The Ring programming language version 1.9 book - Part 71 of 210

Ring Documentation, Release 1.9
exec()
}
Func pHello
lineedit1.settext( "Hello " + lineedit1.text())
Func pClose
oApp.quit()
Program Output:
At ﬁrst we type the name in the textbox
Then we click on the say hello button
64.1. The First GUI Application 669

64.2 The Events Loop
Qt uses Event-Driven and the events loop get the control when we call the exec() method from the qApp class.
Once we call exec(), The events loop starts, and the Widgets starts responding to the different events (Mouse, Key-
board, Timers, etc).
You get the control back again when an event is ﬁred and your callback function is called.
Once the execution of your callback function is done, the control go back again to the events loop.
Useful things to remember
1. We can do most of the work using normal events (Events provided directly by each widget).
2. We can add more events to any widget using the Events Filter.
3. Using Timers we can easily get the control back and check for more things to do.
Also when our callback function is busy with doing time consuming operations, we can call the ProcessEvents()
method from the qApp class to avoid stoping the GUI.
oApp.processevents()
We can avoid calling the exec() method, and create our main loop
It’s not recommended to do that, It’s just an option.
# Instead of calling the exec() method
while true
oApp.processevents() # Respond to GUI Events
# More Thing to do, We have the control!
# .....
end
64.3 Using Layout
The next example is just an upgrade to the previous application to use the vertical layout.
Load "guilib.ring"
MyApp = New qApp {
win1 = new qWidget() {
setwindowtitle("Hello World")
setGeometry(100,100,400,130)
label1 = new qLabel(win1) {
settext("What is your name ?")
setGeometry(10,20,350,30)
setalignment(Qt_AlignHCenter)
}
btn1 = new qpushbutton(win1) {
settext("Say Hello")
setclickevent("pHello()")
}
64.2. The Events Loop 670

settext("Close")
setclickevent("pClose()")
}
lineedit1 = new qlineedit(win1) {
}
layout1 = new qVBoxLayout() {
addwidget(label1)
addwidget(lineedit1)
addwidget(btn1)
addwidget(btn2)
}
win1.setlayout(layout1)
show()
}
exec()
}
Func pHello
lineedit1.settext( "Hello " + lineedit1.text())
Func pClose
MyApp.quit()
The application during the runtime!
64.4 Using the QTextEdit Class
In this example we will use the QTextEdit Class
Load "guilib.ring"
New qApp {
setwindowtitle("QTextEdit Class")
setGeometry(100,100,500,500)
new qtextedit(win1) {
64.4. Using the QTextEdit Class 671

}
show()
}
exec()
}
During the runtime we can paste rich text in the qtextedit widget
64.5 Using the QListWidget Class
In this example we will use the QListWidget Class
Load "guilib.ring"
New qApp {
64.5. Using the QListWidget Class 672

setGeometry(100,100,400,400)
list1 = new qlistwidget(win1) {
setGeometry(150,100,200,200)
alist = ["one","two","three","four","five"]
for x in alist additem(x) next
setcurrentrow(3,2)
win1.setwindowtitle("Items Count : " + count() )
}
settext("selected item")
setclickevent("pWork()")
}
settext("Delete item")
setclickevent("pWork2()")
}
show()
}
exec()
}
func pWork
btn1.settext(string(list1.currentrow()))
func pWork2
list1 {
takeitem(currentrow())
}
The application during the runtime

Another Example:
Load "guilib.ring"
New qApp {
setGeometry(100,100,500,400)
list1 = new qlistwidget(win1) {
setGeometry(150,100,200,200)
for x in alist additem(x) next
setcurrentrow(3,2)
win1.setwindowtitle("Items Count : " + count() )
}
settext("selected item")
setclickevent("pWork()")
}
settext("Delete item")

setclickevent("pWork2()")
}
show()
}
exec()
}
func pWork
nbrOfItems = list1.count()
curItemNbr = list1.currentrow()
curValue = list1.item(list1.currentrow()).text()
win1.setwindowtitle( "After Select - NbrOfItems: " + nbrOfItems +
" CurItemNbr: " + curItemNbr + " CurValue: " + curValue )
btn1.settext( string(list1.currentrow() ) + " --- " +
list1.item(list1.currentrow()).text() )
func pWork2
list1 {
takeitem(currentrow())
nbrOfItems = count()
curItemNbr = currentrow()
curValue = item(currentrow()).text()
win1.setwindowtitle("After Delete - NbrOfItems: " + nbrOfItems +
" CurItemNbr: " + curItemNbr +" CurValue: " + curValue )
}
64.6 Using QTreeView and QFileSystemModel
In this example we will learn how to use the QTreeView widget to represent the File System
Load "guilib.ring"
New qApp {
win1 = New qWidget() {
setwindowtitle("Using QTreeView and QFileSystemModel")
setGeometry(100,100,500,400)
New qtreeview(win1) {
oDir = new QDir()
ofile = new QFileSystemModel()
ofile.setrootpath(oDir.currentpath())
setmodel(ofile)
}
64.6. Using QTreeView and QFileSystemModel 675

show()
}
exec()
}
64.7 Using QTreeWidget and QTreeWidgetItem
In this example we will learn about using the QTreeWidget and QTreeWidgetItem classes
Load "guilib.ring"
New qApp {
setwindowtitle("TreeWidget")
setGeometry(100,100,400,400)
layout1 = new qvboxlayout()
tree1 = new qtreewidget(win1) {
64.7. Using QTreeWidget and QTreeWidgetItem 676

setcolumncount(1)
myitem = new qtreewidgetitem()
myitem.settext(0,"The First Step")
addtoplevelitem(myitem)
for x = 1 to 10
myitem2 = new qtreewidgetitem()
myitem2.settext(0,"hello"+x)
myitem.addchild(myitem2)
for y = 1 to 10
myitem3 = new qtreewidgetitem()
myitem3.settext(0,"hello"+x)
myitem2.addchild(myitem3)
next
next
setheaderlabel("Steps Tree")
}
layout1.addwidget(tree1)
setlayout(layout1)
show()
}
exec()
}
64.7. Using QTreeWidget and QTreeWidgetItem 677

64.8 Using QComboBox Class
In this example we will learn about using the QComboBox class
Load "guilib.ring"
New qApp {
setwindowtitle("Using QComboBox")
setGeometry(100,100,400,400)
New QComboBox(win1) {
for x in aList additem(x,0) next
}
show()
}
exec()
}
64.8. Using QComboBox Class 678

The Ring programming language version 1.9 book - Part 71 of 210

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The Ring programming language version 1.9 book - Part 71 of 210