class TableColumn : public QObject
{
Q_OBJECT
public slots:
void onValueChanged()
{
emit onChanged();
}
signals:
void onChanged();
};
Category Archives: Platforms and frameworks
An example of connecting a signal by name in QT
How I fixed wrong colors in my QML app on Android
I removed android:theme from AndroidManifest.xml:
<activity android:name="net.geographx.MainActivity"
android:configChanges="orientation|uiMode|screenLayout|screenSize|smallestScreenSize|layoutDirection|locale|fontScale|keyboard|keyboardHidden|navigation|mcc|mnc|density"
android:label="@string/app_name"
android:theme="@style/AppTheme"
android:launchMode="singleTask"
android:screenOrientation="portrait"
android:exported="true">
<!-- Splash screen -->
<meta-data android:name="android.app.splash_screen_drawable" android:resource="@drawable/splash"/>
<!-- Splash screen -->
Make QML menu width fit the content
Found an implementation here and added two pixels:
import QtQuick
import QtQuick.Controls
import QtQuick.Layouts
Menu {
width: {
var result = 0;
var padding = 0;
for (var i = 0; i < count; ++i) {
var item = itemAt(i);
result = Math.max(item.contentItem.implicitWidth, result);
padding = Math.max(item.padding, padding);
}
// It looks like two pixels are missing to remove the ellipsis.
// My first idea was that it is leftInset + rightInset, but it does not work.
var missing = 2;
return result + padding * 2 + missing;
}
}
Examples of C++/Objective-C interop
From QT’s Purchasing:
//SKProductsRequestDelegate
-(void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response
{
NSArray<SKProduct *> *products = response.products;
SKProduct *product = [products count] == 1 ? [[products firstObject] retain] : nil;
if (product == nil) {
//Invalid product ID
NSString *invalidId = [response.invalidProductIdentifiers firstObject];
QMetaObject::invokeMethod(backend, "registerQueryFailure", Qt::AutoConnection, Q_ARG(QString, QString::fromNSString(invalidId)));
} else {
//Valid product query
//Create a IosInAppPurchaseProduct
IosInAppPurchaseProduct *validProduct = new IosInAppPurchaseProduct(product, backend->productTypeForProductId(QString::fromNSString([product productIdentifier])));
if (validProduct->thread() != backend->thread()) {
validProduct->moveToThread(backend->thread());
QMetaObject::invokeMethod(backend, "setParentToBackend", Qt::AutoConnection, Q_ARG(QObject*, validProduct));
}
QMetaObject::invokeMethod(backend, "registerProduct", Qt::AutoConnection, Q_ARG(IosInAppPurchaseProduct*, validProduct));
}
[request release];
}
Using Swift in a QT6 app
I simply opened arboreus_examples/qt6/CMake/UsingSwift/UsingSwift_v3/CMakeLists.txt in QT Creator and was able to build it and run.
In its main.cpp it creates a Swift wrapper and calls method:
ASwift* oSwift = new ASwift(&oEngine);
oSwift->mInit();
_A_DEBUG << oSwift->mString();
“Null object reference” exceptions on Android 14 in a QT app
When I switched to QT 6.7.2 and set QT_ANDROID_TARGET_SDK_VERSION "34" (that is Android 14) my QT app started to crash with the following stack traces:
On google Pixel 5 64-bit only 1080x2340 Android 14 (SDK 34) arm64-v8a:
Exception java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Class java.lang.Object.getClass()' on a null object reference
at android.os.Parcel.createExceptionOrNull (Parcel.java:3189)
at android.os.Parcel.createException (Parcel.java:3167)
at android.os.Parcel.readException (Parcel.java:3150)
at android.database.DatabaseUtils.readExceptionFromParcel (DatabaseUtils.java:202)
at android.database.DatabaseUtils.readExceptionFromParcel (DatabaseUtils.java:154)
at android.content.ContentProviderProxy.call (ContentProviderNative.java:764)
at android.content.ContentResolver.call (ContentResolver.java:2466)
at android.content.ContentResolver.call (ContentResolver.java:2446)
at ekfr.a (:com.google.android.gms@242013038@24.20.13 (190400-633713831):29)
at com.google.android.gms.wallet.intentoperation.setupwizard.PaymentsSetupWizardAccountChangeIntentOperation.onHandleIntent (:com.google.android.gms@242013038@24.20.13 (190400-633713831):252)
at com.google.android.chimera.IntentOperation.onHandleIntent (:com.google.android.gms@242013038@24.20.13 (190400-633713831):2)
at ajdw.onHandleIntent (:com.google.android.gms@242013038@24.20.13 (190400-633713831):8)
at pbh.run (:com.google.android.gms@242013038@24.20.13 (190400-633713831):70)
at pbg.run (:com.google.android.gms@242013038@24.20.13 (190400-633713831):152)
at elbx.run (:com.google.android.gms@242013038@24.20.13 (190400-633713831):21)
at java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:644)
at java.lang.Thread.run (Thread.java:1012)
QT stopped compiling with QT_NO_EXCEPTIONS
QT 6.7.2 failed to build with QT_NO_EXCEPTIONS for Android with the following errors:
C:/dev/repos/qt-everywhere-src-6.7.2/qtbase/src/corelib/io/qprocess_unix.cpp:889:29: error: use of undeclared identifier 'e'
failChildProcess(d, e.what(), FakeErrnoForThrow);
^
C:/dev/repos/qt-everywhere-src-6.7.2/qtbase/src/corelib/io/qprocess_unix.cpp:890:7: error: expected expression
} QT_CATCH (...) {
^
C:/dev/repos/qt-everywhere-src-6.7.2/qtbase/src/corelib/global/qexceptionhandling.h:28:23: note: expanded from macro 'QT_CATCH'
# define QT_CATCH(A) else
^
2 errors generated.
[673/5992] Building CXX object qtbase/src/corelib/CMakeFiles/Core.dir/itemmodels/qabstractitemmodel.cpp.o
ninja: build stopped: subcommand failed.
Building Lines Game for MacOS and iOS
To build my app for iOS I tried to run CMake from the command line without QT Creator:
cmake -S /Users/admin/dev/repos/examples/src/LinesGame/LinesGameQt -B . -DCMAKE_GENERATOR:STRING=Xcode \
-DCMAKE_PROJECT_INCLUDE_BEFORE:FILEPATH=./.qtc/package-manager/auto-setup.cmake -DQT_QMAKE_EXECUTABLE:FILEPATH=/Users/admin/dev/libs/QT6/release/iOS/bin/qmake6 \
-DCMAKE_PREFIX_PATH:PATH=/Users/admin/dev/libs/QT6/release/iOS \
-DCMAKE_C_COMPILER:FILEPATH=/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang \
-DCMAKE_CXX_COMPILER:FILEPATH=/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ \
-DCMAKE_TOOLCHAIN_FILE:FILEPATH=/Users/admin/dev/libs/QT6/release/iOS/lib/cmake/Qt6/qt.toolchain.cmake \
-DCMAKE_OSX_ARCHITECTURES:STRING=arm64 -DCMAKE_OSX_SYSROOT:STRING=iphoneos -DCMAKE_CXX_FLAGS_INIT:STRING= \
-DCMAKE_XCODE_ATTRIBUTE_DEVELOPMENT_TEAM:STRING=XXXXXXX
