Painting behind system bars using Qt/Qml

[J.Hilk]

Hello every one,

I spend a good amount of time this weekend to figure out how to paint correctly behind the Status/Navigation bar on Android/iOS devices to customize those areas or to simply extend components (images mostly) behind them.

I managed it and wanted to share my results, as I'm sure, its a feature some(many?) would like to know/have.

I have a git repository with an example application:
Git Repository

And I post the readme here as well

Greetings!

---

PaintBehindSystemBars

Have you ever wonndered how Apps like GooleMaps paint the map content behind the status and navigation bar?

Example GoogleMaps

This repository show how to expand your basic QML application, so that you can paint behind the system bars and how to know where the bars are, for iOS and Android.

Let's start with the easier of the two:

iOS

Inside your main.qml specify the window flag Qt.MaximizeUsingFullscreenGeometryHint

main.qml

flags:Qt.Window | Qt.WindowTitleHint | Qt.WindowSystemMenuHint | (Qt.platform.os === "ios" ? Qt.MaximizeUsingFullscreenGeometryHint : 0)

that will allow the Window root component to paint behinde the bars

Android

For Android the process is a bit more complicated. First of we need to expand QtActivity with our own class: MyActivity and set the window flags

WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS | WindowManager.LayoutParams.FLAG_TRANSLUCENT_NAVIGATION

Than we can set the status and navigation bar to a transparent color.

MyActivity.java

public class MyActivity extends QtActivity
{
    @Override
    public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setCustomStatusAndNavBar();
    } // onCreate

    void setCustomStatusAndNavBar() {
        //First check sdk version, custom/transparent System_bars are only available after LOLLIPOP
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            Window window = getWindow();

            //The Window flag 'FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS' will allow us to paint the background of the status bar ourself and automatically expand the canvas
            //If you want to simply set a custom background color for the navbar, use the following addFlags call
//            window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);

            //The Window flag 'FLAG_TRANSLUCENT_NAVIGATION' will allow us to paint the background of the navigation bar ourself
            //But we will also have to deal with orientation and OEM specifications, as the nav bar may or may not depend on the orientation of the device
            window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS | WindowManager.LayoutParams.FLAG_TRANSLUCENT_NAVIGATION);

            window.getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);

            //Set Statusbar Transparent
            window.setStatusBarColor(Color.TRANSPARENT);
            //Statusbar background is now transparent, but the icons and text are probably white and not really readable, as we have a bright background color
            //We set/force a light theme for the status bar to make those dark
            View decor = window.getDecorView();
            decor.setSystemUiVisibility(decor.getSystemUiVisibility() | View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR);

            //Set Navbar to desired color (0xAARRGGBB) set alpha value to 0 if you want a solid color
            window.setNavigationBarColor(0xFFD3D3D3);
        }
    }
}    

make sure to replace, inside the AndroidManifest.xml the reference to QtActivity with the extended class MyActivity
and to add 'com.android.support:appcompat-v7:25.3.1' to your build.gradle dependencies

Margins

In either iOS or Android you will want to know the new margins you will have to respect. Therefore I introcuded the class SafeArea

The iOS part makes use of a private class QPlatformWindow. To properly use this class this QT += gui-private needs to be added to your *.pro file

SafeArea.h

Q_INVOKABLE QVariantMap getSafeAreaMargins(QQuickWindow *window){
    QVariantMap map;
    QMargins margins;
#if !defined (Q_OS_ANDROID)
    QPlatformWindow *platformWindow = static_cast<QPlatformWindow *>(window->handle());
    if(!platformWindow)
        return QVariantMap();
    margins = platformWindow->safeAreaMargins();
#else
    ...
#endif
    map["top"] = margins.top();
    map["right"] = margins.right();
    map["bottom"] = margins.bottom();
    map["left"] = margins.left();

    return map;
}

Sadly QPlatformWindow has currently no support for Android, it may be added. You can follow the ticket here!
So for Android we have to go the extra mile and add a couple of Java functions, to call up on.

Previously we extended QtActivity in MyActivity.java.
We expand this class with the custom functions statusBarHeight, safeAreaTop getNavBarPosition to use inside SafeArea

MyActivity.java

/*If we decide to draw behind the statusbar, we need to know the new safea rea on top,
      to not draw text or position buttons behind the status bar.
      Those would be unclickable and potentially unreadable
      This function returns the hight of the statusbar */
    public double statusBarHeight() {
        double result = 0;
        int resourceId = getResources().getIdentifier("status_bar_height", "dimen", "android");
        if (resourceId > 0) {
            result = getResources().getDimension(resourceId);
        }

        return result;
    }

    public int safeAreaTop() {
        //For devices that have a display cutout, the cutout may be bigger than the statusbar height
        //See 'Tall cutout' setting on a device's Developer options
        //To compensate, fetch the SafeInset for the top and use the maximum of the safeInsert and the statusbarHeight as safe margin
        DisplayCutout cutout = getWindow().getDecorView().getRootWindowInsets().getDisplayCutout();
        if(cutout != null) {
            int cutoutHeight = cutout.getSafeInsetTop();
            if(cutoutHeight > 0)
                return cutoutHeight;
        }
        return 0;
    }

    /*If we decide to draw the behind the navbar, we need to know the new safearea,
      so to not draw text or position buttons behind the nav bar.
    Those would be unclickable and potentially unreadable.
    ATTENTION:
    Compared to the statusbar, there is no guarantee that the navbar will be at the bottom of your screen
    This function returns the hight of the Navigation bar */
    public double navBarHeight() {
        double result = 0;
        int resourceId = getResources().getIdentifier("navigation_bar_height", "dimen", "android");
        if (resourceId > 0) {
            result = getResources().getDimension(resourceId);
        }
        return result;
    }

    public int getNavBarPosition() {
        Resources res= getResources();
        int resourceId = res.getIdentifier("config_showNavigationBar", "bool", "android");
        boolean hasMenu = false;
        if (resourceId > 0)
            hasMenu =  res.getBoolean(resourceId);

        if(!hasMenu)
           return -1;

        Display display = getWindowManager().getDefaultDisplay();
        int rotation = display.getRotation();

        switch (rotation) {
            case Surface.ROTATION_90:
                return 1;
            case Surface.ROTATION_180:
                return 3;
            case Surface.ROTATION_270:
                return 2;
            default:
                return 0;
        }
    }

SafeArea.h

  Q_UNUSED(window)
  // We paint behind the Status bar -> StatusBar height is requiered
  const QAndroidJniObject activity = QtAndroid::androidActivity();
  double statusBarHeight = static_cast<double>(activity.callMethod<jdouble>("statusBarHeight"));
  statusBarHeight = qMax(statusBarHeight, static_cast<double>(activity.callMethod<jint>("safeAreaTop")));

  //!WARNING this function block does not yet deal with cutouts correctly, when the device is rotated

  //Since we have AA_EnableHighDpiScaling activated,
  //we will have to devide the returned value by the device pixel ratio, to use the value in QML
  static const double devicePixelRatio = QGuiApplication::primaryScreen()->devicePixelRatio();

  statusBarHeight /= devicePixelRatio;
  margins.setTop(statusBarHeight);

  const int navBarPosition = static_cast<int>(activity.callMethod<jint>("getNavBarPosition"));
  const double navBarHeight = static_cast<double>(activity.callMethod<jdouble>("navBarHeight")) / devicePixelRatio;
  switch (navBarPosition) {
  case -1: break;//No navBar
  case 0: margins.setBottom(navBarHeight);break;
  case 1: margins.setRight(navBarHeight); break;
  case 2: margins.setLeft(navBarHeight);  break;
  case 3:
  default:
      Q_ASSERT_X(false,"SafeArea","NavigationBar position is in an unhandeled position");
      break;
  }

Register SafeArea class to be used inside main.qml

qmlRegisterType<SafeArea>("SafeArea", 1,0, "SafeArea");

The orientation changed signal will most likely be emitted before the SafeArea class can fetch the new margins, therefore the delay via the Timer component

main.qml

    Timer{
        id: timerNewSafeMargins
        running: false
        repeat: false
        interval: 10
        onTriggered:{
            var map = safeMargins.getSafeAreaMargins(root)
            safeMargins.safeMarginLeft = map["left"]
            safeMargins.safeMarginRight = map["right"]
            safeMargins.safeMarginTop = map["top"]
            safeMargins.safeMarginBottom = map["bottom"]
        }
    }
    SafeArea{
        id:safeMargins

        property int safeMarginLeft: getSafeAreaMargins(root)["left"]
        property int safeMarginRight: getSafeAreaMargins(root)["right"]
        property int safeMarginTop: getSafeAreaMargins(root)["top"]
        property int safeMarginBottom: getSafeAreaMargins(root)["bottom"]
        onSafeMarginBottomChanged: console.log("safeMarginBottom", safeMarginBottom)

        readonly property bool isPortrait: (Screen.primaryOrientation === Qt.PortraitOrientation ||
                                            Screen.primaryOrientation === Qt.InvertedPortraitOrientation)
        onIsPortraitChanged:{
            timerNewSafeMargins.start()
        }

Example images

iOS

Android

[shokarta]

Hello and thanks for the great work...
in nowadays.. wouldnt be posisble you would rewrite to Qt6?

EDIT: basicaly I only replaced:

const QAndroidJniObject activity = QtAndroid::androidActivity();

by

QJniObject activity = QNativeInterface::QAndroidApplication::context();

and of course include proper header:

 // for whatever reason i cant pass this include here as Qt spam bot wont allow

and seems to work fine...

however, as I looked through the code, the height of status/navi bar it returns only in Android, correct?
there is no *.mm to figure out the height of bars in iOS

Unfortunatelly, i can not test... however ive spend also huge amount of time to figure this time, most helpful (but also outdated) info i gathered from:

which also includes the function to get height of statusbar in iOS via *.mm file...
https://sudonull.com/post/73911-Native-Android-and-iOS-code-in-Qt-using-status-bar-as-an-example
so how can we combine this also with your best solution?

EDIT2: and huge cherry on the top would be to be able to change status/navi bar foreground style between dark and light :D so if our content will be light, then we can set the time and other stuff in statusbar to dark text color so its readable

[shokarta]

This post is deleted!

[J.Hilk]

@shokarta

it should work 1:1 in Qt6 as for Qt5, does it not work for you? If so, what doesn't ?

[shokarta]

const QAndroidJniObject activity = QtAndroid::androidActivity();

does not work on Qt6, so I replaced by:

QJniObject activity = QNativeInterface::QAndroidApplication::context();

maybe i did few other little modifications on the way to make it work on Qt6, I will check bit later.

Anyway... as I cant test it now without Mac, does this also work for iOS?
As I dont see included mm file to gather info like:

//[UIApplication sharedApplication].statusBarFrame.size.height; // deprecated by iOS11
[UIApplication sharedApplication].windows.firstObject.safeAreaInsets.top;  // probably current iOS support?
//[UIApplication sharedApplication].keyWindow.safeAreaInsets.top; // one of options to gather, need to test
//[UIApplication sharedApplication].windows[0].safeAreaInsets.top; // one of options to gather, need to test
//[UIApplication sharedApplication].delegate.windows.safeAreaInsets.top; // one of options to gather, need to test

I cant imagine how QT can know this safeArea margins on its own

[J.Hilk]

Hi @shokarta

just now noticed your edits in the earlier posts ! I didn't get a notification for that, so sorry about that!

Anyway... as I cant test it now without Mac, does this also work for iOS?
As I dont see included mm file to gather info like:

for iOS there are no extra steps needed. in safe area.h you'll see

#if !defined (Q_OS_ANDROID)
        QPlatformWindow *platformWindow = static_cast<QPlatformWindow *>(window->handle());
        if(!platformWindow)
            return QVariantMap();
        margins = platformWindow->safeAreaMargins();
    #else

QPlatformWindow worked perfectly fine for iOS. Well not entirely correct, the changed signal is emitted before new safe areas are actually able to be read, IIRC. That's why the timer is in the QML file.

does not work on Qt6, so I replaced by:
....

ok makes sense, I'll have to compile and update it for Qt6 than. Can't leave it incomplete! I'll end up switching to Qt6 myself someday too

[shokarta]

Great news :)
also one thing... i see in your .java you set the transparent statusbar and navigationbar... however this also does not work...
at least not fully... its transparent, but its shadowed over... something like:

does it have a fix in qt6?

[shokarta]

@J-Hilk I have spent couple days to update it to current SDK as half of stuff are deprecated.
Its 100% based on your example :D
would there be possible you could have a quick look to see why it returns 0 when obviously it shall return a values?
I think there would be only some import missing... however as I never worked with java, I can not know :(

package org.myapp.activity;

import org.qtproject.qt.android.QtNative;
import org.qtproject.qt.android.bindings.QtActivity;

import android.os.*;
import android.content.*;
import android.app.*;

import android.content.res.Resources;
import android.content.res.Configuration;
import android.util.DisplayMetrics;

import android.view.Display;

import android.hardware.display.DisplayManager;
import android.view.Surface;
import android.view.View;
import android.view.DisplayCutout;
import android.view.Window;
import android.view.WindowManager;
import android.view.WindowInsets;
import android.view.WindowInsetsController;
import android.graphics.Color;

import androidx.core.view.WindowInsetsCompat;
import androidx.core.view.WindowInsetsCompat.Type.InsetsType;


public class MyActivity extends QtActivity
{
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setCustomStatusAndNavBar();
	} // onCreate


	void setCustomStatusAndNavBar() {

		// First check sdk version, custom/transparent System_bars are only available after LOLLIPOP
		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
			Window window = getWindow();

			// The Window flag 'FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS' will allow us to paint the background of the status bar ourself and automatically expand the canvas
			// If you want to simply set a custom background color (including transparent) for the statusBar/navigationBar, use the following addFlags call
			window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);

			// The Window flag 'FLAG_TRANSLUCENT_NAVIGATION' will allow us to paint the background of the navigation bar ourself
			// But we will also have to deal with orientation and OEM specifications, as the navigationBar may or may not depend on the orientation of the device
			//window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS | WindowManager.LayoutParams.FLAG_TRANSLUCENT_NAVIGATION);		// DEPRECATED (NOTE: is this needed as also setStatusBarColor() and setNavigationBarColor() are deprecated?)

			window.getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);					// DEPRECATED
			// TODO: Use WindowInsetsController instead (NOTE: is this needed as also setStatusBarColor() and setNavigationBarColor() are deprecated?)

			// Set StatusBar Transparent
			window.setStatusBarColor(Color.TRANSPARENT);			// DEPRECATED
			// TODO: Draw proper background behind WindowInsets.Type#statusBars()} instead

			//Set NavigationBar to desired color (0xAARRGGBB) set alpha value to 0 if you want a solid color
			window.setNavigationBarColor(Color.TRANSPARENT);		// DEPRECATED
			// TODO: Draw proper background behind WindowInsets.Type#navigationBars() instead


			// Statusbar background is now transparent, but the icons and text are probably white and not really readable, as we have a bright background color
			// We set/force a light theme for the status bar to make those dark
			View decor = window.getDecorView();
			decor.setSystemUiVisibility(decor.getSystemUiVisibility() | View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR);			// DEPRECATED (NOTE: is this needed as also setStatusBarColor() and setNavigationBarColor() are deprecated?)

		}
	}

	
	// outdated https://medium.com/javarevisited/how-to-get-status-bar-height-in-android-programmatically-c127ad4f8a5d
	public double statusBarHeight() {

		// Method 1: Using Resources (still working, but preferable use current API solution)
		// double result = 0;
		// int resourceId = getResources().getIdentifier("status_bar_height", "dimen", "android");
		// if (resourceId > 0) {
		//    result = getResources().getDimension(resourceId);
		// }
		// return result;


		// Method 2: Using Window Insets (API 30+)
		WindowInsets windowInsets = getWindow().getDecorView().getRootWindowInsets();
		double statusBarHeight = windowInsets.getInsets(WindowInsets.Type.statusBars()).top;	// returns 0 (wrongly)
		return statusBarHeight;


		// Method 3: Using Display Metrics
		// Rect rectangle = new Rect();
		// Window window = getWindow();
		// window.getDecorView().getWindowVisibleDisplayFrame(rectangle);
		// int statusBarHeight = rectangle.top;
		// return statusBarHeight;
	}

	public int safeAreaTop() {

		// Still working, but preferable use current API solution
		// DisplayCutout cutout = getWindow().getDecorView().getRootWindowInsets().getDisplayCutout();
		// if(cutout != null) {
		//     int cutoutHeight = cutout.getSafeInsetTop();
		//     if (cutoutHeight > 0) {
		//         return cutoutHeight;
		//		}
		// }
		// return 0;


		// Using Window Insets (API 30+)
		WindowInsets windowInsets = getWindow().getDecorView().getRootWindowInsets();
		int cutoutHeight = windowInsets.getInsets(WindowInsets.Type.displayCutout()).top;	// returns 0 (wrongly)
		return cutoutHeight;
	}

	// If we decide to draw the behind the navigationBar, we need to know the new safearea,
	// so to not draw text or position buttons behind the nav bar.
	// Those would be unclickable and potentially unreadable.
	// ATTENTION:
	// Compared to the statuBbar, there is no guarantee that the behind will be at the bottom of your screen
	// This function returns the hight of the Navigation bar */
	public double navBarHeight() {
	
		// Method 1: Using Resources (still working, but preferable use current API solution)
		// double result = 0;
		// int resourceId = getResources().getIdentifier("navigation_bar_height", "dimen", "android");
		// if (resourceId > 0) {
		//    result = getResources().getDimension(resourceId);
		// }
		// return result;


		// Method 2: Using Window Insets (API 30+)
		WindowInsets windowInsets = getWindow().getDecorView().getRootWindowInsets();
		double navigationBarHeight = windowInsets.getInsets(WindowInsets.Type.navigationBars()).top;	// returns 0 (wrongly)
		return navigationBarHeight;


		// Method 3: Using Display Metrics
		// Rect rectangle = new Rect();
		// Window window = getWindow();
		// window.getDecorView().getWindowVisibleDisplayFrame(rectangle);
		// int navigationBarHeight = rectangle.bottom;
		// return navigationBarHeight;
	}

	public int getNavBarPosition() {

		Resources res = getResources();
		int resourceId = res.getIdentifier("config_showNavigationBar", "bool", "android");
		boolean hasMenu = false;
		if (resourceId > 0) {
			hasMenu =  res.getBoolean(resourceId);
		}
		if (!hasMenu) {
			return -1;
		}


		// https://stackoverflow.com/questions/69724946/getdisplay-return-display
		// Display display = getWindowManager().getDefaultDisplay();		// getDefaultDisplay() deprecated
		DisplayManager displayManager = (DisplayManager) getSystemService(Context.DISPLAY_SERVICE);
		Display display = displayManager.getDisplay(Display.DEFAULT_DISPLAY);
		int rotation = display.getRotation();

		switch (rotation) {
			case Surface.ROTATION_90:
				return 1;
			case Surface.ROTATION_180:
				return 3;
			case Surface.ROTATION_270:
				return 2;
			default:
				return 0;
		}
	}
}

[Patriciabin]

This post is deleted!

[Mike is ok]

I am Qt6.5.3, as shown in the picture. How can I modify the system status bar to be fully transparent? I want the status bar of Android to have the same color as the interface of the application, but I have been unable to achieve this

[Pl45m4]

@Mike-is-ok

Hi and welcome,

it would have better to start a new topic for your issue.

Anyway, now that you created it here, check out this github repo, it might help:

• https://github.com/jpnurmi/qtstatusbar

[Mike is ok]

@Pl45m4
Thank you very much for your reply. I will try this case.