BasicListUI (Java SE 15 & JDK 15)
Description: declaration: module: java.desktop, package: javax.swing.plaf.basic, class: BasicListUI
Keywords: javax.swing.plaf.basic.BasicListUI class

Module java.desktop
Package javax.swing.plaf.basic

# Class BasicListUI

java.lang.Object
javax.swing.plaf.ComponentUI
javax.swing.plaf.ListUI
javax.swing.plaf.basic.BasicListUI

Direct Known Subclasses:
  `SynthListUI`

    public class BasicListUI
    extends ListUI

An extensible implementation of `ListUI`.

`BasicListUI` instances cannot be shared between multiple lists.

- ## Nested Class Summary

  Nested Classes
  Modifier and Type | Class | Description
  --- | --- | ---
  `class` | `BasicListUI.FocusHandler` | This class should be treated as a "protected" inner class.
  `class` | `BasicListUI.ListDataHandler` | The `ListDataListener` that's added to the `JLists` model at `installUI time`, and whenever the JList.model property changes.
  `class` | `BasicListUI.ListSelectionHandler` | The ListSelectionListener that's added to the JLists selection model at installUI time, and whenever the JList.selectionModel property changes.
  `class` | `BasicListUI.MouseInputHandler` | Mouse input, and focus handling for JList.
  `class` | `BasicListUI.PropertyChangeHandler` | The PropertyChangeListener that's added to the JList at installUI time.

- ## Field Summary

  Fields
  Modifier and Type | Field | Description
  --- | --- | ---
  `protected int` | `cellHeight` | The height of cell.
  `protected int[]` | `cellHeights` | The array of cells' height
  `protected static int` | `cellRendererChanged` | The bit relates to cell renderer changed property.
  `protected int` | `cellWidth` | The width of cell.
  `protected static int` | `fixedCellHeightChanged` | The bit relates to fixed cell height changed property.
  `protected static int` | `fixedCellWidthChanged` | The bit relates to fixed cell width changed property.
  `protected FocusListener` | `focusListener` | `FocusListener` that attached to `JList`.
  `protected static int` | `fontChanged` | The bit relates to font changed property.
  `protected JList<Object>` | `list` | The instance of `JList`.
  `protected ListDataListener` | `listDataListener` | `ListDataListener` that attached to `JList`.
  `protected ListSelectionListener` | `listSelectionListener` | `ListSelectionListener` that attached to `JList`.
  `protected static int` | `modelChanged` | The bit relates to model changed property.
  `protected MouseInputListener` | `mouseInputListener` | `MouseInputListener` that attached to `JList`.
  `protected PropertyChangeListener` | `propertyChangeListener` | `PropertyChangeListener` that attached to `JList`.
  `protected static int` | `prototypeCellValueChanged` | The bit relates to prototype cell value changed property.
  `protected CellRendererPane` | `rendererPane` | The instance of `CellRendererPane`.
  `protected static int` | `selectionModelChanged` | The bit relates to selection model changed property.
  `protected int` | `updateLayoutStateNeeded` | The value represents changes to `JList` model.

- ## Constructor Summary

  Constructors
  Constructor | Description
  --- | ---
  `BasicListUI()` |

- ## Method Summary

  Modifier and Type | Method | Description
  --- | --- | ---
  `protected int` | `convertRowToY​(int row)` | Return the `JList` relative Y coordinate of the origin of the specified row or -1 if row isn't valid.
  `protected int` | `convertYToRow​(int y0)` | Convert the `JList` relative coordinate to the row that contains it, based on the current layout.
  `protected FocusListener` | `createFocusListener()` | Returns an instance of `FocusListener`.
  `protected ListDataListener` | `createListDataListener()` | Creates an instance of `ListDataListener` that's added to the `JLists` by model as needed.
  `protected ListSelectionListener` | `createListSelectionListener()` | Creates an instance of `ListSelectionHandler` that's added to the `JLists` by selectionModel as needed.
  `protected MouseInputListener` | `createMouseInputListener()` | Creates a delegate that implements `MouseInputListener`.
  `protected PropertyChangeListener` | `createPropertyChangeListener()` | Creates an instance of `PropertyChangeHandler` that's added to the `JList` by `installUI()`.
  `static ComponentUI` | `createUI​(JComponent list)` | Returns a new instance of `BasicListUI`.
  `int` | `getBaseline​(JComponent c, int width, int height)` | Returns the baseline.
  `Component.BaselineResizeBehavior` | `getBaselineResizeBehavior​(JComponent c)` | Returns an enum indicating how the baseline of the component changes as the size changes.
  `Dimension` | `getPreferredSize​(JComponent c)` | The preferredSize of the list depends upon the layout orientation.
  `protected int` | `getRowHeight​(int row)` | Returns the height of the specified row based on the current layout.
  `protected void` | `installDefaults()` | Initializes list properties such as font, foreground, and background, and adds the CellRendererPane.
  `protected void` | `installKeyboardActions()` | Registers the keyboard bindings on the `JList` that the `BasicListUI` is associated with.
  `protected void` | `installListeners()` | Creates and installs the listeners for the JList, its model, and its selectionModel.
  `void` | `installUI​(JComponent c)` | Initializes `this.list` by calling `installDefaults()`, `installListeners()`, and `installKeyboardActions()` in order.
  `int` | `locationToIndex​(JList<?> list, Point location)` | Returns the cell index in the specified `JList` closest to the given location in the list's coordinate system.
  `protected void` | `maybeUpdateLayoutState()` | If updateLayoutStateNeeded is non zero, call updateLayoutState() and reset updateLayoutStateNeeded.
  `void` | `paint​(Graphics g, JComponent c)` | Paint the rows that intersect the Graphics objects clipRect.
  `protected void` | `paintCell​(Graphics g, int row, Rectangle rowBounds, ListCellRenderer<Object> cellRenderer, ListModel<Object> dataModel, ListSelectionModel selModel, int leadIndex)` | Paint one List cell: compute the relevant state, get the "rubber stamp" cell renderer component, and then use the `CellRendererPane` to paint it.
  `protected void` | `selectNextIndex()` | Selected the previous row and force it to be visible.
  `protected void` | `selectPreviousIndex()` | Selected the previous row and force it to be visible.
  `protected void` | `uninstallDefaults()` | Sets the list properties that have not been explicitly overridden to `null`.
  `protected void` | `uninstallKeyboardActions()` | Unregisters keyboard actions installed from `installKeyboardActions`.
  `protected void` | `uninstallListeners()` | Removes the listeners from the JList, its model, and its selectionModel.
  `void` | `uninstallUI​(JComponent c)` | Uninitializes `this.list` by calling `uninstallListeners()`, `uninstallKeyboardActions()`, and `uninstallDefaults()` in order.
  `protected void` | `updateLayoutState()` | Recompute the value of cellHeight or cellHeights based and cellWidth, based on the current font and the current values of fixedCellWidth, fixedCellHeight, and prototypeCellValue.

  ### Methods declared in class javax.swing.plaf.ListUI

  `getCellBounds, indexToLocation`

  ### Methods declared in class javax.swing.plaf.ComponentUI

  `contains, getAccessibleChild, getAccessibleChildrenCount, getMaximumSize, getMinimumSize, update`

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

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

- ## Field Details

  - ### list

    protected JList<Object> list
    The instance of `JList`.

  - ### rendererPane

    protected CellRendererPane rendererPane
    The instance of `CellRendererPane`.

  - ### focusListener

    protected FocusListener focusListener
    `FocusListener` that attached to `JList`.

  - ### mouseInputListener

    protected MouseInputListener mouseInputListener
    `MouseInputListener` that attached to `JList`.

  - ### listSelectionListener

    protected ListSelectionListener listSelectionListener
    `ListSelectionListener` that attached to `JList`.

  - ### listDataListener

    protected ListDataListener listDataListener
    `ListDataListener` that attached to `JList`.

  - ### propertyChangeListener

    protected PropertyChangeListener propertyChangeListener
    `PropertyChangeListener` that attached to `JList`.

  - ### cellHeights

    protected int[] cellHeights
    The array of cells' height

  - ### cellHeight

    protected int cellHeight
    The height of cell.

  - ### cellWidth

    protected int cellWidth
    The width of cell.

  - ### updateLayoutStateNeeded

    protected int updateLayoutStateNeeded
    The value represents changes to `JList` model.

  - ### modelChanged

    protected static final int modelChanged
    The bit relates to model changed property.
    See Also:
      Constant Field Values

  - ### selectionModelChanged

    protected static final int selectionModelChanged
    The bit relates to selection model changed property.
    See Also:
      Constant Field Values

  - ### fontChanged

    protected static final int fontChanged
    The bit relates to font changed property.
    See Also:
      Constant Field Values

  - ### fixedCellWidthChanged

    protected static final int fixedCellWidthChanged
    The bit relates to fixed cell width changed property.
    See Also:
      Constant Field Values

  - ### fixedCellHeightChanged

    protected static final int fixedCellHeightChanged
    The bit relates to fixed cell height changed property.
    See Also:
      Constant Field Values

  - ### prototypeCellValueChanged

    protected static final int prototypeCellValueChanged
    The bit relates to prototype cell value changed property.
    See Also:
      Constant Field Values

  - ### cellRendererChanged

    protected static final int cellRendererChanged
    The bit relates to cell renderer changed property.
    See Also:
      Constant Field Values

- ## Constructor Details

  - ### BasicListUI

    public BasicListUI()

- ## Method Details

  - ### paintCell

    protected void paintCell​(Graphics g, int row, Rectangle rowBounds, ListCellRenderer<Object> cellRenderer, ListModel<Object> dataModel, ListSelectionModel selModel, int leadIndex)
    Paint one List cell: compute the relevant state, get the "rubber stamp" cell renderer component, and then use the `CellRendererPane` to paint it. Subclasses may want to override this method rather than `paint()`.
    Parameters:
      `g` - an instance of `Graphics`
      `row` - a row
      `rowBounds` - a bounding rectangle to render to
      `cellRenderer` - a list of `ListCellRenderer`
      `dataModel` - a list model
      `selModel` - a selection model
      `leadIndex` - a lead index
    See Also:
      `paint(java.awt.Graphics, javax.swing.JComponent)`

  - ### paint

    public void paint​(Graphics g, JComponent c)
    Paint the rows that intersect the Graphics objects clipRect. This method calls paintCell as necessary. Subclasses may want to override these methods.
    Overrides:
      `paint` in class `ComponentUI`
    Parameters:
      `g` - the `Graphics` context in which to paint
      `c` - the component being painted; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components
    See Also:
      `paintCell(java.awt.Graphics, int, java.awt.Rectangle, javax.swing.ListCellRenderer<java.lang.Object>, javax.swing.ListModel<java.lang.Object>, javax.swing.ListSelectionModel, int)`

  - ### getBaseline

    public int getBaseline​(JComponent c, int width, int height)
    Returns the baseline.
    Overrides:
      `getBaseline` in class `ComponentUI`
    Parameters:
      `c` - `JComponent` baseline is being requested for
      `width` - the width to get the baseline for
      `height` - the height to get the baseline for
    Returns:
      baseline or a value < 0 indicating there is no reasonable baseline
    Throws:
      `NullPointerException` - if `c` is `null`
      `IllegalArgumentException` - if width or height is < 0
    Since:
      1.6
    See Also:
      `JComponent.getBaseline(int, int)`

  - ### getBaselineResizeBehavior

    public Component.BaselineResizeBehavior getBaselineResizeBehavior​(JComponent c)
    Returns an enum indicating how the baseline of the component changes as the size changes.
    Overrides:
      `getBaselineResizeBehavior` in class `ComponentUI`
    Parameters:
      `c` - `JComponent` to return baseline resize behavior for
    Returns:
      an enum indicating how the baseline changes as the component size changes
    Throws:
      `NullPointerException` - if `c` is `null`
    Since:
      1.6
    See Also:
      `JComponent.getBaseline(int, int)`

  - ### getPreferredSize

    public Dimension getPreferredSize​(JComponent c)
    The preferredSize of the list depends upon the layout orientation.

    Describes the preferred size for each layout orientation
    Layout Orientation | Preferred Size
    --- | ---
    JList.VERTICAL | The preferredSize of the list is total height of the rows and the maximum width of the cells. If JList.fixedCellHeight is specified then the total height of the rows is just (cellVerticalMargins + fixedCellHeight) * model.getSize() where rowVerticalMargins is the space we allocate for drawing the yellow focus outline. Similarly if fixedCellWidth is specified then we just use that.
    JList.VERTICAL_WRAP | If the visible row count is greater than zero, the preferredHeight is the maximum cell height * visibleRowCount. If the visible row count is <= 0, the preferred height is either the current height of the list, or the maximum cell height, whichever is bigger. The preferred width is than the maximum cell width * number of columns needed. Where the number of columns needs is list.height / max cell height. Max cell height is either the fixed cell height, or is determined by iterating through all the cells to find the maximum height from the ListCellRenderer.
    JList.HORIZONTAL_WRAP | If the visible row count is greater than zero, the preferredHeight is the maximum cell height * adjustedRowCount. Where visibleRowCount is used to determine the number of columns. Because this lays out horizontally the number of rows is then determined from the column count. For example, lets say you have a model with 10 items and the visible row count is 8. The number of columns needed to display this is 2, but you no longer need 8 rows to display this, you only need 5, thus the adjustedRowCount is 5. If the visible row count is <= 0, the preferred height is dictated by the number of columns, which will be as many as can fit in the width of the `JList` (width / max cell width), with at least one column. The preferred height then becomes the model size / number of columns * maximum cell height. Max cell height is either the fixed cell height, or is determined by iterating through all the cells to find the maximum height from the ListCellRenderer.

    The above specifies the raw preferred width and height. The resulting preferred width is the above width + insets.left + insets.right and the resulting preferred height is the above height + insets.top + insets.bottom. Where the `Insets` are determined from `list.getInsets()`.
    Overrides:
      `getPreferredSize` in class `ComponentUI`
    Parameters:
      `c` - The JList component.
    Returns:
      The total size of the list.
    See Also:
      `JComponent.getPreferredSize()`, `LayoutManager.preferredLayoutSize(java.awt.Container)`

  - ### selectPreviousIndex

    protected void selectPreviousIndex()
    Selected the previous row and force it to be visible.
    See Also:
      `JList.ensureIndexIsVisible(int)`

  - ### selectNextIndex

    protected void selectNextIndex()
    Selected the previous row and force it to be visible.
    See Also:
      `JList.ensureIndexIsVisible(int)`

  - ### installKeyboardActions

    protected void installKeyboardActions()
    Registers the keyboard bindings on the `JList` that the `BasicListUI` is associated with. This method is called at installUI() time.
    See Also:
      `installUI(javax.swing.JComponent)`

  - ### uninstallKeyboardActions

    protected void uninstallKeyboardActions()
    Unregisters keyboard actions installed from `installKeyboardActions`. This method is called at uninstallUI() time - subclassess should ensure that all of the keyboard actions registered at installUI time are removed here.
    See Also:
      `installUI(javax.swing.JComponent)`

  - ### installListeners

    protected void installListeners()
    Creates and installs the listeners for the JList, its model, and its selectionModel. This method is called at installUI() time.
    See Also:
      `installUI(javax.swing.JComponent)`, `uninstallListeners()`

  - ### uninstallListeners

    protected void uninstallListeners()
    Removes the listeners from the JList, its model, and its selectionModel. All of the listener fields, are reset to null here. This method is called at uninstallUI() time, it should be kept in sync with installListeners.
    See Also:
      `uninstallUI(javax.swing.JComponent)`, `installListeners()`

  - ### installDefaults

    protected void installDefaults()
    Initializes list properties such as font, foreground, and background, and adds the CellRendererPane. The font, foreground, and background properties are only set if their current value is either null or a UIResource, other properties are set if the current value is null.
    See Also:
      `uninstallDefaults()`, `installUI(javax.swing.JComponent)`, `CellRendererPane`

  - ### uninstallDefaults

    protected void uninstallDefaults()
    Sets the list properties that have not been explicitly overridden to `null`. A property is considered overridden if its current value is not a `UIResource`.
    See Also:
      `installDefaults()`, `uninstallUI(javax.swing.JComponent)`, `CellRendererPane`

  - ### installUI

    public void installUI​(JComponent c)
    Initializes `this.list` by calling `installDefaults()`, `installListeners()`, and `installKeyboardActions()` in order.
    Overrides:
      `installUI` in class `ComponentUI`
    Parameters:
      `c` - the component where this UI delegate is being installed
    See Also:
      `installDefaults()`, `installListeners()`, `installKeyboardActions()`

  - ### uninstallUI

    public void uninstallUI​(JComponent c)
    Uninitializes `this.list` by calling `uninstallListeners()`, `uninstallKeyboardActions()`, and `uninstallDefaults()` in order. Sets this.list to null.
    Overrides:
      `uninstallUI` in class `ComponentUI`
    Parameters:
      `c` - the component from which this UI delegate is being removed; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components
    See Also:
      `uninstallListeners()`, `uninstallKeyboardActions()`, `uninstallDefaults()`

  - ### createUI

    public static ComponentUI createUI​(JComponent list)
    Returns a new instance of `BasicListUI`. `BasicListUI` delegates are allocated one per `JList`.
    Parameters:
      `list` - a component
    Returns:
      a new `ListUI` implementation for the Windows look and feel.

  - ### locationToIndex

    public int locationToIndex​(JList<?> list, Point location)
    Returns the cell index in the specified `JList` closest to the given location in the list's coordinate system. To determine if the cell actually contains the specified location, compare the point against the cell's bounds, as provided by `getCellBounds`. This method returns `-1` if the list's model is empty.
    Specified by:
      `locationToIndex` in class `ListUI`
    Parameters:
      `list` - the list
      `location` - the coordinates of the point
    Returns:
      the cell index closest to the given location, or `-1`
    Throws:
      `NullPointerException` - if `location` is null

  - ### getRowHeight

    protected int getRowHeight​(int row)
    Returns the height of the specified row based on the current layout.
    Parameters:
      `row` - a row
    Returns:
      the specified row height or -1 if row isn't valid
    See Also:
      `convertYToRow(int)`, `convertRowToY(int)`, `updateLayoutState()`

  - ### convertYToRow

    protected int convertYToRow​(int y0)
    Convert the `JList` relative coordinate to the row that contains it, based on the current layout. If `y0` doesn't fall within any row, return -1.
    Parameters:
      `y0` - a relative Y coordinate
    Returns:
      the row that contains y0, or -1
    See Also:
      `getRowHeight(int)`, `updateLayoutState()`

  - ### convertRowToY

    protected int convertRowToY​(int row)
    Return the `JList` relative Y coordinate of the origin of the specified row or -1 if row isn't valid.
    Parameters:
      `row` - a row
    Returns:
      the Y coordinate of the origin of row, or -1
    See Also:
      `getRowHeight(int)`, `updateLayoutState()`

  - ### maybeUpdateLayoutState

    protected void maybeUpdateLayoutState()
    If updateLayoutStateNeeded is non zero, call updateLayoutState() and reset updateLayoutStateNeeded. This method should be called by methods before doing any computation based on the geometry of the list. For example it's the first call in paint() and getPreferredSize().
    See Also:
      `updateLayoutState()`

  - ### updateLayoutState

    protected void updateLayoutState()
    Recompute the value of cellHeight or cellHeights based and cellWidth, based on the current font and the current values of fixedCellWidth, fixedCellHeight, and prototypeCellValue.
    See Also:
      `maybeUpdateLayoutState()`

  - ### createMouseInputListener

    protected MouseInputListener createMouseInputListener()
    Creates a delegate that implements `MouseInputListener`. The delegate is added to the corresponding `java.awt.Component` listener lists at `installUI()` time. Subclasses can override this method to return a custom `MouseInputListener`, e.g.

         class MyListUI extends BasicListUI {
            protected MouseInputListener createMouseInputListener() {
                return new MyMouseInputHandler();
            }
            public class MyMouseInputHandler extends MouseInputHandler {
                public void mouseMoved(MouseEvent e) {
                    // do some extra work when the mouse moves
                    super.mouseMoved(e);
                }
            }
         }

    Returns:
      an instance of `MouseInputListener`
    See Also:
      `BasicListUI.MouseInputHandler`, `installUI(javax.swing.JComponent)`

  - ### createFocusListener

    protected FocusListener createFocusListener()
    Returns an instance of `FocusListener`.
    Returns:
      an instance of `FocusListener`

  - ### createListSelectionListener

    protected ListSelectionListener createListSelectionListener()
    Creates an instance of `ListSelectionHandler` that's added to the `JLists` by selectionModel as needed. Subclasses can override this method to return a custom `ListSelectionListener`, e.g.

         class MyListUI extends BasicListUI {
            protected ListSelectionListener createListSelectionListener() {
                return new MySelectionListener();
            }
            public class MySelectionListener extends ListSelectionHandler {
                public void valueChanged(ListSelectionEvent e) {
                    // do some extra work when the selection changes
                    super.valueChange(e);
                }
            }
         }

    Returns:
      an instance of `ListSelectionHandler`
    See Also:
      `BasicListUI.ListSelectionHandler`, `installUI(javax.swing.JComponent)`

  - ### createListDataListener

    protected ListDataListener createListDataListener()
    Creates an instance of `ListDataListener` that's added to the `JLists` by model as needed. Subclasses can override this method to return a custom `ListDataListener`, e.g.

         class MyListUI extends BasicListUI {
            protected ListDataListener createListDataListener() {
                return new MyListDataListener();
            }
            public class MyListDataListener extends ListDataHandler {
                public void contentsChanged(ListDataEvent e) {
                    // do some extra work when the models contents change
                    super.contentsChange(e);
                }
            }
         }

    Returns:
      an instance of `ListDataListener`
    See Also:
      `ListDataListener`, `JList.getModel()`, `installUI(javax.swing.JComponent)`

  - ### createPropertyChangeListener

    protected PropertyChangeListener createPropertyChangeListener()
    Creates an instance of `PropertyChangeHandler` that's added to the `JList` by `installUI()`. Subclasses can override this method to return a custom `PropertyChangeListener`, e.g.

         class MyListUI extends BasicListUI {
            protected PropertyChangeListener createPropertyChangeListener() {
                return new MyPropertyChangeListener();
            }
            public class MyPropertyChangeListener extends PropertyChangeHandler {
                public void propertyChange(PropertyChangeEvent e) {
                    if (e.getPropertyName().equals("model")) {
                        // do some extra work when the model changes
                    }
                    super.propertyChange(e);
                }
            }
         }

    Returns:
      an instance of `PropertyChangeHandler`
    See Also:
      `PropertyChangeListener`, `installUI(javax.swing.JComponent)`