From bd0f3345a938b35ce6a12f6150373b0955b8dd12 Mon Sep 17 00:00:00 2001 From: Timothy Pearson Date: Sun, 10 Jul 2011 15:24:15 -0500 Subject: Add Qt3 development HEAD version --- doc/html/tutorial1-06.html | 188 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 188 insertions(+) create mode 100644 doc/html/tutorial1-06.html (limited to 'doc/html/tutorial1-06.html') diff --git a/doc/html/tutorial1-06.html b/doc/html/tutorial1-06.html new file mode 100644 index 0000000..e7b2a8a --- /dev/null +++ b/doc/html/tutorial1-06.html @@ -0,0 +1,188 @@ + + + + + +Qt Tutorial - Chapter 6: Building Blocks Galore! + + + + + + + +

Qt Tutorial - Chapter 6: Building Blocks Galore!

+ + +

This example shows how to encapsulate two widgets into a new component and +how easy it is to use many widgets. For the first time, we use a custom +widget as a child widget. +

/****************************************************************
+**
+** Qt tutorial 6
+**
+****************************************************************/
+
+#include <qapplication.h>
+#include <qpushbutton.h>
+#include <qslider.h>
+#include <qlcdnumber.h>
+#include <qfont.h>
+#include <qvbox.h>
+#include <qgrid.h>
+
+class LCDRange : public QVBox
+{
+public:
+    LCDRange( QWidget *parent=0, const char *name=0 );
+};
+
+LCDRange::LCDRange( QWidget *parent, const char *name )
+        : QVBox( parent, name )
+{
+    QLCDNumber *lcd  = new QLCDNumber( 2, this, "lcd"  );
+    QSlider * slider = new QSlider( Horizontal, this, "slider" );
+    slider->setRange( 0, 99 );
+    slider->setValue( 0 );
+    connect( slider, SIGNAL(valueChanged(int)), lcd, SLOT(display(int)) );
+}
+
+class MyWidget : public QVBox
+{
+public:
+    MyWidget( QWidget *parent=0, const char *name=0 );
+};
+
+
+MyWidget::MyWidget( QWidget *parent, const char *name )
+        : QVBox( parent, name )
+{
+    QPushButton *quit = new QPushButton( "Quit", this, "quit" );
+    quit->setFont( QFont( "Times", 18, QFont::Bold ) );
+
+    connect( quit, SIGNAL(clicked()), qApp, SLOT(quit()) );
+
+    QGrid *grid = new QGrid( 4, this );
+
+    for( int r = 0 ; r < 4 ; r++ )
+        for( int c = 0 ; c < 4 ; c++ )
+            (void)new LCDRange( grid );
+}
+
+int main( int argc, char **argv )
+{
+    QApplication a( argc, argv );
+
+    MyWidget w;
+    a.setMainWidget( &w );
+    w.show();
+    return a.exec();
+}
+

+ + + +

Line-by-line Walkthrough +

    class LCDRange : public QVBox
+    {
+    public:
+        LCDRange( QWidget *parent=0, const char *name=0 );
+    };
+

The LCDRange widget is a widget without any API. It just has a +constructor. This sort of widget is not very useful, so we'll add some API later. +

    LCDRange::LCDRange( QWidget *parent, const char *name )
+            : QVBox( parent, name )
+    {
+        QLCDNumber *lcd  = new QLCDNumber( 2, this, "lcd"  );
+        QSlider * slider = new QSlider( Horizontal, this, "slider" );
+        slider->setRange( 0, 99 );
+        slider->setValue( 0 );
+        connect( slider, SIGNAL(valueChanged(int)), lcd, SLOT(display(int)) );
+    }
+

This is lifted straight from the +MyWidget constructor in Chapter 5. +The only differences are that the button is left out and the class +is renamed. +

    class MyWidget : public QVBox
+    {
+    public:
+        MyWidget( QWidget *parent=0, const char *name=0 );
+    };
+

MyWidget, too, contains no API except a constructor. +

    MyWidget::MyWidget( QWidget *parent, const char *name )
+            : QVBox( parent, name )
+    {
+        QPushButton *quit = new QPushButton( "Quit", this, "quit" );
+        quit->setFont( QFont( "Times", 18, QFont::Bold ) );
+
+        connect( quit, SIGNAL(clicked()), qApp, SLOT(quit()) );
+

The push button that used to be in what is now LCDRange has been +separated so that we can have one "Quit" button and many LCDRange +objects. +

        QGrid *grid = new QGrid( 4, this );
+

We create a QGrid object with four columns. The QGRid widget +automatically arranges its children in rows and columns; you can +specify the number of rows or of columns, and QGrid will discover its +new children and fit them into the grid. +

        for( int r = 0 ; r < 4 ; r++ )
+            for( int c = 0 ; c < 4 ; c++ )
+                (void)new LCDRange( grid );
+

Four columns, four rows. +

We create 4*4 LCDRanges, all of which are children of the grid object. +The QGrid widget will arrange them. +

}
+

That's all. +

Behavior +

This program shows how easy it is to use many widgets at a time. Each +one behaves like the slider and LCD number in the previous +chapter. Again, the difference lies in the implementation. +

(See Compiling for how to create a +makefile and build the application.) +

Exercises +

Initialize each slider with a different/random value on startup. +

The source contains three occurrences of "4". What happens if you +change the one in the QGrid constructor call? What about the other +two? Why is this? +

You're now ready for Chapter 7. +

[Previous tutorial] +[Next tutorial] +[Main tutorial page] +

+ +

Trademarks +

Qt 3.3.8

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