Andriod启动过程中是如何正确加载.kl和.kcm的键盘布局文件？本文就从Honeycomb代码入手，详细介绍开机启动时键盘布局文件的加载过程。
Honeycom相较与之前的版本，加入了一个.idc后缀的配置文件，使在不修改系统代码的前提下，我们就可以使用自定义的键盘布局文件，系统中与键盘布局相关的目录为/system/usr/keychars，/system/usr/keylayout，/system/usr/idc
一、系统启动过程中SystemServer添加WindowManagerService
Slog.i(TAG, "Window Manager");
wm = WindowManagerService.main(context, power,
factoryTest != SystemServer.FACTORY_TEST_LOW_LEVEL);
ServiceManager.addService(Context.WINDOW_SERVICE, wm);
((ActivityManagerService)ServiceManager.getService("activity"))
.setWindowManager(wm);
二、WindowManagerService.java的构造函数，在加载键盘布局方面做了两件事情：1.初始化，构造一个InputManager实例；2.启动，由InputManager.java start()函数实现
private WindowManagerService(Context context, PowerManagerService pm,
……..
……..
mInputManager = new InputManager(context, this); //构造InputManager实例
PolicyThread thr = new PolicyThread(mPolicy, this, context, pm);
thr.start();
synchronized (thr) {
while (!thr.mRunning) {
try {
thr.wait();
} catch (InterruptedException e) {
}
}
}
mInputManager.start(); //调用InputManager.java start()函数
// Add ourself to the Watchdog monitors.
Watchdog.getInstance().addMonitor(this);
}
三、InputManager.java是本地c代码的包装类，对com_android_server_InputManager.cpp接口函数进行包装，以提供其他java文件调取。
1.初始化，InputManager.java构造函数中的init()最后调用nativeInit(mCallbacks)，
public InputManager(Context context, WindowManagerService windowManagerService) {
this.mContext = context;
this.mWindowManagerService = windowManagerService;
this.mCallbacks = new Callbacks();
init(); //调用init()函数
}
private void init() {
Slog.i(TAG, "Initializing input manager");
nativeInit(mCallbacks); //java接口，由本地函数实现
}
2. 启动，InputManager.java的start()最后调用nativeStart()：
public void start() {
Slog.i(TAG, "Starting input manager");
nativeStart(); //java接口，由本地函数实现
}
四、com_android_server_InputManager.cpp实现InutManager.java的nativeInit(mCallbacks和nativeStart()，当然还实现了其他功能的接口函数，这里不再介绍，对于android如何实现java和c之间的转换，我想对于了解jni的来说不难理解。不懂的可以看此文章学习：http://hi.baidu.com/kellyvivian/blog/item/09cfb541179d2f3387947397.html
1.初始化，android_server_InputManager_nativeInit在被执行的时候会new一个NativeInputManager(callbacks)实例，NativeInputManager(callbacks)接着又会new一个InputManager(eventHub, this, this)实例
static void android_server_InputManager_nativeInit(JNIEnv* env, jclass clazz,
jobject callbacks) {
if (gNativeInputManager == NULL) {
gNativeInputManager = new NativeInputManager(callbacks);
} else {
LOGE("Input manager already initialized.");
jniThrowRuntimeException(env, "Input manager already initialized.");
}
}
NativeInputManager::NativeInputManager(jobject callbacksObj) :
mFilterTouchEvents(-1), mFilterJumpyTouchEvents(-1), mVirtualKeyQuietTime(-1),
mMaxEventsPerSecond(-1) {
JNIEnv* env = jniEnv();
mCallbacksObj = env->NewGlobalRef(callbacksObj);
…….
sp eventHub = new EventHub();
mInputManager = new InputManager(eventHub, this, this);
}
2.启动，android_server_InputManager_nativeStart中gNativeInputManager->getInputManager()->start()最终调用的是InputManager.cpp的start()函数
static void android_server_InputManager_nativeStart(JNIEnv* env, jclass clazz) {
if (checkInputManagerUnitialized(env)) {
return;
}
status_t result = gNativeInputManager->getInputManager()->start();
if (result) {
jniThrowRuntimeException(env, "Input manager could not be started.");
}
}
五、InputManager.cpp中主要有三个函数：initialize()初始化函数，在构造函数中调用；start()开启线程函数；stop()取消线程函数，在虚构函数中调用。
1.初始化，InputManager.cpp构造函数调用initialize()，期间new一个InputReaderThread线程
InputManager::InputManager(
const sp& eventHub,
const sp& readerPolicy,
const sp& dispatcherPolicy) {
mDispatcher = new InputDispatcher(dispatcherPolicy);
mReader = new InputReader(eventHub, readerPolicy, mDispatcher);
initialize();
}
void InputManager::initialize() {
mReaderThread = new InputReaderThread(mReader);
mDispatcherThread = new InputDispatcherThread(mDispatcher);
}
2.启动，mReaderThread->run("InputReader", PRIORITY_URGENT_DISPLAY)开启初始化时new的InputReaderThread线程
status_t InputManager::start() {
……..
result = mReaderThread->run("InputReader", PRIORITY_URGENT_DISPLAY);
if (result) {
LOGE("Could not start InputReader thread due to error %d.", result);
mDispatcherThread->requestExit();
return result;
}
return OK;
}
六、InputReader.cpp中定义了InputReaderThread类，继承于Thread类
1.初始化，InputReaderThread构造函数，初始化一个Thread类
InputReaderThread::InputReaderThread(const sp& reader) :
Thread( true), mReader(reader) {
}
2.启动，run启动线程，Thread run()方法又调用InputReaderThread 的虚函数threadLoop()，接着调用InputReader的loopOnce()方法，最后调用EventHub.cpp的getEvent(& rawEvent)方法
bool InputReaderThread::threadLoop() {
mReader->loopOnce();
return true;
}
void InputReader::loopOnce() {
RawEvent rawEvent;
mEventHub->getEvent(& rawEvent);
#if DEBUG_RAW_EVENTS
LOGD("Input event: device=%d type=0x%x scancode=%d keycode=%d value=%d",
rawEvent.deviceId, rawEvent.type, rawEvent.scanCode, rawEvent.keyCode,
rawEvent.value);
#endif
process(& rawEvent);
}
七、EventHub.cpp是android输入系统的硬件抽象层，维护输入设备的运行，包括Keyboard、 TouchScreen、TraceBall等。
EventHub.cpp中依次执行getEvent()–>openPlatformInput()–>scanDir(DEVICE_PATH)–> openDevice(devname)
bool EventHub::openPlatformInput(void) {
int res, fd;
………
// Reserve fd index 0 for inotify.
struct pollfd pollfd;
pollfd.fd = fd;
pollfd.events = POLLIN;
pollfd.revents = 0;
mFds.push(pollfd);
mDevices.push(NULL);
res = scanDir(DEVICE_PATH); //DEVICE_PATH = "/dev/input"
if(res < 0) {
LOGE("scan dir failed for %s\n", DEVICE_PATH);
}
return true;
}
int EventHub::scanDir(const char *dirname)
{
……
openDevice(devname);
}
closedir(dir);
return 0;
}
openDevice方法会打开/dev/input目录下的所有设备文件，读取name、version、id等设备信息，然后执行loadConfiguration()方法，如果键盘设备就会执行loadKeyMap()这个方法
int EventHub::openDevice(const char *devicePath) {
……
// Load the configuration file for the device.
loadConfiguration(device);
……
if ((device->classes & INPUT_DEVICE_CLASS_KEYBOARD) != 0) {
// Load the keymap for the device.
status_t status = loadKeyMap(device);
……
}
……
}
Honeycomb与之前版本不同之处是加入loadConfiguration()方法，它获取与当前设备驱动Vendor、Product、Version匹配的配置文件名，或者是Vendor、Product匹配的配置文件名，具体可查看Input.cpp中getInputDeviceConfigurationFilePathByDeviceIdentifie和getInputDeviceConfigurationFilePathByName方法。
如： kernel/ drivers/input/keyboard/atkbd.c键盘驱动中定义了 input_dev->id.vendor = 0×0001; input_dev->id.product = 0×0001; input_dev->id.version = 0xab41，那么与之对应的配置名为Vendor_0001_Product_0001_Version_ad41.idc，返回这个文件的全路径并赋值给device->configurationFile。如果/system/user/idc下存在此文件，接下来调用PropertyMap.cpp的load()方法解析该配置文件并将解析后的信息保存到device->configuration中。
void EventHub::loadConfiguration(Device* device) {
device->configurationFile = getInputDeviceConfigurationFilePathByDeviceIdentifier(
device->identifier, INPUT_DEVICE_CONFIGURATION_FILE_TYPE_CONFIGURATION);
if (device->configurationFile.isEmpty()) {
LOGD("No input device configuration file found for device ‘%s’.",
device->identifier.name.string());
} else {
status_t status = PropertyMap::load(device->configurationFile,
&device->configuration);
if (status) {
LOGE("Error loading input device configuration file for device ‘%s’. "
"Using default configuration.",
device->identifier.name.string());
}
}
}
EventHub.cpp中loadKeyMap又调用了Keyboard.cpp的KeyMap::load()方法
status_t EventHub::loadKeyMap(Device* device) {
return device->keyMap.load(device->identifier, device->configuration);
}
八、在Keyboard.cpp的load方法中，首先判断deviceConfiguration参数是否为空，deviceConfiguration的赋值就是上面loadConfiguration()方法所做的工作。
如果有.idc的配置文件，那么获取key为keyboard.layout的value给keyLayoutName和key为keyboard.characterMap的value给keyCharacterMapName，最后调用loadKeyLayout和loadKeyCharacterMap方法加载此键盘布局文件；如果没有对应的.idc配置文件，则deviceConfiguration为空，就会接着执行probeKeyMap(deviceIdenfifier, String8("Generic"))方法
status_t KeyMap::load(const InputDeviceIdentifier& deviceIdenfifier,
const PropertyMap* deviceConfiguration) {
// Use the configured key layout if available.
if (deviceConfiguration) {
String8 keyLayoutName;
if (deviceConfiguration->tryGetProperty(String8("keyboard.layout"),
keyLayoutName)) {
status_t status = loadKeyLayout(deviceIdenfifier, keyLayoutName);
if (status == NAME_NOT_FOUND) {
LOGE("Configuration for keyboard device ‘%s’ requested keyboard layout ‘%s’ but "
"it was not found.",
deviceIdenfifier.name.string(), keyLayoutName.string());
}
}
String8 keyCharacterMapName;
if (deviceConfiguration->tryGetProperty(String8("keyboard.characterMap"),
keyCharacterMapName)) {
status_t status = loadKeyCharacterMap(deviceIdenfifier, keyCharacterMapName);
if (status == NAME_NOT_FOUND) {
LOGE("Configuration for keyboard device ‘%s’ requested keyboard character "
"map ‘%s’ but it was not found.",
deviceIdenfifier.name.string(), keyLayoutName.string());
}
}
if (isComplete()) {
return OK;
}
}
……
if (probeKeyMap(deviceIdenfifier, String8("Generic"))) {
return OK;
}
……
}
probeKeyMap方法判断名为Gerneric的布局文件是否存在，若存在就会调用loadKeyLayout和loadKeyCharacterMap方法加载此键盘布局文件
bool KeyMap::probeKeyMap(const InputDeviceIdentifier& deviceIdentifier,
const String8& keyMapName) {
if (!haveKeyLayout()) {
loadKeyLayout(deviceIdentifier, keyMapName);
}
if (!haveKeyCharacterMap()) {
loadKeyCharacterMap(deviceIdentifier, keyMapName);
}
return isComplete();
}
至此，Android Honeycomb已经正确加载了键盘布局文件，那么我们如何定制和使用自己的键盘布局文件呢？
附件：qwerty.idc配置文件内容
# Copyright (C) 2010 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# Emulator keyboard configuration file #1.
#
touch.deviceType = touchScreen
touch.orientationAware = 1
keyboard.layout = qwerty
keyboard.characterMap = qwerty
keyboard.orientationAware = 1
keyboard.builtIn = 1
cursor.mode = navigation
cursor.orientationAware = 1
