(一)Lights应用层
SystemUI——系统应用,其主要功能:状态栏信息显示、通知面板、截图/壁纸/屏保服务等;
代码:
packages/apps/Settings/src/com/android/settings/BrightnessPreference.java
frameworks/base/packages/SystemUI/src/com/android/systemui/settings/BrightnessController.java
frameworks/base/packages/SystemUI/src/com/android/systemui/settings/BrightnessDialog.java
- 1)当用户点击BrightnessPreference的时候,有BrightnessPreference做对应处理
- onclick() 发送一个显示亮度对话框的广播
- 2)对广播进行注册并处理,在BrightnessDialog中初始化拖动条等相关控件
- 3)对亮度的调节使用BrightnessController类
*************************BrightnessController************************
- 获取设备的最大和最小亮度值、及亮度调节模式
- 设置屏幕亮度
//获取IPowerManager对象mPower= IPowerManager.Stub.asInterface(ServiceManager.getService("power"));//设置屏幕亮度private void setBrightness(int brightness) {try {mPower.setTemporaryScreenBrightnessSettingOverride(brightness);} catch (RemoteException ex) {}}
- 亮度值和亮度模式的读取和存储
setMode(int mode) //设置亮度模式,0表示手动,1表示自动Settings.System.putIntForUser() //通过此接口来存储mode及亮度值Settings.System.getIntForUser() //通过此接口来读取mode及亮度值
4)BrightnessController的监听机制
BrightnessController中有个内部类BrightnessObserver,继承自ContentObserverprivate class BrightnessObserver extends ContentObserver{…}
对ContentProvider中指定的URI进行监听,如果该URI对应的数据发生了变化就可以及时得到监听并处理。
BrightnessObserver主要监听:亮度调节模式、亮度值的变化;
当监听到uri发生变化时,回调onChange函数。
updateMode(); //更新模式
updateSlider(); //更新拖动条
(二)Lights服务接口
代码:
frameworks\base\core\java\android\os\IPowerManager.aidl
注:
android系统提供了一种描述语言来定义具有跨进程访问能力的服务接口,这种描述语言称为Android接口描述语言(Android Interface Definition Language, AIDL)。以AIDL定义的服务接口文件以aidl为后缀名,在编译时,编译系统会将它们转换成java文件,这是需要在\frameworks\base\Android.mk文件中添加对应的aidl文件,才会转换为java文件。
IPowerManager只是提供服务的接口,如:
interface IPowerManager{…// temporarily overrides the screen brightness settings to allow the user to// see the effect of a settings change without applying it immediatelyvoid setTemporaryScreenBrightnessSettingOverride(int brightness);void setTemporaryScreenAutoBrightnessAdjustmentSettingOverride(float adj);…}
具体实现在——>framework层
(三)Lights框架层(Framework)
(1)JAVA层
1)frameworks\base\core\java\android\os\PowerManager.java中,如下:public void setBacklightBrightness(int brightness) {try {mService.setTemporaryScreenBrightnessSettingOverride(brightness);} catch (RemoteException e) {}}
2)接着调用PowerManagerService的接口(注意:真正的系统调用在frameworks/base/services)
frameworks\base\services\java\com\android\server\PowerManagerService.java,如下: public void setTemporaryScreenBrightnessSettingOverride(int brightness) {mContext.enforceCallingOrSelfPermission(android.Manifest.permission.DEVICE_POWER, null);…}
3)frameworks\base\services\core\java\com\android\server\lights\LightsService.java
依次调用setBrightness()--->setLightLocked()--->setLight_native()
(2)Native层
【衔接底层c/c++库与Java应用程序间的接口正是JNI(Java Native Interface)】
而setLight_native是JNI接口函数,主要在jni下实现,如:
frameworks\base\services\core\jni\com_android_server_lights_LightsService.cpp而在JNI层中会init一个native,其中又会引用HAL层,具体如下:HAL层调用:devices->lights[light]->set_light(devices->lights[light],&state);
(四)Lights本地层(HAL-硬件抽象层)
首先记住几个重要的结构体:
在hardware\libhardware\include\hardware\lights.h下定义:light_state_t 、 light_device_t在hardware\libhardware\include\hardware\hardware.h下定义: hw_module_t、hw_device_t
具体实现:
hardware\qcom\display\liblight\lights.cstatic intopen_lights(const struct hw_module_t* module, char const* name, struct hw_device_t** device) static int
set_light_backlight(structlight_device_t* dev, struct light_state_t const* state)
其中set_light_backlight()把背光亮度值brightness写入/sys/class/leds/lcd-backlight/brightness文件中。(通过write_int(LCD_FILE, brightness);进行写入)然后LED驱动再读取此值,进行背光调节。
(五)Lights驱动层(Driver)
背光驱动提供的用于调节亮度接口是:/sys/class/leds/lcd-backlight/brightness。这个接口由LED驱动注册得来,源码位于Kernel/driver/leds/led-class.c中
上面,set_light_backlight()通过write()把背光值写入到/sys/class/leds/lcd-backlight/brightness文件后,会触发调用led_brightness_store函数,经过led_brightness_store() --->led_set_brightness()--->led_cdev->brightness_set(led_cdev,value)的调用流程,最后调用到xxx_led_set(),