當事件發生時，要求程式畫出一個文字欄位，把 tool tip 要顯示的東西放在欄位上。
範例的滑鼠停留事件可以參考 [1]。
以下先節錄 [1] 定義的 tool tip 事件的 class。
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import org.eclipse.swt.SWT;import org.eclipse.swt.events.HelpEvent;import org.eclipse.swt.events.HelpListener;import org.eclipse.swt.events.MouseAdapter;import org.eclipse.swt.events.MouseEvent;import org.eclipse.swt.events.MouseTrackAdapter;import org.eclipse.swt.graphics.Image;import org.eclipse.swt.graphics.Point;import org.eclipse.swt.graphics.Rectangle;import org.eclipse.swt.layout.FillLayout;import org.eclipse.swt.layout.GridData;import org.eclipse.swt.layout.GridLayout;import org.eclipse.swt.widgets.Control;import org.eclipse.swt.widgets.Display;import org.eclipse.swt.widgets.Label;import org.eclipse.swt.widgets.Shell;import org.eclipse.swt.widgets.Table;import org.eclipse.swt.widgets.ToolBar;import org.eclipse.swt.widgets.Tree;import org.eclipse.swt.widgets.Widget;/** * Emulated tooltip handler Notice that we could display anything in a tooltip * besides text and images. For instance, it might make sense to embed large * tables of data or buttons linking data under inspection to material * elsewhere, or perform dynamic lookup for creating tooltip text on the fly. */public class ToolTipHandler { private Shell parentShell; private Shell tipShell; private Label tipLabelImage, tipLabelText; private Widget tipWidget; // widget this tooltip is hovering over private Point tipPosition; // the position being hovered over /** * Creates a new tooltip handler * @param parent * the parent Shell */ public ToolTipHandler(Shell parent) { final Display display = parent.getDisplay(); this.parentShell = parent; tipShell = new Shell(parent, SWT.ON_TOP | SWT.TOOL); GridLayout gridLayout = new GridLayout(); gridLayout.numColumns = 2; gridLayout.marginWidth = 2; gridLayout.marginHeight = 2; tipShell.setLayout(gridLayout); tipShell.setBackground(display.getSystemColor(SWT.COLOR_INFO_BACKGROUND)); tipLabelImage = new Label(tipShell, SWT.NONE); tipLabelImage.setForeground(display.getSystemColor(SWT.COLOR_INFO_FOREGROUND)); tipLabelImage.setBackground(display.getSystemColor(SWT.COLOR_INFO_BACKGROUND)); tipLabelImage.setLayoutData( new GridData(GridData.FILL_HORIZONTAL | GridData.VERTICAL_ALIGN_CENTER)); tipLabelText = new Label(tipShell, SWT.NONE); tipLabelText.setForeground(display.getSystemColor(SWT.COLOR_INFO_FOREGROUND)); tipLabelText.setBackground(display.getSystemColor(SWT.COLOR_INFO_BACKGROUND)); tipLabelText.setLayoutData( new GridData(GridData.FILL_HORIZONTAL | GridData.VERTICAL_ALIGN_CENTER)); } /** * Enables customized hover help for a specified control * * @control the control on which to enable hoverhelp */ public void activateHoverHelp(final Control control) { // Get out of the way if we attempt to activate the control underneath the tooltip control.addMouseListener(new MouseAdapter() { public void mouseDown(MouseEvent e) { if (tipShell.isVisible()) tipShell.setVisible(false); } }); // Trap hover events to pop-up tooltip control.addMouseTrackListener(new MouseTrackAdapter() { public void mouseExit(MouseEvent e) { if (tipShell.isVisible()) tipShell.setVisible(false); tipWidget = null; } public void mouseHover(MouseEvent event) { Point pt = new Point(event.x, event.y); Widget widget = event.widget; if (widget instanceof ToolBar) { ToolBar w = (ToolBar) widget; widget = w.getItem(pt); } if (widget instanceof Table) { Table w = (Table) widget; widget = w.getItem(pt); } if (widget instanceof Tree) { Tree w = (Tree) widget; widget = w.getItem(pt); } if (widget == null) { tipShell.setVisible(false); tipWidget = null; return; } if (widget == tipWidget) return; tipWidget = widget; tipPosition = control.toDisplay(pt); String text = (String) widget.getData("TIP_TEXT"); Image image = (Image) widget.getData("TIP_IMAGE"); tipLabelText.setText(text != null ? text : ""); tipLabelImage.setImage(image); // accepts null tipShell.pack(); setHoverLocation(tipShell, tipPosition); tipShell.setVisible(true); } }); // Trap F1 Help to pop up a custom help box control.addHelpListener(new HelpListener() { public void helpRequested(HelpEvent event) { if (tipWidget == null) return; ToolTipHelpTextHandler handler = (ToolTipHelpTextHandler) tipWidget .getData("TIP_HELPTEXTHANDLER"); if (handler == null) return; String text = handler.getHelpText(tipWidget); if (text == null) return; if (tipShell.isVisible()) { tipShell.setVisible(false); Shell helpShell = new Shell(parentShell, SWT.SHELL_TRIM); helpShell.setLayout(new FillLayout()); Label label = new Label(helpShell, SWT.NONE); label.setText(text); helpShell.pack(); setHoverLocation(helpShell, tipPosition); helpShell.open(); } } }); } /** * Sets the location for a hovering shell * * @param shell * the object that is to hover * @param position * the position of a widget to hover over * @return the top-left location for a hovering box */ private void setHoverLocation(Shell shell, Point position) { Rectangle displayBounds = shell.getDisplay().getBounds(); Rectangle shellBounds = shell.getBounds(); shellBounds.x = Math.max( Math.min(position.x, displayBounds.width - shellBounds.width), 0); shellBounds.y = Math.max( Math.min(position.y + 16, displayBounds.height - shellBounds.height), 0); shell.setBounds(shellBounds); } /** * ToolTip help handler */ public interface ToolTipHelpTextHandler { /** * Get help text * @param widget * the widget that is under help * @return a help text string */ public String getHelpText(Widget widget); }} |
接著當需要放 tool tip 時，可以加入以下的程式碼。
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Shell shell = new Shell();ToolTipHandler tooltipHandler = new ToolTipHandler(shell.getShell());// Initial table and table item.Table table = new Table(shell, SWT.BORDER);TableItem item = new TableItem(table, SWT.PUSH);// Set properties about tool tip.item.setData("TIP_TEXT", "tool tip");item.setData("TIP_HELPTEXTHANDLER", new ToolTipHelpTextHandler() { public String getHelpText(Widget widget) { Item item = (Item) widget; return "tool tip" }});// Activate the tool tip on the table. (Bind events for the Control object)tooltipHandler.activateHoverHelp(table); |
不過詳細的原理我還沒仔細看，所以暫時先不加註語法的解釋了。
需要其他的範例的話，可以直接參考 [1] 的原始碼，上面有好幾種介面的使用範例
並且在 [1] 的範例中，都是有在 tool tip 上放圖的。
PS. 不過要直接執行 [1] 的範例程式碼時，記得自己放 notification.gif 和 warning.gif 兩個圖檔！
參考資料：
1、How to implement hover help feedback using the MouseTrackListener
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