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JClass LiveTable Pro Basics

Table Anatomy · Text Component Management · Table Contexts

Using HTML Files to Set Properties · Displaying Reserved Characters within Cells

The JClass LiveTable Pro component is a scrollable window that displays text, images, Universal Resource Locator (URLs), or components in rows and columns. JClass LiveTable Pro also automatically handles interaction with a user: resizing rows/columns, text editing, scrolling, and cell selection.

Table Anatomy

Components of a Table

JClass LiveTable Pro provides a scrollable viewing area into its cells and labels. There are often far more cells than there is room to display. Scrollbars can be particularly useful when displaying large tables of information in an applet on a Web page. Instead of having to resize or scroll the browser display, the user can scroll the information within the table.

The following list defines the elements that are new to Java programmers:

Cell

A cell is an individual container of table data. A cell can contain text or any of the following objects:

If you intend to display a type of object not listed above (i.e. an integer) toString() is called to get displayable text.

A cell is visible if it is currently scrolled into view. The entire collection of displayed cells is called the cell area. Frozen cells or columns are non-scrollable cells.

Label

A non-editable cell appearing in a row at the top of the table, or in a column at the left side of a table. Like cells, labels can contain text or a component, and can display an image or URL.

Current Cell

This is the cell that currently has the user input focus. End-users can enter and edit the value of this cell (unless this ability is disabled).

Text Component Management

JClass LiveTable Pro creates and manages several child components for its own internal use. There are AWT components, plus two Scrollbars.

Standard Java components used by JClass LiveTable Pro

TextComponent

This component is the current cell. It moves a highlight rectangle. If the user types or clicks in the current cell, TextComponent is made visible and is displayed over the cell. It is unmanaged when the user traverses to another cell. It can be an AWT TextField or TextArea, depending on whether the cell contains more than one line of text or the cell's Multiline property has been set.

Scrollbar Components

These components are created and displayed if the number of rows or columns in the table is greater than the number of rows or columns visible on the screen. They provide end-users with the ability to scroll through the entire table.

Table Contexts

A context is composed of a row and column index, both zero-based. The current context specifies the portion of a table's cells and labels that an application sets and retrieves attributes for. Context defines the current context.

Cell and Label Referencing

The following describes the types of table contexts you can reference:

A Cell

Referenced by a row index and a column index, starting from zero. For example, the location of the second cell in the second row is (1, 1).

A Row Label

Referenced by a row index and the constant LABEL. For example, the second row's label is located at 1, LABEL). To reference all row labels, use (ALL, LABEL).

A Column Label

Referenced by the constant LABEL and a column index. For example, the second column's label is located at (LABEL, 1). To reference all column labels, use (LABEL, ALL).

All Cells in Row/Column

Referenced by the constant ALLCELLS. For example, to reference all of the cells in the second row, use (1, ALLCELLS).

Entire Row/Column

Referenced by the constant ALL and includes the label. For example, to reference the entire second column, use (ALL, 1).

All Cells in Table

Referenced by (ALLCELLS, ALLCELLS).

Entire Table

Referenced by (ALL, ALL) and includes the labels.

Range

Referenced by the location of the top-left cell/label and the location of the bottom-right cell/label in the range. A range is a block of cells and/or labels, and can be referenced as one context.

Setting Cell/Label Properties

Property specification lists values for a single property. In an HTML file, each member contains a context. It also contains a value surrounded by parentheses. The following property file fragment sets background colors for several contexts: 
     table.setBackground(JCTblEnum.ALL, JCTblEnum.ALL, Color.yellow);
     table.setForeground(JCTblEnum.ALL, JCTblEnum.ALL, Color.blue);
     table.setBackground(0, 3, Color.red);
     table.setForeground(0, 3, Color.yellow);

In this case, all of the backgrounds in the table are set to yellow, and their foregrounds (text) are set to black. The subsequent Backgroundand Foreground members and override this general condition by setting the background to red and the foreground to yellow for the cell located at 0, 3.

Using HTML Files to Set Properties

Sometimes, it is better to set the values of properties within a program using HTML files instead of hard-coded values. Property files provide the following benefits:

Most JClass LiveTable Pro properties can be set in HTML files, including properties. However, most properties are too complex or too obscure for end-users to want to modify them. HTML files for all the components in an application can be combined to create an application defaults file.

Displaying Reserved Characters within Cells

There are a number of characters which have been reserved for use within JClass LiveTable Pro. The following characters are reserved in JClass LiveTable Pro:

If any of these characters are to be displayed within a cell, they must be "escaped". The backslash character ("\") tells the JClass LiveTable Pro to escape the character that follows it--in other words, it ignores the usual function associated with the character, and simply displays it on-screen. Similarly, if the pipe, newline or round bracket characters have to be displayed within a cell, they are escaped by typing \|, \\n, \(, and \) respectively.