How does android4.x handle power buttons?

Document directory

•  
• 3.1 message timeout Process
• 3.2 reboot system call Process

1. Introduction

Android4.x processes the power (keyevent. keycode_power) and home (keyevent. keycode_home) keys in phonewindowmanager of the framework and does not transmit these keys to upper-layer applications. If you need to send these keys to activity and service, you need to "Send a broadcast when phonewindowmanager processes these keys, and then process them after the application receives the broadcast ".

If the application only needs to obtain the standby, wake-up, shutdown, and network status change messages, you can listen to the following broadcast messages:
1) Standby:
Broadcast message: Android. Intent. Action. screen_off (CODE)
2) Wake up:
Broadcast message: Android. Intent. Action. screen_on (CODE)
3) shutdown:
Broadcast message: Android. Intent. Action. action_shutdown (XML or code)
4) network status changes:
Broadcast message: android.net. Conn. connectivity_change (XML or code)
Then, call the following isnetworkavailable to obtain the current network status.
Public static Boolean isnetworkavailable (context ){

Connectivitymanager Mgr = (connectivitymanager) Context
. Getsystemservice (context. connectivity_service );
Networkinfo [] info = Mgr. getallnetworkinfo ();
If (info! = NULL ){
For (INT I = 0; I <info. length; I ++ ){
If (info [I]. getstate () = networkinfo. state. Connected ){
Return true;
}
}
}
Return false;
}

2. Short Press key processing process

The short press power key processing process is shown in:

3. process long press the power key

The process of long press the power key is shown in:

 

3.1 message timeout Process

If you press the power key (more than 500 ms), the message (message. Callback is mpowerlongpress) will be executed. Mpowerlongpress (phonewindowmanager. Java) is defined as follows:

    private final Runnable mPowerLongPress = new Runnable() {        public void run() {            // The context isn't read            if (mLongPressOnPowerBehavior < 0) {                mLongPressOnPowerBehavior = mContext.getResources().getInteger(                        com.android.internal.R.integer.config_longPressOnPowerBehavior);            }            switch (mLongPressOnPowerBehavior) {            case LONG_PRESS_POWER_NOTHING:                break;            case LONG_PRESS_POWER_GLOBAL_ACTIONS:                mPowerKeyHandled = true;                performHapticFeedbackLw(null, HapticFeedbackConstants.LONG_PRESS, false);                sendCloseSystemWindows(SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS);                showGlobalActionsDialog();                break;            case LONG_PRESS_POWER_SHUT_OFF:                mPowerKeyHandled = true;                performHapticFeedbackLw(null, HapticFeedbackConstants.LONG_PRESS, false);                sendCloseSystemWindows(SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS);                ShutdownThread.shutdown(mContext, true);                break;            }        }    };

It is an anonymous internal class, it is an object reference of the class implementing runnable, so

New runnable (){

Public void run (){

...

}

};

It includes the objects that define this class (except that this class has no name) and instantiate this class.

When timeout occurs, the execution process is shown in:

3.2 reboot system call Process

Shows the reboot system call process:

 

4. How to Deal with short and long power keys

Long press the power key: the shutdown confirmation dialog box is displayed. (After keydown, if keyup is not received within ms, the shutdown confirmation dialog box is displayed)

Short press the power key: Run <wmactions = 4> During keyup or wake up (run <wmactions = 2> During keydown)

For long-pressed power keys, the interceptkeybeforequeueing function of phonewindowmanager. Java is used for processing. The related code is as follows:

            case KeyEvent.KEYCODE_POWER: {                result &= ~ACTION_PASS_TO_USER;                if (down) {                    if (isScreenOn && !mPowerKeyTriggered                            && (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) {                        mPowerKeyTriggered = true;                        mPowerKeyTime = event.getDownTime();                        interceptScreenshotChord();                    }                                       ...                    // Power Key down, set mPowerLongPress executing after 500ms                    interceptPowerKeyDown(!isScreenOn || hungUp                            || mVolumeDownKeyTriggered || mVolumeUpKeyTriggered);                } else {                    mPowerKeyTriggered = false;                    cancelPendingScreenshotChordAction();                    if (interceptPowerKeyUp(canceled || mPendingPowerKeyUpCanceled)) {                        result = (result & ~ACTION_POKE_USER_ACTIVITY) | ACTION_GO_TO_SLEEP;                    }                    // Power key up, remove the mPowerLongPress, that is, if user release                    // power key during 500ms, mPowerLongPress will not be execute, then execute sleep                    mPendingPowerKeyUpCanceled = false;                }                break;            }

    private void interceptPowerKeyDown(boolean handled) {        mPowerKeyHandled = handled;        if (!handled) {            mHandler.postDelayed(mPowerLongPress, ViewConfiguration.getGlobalActionKeyTimeout()/*500ms*/);        }    }    private boolean interceptPowerKeyUp(boolean canceled) {        if (!mPowerKeyHandled) {            mHandler.removeCallbacks(mPowerLongPress);            return !canceled;        }        return false;    }