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USB充电插拔与USB Debugging connect提示
在 packages/apps/Settings/src/com/android/settings/DevelopmentSettings.java 找到关于 USB Debug Enable 的代码:
Java代码
- Settings.Secure.putInt(getContentResolver(), Settings.Secure.ADB_ENABLED,0);
此文件中,将根据用户设置将其值保存到 Settings 数据库中。别处将根据其值动态变化做出相应动作
经搜索,在 frameworks/base/services/java/com/android/server/NotificationManagerService.java 中存在利用该值判断是否在状态栏中进行通知。代码如下:
别处将根据其值动态变化做出相应动作如状态栏消息提示。
Java代码
- void observe() {
- ContentResolver resolver = mContext.getContentResolver();
- resolver.registerContentObserver(Settings.Secure.getUriFor(
- Settings.Secure.ADB_ENABLED), false, this);
- update();
- }
- @Override public void onChange(boolean selfChange) {
- update();
- }
- public void update() {
- ContentResolver resolver = mContext.getContentResolver();
- mAdbEnabled = Settings.Secure.getInt(resolver,
- Settings.Secure.ADB_ENABLED, 0) !=0;
- updateAdbNotification();
- }
当激活时,在状态栏中给出通知提示:
C-sharp代码
- notificationManager.notify(
- com.android.internal.R.string.adb_active_notification_title,
- mAdbNotification);
通知的内容在资源字符串(英文)在字符串资源文件 frameworks/base/core/res/res/values/strings.xml 中,定义如下:
Xhtml代码
- <!-- Title of notification shown when ADB is actively connected to the phone. -->
- <stringname="adbactivenotificationtitle">USB debugging connected</string>
- <!-- Message of notification shown when ADB is actively connected to the phone. -->
- <stringname="adbactivenotificationmessage">A computer is connected to your phone.</string>
改变该 Settings 值将通过如下方式影响到实际使用:
在文件中 frameworks/base/services/java/com/android/server/SystemServer.java
Java代码
- private class AdbSettingsObserver extends ContentObserver {
- public AdbSettingsObserver() {
- super(null);
- }
- @Override
- public void onChange(boolean selfChange) {
- boolean enableAdb = (Settings.Secure.getInt(mContentResolver,
- Settings.Secure.ADB_ENABLED, 0) > 0);
- // setting this secure property will start or stop adbd
- SystemProperties.set("persist.service.adb.enable", enableAdb ? "1" : "0");
- }
- }
可见,当设置系统属性 persist.service.adb.enable 的值时,将影响到 adbd 守护进程相应动作 ( 停止和开启 ) ,这将影响到是否查看 log 等供开发者使用的 adb 功能。
Bug 案例分析:
Java代码
- private void updateAdbNotification() {
- Log.d(TAG, "2. mBatteryPlugged="+mBatteryPlugged);
- if (mAdbEnabled && mBatteryPlugged == BatteryManager.BATTERYPLUGGEDUSB) {
- Log.d(TAG, "adb enabled, Battery Plugged usb");
- if ("0".equals(SystemProperties.get("persist.adb.notify"))) {
- Log.d(TAG, "return directly");
- return;
- }
- if (!mAdbNotificationShown) {
- //…省略部分代码
- mAdbNotificationShown = true;
- notificationManager.notify(
- com.android.internal.R.string.adb_active_notification_title,
- mAdbNotification);
- }
- }
- } else if (mAdbNotificationShown) {
- //…省略部分代码
- mAdbNotificationShown = false;
- notificationManager.cancel(
- com.android.internal.R.string.adb_active_notification_title);
- }
- }
- }
症状:当插上 USB 线与 PC 相连再拔掉时,才显示“ USB Debugging connected ”
分析:通过上述介绍的代码搜索,只有 NotificationManagerService.java 才会出现此提示,也就是说只要当监测到用户修改 Settings 中的设置值时和接收到 intent (即 usb 插拔充电)时才会调用 updateAdbNotification() 函数:
log信息:
Xhtml代码
- D/NotificationService( 1557): mBatteryPlugged=1
- D/NotificationService( 1557): 2. mBatteryPlugged=1
- D/NotificationService( 1557): mBatteryPlugged=1
- D/NotificationService( 1557): 2. mBatteryPlugged=1
- D/NotificationService( 1557): mBatteryPlugged=2
- D/NotificationService( 1557): 2. mBatteryPlugged=2
- D/NotificationService( 1557): adb enabled, Battery Plugged usb
- D/NotificationService( 1557): adb show notification
- D/NotificationService( 1557): mBatteryPlugged=0
- D/NotificationService( 1557): 2. mBatteryPlugged=0
- D/NotificationService( 1557): adb cancel notification
- D/NotificationService( 1557): mBatteryPlugged=0
- D/NotificationService( 1557): 2. mBatteryPlugged=0
结合 log 看出, mBatteryPlugged 在usb线连上时 为 1 (即 BATTERY_PLUGGED_AC ,不是2即 BatteryManager.BATTERY_PLUGGED_USB )而不能进入,在拔掉瞬间为 2 ,则发出提示;在拔掉之后为0。
mBatteryPlugged 的值来自于 Intent :
Java代码
- mBatteryPlugged = intent.getIntExtra("plugged",0);
- updateAdbNotification();
它发起于下面代码(见文件 frameworks/base/services/java/com/android/server/BatteryService.java )
C-sharp代码
- private synchronized final void update() {
- native_update();//JNI层去读取各种值
- boolean logOutlier = false;
- long dischargeDuration = 0;
- mBatteryLevelCritical = mBatteryLevel <= CRITICAL_BATTERY_LEVEL;
- if (mAcOnline) {
- mPlugType = BatteryManager.BATTERY_PLUGGED_AC;
- } else if (mUsbOnline) {
- mPlugType = BatteryManager.BATTERY_PLUGGED_USB;
- } else {
- mPlugType = BATTERY_PLUGGED_NONE;
- }
在文件中 com_android_server_BatteryService.cpp 中,函数:
Java代码
- static void android_server_BatteryService_update(JNIEnv* env, jobject obj)
会从 sys 系统下读取需要的值:
C-sharp代码
- #define AC_ONLINE_PATH "/sys/class/power_supply/ac/online"
- #define USB_ONLINE_PATH "/sys/class/power_supply/usb/online"
- #define BATTERY_STATUS_PATH "/sys/class/power_supply/battery/status"
- #define BATTERY_HEALTH_PATH "/sys/class/power_supply/battery/health"
- #define BATTERY_PRESENT_PATH "/sys/class/power_supply/battery/present"
- #define BATTERY_CAPACITY_PATH "/sys/class/power_supply/battery/capacity"
- #define BATTERY_VOLTAGE_PATH "/sys/class/power_supply/battery/batt_vol"
- #define BATTERY_TEMPERATURE_PATH "/sys/class/power_supply/battery/batt_temp"
- #define BATTERY_TECHNOLOGY_PATH "/sys/class/power_supply/battery/technology"
其中前 2 项标明了是 AC 还是 USB 充电。
因此,问题产生在系统底层识别 usb 充电信息错误,导致错误的时刻去显示 USB Debugging connect 信息。
总结:
当系统的 BatteryService ( BatteryService.java )调用 JNI 层( com_android_server_BatteryService.cpp ),通过 sys 系统文件获得充电(如 usb 充电)及电池信息,然后通过 intent 发送出去。 NotificationManagerService.java 在接收到广播信息后,分析是 usb 充电则采取相应的提示信息。
另外, NotificationManagerService 还监听着 Settings 里用户是否修改了设置的值,采取相应动作(是否更新提示信息、是否停掉或开启 adbd 守护进程等)。