Qt on Android: App screenshot

On the desktop platform, Qscreen::grabwindow can take screenshots of your app, which is no use on Android, but there are workarounds.

In two cases, Qt Widgets and Qt Quick.

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Qt Widgets

The key is a function: Qwidget::render, this method can be a qwidget (including its children) to render the content of a qpixmap, and then we use the Qpixmap save method can be saved.

Here is the key code:

void Widget::ongrab () {    Qpixmap *pixmap = new Qpixmap (size ());    Render (PIXMAP);    QString Savedpath = qstandardpaths::writablelocation (qstandardpaths::P ictureslocation);    if (Savedpath.isempty ())    {        Savedpath = Qdir::currentpath ();    }    M_savedpathlabel->settext (Savedpath);    M_savedpathlabel->adjustsize ();    Savedpath + = "/grabwidgets.png";    BOOL ret = Pixmap->save (savedpath);    if (ret)    {        m_savedpathlabel->settext ("OK.") +savedpath);    }    else    {        m_savedpathlabel->settext ("Failed.") +savedpath);}    }

The first two lines of the Ongrab () method create a Qpixmap with the size of the widget, and then call the Render method. The next code is to save the image to the default image directory of your Android device.

Qt Quick

Qt Quick application, there will be a qquickwindow, and Qquickwindow has a Grabwindow method, you can apply the current window to save the content as a picture.

This involves mixing QML with C + + programming, referring to myqt Quick Core programming , or "QT quick QML and C + + mixed programming ."

C + + code

Header file Grabber.h:

Class Grabber:public qobject{    q_objectpublic:    Grabber (Qobject *parent = 0);    Q_invokable QString Grab (Qquickwindow *w);};

Key code in the source file Grabber.cpp:

QString Grabber::grab (Qquickwindow *w) {    qimage image = W->grabwindow ();    if (Image.isnull ()) return QString ();    QString Savedpath = qstandardpaths::writablelocation (qstandardpaths::P ictureslocation);    if (Savedpath.isempty ())    {        Savedpath = Qdir::currentpath ();    }    Savedpath + = "/grabqml.png";    BOOL ret = Image.Save (savedpath);    if (ret)    {        return savedpath;    }    return QString ();}

It is also necessary to set a Qmlcontext property in the main () function, which is the following code:

    Grabber *grabber = new Grabber;    Engine.rootcontext ()->setcontextproperty ("grabber", grabber);

Then we can use Grabber in the Qml file.

QML Code

My test QML documentation is MAIN.QML as follows:

Import QtQuick 2.2import Qtquick.window 2.0import qtquick.controls 1.1Window {id:rootwin;    Visible:true;    Title:qstr ("Hello Grab QML");    ObjectName: "Rootwin";        Text {text:qstr ("Hello Grab QML");        Color: "Blue";        font.pointsize:16;    Anchors.centerIn:parent;        } Rectangle {anchors.top:parent.top;        Anchors.horizontalCenter:parent.horizontalCenter;        width:120;        height:120;    Color: "Blue";        } Text {Id:savedpath;        Anchors.left:parent.left;        Anchors.bottom:parent.bottom;        Anchors.bottommargin:4;        Color: "Red";    Font.pointsize:12;        } Button {id:grab;        Anchors.bottom:savedPath.top;        Anchors.bottommargin:4;        Anchors.horizontalCenter:parent.horizontalCenter;        Text: "Grab";            OnClicked: {var saved = Grabber.grab (Rootwin);            if (Saved.length = = 0) {Savedpath.text = "failed!"; }else{savedpath.text= "OK-" + saved; }        }    }}

I call Grabber.grab () within the onclicked signal processor of the grab button to complete the operation and display the path successfully.

OK, so much more.

To learn more about Qt on Android, you can refer to "Qt on Androidcore programming " or "Qt on Android column" For more QT Quick (QML) content, refer toqt Quick Core programming "or" Qt quick column ".

Qt on Android: App screenshot