![]() ![]() While it might appear that JTable and JTree objects are focus cycle roots, they are not.Ī focus traversal policy determines the order in which a group of components are navigated. The following Swing objects can be focus cycle roots: JApplet, JDesktopPane, JDialog, JEditorPane, JFrame, JInternalFrame, and JWindow. A focus cycle root can itself contain one or more focus cycle roots. By default, every JWindow and JInternalFrame component can be a focus cycle root. The focus cycle root is the container that is the root for a particular focus traversal cycle. JWindow component, or to use an undecoratedĪ focus cycle (or focus traversal cycle) is a set of components that share a common ancestor in the containment hierarchy. The solution is either to specify a visible owning frame when creating the The result is that components in the JWindow component might not be able to get the focus. By default, if you do not specify an owning frame for a JWindow component, an invisible owning frame is created for it. JWindow and focus: To use a JWindow component in your GUI, you should know that the JWindow component's owning frame must be visible in order for any components in the window to get the focus. The FocusConceptsDemo example illustrates a few concepts. To fix this issue, you need to make sure that it satisfies all the requirements outlined in Making a Custom Component Focusable. A custom component is not getting the focus.Input verification is a solution to this problem. A component must to be prevented from losing focus, or you need to check a value in a component before it loses focus.For more details see Customizing Focus Traversal. To fix this issue, you can change the containment hierarchy, you can change the order that the components are added to their containers, or you can create a custom focus traversal policy. As shown in a code snippet in the preceding section, you can use the requestFocusInWindow method to set the focus on a component when the window becomes visible. The ordering is right but the first component with the focus is not set.In most cases it behaves in a reasonable manner, and if it does not you can tweak its behavior in various ways. The focus subsystem is designed to do the right thing as invisibly as possible. Tracking Focus Changes to Multiple Components.The rest of this section covers the following topics: This button will have the initial focus.įtVisible(true) //Display the window.Īlternatively, you can apply a custom FocusTraversalPolicy to the frame and call the getDefaultComponent method to determine which component will gain the focus. JButton button = new JButton("I am first") įrame.getContentPane().add(panel) //Add it to the panel Create the component that will have the initial focus. JPanel panel = new JPanel(new BorderLayout()) This code snippet shows how to give a particular component the focus every time the window gains the focus: A component can also be given the focus programmatically, such as when its containing frame or dialog-box is made visible. However, on other operating systems, such as Solaris™ Operating System, the window manager may choose the focused window based on cursor position, and in these cases the behavior of the Window.toFront method is different.Ī component generally gains the focus when the user clicks it, or when the user tabs between components, or otherwise interacts with a component. Window.toFront method moves the window to the front, thereby giving it the focus. On some operating systems, such as Microsoft Windows, the front window usually becomes the focused window. There is no foolproof way, across all platforms, to ensure that a window gains the focus. Only one component at a time in the window system can have the keyboard focus.Įxactly how a window gains the focus depends on the windowing system. These visual cues let the user know to which component any typing will relate. The window containing the component is also more prominent than other windows onscreen. For a key press to affect a component, the component must have the keyboard focus.įrom the user's point of view, the component with the keyboard focus is generally prominent with a dotted or black border, for example. Many components even those primarily operated with the mouse, such as buttons can be operated with the keyboard. ![]()
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