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java.lang.Objectcom.trolltech.qt.internal.QSignalEmitterInternal
com.trolltech.qt.QSignalEmitter
com.trolltech.qt.QtJambiObject
com.trolltech.qt.core.QObject
com.trolltech.qt.gui.QWidget
com.trolltech.qt.gui.QFrame
com.trolltech.qt.gui.QAbstractScrollArea
com.trolltech.qt.gui.QScrollArea
public class QScrollArea
The QScrollArea class provides a scrolling view onto another widget. A scroll area is used to display the contents of a child widget within a frame. If the widget exceeds the size of the frame, the view can provide scroll bars so that the entire area of the child widget can be viewed. The child widget must be specified with setWidget()
. For example:
QLabel imageLabel = new QLabel(); QImage image = new QImage("happyguy.png"); imageLabel.setPixmap(QPixmap.fromImage(image)); QScrollArea scrollArea = new QScrollArea(); scrollArea.setBackgroundRole(QPalette.ColorRole.Dark); scrollArea.setWidget(imageLabel);The code above creates a scroll area (shown in the images below) containing an image label. When scaling the image, the scroll area can provide the necessary scroll bars:
![]() | ![]() | ![]() |
scroll bar policies
. You can control the appearance of the scroll bars using the inherited functionality from QAbstractScrollArea
. For example, you can set the QAbstractScrollArea::horizontalScrollBarPolicy
and QAbstractScrollArea::verticalScrollBarPolicy
properties. Or if you want the scroll bars to adjust dynamically when the contents of the scroll area changes, you can use the horizontalScrollBar()
and verticalScrollBar()
functions (which enable you to access the scroll bars) and set the scroll bars' values whenever the scroll area's contents change, using the QScrollBar::setValue() function.
You can retrieve the child widget using the widget()
function. The view can be made to be resizable with the setWidgetResizable()
function. The alignment of the widget can be specified with setAlignment()
.
Two convenience functions ensureVisible()
and ensureWidgetVisible()
ensure a certain region of the contents is visible inside the viewport, by scrolling the contents if necessary.Size Hints and Layouts
When using a scroll area to display the contents of a custom widget, it is important to ensure that the size hint
of the child widget is set to a suitable value. If a standard QWidget
is used for the child widget, it may be necessary to call QWidget::setMinimumSize()
to ensure that the contents of the widget are shown correctly within the scroll area.
If a scroll area is used to display the contents of a widget that contains child widgets arranged in a layout, it is important to realise that the size policy of the layout will also determine the size of the widget. This is especially useful to know if you intend to dynamically change the contents of the layout. In such cases, setting the layout's size constraint
property to one which provides constraints on the minimum and/or maximum size of the layout (e.g., QLayout::SetMinAndMaxSize
) will cause the size of the the scroll area to be updated whenever the contents of the layout changes.
For a complete example using the QScrollArea class, see the Image Viewer example. The example shows how to combine QLabel
and QScrollArea to display an image.
QAbstractScrollArea
, QScrollBar
, and Image Viewer Example.
Nested Class Summary |
---|
Nested classes/interfaces inherited from class com.trolltech.qt.gui.QFrame |
---|
QFrame.Shadow, QFrame.Shape, QFrame.StyleMask |
Nested classes/interfaces inherited from class com.trolltech.qt.gui.QWidget |
---|
QWidget.RenderFlag, QWidget.RenderFlags |
Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter |
---|
QSignalEmitter.AbstractSignal, QSignalEmitter.Signal0, QSignalEmitter.Signal1, QSignalEmitter.Signal2, QSignalEmitter.Signal3, QSignalEmitter.Signal4, QSignalEmitter.Signal5, QSignalEmitter.Signal6, QSignalEmitter.Signal7, QSignalEmitter.Signal8, QSignalEmitter.Signal9 |
Nested classes/interfaces inherited from class com.trolltech.qt.internal.QSignalEmitterInternal |
---|
com.trolltech.qt.internal.QSignalEmitterInternal.AbstractSignalInternal |
Field Summary |
---|
Fields inherited from class com.trolltech.qt.gui.QWidget |
---|
customContextMenuRequested |
Fields inherited from class com.trolltech.qt.internal.QSignalEmitterInternal |
---|
currentSender |
Constructor Summary | |
---|---|
QScrollArea()
Constructs an empty scroll area with the given parent. |
|
QScrollArea(QWidget parent)
Constructs an empty scroll area with the given parent. |
Method Summary | |
---|---|
Qt.Alignment |
alignment()
This property holds the alignment of the scroll area's widget. |
void |
ensureVisible(int x,
int y)
Scrolls the contents of the scroll area so that the point (x, y) is visible inside the region of the viewport with margins specified in pixels by xmargin and ymargin. |
void |
ensureVisible(int x,
int y,
int xmargin)
Scrolls the contents of the scroll area so that the point (x, y) is visible inside the region of the viewport with margins specified in pixels by xmargin and ymargin. |
void |
ensureVisible(int x,
int y,
int xmargin,
int ymargin)
Scrolls the contents of the scroll area so that the point (x, y) is visible inside the region of the viewport with margins specified in pixels by xmargin and ymargin. |
void |
ensureWidgetVisible(QWidget childWidget)
Scrolls the contents of the scroll area so that the childWidget of QScrollArea::widget() is visible inside the viewport with margins specified in pixels by xmargin and ymargin. |
void |
ensureWidgetVisible(QWidget childWidget,
int xmargin)
Scrolls the contents of the scroll area so that the childWidget of QScrollArea::widget() is visible inside the viewport with margins specified in pixels by xmargin and ymargin. |
void |
ensureWidgetVisible(QWidget childWidget,
int xmargin,
int ymargin)
Scrolls the contents of the scroll area so that the childWidget of QScrollArea::widget() is visible inside the viewport with margins specified in pixels by xmargin and ymargin. |
void |
setAlignment(Qt.Alignment arg__1)
This property holds the alignment of the scroll area's widget. |
void |
setAlignment(Qt.AlignmentFlag[] arg__1)
|
void |
setWidget(QWidget widget)
Sets the scroll area's widget. |
void |
setWidgetResizable(boolean resizable)
This property holds whether the scroll area should resize the view widget. |
QWidget |
takeWidget()
Removes the scroll area's widget, and passes ownership of the widget to the caller. |
QWidget |
widget()
Returns the scroll area's widget, or 0 if there is none. |
boolean |
widgetResizable()
This property holds whether the scroll area should resize the view widget. |
Methods inherited from class com.trolltech.qt.gui.QFrame |
---|
frameRect, frameShadow, frameShape, frameStyle, frameWidth, lineWidth, midLineWidth, setFrameRect, setFrameShadow, setFrameShape, setFrameStyle, setLineWidth, setMidLineWidth |
Methods inherited from class com.trolltech.qt.core.QObject |
---|
childEvent, children, connectSlotsByName, customEvent, disposeLater, dumpObjectInfo, dumpObjectTree, dynamicPropertyNames, event, eventFilter, findChild, findChild, findChild, findChildren, findChildren, findChildren, findChildren, indexOfProperty, installEventFilter, isWidgetType, killTimer, moveToThread, objectName, parent, properties, property, removeEventFilter, setObjectName, setParent, setProperty, startTimer, timerEvent, toString, userProperty |
Methods inherited from class com.trolltech.qt.QtJambiObject |
---|
dispose, disposed, equals, finalize, reassignNativeResources, tr, tr, tr |
Methods inherited from class com.trolltech.qt.QSignalEmitter |
---|
blockSignals, disconnect, disconnect, signalsBlocked, signalSender, thread |
Methods inherited from class com.trolltech.qt.internal.QSignalEmitterInternal |
---|
__qt_signalInitialization |
Methods inherited from class java.lang.Object |
---|
clone, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Methods inherited from interface com.trolltech.qt.QtJambiInterface |
---|
disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership |
Constructor Detail |
---|
public QScrollArea()
setWidget()
.
public QScrollArea(QWidget parent)
setWidget()
.
Method Detail |
---|
public final Qt.Alignment alignment()
public final void ensureVisible(int x, int y, int xmargin)
public final void ensureVisible(int x, int y)
public final void ensureVisible(int x, int y, int xmargin, int ymargin)
public final void ensureWidgetVisible(QWidget childWidget, int xmargin)
QScrollArea::widget()
is visible inside the viewport with margins specified in pixels by xmargin and ymargin. If the specified point cannot be reached, the contents are scrolled to the nearest valid position. The default value for both margins is 50 pixels.
public final void ensureWidgetVisible(QWidget childWidget)
QScrollArea::widget()
is visible inside the viewport with margins specified in pixels by xmargin and ymargin. If the specified point cannot be reached, the contents are scrolled to the nearest valid position. The default value for both margins is 50 pixels.
public final void ensureWidgetVisible(QWidget childWidget, int xmargin, int ymargin)
QScrollArea::widget()
is visible inside the viewport with margins specified in pixels by xmargin and ymargin. If the specified point cannot be reached, the contents are scrolled to the nearest valid position. The default value for both margins is 50 pixels.
public final void setAlignment(Qt.AlignmentFlag[] arg__1)
public final void setAlignment(Qt.Alignment arg__1)
public final void setWidget(QWidget widget)
The widget becomes a child of the scroll area, and will be destroyed when the scroll area is deleted or when a new widget is set.
The widget's autoFillBackground
property will be set to true.
If the scroll area is visible when the widget is added, you must show()
it explicitly.
Note that You must add the layout of widget before you call this function; if you add it later, the widget will not be visible - regardless of when you show()
the scroll area. In this case, you can also not show()
the widget later.
widget()
.
public final void setWidgetResizable(boolean resizable)
widget()
->resize(), and the scroll area will automatically adjust itself to the new size. If this property is set to true, the scroll area will automatically resize the widget in order to avoid scroll bars where they can be avoided, or to take advantage of extra space.
public final QWidget takeWidget()
widget()
.
public final QWidget widget()
setWidget()
.
public final boolean widgetResizable()
widget()
->resize(), and the scroll area will automatically adjust itself to the new size. If this property is set to true, the scroll area will automatically resize the widget in order to avoid scroll bars where they can be avoided, or to take advantage of extra space.
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