Class ComponentView

java.lang.Object
javax.swing.text.View
javax.swing.text.ComponentView
All Implemented Interfaces:
SwingConstants
Direct Known Subclasses:
FormView, ObjectView 
public class ComponentView extends View
Component decorator that implements the view interface. The entire element is used to represent the component. This acts as a gateway from the display-only View implementations to interactive lightweight components (ie it allows components to be embedded into the View hierarchy).

The component is placed relative to the text baseline according to the value returned by Component.getAlignmentY. For Swing components this value can be conveniently set using the method JComponent.setAlignmentY. For example, setting a value of 0.75 will cause 75 percent of the component to be above the baseline, and 25 percent of the component to be below the baseline.

This class is implemented to do the extra work necessary to work properly in the presence of multiple threads (i.e. from asynchronous notification of model changes for example) by ensuring that all component access is done on the event thread.

The component used is determined by the return value of the createComponent method. The default implementation of this method is to return the component held as an attribute of the element (by calling StyleConstants.getComponent). A limitation of this behavior is that the component cannot be used by more than one text component (i.e. with a shared model). Subclasses can remove this constraint by implementing the createComponent to actually create a component based upon some kind of specification contained in the attributes. The ObjectView class in the html package is an example of a ComponentView implementation that supports multiple component views of a shared model.

Field Summary

Fields declared in class javax.swing.text.View

BadBreakWeight, ExcellentBreakWeight, ForcedBreakWeight, GoodBreakWeight, X_AXIS, Y_AXIS

Fields declared in interface javax.swing.SwingConstants

BOTTOM, CENTER, EAST, HORIZONTAL, LEADING, LEFT, NEXT, NORTH, NORTH_EAST, NORTH_WEST, PREVIOUS, RIGHT, SOUTH, SOUTH_EAST, SOUTH_WEST, TOP, TRAILING, VERTICAL, WEST

Constructor Summary

Constructor Description
ComponentView(Element elem)
Creates a new ComponentView object.

Method Summary

Modifier and Type Method Description
protected Component createComponent()
Create the component that is associated with this view.
float getAlignment(int axis)
Determines the desired alignment for this view along an axis.
final Component getComponent()
Fetch the component associated with the view.
float getMaximumSpan(int axis)
Determines the maximum span for this view along an axis.
float getMinimumSpan(int axis)
Determines the minimum span for this view along an axis.
float getPreferredSpan(int axis)
Determines the preferred span for this view along an axis.
Shape modelToView(int pos, Shape a, Position.Bias b)
Provides a mapping from the coordinate space of the model to that of the view.
void paint(Graphics g, Shape a)
The real paint behavior occurs naturally from the association that the component has with its parent container (the same container hosting this view).
void setParent(View p)
Sets the parent for a child view.
int viewToModel(float x, float y, Shape a, Position.Bias[] bias)
Provides a mapping from the view coordinate space to the logical coordinate space of the model.

Methods declared in class javax.swing.text.View

append, breakView, changedUpdate, createFragment, forwardUpdate, forwardUpdateToView, getAttributes, getBreakWeight, getChildAllocation, getContainer, getDocument, getElement, getEndOffset, getGraphics, getNextVisualPositionFrom, getParent, getResizeWeight, getStartOffset, getToolTipText, getView, getViewCount, getViewFactory, getViewIndex, getViewIndex, insert, insertUpdate, isVisible, modelToView, modelToView, preferenceChanged, remove, removeAll, removeUpdate, replace, setSize, updateChildren, updateLayout, viewToModel

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

ComponentView

public ComponentView(Element elem)
Creates a new ComponentView object.
Parameters:
elem - the element to decorate

Method Details

createComponent

protected Component createComponent()
Create the component that is associated with this view. This will be called when it has been determined that a new component is needed. This would result from a call to setParent or as a result of being notified that attributes have changed.
Returns:
the component that is associated with this view

getComponent

public final Component getComponent()
Fetch the component associated with the view.
Returns:
the component associated with the view

paint

public void paint(Graphics g, Shape a)
The real paint behavior occurs naturally from the association that the component has with its parent container (the same container hosting this view). This is implemented to do nothing.
Specified by:
paint in class View
Parameters:
g - the graphics context
a - the shape
See Also:

getPreferredSpan

public float getPreferredSpan(int axis)
Determines the preferred span for this view along an axis. This is implemented to return the value returned by Component.getPreferredSize along the axis of interest.
Specified by:
getPreferredSpan in class View
Parameters:
axis - may be either View.X_AXIS or View.Y_AXIS
Returns:
the span the view would like to be rendered into >=0. Typically the view is told to render into the span that is returned, although there is no guarantee. The parent may choose to resize or break the view.
Throws:
IllegalArgumentException - for an invalid axis

getMinimumSpan

public float getMinimumSpan(int axis)
Determines the minimum span for this view along an axis. This is implemented to return the value returned by Component.getMinimumSize along the axis of interest.
Overrides:
getMinimumSpan in class View
Parameters:
axis - may be either View.X_AXIS or View.Y_AXIS
Returns:
the span the view would like to be rendered into >=0. Typically the view is told to render into the span that is returned, although there is no guarantee. The parent may choose to resize or break the view.
Throws:
IllegalArgumentException - for an invalid axis
See Also:

getMaximumSpan

public float getMaximumSpan(int axis)
Determines the maximum span for this view along an axis. This is implemented to return the value returned by Component.getMaximumSize along the axis of interest.
Overrides:
getMaximumSpan in class View
Parameters:
axis - may be either View.X_AXIS or View.Y_AXIS
Returns:
the span the view would like to be rendered into >=0. Typically the view is told to render into the span that is returned, although there is no guarantee. The parent may choose to resize or break the view.
Throws:
IllegalArgumentException - for an invalid axis
See Also:

getAlignment

public float getAlignment(int axis)
Determines the desired alignment for this view along an axis. This is implemented to give the alignment of the embedded component.
Overrides:
getAlignment in class View
Parameters:
axis - may be either View.X_AXIS or View.Y_AXIS
Returns:
the desired alignment. This should be a value between 0.0 and 1.0 where 0 indicates alignment at the origin and 1.0 indicates alignment to the full span away from the origin. An alignment of 0.5 would be the center of the view.

setParent

public void setParent(View p)
Sets the parent for a child view. The parent calls this on the child to tell it who its parent is, giving the view access to things like the hosting Container. The superclass behavior is executed, followed by a call to createComponent if the parent view parameter is non-null and a component has not yet been created. The embedded components parent is then set to the value returned by getContainer. If the parent view parameter is null, this view is being cleaned up, thus the component is removed from its parent.

The changing of the component hierarchy will touch the component lock, which is the one thing that is not safe from the View hierarchy. Therefore, this functionality is executed immediately if on the event thread, or is queued on the event queue if called from another thread (notification of change from an asynchronous update).

Overrides:
setParent in class View
Parameters:
p - the parent

modelToView

public Shape modelToView(int pos, Shape a, Position.Bias b) throws BadLocationException
Provides a mapping from the coordinate space of the model to that of the view.
Specified by:
modelToView in class View
Parameters:
pos - the position to convert >=0
a - the allocated region to render into
b - the bias toward the previous character or the next character represented by the offset, in case the position is a boundary of two views; b will have one of these values:
  • Position.Bias.Forward
  • Position.Bias.Backward
Returns:
the bounding box of the given position is returned
Throws:
BadLocationException - if the given position does not represent a valid location in the associated document
See Also:

viewToModel

public int viewToModel(float x, float y, Shape a, Position.Bias[] bias)
Provides a mapping from the view coordinate space to the logical coordinate space of the model.
Specified by:
viewToModel in class View
Parameters:
x - the X coordinate >=0
y - the Y coordinate >=0
a - the allocated region to render into
bias - the returned bias
Returns:
the location within the model that best represents the given point in the view
See Also:

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https://docs.oracle.com/en/java/javase/17/docs/api/java.desktop/javax/swing/text/ComponentView.html