anyone got an Android code to detect OS-theme (dark/light?) ?

TomZ

If anyone knows of an example on how to detect if the OS is in light or dark theme, I would be very happy if they can share a link or the relevant code here!

Thank you.

TomZ

@JoeCFD sweet!

in the mean time I figured out the pure JNI code;

auto context = QJniObject(QNativeInterface::QAndroidApplication::context());
// In Java:
//   context.getResources().getConfiguration().uiMode
auto resources = context.callObjectMethod("getResources",
"()Landroid/content/res/Resources;");
auto config = resources.callObjectMethod("getConfiguration",
"()Landroid/content/res/Configuration;");
auto uiMode = config.getField<jint>("uiMode");
constexpr int UI_MODE_NIGHT_MASK = 0x30;
constexpr int UI_MODE_NIGHT_YES = 0x20;
const bool dark = (uiMode & UI_MODE_NIGHT_MASK) == UI_MODE_NIGHT_YES;

JoeCFD

@TomZ Try this out.

    public static boolean isDarkTheme(Activity activity) {
        int currentNightMode = activity.getResources().getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK;
        return currentNightMode == Configuration.UI_MODE_NIGHT_YES;
    }

or

package com.yourpackage;

import android.content.Context;
import android.content.res.Configuration;

public class ThemeDetector {
    public static String getSystemTheme(Context context) {
        int currentNightMode = context.getResources().getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK;
        if (currentNightMode == Configuration.UI_MODE_NIGHT_YES) {
            return "dark";
        } else {
            return "light";
        }
    }
}

TomZ

@JoeCFD thank you!

I've been trying for a couple of hours anything I can to actually call this from C++, this is as far as I have come (the docs on the Android stuff is significantly lower quality than the rest of Qt).

But I can't figure it out. This doesn't compile. No clue what "Args" are as mentioned in the documentation.

auto context = QJniObject(QNativeInterface::QAndroidApplication::context());
QJniObject retStr = QJniObject::callStaticObjectMethod("org/flowee/ThemeDetector",
"getSystemTheme", "()Lorg/flowee/ThemeDetector;", context);

yap, 2 lines. Still trying after 3 hours. [hair pulling emoti]

ps. using Qt 6.5.1

JoeCFD

@TomZ said in anyone got an Android code to detect OS-theme (dark/light?) ?:

"()Lorg/flowee/ThemeDetector;"

I guess this one is wrong. Here you define the data type you pass into the func

"()Lorg/flowee/ThemeDetector;"

for example passing a string is like

"(Landorid/content/Context;)LJava/lang/String;"

read the doc carefully.

TomZ

another attempt in a different direction, a little progress made, I guess...

auto context = QJniObject(QNativeInterface::QAndroidApplication::context());
auto resources = context.callObjectMethod("getResources", "()Landroid.content.res.Resources;");

Got stuck on using 'callMethod' which didn't work, but callObjectMethod' does. No clue what the difference is.

TomZ

@JoeCFD said in anyone got an Android code to detect OS-theme (dark/light?) ?:

read the doc carefully.

The only docs I found is the QJNiObject API docs. Do you know of any better ones?

JoeCFD

@TomZ In Qt5, the following is good enough. Have not tried Qt6

QAndroidJniObject::callStaticObjectMethod(...)

This does not exist in Qt6 anymore.

https://forum.qt.io/topic/138952/help-qt6-calling-android-java-from-c/2

A full and pretty new example for Qt6:
https://scythe-studio.com/de/blog/how-to-interface-qt-with-android-java-code-2023

TomZ

@JoeCFD In Qt6 the calling of the class you pasted seems completely impossible by design.

You can't pass in non-trivial objects, is what clang tells me.

error: cannot pass object of non-trivial type 'QJniObject' through variadic function; call will abort at runtime [-Wnon-pod-varargs]
"getSystemTheme", "(Landoroid/content/Context;)L;", context);

JoeCFD

@TomZ you read my post above.

TomZ

@JoeCFD said in anyone got an Android code to detect OS-theme (dark/light?) ?:

read the doc carefully.

maybe that changed between Qt5 and Qt6, but in the QJniObject docs it states:

Method signatures are written as "(ArgumentsTypes)ReturnType", see JNI Types.

JoeCFD

@TomZ I posted two links above. The second one has detailed info.

TomZ

@JoeCFD sweet!

in the mean time I figured out the pure JNI code;

auto context = QJniObject(QNativeInterface::QAndroidApplication::context());
// In Java:
//   context.getResources().getConfiguration().uiMode
auto resources = context.callObjectMethod("getResources",
"()Landroid/content/res/Resources;");
auto config = resources.callObjectMethod("getConfiguration",
"()Landroid/content/res/Configuration;");
auto uiMode = config.getField<jint>("uiMode");
constexpr int UI_MODE_NIGHT_MASK = 0x30;
constexpr int UI_MODE_NIGHT_YES = 0x20;
const bool dark = (uiMode & UI_MODE_NIGHT_MASK) == UI_MODE_NIGHT_YES;