I am creating a simple Mahjong game for a final project at school and seem to be having some troubles with the drawString() method on the Graphics/Graphics2D object. I call the drawString method and see nothing written to the screen.
In my scenario I have extended the JFrame class and overridden the paintComponent() method to create a custom graphical object, specifically a mahjong tile. Using polygons described in various arrays I create a faux 3D view of a tile drawing the face, right side, and bottom of the tile. These polygons are filled using GradientPaint objects to give the tile a better appearance. Here is what it looks like:
My Tile class looks like this (note: some code was omitted for brevity):
public class Tile extends JPanel
{
private int _width;
private int _height;
private int _depth;
/**
* Accessor to get the center of the face of the rendered
* mahjong tile.
*
* @return A point containing the center of the face of the tile.
*/
public Point getCenter()
{
return new Point(_width / 2, _height / 2);
}
/**
* The default constructor creates a tile that is proportionally
* calculated to 80 pixels wide.
*/
public Tile()
{
this(80);
}
/**
* Given the width parameter a mahjong tile is drawn according to
* the proportions of a size 8 mahjong tile.
*
* @param width The width of the tile to be rendered.
*/
public Tile(int width)
{
_width = width;
_height = (int)(width * 1.23);
_depth = (int)((width * 0.3) / 2);
setPreferredSize(new Dimension((_width + _depth) + 1, (_height + _depth) + 1));
}
@Override public void paintComponent(Graphics g)
{
// ... setup polygon arrays ...
super.paintComponent(g);
Graphics2D g2d = (Graphics2D)g;
// Turn on anti-aliasing.
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// ... setup various gradients ...
// Fill the face of the tile.
g2d.setPaint(faceGradient);
g2d.fillPolygon(faceXPolyPoints, faceYPolyPoints, faceXPolyPoints.length);
// Fill the right side of the top portion of the tile.
g2d.setPaint(ivoryRightSideGradient);
g2d.fillPolygon(ivoryRightSideXPolyPoints, ivoryRightSideYPolyPoints, ivoryRightSideXPolyPoints.length);
// Fill the bottom side of the top portion of the tile.
g2d.setPaint(ivoryBottomGradient);
g2d.fillPolygon(ivoryBottomXPolyPoints, ivoryBottomYPolyPoints, ivoryBottomXPolyPoints.length);
// Fill the right side of the bottom portion of the tile.
g2d.setPaint(jadeRightSideGradient);
g2d.fillPolygon(jadeRightSideXPolyPoints, jadeRightSideYPolyPoints, jadeRightSideXPolyPoints.length);
// Fill the bottom side of the bottom portion of the tile.
g2d.setPaint(jadeBottomGradient);
g2d.fillPolygon(jadeBottomXPolyPoints, jadeBottomYPolyPoints, jadeBottomXPolyPoints.length);
// Draw the outlines for the tile.
g2d.setPaint(Color.BLACK);
g2d.drawPolygon(faceXPolyPoints, faceYPolyPoints, faceXPolyPoints.length);
g2d.drawPolygon(ivoryRightSideXPolyPoints, ivoryRightSideYPolyPoints, ivoryRightSideXPolyPoints.length);
g2d.drawPolygon(ivoryBottomXPolyPoints, ivoryBottomYPolyPoints, ivoryBottomXPolyPoints.length);
g2d.drawPolygon(jadeBottomXPolyPoints, jadeBottomYPolyPoints, jadeBottomXPolyPoints.length);
g2d.drawPolygon(jadeRightSideXPolyPoints, jadeRightSideYPolyPoints, jadeRightSideXPolyPoints.length);
}
}
As you may know, there are many different types of mahjong tiles one being a character tile that displays various Chinese characters on the tile face. So my Tile class sets up the basic drawing of a tile and I create a new CharacterTile class that extends/inherits the Tile class. The code for that class follows:
public class CharacterTile extends Tile
{
private Character _character;
public CharacterTile(Character character)
{
super();
_character = character;
}
@Override public void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2d = (Graphics2D)g;
String charToWrite;
switch (_character)
{
case ONE:
charToWrite = "\u4E00";
break;
case TWO:
charToWrite = "\u4E8C";
break;
case THREE:
charToWrite = "\u4E09";
break;
case FOUR:
charToWrite = "\u56DB";
break;
case FIVE:
charToWrite = "\u4E94";
break;
case SIX:
charToWrite = "\u516D";
break;
case SEVEN:
charToWrite = "\u4E03";
break;
case EIGHT:
charToWrite = "\u516B";
break;
case NINE:
charToWrite = "\u4E5D";
break;
case NORTH:
charToWrite = "\u5317";
break;
case EAST:
charToWrite = "\u6771";
break;
case WEST:
charToWrite = "\u897F";
break;
case SOUTH:
charToWrite = "\u5357";
break;
case RED:
charToWrite = "\u4E2D";
break;
case GREEN:
charToWrite = "\u767C";
break;
case WAN:
charToWrite = "\u842C";
break;
default:
charToWrite = "?";
break;
}
g2d.drawString(charToWrite, 0, 0);
}
}
As you can see the default constructor for the CharacterTile class accepts an enum indicating the desired face value. Inside the overridden paintComponent I have a switch statement that sets the appropriate character to write and then I call the g2d.drawString() method to write the character in the upper left corner. The problem? It doesn’t write anything. What am I doing wrong?
You need to specify the bottom/left coordinate when you draw a string. Try something like:
Also, you need to make sure the component has a valid size. By default the size is (0, 0), which means there is nothing to paint. This is generally done by specifying a preferred size and then let the layout manager set the size.