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java.lang.Objectcom.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("happyguy.png"); imageLabel->setPixmap(QPixmap::fromImage(image)); scrollArea = new QScrollArea; scrollArea->setBackgroundRole(QPalette::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:
![]() | ![]() | ![]() |
The scroll bars appearance depends on the currently set 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.
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.
Two convenience functions ensureVisible and ensureWidgetVisible ensure a certain region of the contents is visible inside the viewport, by scrolling the contents if necessary.
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.
Viewer Example
Nested Class Summary |
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Nested classes/interfaces inherited from class com.trolltech.qt.gui.QFrame |
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QFrame.Shadow, QFrame.Shape, QFrame.StyleMask |
Nested classes/interfaces inherited from class com.trolltech.qt.gui.QWidget |
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QWidget.RenderFlag, QWidget.RenderFlags |
Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter |
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QSignalEmitter.AbstractSignal, QSignalEmitter.Signal0, QSignalEmitter.Signal1<A>, QSignalEmitter.Signal2<A,B>, QSignalEmitter.Signal3<A,B,C>, QSignalEmitter.Signal4<A,B,C,D>, QSignalEmitter.Signal5<A,B,C,D,E>, QSignalEmitter.Signal6<A,B,C,D,E,F>, QSignalEmitter.Signal7<A,B,C,D,E,F,G>, QSignalEmitter.Signal8<A,B,C,D,E,F,G,H>, QSignalEmitter.Signal9<A,B,C,D,E,F,G,H,I> |
Field Summary |
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Fields inherited from class com.trolltech.qt.gui.QWidget |
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customContextMenuRequested |
Constructor Summary | |
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QScrollArea()
Equivalent to QScrollArea(0). |
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QScrollArea(QWidget parent)
Constructs an empty scroll area with the given parent. |
Method Summary | |
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Qt.Alignment |
alignment()
Returns the alignment of the scroll area's widget. |
void |
ensureVisible(int x,
int y)
Equivalent to ensureVisible(x, y, 50, 50). |
void |
ensureVisible(int x,
int y,
int xmargin)
Equivalent to ensureVisible(x, y, xmargin, 50). |
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)
Equivalent to ensureWidgetVisible(childWidget, 50, 50). |
void |
ensureWidgetVisible(QWidget childWidget,
int xmargin)
Equivalent to ensureWidgetVisible(childWidget, xmargin, 50). |
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. |
boolean |
event(QEvent arg__1)
This function is reimplemented for internal reasons. |
boolean |
eventFilter(QObject arg__1,
QEvent arg__2)
This function is reimplemented for internal reasons. |
protected boolean |
focusNextPrevChild(boolean next)
This function is reimplemented for internal reasons. |
static QScrollArea |
fromNativePointer(QNativePointer nativePointer)
This function returns the QScrollArea instance pointed to by nativePointer |
protected void |
resizeEvent(QResizeEvent arg__1)
This function is reimplemented for internal reasons. |
protected void |
scrollContentsBy(int dx,
int dy)
This function is reimplemented for internal reasons. |
void |
setAlignment(Qt.Alignment arg__1)
Sets the alignment of the scroll area's widget to arg__1. |
void |
setAlignment(Qt.AlignmentFlag... arg__1)
Sets the alignment of the scroll area's widget to arg__1. |
void |
setWidget(QWidget widget)
Sets the scroll area's widget. |
void |
setWidgetResizable(boolean resizable)
Sets whether the scroll area should resize the view widget to resizable. |
QSize |
sizeHint()
This function is reimplemented for internal reasons. |
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()
Returns whether the scroll area should resize the view widget. |
Methods inherited from class com.trolltech.qt.gui.QFrame |
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changeEvent, drawFrame, frameRect, frameShadow, frameShape, frameStyle, frameWidth, lineWidth, midLineWidth, setFrameRect, setFrameShadow, setFrameShape, setFrameStyle, setLineWidth, setMidLineWidth |
Methods inherited from class com.trolltech.qt.core.QObject |
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blockSignals, childEvent, children, connectSlotsByName, customEvent, disposeLater, dumpObjectInfo, dumpObjectTree, dynamicPropertyNames, findChild, findChild, findChild, findChildren, findChildren, findChildren, findChildren, installEventFilter, isWidgetType, killTimer, moveToThread, objectName, parent, property, removeEventFilter, setObjectName, setParent, setProperty, signalsBlocked, startTimer, thread, timerEvent |
Methods inherited from class com.trolltech.qt.QtJambiObject |
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dispose, disposed, finalize, reassignNativeResources, tr, tr, tr |
Methods inherited from class com.trolltech.qt.QSignalEmitter |
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disconnect, disconnect, signalSender |
Methods inherited from class java.lang.Object |
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clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Methods inherited from interface com.trolltech.qt.QtJambiInterface |
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disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership |
Constructor Detail |
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public QScrollArea()
Equivalent to QScrollArea(0).
public QScrollArea(QWidget parent)
Constructs an empty scroll area with the given parent.
Method Detail |
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public final Qt.Alignment alignment()
Returns the alignment of the scroll area's widget.
By default, the widget stays rooted to the top-left corner of the scroll area.
public final void ensureVisible(int x, int y, int xmargin)
Equivalent to ensureVisible(x, y, xmargin, 50).
public final void ensureVisible(int x, int y)
Equivalent to ensureVisible(x, y, 50, 50).
public final 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. 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)
Equivalent to ensureWidgetVisible(childWidget, xmargin, 50).
public final void ensureWidgetVisible(QWidget childWidget)
Equivalent to ensureWidgetVisible(childWidget, 50, 50).
public final 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. 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)
Sets the alignment of the scroll area's widget to arg__1.
By default, the widget stays rooted to the top-left corner of the scroll area.
public final void setAlignment(Qt.Alignment arg__1)
Sets the alignment of the scroll area's widget to arg__1.
By default, the widget stays rooted to the top-left corner of the scroll area.
public final void setWidget(QWidget widget)
Sets the scroll area's 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.
Note that if the scroll area is visible when the widget is added, you must show() it explicitly.
public final void setWidgetResizable(boolean resizable)
Sets whether the scroll area should resize the view widget to resizable.
If this property is set to false (the default), the scroll area honors the size of its widget. Regardless of this property, you can programmatically resize the widget using 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()
Removes the scroll area's widget, and passes ownership of the widget to the caller.
public final QWidget widget()
Returns the scroll area's widget, or 0 if there is none.
public final boolean widgetResizable()
Returns whether the scroll area should resize the view widget.
If this property is set to false (the default), the scroll area honors the size of its widget. Regardless of this property, you can programmatically resize the widget using 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 boolean event(QEvent arg__1)
This function is reimplemented for internal reasons.
event
in class QAbstractScrollArea
public boolean eventFilter(QObject arg__1, QEvent arg__2)
This function is reimplemented for internal reasons.
eventFilter
in class QObject
protected boolean focusNextPrevChild(boolean next)
This function is reimplemented for internal reasons.
focusNextPrevChild
in class QWidget
protected void resizeEvent(QResizeEvent arg__1)
This function is reimplemented for internal reasons.
resizeEvent
in class QAbstractScrollArea
protected void scrollContentsBy(int dx, int dy)
This function is reimplemented for internal reasons.
scrollContentsBy
in class QAbstractScrollArea
public QSize sizeHint()
This function is reimplemented for internal reasons.
sizeHint
in class QAbstractScrollArea
public static QScrollArea fromNativePointer(QNativePointer nativePointer)
nativePointer
- the QNativePointer of which object should be returned.
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