Qt Quick for Android Studio Projects

class MainActivity : AppCompatActivity(), QtQmlStatusChangeListener {
    ...
}
			

The onStatusChanged implementation:

@Override
public void onStatusChanged(QtQmlStatus qtQmlStatus, QtQuickViewContent content) {
    Log.i(TAG, "Status of QtQuickView: " + qtQmlStatus);
    // Show current QML View status in a textview
    m_qmlStatus.setText(getString(R.string.qml_view_status, m_statusNames.get(qtQmlStatus)));
    updateColorDisplay();
    if (content == m_firstQmlContent) {
        // Connect signal listener to "onClicked" signal from main.qml
        // addSignalListener returns int which can be used later to identify the listener
        if (qtQmlStatus == QtQmlStatus.READY && m_switch.isChecked()) {
            m_qmlButtonSignalListenerId = m_firstQmlContent.connectOnClickedListener(
                    (String name, Void v) -> {
                        Log.i(TAG, "QML button clicked");
                        m_androidControlsLayout.setBackgroundColor(Color.parseColor(
                                m_colors.getColor()
                        ));
                    });
        }
    }
}
				

override fun onStatusChanged(status: QtQmlStatus?, content: QtQuickViewContent?) {
    Log.v(TAG, "Status of QtQuickView: $status")
    // Show current QML View status in a textview
    m_binding.qmlStatusText.text = getString(R.string.qml_view_status, m_statusNames[status])
    updateColorDisplay()
    if (content == m_firstQmlContent) {
        // Connect signal listener to "onClicked" signal from main.qml
        // addSignalListener returns int which can be used later to identify the listener
        if (status == QtQmlStatus.READY && m_binding.disconnectQmlListenerSwitch.isChecked) {
            m_qmlButtonSignalListenerId =
                m_firstQmlContent.connectOnClickedListener { _: String, _: Void? ->
                    Log.i(TAG, "QML button clicked")
                    m_binding.kotlinRelative.setBackgroundColor(
                        Color.parseColor(
                            m_colors.getColor()
                        )
                    )
                }
        }
    }
}
			

The MainActivity is set as the statusChangeListener 的 m_mainQmlContent and m_secondQmlContent 采用 QtQuickViewContent.setStatusChangeListener 方法。

m_firstQmlContent.setStatusChangeListener(this);
m_secondQmlContent.setStatusChangeListener(this);
				

m_firstQmlContent.setStatusChangeListener(this)
m_secondQmlContent.setStatusChangeListener(this)
			

The overridden callback function onStatusChanged() receives StatusChanged() signal containing the current status, a QtQmlStatus Enum, of the loading of the current QtQuickViewContent 到 QtQuickView . If this QtQmlStatus is confirmed to be QtQmlStatus.READY , we can start interacting with the QML view.

Getting and setting QML component property values

Getting and setting QML component property values happens through the methods described in the Main.java class. In this case we use the m_mainQmlContent.setColorStringProperty() and m_mainQmlContent.getColorStringProperty() methods. These methods are generated according to what properties the QML component includes.

public void onClickListener() {
    // Set the QML view root object property "colorStringFormat" value to
    // color from Colors.getColor()
    m_firstQmlContent.setColorStringFormat(m_colors.getColor());
    updateColorDisplay();
}
private void updateColorDisplay() {
    String qmlBackgroundColor = m_firstQmlContent.getColorStringFormat();
    // Display the QML View background color code
    m_qmlViewBackgroundText.setText(qmlBackgroundColor);
    // Display the QML View background color in a view
    // if qmlBackGroundColor is not null
    if (qmlBackgroundColor != null) {
        m_colorBox.setBackgroundColor(Color.parseColor(qmlBackgroundColor));
    }
}
				

private fun onClickListener() {
    // Set the QML view root object property "colorStringFormat" value to
    // color from Colors.getColor()
    m_firstQmlContent.colorStringFormat = m_colors.getColor()
    updateColorDisplay()
}
private fun updateColorDisplay() {
    val qmlBackgroundColor = m_firstQmlContent.colorStringFormat
    // Display the QML View background color code
    m_binding.qmlViewBackgroundText.text = qmlBackgroundColor
    // Display the QML View background color in a view
    // if qmlBackgroundColor is not null
    if (qmlBackgroundColor != null) {
        m_binding.qmlColorBox.setBackgroundColor(Color.parseColor(qmlBackgroundColor))
    }
}
			

With the m_mainQmlContent.setColorStringProperty() method we set the colorStringFormat property value of the m_mainQmlContent a random color value that is fetched from the Colors.java (或 Colors.kt ) class.

The m_mainQmlContent.getColorStringProperty() method is used here to fetch the current background color of the root object of the m_mainQmlContent and then show it to the user on the Java/Kotlin Android side of the application.

m_secondQmlContent 拥有 Grid QML component which we can rotate from the Java side with the generated m_secondQmlContent.setGridRotation() 方法。

private void rotateQmlGrid() {
    Integer previousGridRotation = m_secondQmlContent.getGridRotation();
    if (previousGridRotation != null) {
        m_secondQmlContent.setGridRotation(previousGridRotation + 45);
    }
}
				

private fun rotateQmlGrid() {
    val previousGridRotation = m_secondQmlContent.gridRotation
    if (previousGridRotation != null) {
        m_secondQmlContent.gridRotation = previousGridRotation + 45
    }
}
			

if (status == QtQmlStatus.READY && m_binding.disconnectQmlListenerSwitch.isChecked) {
    m_qmlButtonSignalListenerId =
        m_firstQmlContent.connectOnClickedListener { _: String, _: Void? ->
            Log.i(TAG, "QML button clicked")
            m_binding.kotlinRelative.setBackgroundColor(
                Color.parseColor(
                    m_colors.getColor()
                )
            )
        }
}
	

The onClicked() signal is emitted every time the button on the QML component is clicked. This listener then receives that signal, and the background color of the layout holding the Android side of the application is set to a random color value fetched from the Colors.java 类。

Next, the signal listener is disconnected using the QtQuickViewContent.disconnectSignalListener() method by giving it the unique signal listener ID.

m_firstQmlContent.disconnectSignalListener(m_qmlButtonSignalListenerId);
		

m_firstQmlContent.disconnectSignalListener(m_qmlButtonSignalListenerId)
	

If you haven't already, check out the Qt Academy: Embedding Qt Quick 3D Content in an Android App course that introduces the tools and APIs referenced in this example.

Qt Quick Android 类 Using QtAbstractItemModel in Android Studio Projects