android safe mode..

在 framework/base/service/com/android/server/wm/WindowManagerService.java:

    public boolean detectSafeMode() {
        if (!mInputMonitor.waitForInputDevicesReady(
                INPUT_DEVICES_READY_FOR_SAFE_MODE_DETECTION_TIMEOUT_MILLIS)) {
            Slog.w(TAG, "Devices still not ready after waiting "
                   + INPUT_DEVICES_READY_FOR_SAFE_MODE_DETECTION_TIMEOUT_MILLIS
                   + " milliseconds before attempting to detect safe mode.");
        }

        int menuState = mInputManager.getKeyCodeState(-1, InputDevice.SOURCE_ANY,
                KeyEvent.KEYCODE_MENU);
        int sState = mInputManager.getKeyCodeState(-1, InputDevice.SOURCE_ANY, KeyEvent.KEYCODE_S);
        int dpadState = mInputManager.getKeyCodeState(-1, InputDevice.SOURCE_DPAD,
                KeyEvent.KEYCODE_DPAD_CENTER);
        int trackballState = mInputManager.getScanCodeState(-1, InputDevice.SOURCE_TRACKBALL,
                InputManagerService.BTN_MOUSE);
        int volumeDownState = mInputManager.getKeyCodeState(-1, InputDevice.SOURCE_ANY,
                KeyEvent.KEYCODE_VOLUME_DOWN);
        mSafeMode = menuState > 0 || sState > 0 || dpadState > 0 || trackballState > 0
                || volumeDownState > 0;
        try {
            if (SystemProperties.getInt(ShutdownThread.REBOOT_SAFEMODE_PROPERTY, 0) != 0) {
                mSafeMode = true;
                SystemProperties.set(ShutdownThread.REBOOT_SAFEMODE_PROPERTY, "");
            }
        } catch (IllegalArgumentException e) {
        }
        if (mSafeMode) {
            Log.i(TAG, "SAFE MODE ENABLED (menu=" + menuState + " s=" + sState
                    + " dpad=" + dpadState + " trackball=" + trackballState + ")");
        } else {
            Log.i(TAG, "SAFE MODE not enabled");
        }
        mPolicy.setSafeMode(mSafeMode);
        return mSafeMode;
    }

所以有很多方式(按鍵)進入 safemode:

• menu button
• dpad (?) button
• mouse button
• volume down

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ref:https://www.asus.com/tw/support/faq/1005163