android – Preventing status bar expansion-ThrowExceptions

Exception or error:

Is there anyway to prevent users from sliding the status bar (expand) or collapsing back?

I’m trying out a lockscreen replacement and seems like it’s a must-have feature. Is there any possible way to do it without requiring root privileges?

How to solve:

You can actually prevent the status bar from expanding, without rooting phone. See this link. This draws a window the height of the status bar and consumes all touch events.

Call the following code just after onCreate().

public static void preventStatusBarExpansion(Context context) {
    WindowManager manager = ((WindowManager) context.getApplicationContext()
            .getSystemService(Context.WINDOW_SERVICE));

    Activity activity = (Activity)context;
    WindowManager.LayoutParams localLayoutParams = new WindowManager.LayoutParams();
    localLayoutParams.type = WindowManager.LayoutParams.TYPE_SYSTEM_ERROR;
    localLayoutParams.gravity = Gravity.TOP;
    localLayoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE|

    // this is to enable the notification to recieve touch events
    WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL |

    // Draws over status bar
    WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN;

    localLayoutParams.width = WindowManager.LayoutParams.MATCH_PARENT;
    //https://stackoverflow.com/questions/1016896/get-screen-dimensions-in-pixels
    int resId = activity.getResources().getIdentifier("status_bar_height", "dimen", "android");
    int result = 0;
    if (resId > 0) {
        result = activity.getResources().getDimensionPixelSize(resId);
    }

    localLayoutParams.height = result;

    localLayoutParams.format = PixelFormat.TRANSPARENT;

    customViewGroup view = new customViewGroup(context);

    manager.addView(view, localLayoutParams);
}

public static class customViewGroup extends ViewGroup {

    public customViewGroup(Context context) {
        super(context);
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        Log.v("customViewGroup", "**********Intercepted");
        return true;
    }
}

###

Short answer: this is impossible!

Now should you be interested to know why this is impossible:

There are two permissions for manipulating the system status bar, EXPAND_STATUS_BAR and STATUS_BAR. The former can be requested by any application, but the later is reserved for applications signed with the platform signature (system applications, not third-party). It is possible to expand/ collapse the system status bar (see “How to open or expand status bar through intent?”) but note that reflection is required because the StatusBarManager class is not part of the SDK. The disable method, which is used by the Android dialer to prevent the status bar from being expanded, cannot be accessed by an application without the aforementioned STATUS_BAR permission.

Sources: personal experience 🙂

###

First of all, it’s impossible to modify the Status Bar if your app is not signed with the phone’s rom certified, if you try to modify it you’ll get an Security Exception.

Update: In new APIs the method is “collapsePanels” instead of “collapse”.

The only way I’ve found after several hours of work is by overriding the “onWindowFocusChanged” method of the activity and when it loses the focus (maybe the user has touched the notifications bar), force to collapse the StatusBar, here is the code (working on a Defy+ 2.3.5).

You need to declare the following permission on the manifest:

 <uses-permission android:name="android.permission.EXPAND_STATUS_BAR"/> 

And override the following method:

public void onWindowFocusChanged(boolean hasFocus)
{
        try
        {
           if(!hasFocus)
           {
                Object service  = getSystemService("statusbar");
                Class<?> statusbarManager = Class.forName("android.app.StatusBarManager");
                Method collapse = statusbarManager.getMethod("collapse");
                collapse .setAccessible(true);
                collapse .invoke(service);
           }
        }
        catch(Exception ex)
        {
        }
}

Update: You will have to use your own custom Alert Dialog by overriding it their onWindowFocusChanged method too, because Alert Dialogs have their own focus.

###

This actually can be done via a little hack that I accidentally discovered, but requires the permission android.permission.SYSTEM_ALERT_WINDOW:

What you do is add a view the exact size of the status bar directly to the WindowManager with the certain parameters that covers the status bar and prevents it from receiving touch events:

View disableStatusBarView = new View(context);

WindowManager.LayoutParams handleParams = new WindowManager.LayoutParams(
    WindowManager.LayoutParams.FILL_PARENT,
    <height of the status bar>,
    // This allows the view to be displayed over the status bar
    WindowManager.LayoutParams.TYPE_SYSTEM_ALERT,
    // this is to keep button presses going to the background window
    WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE |
    // this is to enable the notification to recieve touch events
    WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL |
    // Draws over status bar
    WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN,
    PixelFormat.TRANSLUCENT);

handleParams.gravity = Gravity.TOP;
context.getWindow().addView(disableStatusBarView, handleParams);

This will basically create a transparent view over the status bar that will receive all the touch events and block the events from reaching the status bar and therefore prevents it from being expanded.

NOTE: This code is untested, but the concept works.

###

I tried the solutions mentioned by GrantLand and PoOk but both didn’t work in my case. Though, Another solution Clear/Hide Recent Tasks List did the trick for me. I am writing a launcher app for which I had to disable a recent applications menu so user cannot open a locked app from it. Also, I had to prevent against notification bar expansion and this trick made me achieve both. Override OnWindowFocusChanged method in your activity and check if this is what u wanted.

public void onWindowFocusChanged(boolean hasFocus) {
    super.onWindowFocusChanged(hasFocus);

        Log.d("Focus debug", "Focus changed !");

    if(!hasFocus) {
        Log.d("Focus debug", "Lost focus !");

        Intent closeDialog = new Intent(Intent.ACTION_CLOSE_SYSTEM_DIALOGS);
        sendBroadcast(closeDialog);
    }
}

###

For a lockscreen Why don’t you just use the following in your main activity:

@Override
public void onAttachedToWindow() {
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD);
}

If the user doesn’t have a secure lockscreen set the app will let the user pull the status bar down and open activities but that doesn’t matter as the user obviously doesn’t want a secure screen anyway.

If the user does have a secure locksreen set then the app will show the status bar but will not allow interactions with it. This is because the phone is still actually locked and only your activity is allowed to operate until the user unlocks the phone. Also closing your app in anyway will open the standard secure lockscreen. All this is highly desirable because you don’t have to spend all that time coding secure features that you can’t guarantee will be as secure as the stock ones.

If you really don’t want the user to be able to interact with the status bar, maybe you can leave out the flag FLAG_DISMISS_KEYGUARD call. Then just before you are about to unlock the phone set the flag like I showed in the first block. I don’t know if this last part works but it’s worth a try.

Hope that helps

###

Sorry but it does not work. using FLAG_LAYOUT_IN_SCREEN prevents you from catching any touch events.

And BTW:
to add a view to the window use the window manager:

WindowManager winMgr = (WindowManager)getSystemService(WINDOW_SERVICE);
winMgr.addView(disableStatusBar, handleParams); 

###

requestWindowFeature(Window.FEATURE_NO_TITLE);

getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                            WindowManager.LayoutParams.FLAG_FULLSCREEN);

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