SelectionModel (JavaFX 17)

Module javafx.controls
Package javafx.scene.control

## Class SelectionModel<T>

- java.lang.Object
- - javafx.scene.control.SelectionModel<T>

- Type Parameters:
    `T` - The type of the item contained in the control that can be selected.
  Direct Known Subclasses:
    `MultipleSelectionModel`, `SingleSelectionModel`

      public abstract class SelectionModel<T>
      extends Object

  SelectionModel is an abstract class used by UI controls to provide a consistent API for maintaining selection.
  Since:
    JavaFX 2.0

- - ### Property Summary

    Properties
    Type | Property | Description
    --- | --- | ---
    `ReadOnlyIntegerProperty` | `selectedIndex` | Refers to the selected index property, which is used to indicate the currently selected index value in the selection model.
    `ReadOnlyObjectProperty<T>` | `selectedItem` | Refers to the selected item property, which is used to indicate the currently selected item in the selection model.

  - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `SelectionModel()` | Creates a default SelectionModel instance.

  - ### Method Summary

    All Methods Instance Methods Abstract Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `abstract void` | `clearAndSelect​(int index)` | A method that clears any selection prior to setting the selection to the given index.
    `abstract void` | `clearSelection()` | Clears the selection model of all selected indices.
    `abstract void` | `clearSelection​(int index)` | This method will clear the selection of the item in the given index.
    `int` | `getSelectedIndex()` | Returns the integer value indicating the currently selected index in this model.
    `T` | `getSelectedItem()` | Returns the currently selected object (which resides in the selected index position).
    `abstract boolean` | `isEmpty()` | This method is available to test whether there are any selected indices/items.
    `abstract boolean` | `isSelected​(int index)` | This method tests whether the given index is currently selected in this SelectionModel.
    `abstract void` | `select​(int index)` | This will select the given index in the selection model, assuming the index is within the valid range (i.e.
    `abstract void` | `select​(T obj)` | This method will attempt to select the index that contains the given object.
    `ReadOnlyIntegerProperty` | `selectedIndexProperty()` | Refers to the selected index property, which is used to indicate the currently selected index value in the selection model.
    `ReadOnlyObjectProperty<T>` | `selectedItemProperty()` | Refers to the selected item property, which is used to indicate the currently selected item in the selection model.
    `abstract void` | `selectFirst()` | This method will attempt to select the first index in the control.
    `abstract void` | `selectLast()` | This method will attempt to select the last index in the control.
    `abstract void` | `selectNext()` | This method will attempt to select the index directly after the current focused index.
    `abstract void` | `selectPrevious()` | This method will attempt to select the index directly before the current focused index.
    `protected void` | `setSelectedIndex​(int value)` | Sets the value of the property selectedIndex.
    `protected void` | `setSelectedItem​(T value)` | Sets the value of the property selectedItem.

    - ### Methods declared in class java.lang.Object

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

- - ### Property Detail

    - #### selectedIndex

          public final ReadOnlyIntegerProperty selectedIndexProperty

      Refers to the selected index property, which is used to indicate the currently selected index value in the selection model. The selected index is either -1, to represent that there is no selection, or an integer value that is within the range of the underlying data model size.

      The selected index property is most commonly used when the selection model only allows single selection, but is equally applicable when in multiple selection mode. When in this mode, the selected index will always represent the last selection made.

      Note that in the case of multiple selection, it is possible to add a `ListChangeListener` to the collection returned by `MultipleSelectionModel.getSelectedIndices()` to be informed whenever the selection changes, and this will also work in the case of single selection.

      See Also:
        `getSelectedIndex()`, `setSelectedIndex(int)`

    - #### selectedItem

          public final ReadOnlyObjectProperty<T> selectedItemProperty

      Refers to the selected item property, which is used to indicate the currently selected item in the selection model. The selected item is either null, to represent that there is no selection, or an Object that is retrieved from the underlying data model of the control the selection model is associated with.

      The selected item property is most commonly used when the selection model is set to be single selection, but is equally applicable when in multiple selection mode. When in this mode, the selected item will always represent the last selection made.

      See Also:
        `getSelectedItem()`, `setSelectedItem(T)`

  - ### Constructor Detail

    - #### SelectionModel

          public SelectionModel()

      Creates a default SelectionModel instance.

  - ### Method Detail

    - #### selectedIndexProperty

          public final ReadOnlyIntegerProperty selectedIndexProperty()

      Refers to the selected index property, which is used to indicate the currently selected index value in the selection model. The selected index is either -1, to represent that there is no selection, or an integer value that is within the range of the underlying data model size.

      The selected index property is most commonly used when the selection model only allows single selection, but is equally applicable when in multiple selection mode. When in this mode, the selected index will always represent the last selection made.

      Note that in the case of multiple selection, it is possible to add a `ListChangeListener` to the collection returned by `MultipleSelectionModel.getSelectedIndices()` to be informed whenever the selection changes, and this will also work in the case of single selection.

      See Also:
        `getSelectedIndex()`, `setSelectedIndex(int)`

    - #### setSelectedIndex

          protected final void setSelectedIndex​(int value)

      Sets the value of the property selectedIndex.
      Property description:

        Refers to the selected index property, which is used to indicate the currently selected index value in the selection model. The selected index is either -1, to represent that there is no selection, or an integer value that is within the range of the underlying data model size.

        The selected index property is most commonly used when the selection model only allows single selection, but is equally applicable when in multiple selection mode. When in this mode, the selected index will always represent the last selection made.

        Note that in the case of multiple selection, it is possible to add a `ListChangeListener` to the collection returned by `MultipleSelectionModel.getSelectedIndices()` to be informed whenever the selection changes, and this will also work in the case of single selection.

    - #### getSelectedIndex

          public final int getSelectedIndex()

      Returns the integer value indicating the currently selected index in this model. If there are multiple items selected, this will return the most recent selection made.

      Note that the returned value is a snapshot in time - if you wish to observe the selection model for changes to the selected index, you can add a ChangeListener as such:

           SelectionModel sm = ...;
           InvalidationListener listener = ...;
           sm.selectedIndexProperty().addListener(listener);

      Returns:
        the selected index

    - #### selectedItemProperty

          public final ReadOnlyObjectProperty<T> selectedItemProperty()

      Refers to the selected item property, which is used to indicate the currently selected item in the selection model. The selected item is either null, to represent that there is no selection, or an Object that is retrieved from the underlying data model of the control the selection model is associated with.

      The selected item property is most commonly used when the selection model is set to be single selection, but is equally applicable when in multiple selection mode. When in this mode, the selected item will always represent the last selection made.

      See Also:
        `getSelectedItem()`, `setSelectedItem(T)`

    - #### setSelectedItem

          protected final void setSelectedItem​(T value)

      Sets the value of the property selectedItem.
      Property description:

        Refers to the selected item property, which is used to indicate the currently selected item in the selection model. The selected item is either null, to represent that there is no selection, or an Object that is retrieved from the underlying data model of the control the selection model is associated with.

        The selected item property is most commonly used when the selection model is set to be single selection, but is equally applicable when in multiple selection mode. When in this mode, the selected item will always represent the last selection made.

    - #### getSelectedItem

          public final T getSelectedItem()

      Returns the currently selected object (which resides in the selected index position). If there are multiple items selected, this will return the object contained at the index returned by getSelectedIndex() (which is always the index to the most recently selected item).

      Note that the returned value is a snapshot in time - if you wish to observe the selection model for changes to the selected item, you can add a ChangeListener as such:

           SelectionModel sm = ...;
           InvalidationListener listener = ...;
           sm.selectedItemProperty().addListener(listener);

      Returns:
        the selected item

    - #### clearAndSelect

          public abstract void clearAndSelect​(int index)

      A method that clears any selection prior to setting the selection to the given index. The purpose of this method is to avoid having to call `clearSelection()` first, meaning that observers that are listening to the `selected index` property will not see the selected index being temporarily set to -1.
      Parameters:
        `index` - The index that should be the only selected index in this selection model.

    - #### select

          public abstract void select​(int index)

      This will select the given index in the selection model, assuming the index is within the valid range (i.e. greater than or equal to zero, and less than the total number of items in the underlying data model).

      If there is already one or more indices selected in this model, calling this method will not clear these selections - to do so it is necessary to first call `clearSelection()`.

      If the index is already selected, it will not be selected again, or unselected. However, if multiple selection is implemented, then calling select on an already selected index will have the effect of making the index the new selected index (as returned by `getSelectedIndex()`.

      Parameters:
        `index` - The position of the item to select in the selection model.

    - #### select

          public abstract void select​(T obj)

      This method will attempt to select the index that contains the given object. It will iterate through the underlying data model until it finds an item whose value is equal to the given object. At this point it will stop iterating - this means that this method will not select multiple indices.

      Parameters:
        `obj` - The object to attempt to select in the underlying data model.

    - #### clearSelection

          public abstract void clearSelection​(int index)

      This method will clear the selection of the item in the given index. If the given index is not selected, nothing will happen.

      Parameters:
        `index` - The selected item to deselect.

    - #### clearSelection

          public abstract void clearSelection()

      Clears the selection model of all selected indices.

    - #### isSelected

          public abstract boolean isSelected​(int index)

      This method tests whether the given index is currently selected in this SelectionModel.
      Parameters:
        `index` - The index to check as to whether it is currently selected or not.
      Returns:
        True if the given index is selected, false otherwise.

    - #### isEmpty

          public abstract boolean isEmpty()

      This method is available to test whether there are any selected indices/items. It will return true if there are no selected items, and false if there are.
      Returns:
        Will return true if there are no selected items, and false if there are.

    - #### selectPrevious

          public abstract void selectPrevious()

      This method will attempt to select the index directly before the current focused index. If clearSelection is not called first, this method will have the result of selecting the previous index, whilst retaining the selection of any other currently selected indices.

      Calling this method will only succeed if:

      - There is currently a lead/focused index.
      - The lead/focus index is not the first index in the control.
      - The previous index is not already selected.

      If any of these conditions is false, no selection event will take place.

    - #### selectNext

          public abstract void selectNext()

      This method will attempt to select the index directly after the current focused index. If clearSelection is not called first, this method will have the result of selecting the next index, whilst retaining the selection of any other currently selected indices.

      Calling this method will only succeed if:

      - There is currently a lead/focused index.
      - The lead/focus index is not the last index in the control.
      - The next index is not already selected.

      If any of these conditions is false, no selection event will take place.

    - #### selectFirst

          public abstract void selectFirst()

      This method will attempt to select the first index in the control. If clearSelection is not called first, this method will have the result of selecting the first index, whilst retaining the selection of any other currently selected indices.

      If the first index is already selected, calling this method will have no result, and no selection event will take place.

    - #### selectLast

          public abstract void selectLast()

      This method will attempt to select the last index in the control. If clearSelection is not called first, this method will have the result of selecting the last index, whilst retaining the selection of any other currently selected indices.

      If the last index is already selected, calling this method will have no result, and no selection event will take place.