TablePanel class which adds a scrollbar to the east of the
* table canvas.
*
* This TableCanvas class should not have to be used manually.
* All its methods are redirected from the TablePanel class.
*/
public class TableCanvas extends Panel {
int start;
Vector key;
Font font;
int panel_height, panel_width;
FontMetrics fm;
Dimension offscreensize = null;
Image offscreen = null;
Graphics offGraphics = null;
TablePanel panel;
final int vertSpace = 17;
int highlight;
/**
* Constructor method of the TableCanvas class.
* @param parent The panel with a scrollbar where this table canvas
* is going to reside.
*/
public TableCanvas(TablePanel parent) {
this.panel = parent;
this.start = 0;
this.key = new Vector();
this.font = new Font("Courier", Font.PLAIN, 12);
this.fm = this.getFontMetrics(font);
this.highlight = -1;
}
/**
* Initialize the table and set all entries to null.
*/
public void init() {
this.key = new Vector();
}
/**
* Set the starting row, which will be displayed by the table.
* @param start The first row to be shown at any one time.
*/
public void setStart(int start) {
if ((start + 6) < key.size())
this.start = start;
else if (key.size() > 6)
this.start = key.size() - 7;
else
this.start = 0;
}
/**
* Highlight the table entry with the row specified by the parameter.
* There can only be one row highlighted at any one time. If a row
* has already been highlighted and this highlightRow
* method is called on another different row, the previously highlighted
* row will be restored and the new row will be highlighted.
* @param i The row to be highlighted.
*/
public void highlightRow(int i) {
this.highlight = i;
}
/**
* This method is used to restore any highlighted row.
*/
public void restoreRow() {
this.highlight = -1;
}
/**
* This method is called to set the size of the table and hence
* rescale the scrollbar on the panel it resides in.
* @param size The new size of this table.
*/
public void setTableSize(int size) {
key = new Vector(size);
key.setSize(size);
panel.vScrollbar.setValues(panel.vScrollbar.getValue(),
1, 0, size-1);
}
/**
* Set the object specified by the first parameter to the table row
* defined by the second parameter.
* @param obj The object to be added to the table.
* @param posn The row number where the object is going to be added.
*/
public void setTableEntry(Object obj, int posn) {
if (key.size() > posn) {
key.removeElementAt(posn);
key.insertElementAt(obj, posn);
}
}
/**
* Obtain the object placed at the table row specified by the parameter.
* @param posn Table row where the object is to be obtained.
* @return The table object at the row specified by the parameter.
*/
public Object getTableEntryAt(int posn) {
Object result = null;
if (key.size() > posn)
result = key.elementAt(posn);
return result;
}
/**
* Check if the table has been fully filled up.
* @return TRUE if all entries in the table is non-null object;
* FALSE otherwise.
*/
public boolean full() {
boolean f = true;
for (int i = 0; i < tableSize(); i++) {
if (key.elementAt(i) == null) {
f = false;
break;
}
}
return f;
}
/**
* Get the number of rows in the table where the contents are non-null
* object.
* @return The number of non-null object in the table.
*/
public int numOccupied() {
int count = 0;
for (int i = 0; i < tableSize(); i++) {
if (key.elementAt(i) != null)
count++;
}
return count;
}
/**
* Check if a particular row in the table has a non-null object.
* @param i The row number of the table to be checked.
* @return TRUE if the row specified by the parameter is occupied.
*/
public boolean occupied(int i) {
if (i >= 0 && i < tableSize())
return (key.elementAt(i) != null);
else
return true;
}
/**
* Display a status summary of the table regarding the percentage
* of the table being occupied, the number of clusters in the table,
* and a rough idea of the location of the table being occupied.
* @param g Graphical context of the drawing panel where the status
* information is going to be shown.
* @param x The left most position of the status information display.
* @param y The top most position of the status information display.
*/
public void drawClusters(Graphics g, int x, int y) {
g.setColor(Color.lightGray);
g.drawRect(x, y, tableSize()*3 + 2, 21);
g.setColor(Color.red);
g.setFont(font);
int numOccupied = 0;
int numClusters = 0;
for (int i = 0; i < tableSize(); i++) {
if (key.elementAt(i) != null) {
g.fillRect(x+1+i*3, y+1, 3, 20);
numOccupied++;
if (i==0)
numClusters++;
else if (key.elementAt(i-1) == null)
numClusters++;
}
if ( (i%25) == 0 ) {
g.setColor(Color.black);
g.drawString("" + i, x+i*3, y - 2);
g.setColor(Color.red);
}
}
g.setColor(Color.black);
g.drawString("Percent", x - 50, y + 30);
g.drawString("full", x - 40, y + 42);
g.drawString(""+ (numOccupied*100/tableSize()) + "%",
x - 30, y + 16);
g.drawString(""+ numClusters,
x + tableSize()*3 + 10, y + 16);
g.drawString("Clusters",
x + tableSize()*3 + 4, y + 30);
g.drawString("Address", x + tableSize()*3/2 - 20, y - 15);
g.drawString("Keys Placed in Table", x + tableSize()*3/2 - 70, y + 35);
}
/**
* Add an entry to the table and push the existing entries after this
* newly added object one position down.
* @param obj The new object to be added to the table.
* @param posn The position in the table (row) where the new object is to
* be added.
*/
public void addTableEntry(Object obj, int posn) {
if (key.size() >= posn) {
key.insertElementAt(obj, posn);
panel.vScrollbar.setValues(panel.vScrollbar.getValue(),
1, 0, key.size()-1);
}
}
/**
* Get the maximum size of the table (including all null and non-null
* objects).
* @return The maximum size of the table.
*/
public int tableSize() {
return key.size();
}
/**
* Check if the table contains a certain object specified by the parameter.
* @param obj The object which is going to be checked for existence.
* @return TRUE if the object exists; FALSE otherwise.
*/
public boolean contains(Object obj) {
boolean contain = false;
for (int i = 0; i < tableSize(); i++) {
if (obj == null || key.elementAt(i) == null)
continue;
if (obj.equals(key.elementAt(i))) {
contain = true;
break;
}
}
return contain;
}
/**
* Get the location of an object in the table.
* @param obj The object which location is being checked.
* @return The row number of the object passed in as the parameter. This
* method will return -1 if the object does not exist within the current
* table.
*/
public int indexOf(Object obj) {
int index = -1;
for (int i = 0; i < tableSize(); i++) {
if (obj == null || key.elementAt(i) == null)
continue;
if (obj.equals(key.elementAt(i))) {
index = i;
break;
}
}
return index;
}
/**
* Define the default size of the table.
* @return The dimension of the table. By default is: 480x320.
*/
public Dimension preferredSize() {
return new Dimension(480, 320);
}
/**
* This method is invoked by the display manager when the
* repaint() method of the panel is called. This method
* is overridden here to eliminate the flashing characteristic during
* the panel update.
*/
public void update(Graphics g) {
Dimension d = size();
if (d.width < 1 || d.height < 1)
return;
if ((offscreen == null) || (d.width != offscreensize.width) ||
(d.height != offscreensize.height)) {
offscreen = createImage(d.width, d.height);
offscreensize = d;
offGraphics = offscreen.getGraphics();
}
offGraphics.setColor(getBackground());
offGraphics.fillRect(0, 0, d.width, d.height);
offGraphics.setFont(font);
fm = offGraphics.getFontMetrics();
paint(offGraphics);
g.drawImage(offscreen, 0, 0, null);
}
/**
* Method to draw the table canvas.
*/
public void paint(Graphics g) {
panel_height = size().height;
panel_width = size().width;
int row = 1;
for (int i = start; i < key.size(); i++) {
drawBox(g, 0, row, ""+i,
Color.black, Color.lightGray, 3);
String content = (String)key.elementAt(i);
if (content == null) {
drawBox(g, 26, row, content,
Color.black, Color.pink, 28);
} else if (highlight == i)
drawBox(g, 26, row, content,
Color.white, Color.blue, 28);
else
drawBox(g, 26, row, content,
Color.blue, Color.white, 28);
row += vertSpace + 2;;
}
} // paint();
/**
* This method is only called by the paint() method to draw
* each entry of the table as a box.
* @param g Graphical context.
* @param x The left most position of the box.
* @param y The top most position of the box.
* @param str The String object to be drawn inside the box.
* @param fg Foreground color (i.e. the text color) of the box.
* @param bg Background color of the box.
* @param max_length The max_length of the string to be displayed in
* the box.
*/
public void drawBox(Graphics g, int x, int y, String str,
Color fg, Color bg, int max_length) {
int horizSpace = max_length * 8;
g.setColor(bg);
g.fillRect(x, y, horizSpace, vertSpace);
g.setColor(Color.black);
g.drawRect(x, y, horizSpace, vertSpace);
g.setColor(fg);
g.setFont(font);
if (str != null)
g.drawString(str, x + 2, y + vertSpace - 4);
}
} // TableCanvas