如何为Android系统添加一个新的资源包

传统的Android系统只有一个framework-res.apk资源包，第三方厂商在进行rom定制时会直接修改framework-res资源，达到美化目的。但是这种方式跟原生资源的耦合度过高，在系统迁移或者framework ui移植时需要进行人工merge，工作量巨大。通过为Android添加一个新的独立的资源包，可以将厂商定制资源独立出来，可移植、可维护性非常好。

1. 修改build/core/clear_var.mk

LOCAL_USE_LETV_FRAMEWORK_RES:= true

2. 修改build/core/package.mk
以下脚本可以加在 $(R_file_stamp): $(framework_res_package_export_deps) 之前，然后修改$(R_file_stamp): $(framework_res_package_export_deps) 和 $(LOCAL_INTERMEDIATE_TARGETS): \
PRIVATE_AAPT_INCLUDES := $(framework_res_package_export)

如下所示：

ifeq ($(LOCAL_USE_LETV_FRAMEWORK_RES),true)
letv_framework_res_package_export := \
$(call intermediates-dir-for,APPS,letv-framework-res,,COMMON)/package-export.apk
letv_framework_res_package_export_deps := \
$(dir $(letv_framework_res_package_export))src/R.stamp
else
letv_framework_res_package_export :=
letv_framework_res_package_export_deps :=
endif # LOCAL_USE_LETV_FRAMEWORK_RES

$(R_file_stamp): $(framework_res_package_export_deps) $(letv_framework_res_package_export_deps)
$(LOCAL_INTERMEDIATE_TARGETS): \
PRIVATE_AAPT_INCLUDES := $(framework_res_package_export) \
$(letv_framework_res_package_export)
endif # LOCAL_NO_STANDARD_LIBRARIES

3. 修改build/target/product/core.mk
在PRODUCT_PACKAGES增加letv-framework-res

4. 添加一个新的资源包项目，这里在framework/base/core/res同级目录下建立一个新的文件夹letv_res用来存放我们的资源。把res目录下的AndroidManifest.xml和Android.mk拷贝过来，进行修改。
记得设置LOCAL_USE_MY_FRAMEWORK_RES为false。

LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)

LOCAL_MODULE_TAGS := optional

LOCAL_PACKAGE_NAME := letv-framework-res
LOCAL_CERTIFICATE := platform

# Set LOCAL_USE_LETV_FRAMEWORK_RES as false
LOCAL_USE_LETV_FRAMEWORK_RES := false

# Tell aapt to create "extending (non-application)" resource IDs,
# since these resources will be used by many apps.
LOCAL_AAPT_FLAGS := -x

# Install this alongside the libraries.
LOCAL_MODULE_PATH := $(TARGET_OUT_JAVA_LIBRARIES)

# Create package-export.apk, which other packages can use to get
# PRODUCT-agnostic resource data like IDs and type definitions.
LOCAL_EXPORT_PACKAGE_RESOURCES := true

# Include resources generated by system RenderScript files.
framework_GENERATED_SOURCE_DIR := $(call intermediates-dir-for,JAVA_LIBRARIES,framework,,COMMON)/src
framework_RenderScript_STAMP_FILE := $(framework_GENERATED_SOURCE_DIR)/RenderScript.stamp
#LOCAL_RESOURCE_DIR := $(framework_GENERATED_SOURCE_DIR)/renderscript/res $(LOCAL_PATH)/res

include $(BUILD_PACKAGE)

# Make sure the system .rs files get compiled before building the package-export.apk.
#$(resource_export_package): $(framework_RenderScript_STAMP_FILE)

# define a global intermediate target that other module may depend on.
.PHONY: letv-framework-res-package-target
letv-framework-res-package-target: $(LOCAL_BUILT_MODULE)

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="letv" coreApp="true" android:sharedUserId="android.uid.system"
android:sharedUserLabel="@null">

<application android:process="system"
android:persistent="true"
android:hasCode="false"
android:label="@null"
android:allowClearUserData="false"
android:killAfterRestore="false"
android:icon="@null">

</application>

</manifest>

资源的放置跟res下的类似，记得values目录下创建public.xml，public.xml对id的类型区分比较严格，attr必须是0x0x010000开头，drawable必须是0x0x020000开头，其他类型好像就没有限制，直接依次0x0x030000、0x0x040000开始即可。否则，编译过程中会出现segmentation fault错误。

<resources>
<public type="attr" name="cForeground" id="0x03010000" />
<public type="drawable" name="ic_filemanager" id="0x03020000" />
<public type="style" name="LetvTheme" id="0x03030000" />
<public type="string" name="letv" id="0x03040000" />
<public type="dimen" name="letv_width" id="0x03050000" />
<public type="layout" name="letv_text" id="0x03060000" />
</resources>

5.  以上只是解决了资源的编译环境问题，资源的查找过程也需要进行修改，修改 AssetManager.java，在init()后添加代码 addAssetPath("/system/framework/letv-framework-res.apk");

public AssetManager() {
synchronized (this) {
if (DEBUG_REFS) {
mNumRefs = 0;
incRefsLocked(this.hashCode());
}
init();
addAssetPath("/system/framework/letv-framework-res.apk");
if (localLOGV) Log.v(TAG, "New asset manager: " + this);
ensureSystemAssets();
}
}

6. 最后就是资源应用问题。应用程序在xml文件中引用letv-framework-res.apk中的资源时可以使用与原生资源类似的访问方式，首先声明letv xmlns :

xmlns:letv="http://schemas.android.com/apk/res/letv"

然后像@android:drawable @android:dimen这种引用方式改成@letv:drawable @letv:dimen即可。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:letv="http://schemas.android.com/apk/res/letv"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:paddingTop="@letv:dimen/letv_width"
android:orientation="horizontal" >

<ImageView android:id="@+id/file_icon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginBottom="40dp"
android:src="@letv:drawable/ic_filemanager" />

</LinearLayout>