\n");wantUsage = true;goto bail;}bundle.setApkModule(argv[0]);} else if (strcmp(cp, "-feature-of") == 0) {...break;...}...}...
}

3，修改ResourceTable.cpp的构造函数，添加判断是否存在自定义id，如果存在，则修改packageId为自定义id。

ResourceTable::ResourceTable(Bundle* bundle, const String16& assetsPackage, ResourceTable::PackageType type)...
{ssize_t packageId = -1;switch (mPackageType) {...}//判断和设置自定义idif(!bundle->getApkModule().isEmpty()){android::String8 apkModuleVal = bundle->getApkModule();packageId = apkStringToInt(apkModuleVal);}sp<Package> package = new Package(mAssetsPackage, packageId);...
}//将字符串转换为ssize_t类型
ssize_t ResourceTable::apkStringToInt(const String8& s){size_t i = 0;ssize_t val = 0;size_t len=s.length();if (s[i] < '0' || s[i] > '9') {return -1;}// Decimal or hex?if (s[i] == '0' && s[i+1] == 'x') {i += 2;bool error = false;while (i < len && !error) {val = (val*16) + apkgetHex(s[i], &error);i++;}if (error) {return -1;}} else {while (i < len) {if (s[i] < '0' || s[i] > '9') {return false;}val = (val*10) + s[i]-'0';i++;}}if (i == len) {return val;}return -1;
}
//转换为16进制
uint32_t ResourceTable::apkgetHex(char c, bool* outError){if (c >= '0' && c <= '9') {return c - '0';} else if (c >= 'a' && c <= 'f') {return c - 'a' + 0xa;} else if (c >= 'A' && c <= 'F') {return c - 'A' + 0xa;}*outError = true;return 0;
}

还需要在ResourceTable.h文件中声明apkStringToInt()和apkgetHex()函数。
ResourceTable.h位置：android-6.0.0_r1/frameworks/base/tools/aapt/ResourceTable.h
添加到public或private中。

    ssize_t apkStringToInt(const String8& s);uint32_t apkgetHex(char c, bool* outError);

编译和修改错误

修改完毕，开启终端（或控制台）进入到android-6.0.0_r1目录，运行. build/envsetup.sh命令，配置运行环境。配置命令运行完毕，运行cd frameworks/base/tools/aapt，进入到aapt目录。执行mm命令，该命令会编译aapt模块中的代码，并生成可执行文件。运行结果如下：

============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=6.0
TARGET_PRODUCT=full
TARGET_BUILD_VARIANT=eng
TARGET_BUILD_TYPE=release
TARGET_BUILD_APPS=
TARGET_ARCH=arm
TARGET_ARCH_VARIANT=armv7-a
TARGET_CPU_VARIANT=generic
TARGET_2ND_ARCH=
TARGET_2ND_ARCH_VARIANT=
TARGET_2ND_CPU_VARIANT=
HOST_ARCH=x86_64
HOST_OS=darwin
HOST_OS_EXTRA=Darwin-16.0.0-x86_64-i386-64bit
HOST_BUILD_TYPE=release
BUILD_ID=MRA58K
OUT_DIR=out
============================================
host C++: aapt <= frameworks/base/tools/aapt/Main.cpp
host Executable: aapt (out/host/darwin-x86/obj/EXECUTABLES/aapt_intermediates/aapt)
clang: warning: argument unused during compilation: '-pie'
Install: out/host/darwin-x86/bin/aapt\e[0;32m#### make completed successfully (3 seconds) ####\e[00m

生产的文件为aapt，在’android-6.0.0_r1/out/host/darwin-x86/bin/’目录中。
将aapt拷贝到指定目录，进入PluginDemo工程目录，使用aapt对工程进行资源打包，执行的命令如下：

../../../devTools/aapt/aapt package -f -m --apk-module 0x8f -J gen -S res -M AndroidManifest.xml -I ../../../devTools/android/android-sdk-macosx/platforms/android-23
/android.jar -F build/out/res.ap_

该命令执行失败，某个资源id找不到对应的资源。错误信息：

res/layout/xxx.xml:9: error: Error: No resource found that matches the given name (at 'text' with value '@string/xxx').

搜索相关的博客，在区长的专栏的Android aapt实现资源分区（补充携程aapt源码）这篇博客找到了出错的原因和解决方法。

继续看代码，

bool ResTable::stringToValue(Res_value* outValue, String16* outString,const char16_t* s, size_t len,bool preserveSpaces, bool coerceType,uint32_t attrID,const String16* defType,const String16* defPackage,Accessor* accessor,void* accessorCookie,uint32_t attrType,bool enforcePrivate) const
{...if (*s == '@') {if (accessor) {uint32_t rid = accessor->getCustomResourceWithCreation(package, type, name,createIfNotFound);if (rid != 0) {if (kDebugTableNoisy) {ALOGI("Pckg %s:%s/%s: 0x%08x\n",String8(package).string(), String8(type).string(),String8(name).string(), rid);}uint32_t packageId = Res_GETPACKAGE(rid) + 1;if (packageId == 0x00) {outValue->data = rid;outValue->dataType = Res_value::TYPE_DYNAMIC_REFERENCE;return true;} else if (packageId == APP_PACKAGE_ID || packageId == SYS_PACKAGE_ID ) {// We accept packageId's generated as 0x01 in order to support// building the android system resourcesoutValue->data = rid;return true;}}}}if (accessor != NULL) {accessor->reportError(accessorCookie, "No resource found that matches the given name");}return false;}...
}

在if(accessor)代码中对packageId进行验证。如果packageId不是ResourceTable构造函数中设置的3种类型，则出错，无法生成R.java文件和资源包。需要将ResourceTable构造函数中设置的packageId值存储下来，并在if (packageId == APP_PACKAGE_ID || packageId == SYS_PACKAGE_ID )添加一个自定义id判断。

按照区长的博客添加头文件和cpp文件，并添加相应的代码。具体的代码请查看Android aapt实现资源分区（补充携程aapt源码）博客，本文不再写出。
1，创建文件
创建Help.h文件，存放在android-6.0.0_r1/frameworks/base/include/androidfw/。
创建Help.cpp文件，存放在android-6.0.0_r1/frameworks/base/libs/androidfw/。并将Help.cpp添加到android-6.0.0_r1/frameworks/base/libs/androidfw/Android.mk文件。
2，修改代码
在ResourceTable::ResourceTable()函数判断和设置自定义id代码后面添加使用Help记录packageId代码。
在ResTable::stringToValue()函数中添加对Help中记录的packageId判断代码。

重新编译aapt模块，获取新生成的aapt可执行文件。再次运行生成R.java和资源打包命令（与之前的命令相同），成功运行。

生成的R.java文件内容

package com.plugin.test;public final class R {public static final class attr {}public static final class drawable {public static final int p_icon_play=0x8f020000;}public static final class id {public static final int activity_main=0x8f070000;}public static final class layout {public static final int plugin_item=0x8f040000;}public static final class mipmap {public static final int p_icon_lock=0x8f030000;}public static final class string {public static final int app_name=0x8f050000;public static final int p_str=0x8f050001;}public static final class style {public static final int AppBaseTheme=0x8f060000;public static final int AppTheme=0x8f060001;}
}

不再是原来系统默认的0x7f，都是自定义的0x8f。

继续执行命令编译代码，将class转换为dex，并将dex和资源包合并生成的apk。对apk签名，运行apk。apk正常运行