几个编译问题：
1.XText.h
X11/extensions/XTest.h：没有那个文件或目录
编译中断。
sudo apt-get install xorg-dev
2.openssl.h
sudo apt-get install libssl-dev
3.SDL.h
sudo apt-get install libsdl1.2-dev
顺便看了看SDL的介绍：SDL是Simple DirectMedia Layer（简易直控媒体层）的缩写。它是一个跨平台的多媒体库，以用于直接控制底层的多媒体硬件的接口。主要用在开发游戏上。
以后有机会研究一下！
4.jack.h
sudo apt-get install libjack-dev
5.videodev.h
sudo apt-get install libv4l-dev; #注意这里是 libv4L 而不是 libv41；
可是，现在你继续安装，依然会出现上述错误。这是由于这样安装的 libv4L 库把头文件名称改为
/usr/include/libv4l1-videodev.h
等。知道了原因，解决办法也很简单，只需要把出错这行代码的 #include 头文件改掉，即把
#include <linux/videodev.h>
改为
#include <libv4l1-videodev.h>
或者创建一个软链接
sudo ln -s /usr/include/libv4l1-videodev.h /usr/include/linux/videodev.h
6. bzlib.h
sudo apt-get install libbz2-dev
7. faac.h
sudo apt-get install libfaac-dev
8. lame.h
sudo apt-get install liblame-dev
9. theoraenc.h:
sudo apt-get install libtheora-dev
10. x264.h
sudo apt-get install libx264-dev
11. xvidcore.h
sudo apt-get install libxvidcore-dev
12. vdpau.h
sudo apt-get install libvdpau-dev
sudo apt-get install yasm
作者：徐建祥(netpirate@gmail.com)
日期：2009/11/11
网址：http://www.anymobile.org
Android 的系统属性包括两部分：文件保存的持久属性和每次开机导入的cache属性。前者主要保存在下面几个文件中：
bionic/libc/include/sys/_system_properties.h 1 #define PROP_SERVICE_NAME "property_service"
2 #define PROP_PATH_RAMDISK_DEFAULT "/default.prop"
3 #define PROP_PATH_SYSTEM_BUILD "/system/build.prop"
4 #define PROP_PATH_SYSTEM_DEFAULT "/system/default.prop"
5 #define PROP_PATH_LOCAL_OVERRIDE "/data/local.prop"
后者则通过frameworks/base/core/java/android/os/SystemProperties.java的接口定义，
1 private static native String native_get(String key);
2 private static native String native_get(String key, String def);
3 private static native void native_set(String key, String def);
4 public static void set(String key, String val) {
5 if (key.length() > PROP_NAME_MAX) {
6 throw new IllegalArgumentException("key.length > " + PROP_NAME_MAX);
7 }
8 if (val != null && val.length() > PROP_VALUE_MAX) {
9 throw new IllegalArgumentException("val.length > " +
10 PROP_VALUE_MAX);
11 }
12 native_set(key, val);
13 }
该接口类在初始化运行环境中注册对应的cpp接口android_os_SystemProperties.cpp，实际操作通过JNI调用的是cpp文件对应的接口：
frameworks/base/core/jni/AndroidRuntime.cpp
1 namespace android {
2 extern int register_android_os_SystemProperties(JNIEnv *env);
3 }
frameworks/base/core/jni/android_os_SystemProperties.cpp
1 static void SystemProperties_set(JNIEnv *env, jobject clazz, jstring keyJ, jstring valJ)
2 {
3 int err;
4 const char* key;
5 const char* val;
6 key = env->GetStringUTFChars(keyJ, NULL);
7 if (valJ == NULL) {
8 val = ""; /* NULL pointer not allowed here */
9 } else {
10 val = env->GetStringUTFChars(valJ, NULL);
11 }
12 err = property_set(key, val);
13 env->ReleaseStringUTFChars(keyJ, key);
14 if (valJ != NULL) {
15 env->ReleaseStringUTFChars(valJ, val);
16 }
17 }
设置key的value时，需要作鉴权，根据设置程序所在进程的fd获知uid值，比如system server进程可以设置net打头的key，不可以设置gsm打头的key，相关的定义如下：
system/core/include/private/android_filesystem_config.h
1 #define AID_ROOT 0 /* traditional unix root user */
2 #define AID_SYSTEM 1000 /* system server */
3 #define AID_RADIO 1001 /* telephony subsystem, RIL */
4 #define AID_DHCP 1014 /* dhcp client */
5 #define AID_SHELL 2000 /* adb and debug shell user */
6 #define AID_CACHE 2001 /* cache access */
7 #define AID_APP 10000 /* first app user */
system/core/init/property_service.c
1 #define PERSISTENT_PROPERTY_DIR "/data/property"
2 struct {
3 const char *prefix;
4 unsigned int uid;
5 } property_perms[] = {
6 { "net.rmnet0.", AID_RADIO },
7 { "net.gprs.", AID_RADIO },
8 { "ril.", AID_RADIO },
9 { "gsm.", AID_RADIO },
10 { "net.dns", AID_RADIO },
11 { "net.usb0", AID_RADIO },
12 { "net.", AID_SYSTEM },
13 { "dev.", AID_SYSTEM },
14 { "runtime.", AID_SYSTEM },
15 { "hw.", AID_SYSTEM },
16 { "sys.", AID_SYSTEM },
17 { "service.", AID_SYSTEM },
18 { "wlan.", AID_SYSTEM },
19 { "dhcp.", AID_SYSTEM },
20 { "dhcp.", AID_DHCP },
21 { "debug.", AID_SHELL },
22 { "log.", AID_SHELL },
23 { "service.adb.root", AID_SHELL },
24 { "persist.sys.", AID_SYSTEM },
25 { "persist.service.", AID_SYSTEM },
26 { NULL, 0 }
27 };
28 int property_set(const char *name, const char *value)
29 {
30 property_changed(name, value);
31 return 0;
32 }
33 int start_property_service(void)
34 {
35 int fd;
36
37 load_properties_from_file(PROP_PATH_SYSTEM_BUILD);
38 load_properties_from_file(PROP_PATH_SYSTEM_DEFAULT);
39 load_properties_from_file(PROP_PATH_LOCAL_OVERRIDE);
40 /* Read persistent properties after all default values have been loaded. */
41 load_persistent_properties();
42
43 fd = create_socket(PROP_SERVICE_NAME, SOCK_STREAM, 0666, 0, 0);
44 if(fd < 0) return -1;
45 fcntl(fd, F_SETFD, FD_CLOEXEC);
46 fcntl(fd, F_SETFL, O_NONBLOCK);
47
48 listen(fd, 8);
49 return fd;
50 }
51 void handle_property_set_fd(int fd)
52 {
53 switch(msg.cmd) {
54 case PROP_MSG_SETPROP:
55 msg.name[PROP_NAME_MAX-1] = 0;
56 msg.value[PROP_VALUE_MAX-1] = 0;
57
58 if(memcmp(msg.name,"ctl.",4) == 0) {
59 if (check_control_perms(msg.value, cr.uid)) {
60 handle_control_message((char*) msg.name + 4, (char*) msg.value);
61 } else {
62 ERROR("sys_prop: Unable to %s service ctl [%s] uid: %d pid:%d\n",
63 msg.name + 4, msg.value, cr.uid, cr.pid);
64 }
65 } else {
66 if (check_perms(msg.name, cr.uid)) {
67 property_set((char*) msg.name, (char*) msg.value);
68 } else {
69 ERROR("sys_prop: permission denied uid:%d name:%s\n",
70 cr.uid, msg.name);
71 }
72 }
73 break;
74
75 default:
76 break;
77 }
78 }
在开机启动后的init操作中，会执行一个loop循环，当检测到有新的设置时，进入设置流程，鉴权失败会提示相关的异常，如sys_prop: permission denied uid:1000 name:gsm.phone.id
system/core/init/init.c
1 void property_changed(const char *name, const char *value)
2 {
3 if (property_triggers_enabled) {
4 queue_property_triggers(name, value);
5 drain_action_queue();
6 }
7 }
8 int main(int argc, char **argv)
9 {
10 parse_config_file("/init.rc");
11 qemu_init();
12 device_fd = device_init();
13 property_init();
14 fd = open(console_name, O_RDWR);
15 property_set_fd = start_property_service();
16 ufds[0].fd = device_fd;
17 ufds[0].events = POLLIN;
18 ufds[1].fd = property_set_fd;
19 ufds[1].events = POLLIN;
20 ufds[2].fd = signal_recv_fd;
21 ufds[2].events = POLLIN;
22 fd_count = 3;
23 for(;;) {
24 if (ufds[0].revents == POLLIN)
25 handle_device_fd(device_fd);
26
27 if (ufds[1].revents == POLLIN)
28 handle_property_set_fd(property_set_fd);
29 if (ufds[3].revents == POLLIN)
30 handle_keychord(keychord_fd);
31 }
32 return 0;
33 }
想给Androird JellyBean 4.1.0的framework里面添加一个res，把xml写好以后编译时候报错
int ticker = com.android.internal.R.string.xxxxxxxxxx;
^
frameworks/base/services/java/com/android/server/StatusBarManagerService.java:143: cannot find symbol
symbol : variable xxxxxxxxxx
location: class com.android.internal.R.drawable
解决办法很简单，在MakeJavaSymbols.sed里面有：
# Run this on the errors output by javac of missing resource symbols,
# to generate the set of <java-symbol> commands to have aapt generate
# the symbol for them.
#
#
For example: make framework 2>&1 | sed -n -f MakeJavaSymbols.sed | sort -u重新编译会产生
<java-symbol type="string" name="xxxxxxxxxx" />
把这个copy到publlic.xml。再重新编译一次就搞定了。
public.xml也提到
<!-- Private symbols that we need to reference from framework code. See
frameworks/base/core/res/MakeJavaSymbols.sed for how to easily generate
this.
-->
看起来所有private的internal res都必须在这里声明一下。JellyBean以前貌似没有这么麻烦。好在他提供了一个sed，免得全部手写。