在frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManger.java中定义了如下长按事件：
LONG_PRESS_POWER_ASSISTANT: 唤醒助手界面LONG_PRESS_POWER_GO_TO_VOICE_ASSIST: 唤醒语音助手LONG_PRESS_POWER_GLOBAL_ACTIONS: 弹出关机、重启等选项对话框LONG_PRESS_POWER_SHUT_OFF: 关闭所有窗口并关机
我们开机后连上adb，长按并读取调试信息：发现它默认的输出总是LONG_PRESS_POWER_ASSISTANT。我们选择将其注释，并移动到case LONG_PRESS_POWER_GLOBAL_ACTIONS:下，以实现长按弹出关机选项。如果想要实现直接关机，则可以移动到LONG_PRESS_POWER_SHUT_OFF的位置。
switch (behavior) {
case LONG_PRESS_POWER_NOTHING:
break;
case LONG_PRESS_POWER_GLOBAL_ACTIONS:
case LONG_PRESS_POWER_ASSISTANT:
mPowerKeyHandled = true;
performHapticFeedback(HapticFeedbackConstants.LONG_PRESS_POWER_BUTTON, false,
"Power - Long Press - Global Actions");
showGlobalActions();
break;
case LONG_PRESS_POWER_SHUT_OFF:
case LONG_PRESS_POWER_SHUT_OFF_NO_CONFIRM:
mPowerKeyHandled = true;
performHapticFeedback(HapticFeedbackConstants.LONG_PRESS_POWER_BUTTON, false,
"Power - Long Press - Shut Off");
sendCloseSystemWindows(SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS);
mWindowManagerFuncs.shutdown(behavior == LONG_PRESS_POWER_SHUT_OFF);
break;
case LONG_PRESS_POWER_GO_TO_VOICE_ASSIST:
mPowerKeyHandled = true;
performHapticFeedback(HapticFeedbackConstants.LONG_PRESS_POWER_BUTTON, false,
"Power - Long Press - Go To Voice Assist");
// Some devices allow the voice assistant intent during setup (and use that intent
// to launch something else, like Settings). So we explicitly allow that via the
// config_allowStartActivityForLongPressOnPowerInSetup resource in config.xml.
launchVoiceAssist(mAllowStartActivityForLongPressOnPowerDuringSetup);
break;
// case LONG_PRESS_POWER_ASSISTANT:
// mPowerKeyHandled = true;
// performHapticFeedback(HapticFeedbackConstants.ASSISTANT_BUTTON, false,
// "Power - Long Press - Go To Assistant");
// final int powerKeyDeviceId = Integer.MIN_VALUE;
// launchAssistAction(null, powerKeyDeviceId, eventTime,
// AssistUtils.INVOCATION_TYPE_POWER_BUTTON_LONG_PRESS);
// break;
}