Java - Fonts and Graphics (from 21 Days)
Refererences and Links.
-----Feb/??/2003 ??? :
Notes.
DAY 12: Color, Fonts, and Graphics. (pg.297-328: 32 pages)
===Introduction and Graphics Classes (pg.297)
- For graphics, use classes of java.awt and javax.swing packages.
- With Java2D classes, you can do better visual effects, and with little code. Such as:
» Anti-aliased objs » Gradient fill patterns » Draw lines of varied widths.
- java.awt's Graphics class contains most of the methods for basic drawing.
- "Objects of this class represent an environment in which something can be drawn,
whether it's an applet window, a section in a graphical user interface, or a printer."
» ie, A Graphics or Graphics2D object REPRESENTS AN AREA BEING DRAWN TO.
- Can draw: arcs, circles, lines, ovals, rectangles (polygons), and text.
- An applet can be thought of as a canvas to draw on.
» The Graphics obj, already created. It is a parameter to one of the paint() methods.
» To draw on an applet: "import java.awt.*;" (and maybe often: "import java.util.*;").
===Creating a Drawing Surface (pg.298)
- JPanel can be drawn on.
/***(quoted from: Sun's documentation)***********************************************
===protected void paintComponent(Graphics g)
- myNote: Method for "javax.swing.JPanel" (superclass is "javax.swing.JComponent").
» D21NOTE: paintComponent(Graphics) method called automatically when component
needs redisplayed. JPanel's paintComponent(Graphics) has SAME PURPOSE AS
APPLET'S paint(Graphics).
- Calls the UI delegate's paint method ...
- IF you override this in a subclass you should NOT make permanent changes to
the passed in Graphics. For example, you should not alter the clip Rectangle
or modify the transform. If you need to ...
- Parameters:
g - the Graphics object to protect
- See Also:
paint(java.awt.Graphics), ComponentUI
===Container getContentPane()
- myNote: Method of "javax.swing.JFrame".
- Returns the contentPane object for this frame.
» D21Note: The contentPane obj represents the part of the frame that can
contain other components.
************************************************************************************/
- To add JPanel to JFrame window: "myJFrame.getContentPane().add(myJPanel);"
- paintComponent(Graphics) is available for class JPanel and is actually from its
superclass, Class JComponent.
» By subclassing JPanel further to create your own class, you can override the
paintComponent method and place all graphic calls in this method.
===Casting a Graphics2D Object (pg.299)
- To draw, use a Graphics obj or a Graphics2D obj. To choose "which class...depends
on whether you'll be using the Java2D graphics features introduced in Java 2."
- To use Java2D features from a "Graphics obj", you must create a new "Graphics2D obj".
For example: Graphics2D graphics2obj = (Graphics2D)graphics_Obj;
- To use Graphics2D methods, do not mix with Graphics calls. (pg.318.middle)
===An Application - Map.java (pg.299)
- Start of Map.java. I called it MapStart.java.
- Note: Redraw seems to not work right, yet. And adding look and feel did not help.
===Coordinates (pg.301)
- Pixels are the units. They are integer.
- The origion (0,0) is at the top left.
. Positive x values go towards right.
. Positive y values go towards bottom.
===Draw and Fill (pg.301)
- Most shapes can be drawn or filled. For both, the outline is done in the current color.
- In the next chapter, Day 13, we use the Image class to display gif and jpg files.
- comp2D.setBackground(Color.lightGray); // Will NOT redraw bckGrnd with just this one line.
comp2D.clearRect(x,y,width,height); // Will clear the indicated rectangle.
===Shapes: Line, Rectangle, Polygon, Oval, and Arc (pg.302)
- Most or all of the following draw methods belong to class java.awt.Graphics.
- public abstract void drawLine(int x1, int y1, int x2, int y2);
"Draws a line, using the current color, between the points (x1, y1) and
(x2, y2) in this graphics context's coordinate system." (sun docs)
. Place the call in JPanel's paintComponent(Graphics) or APPLET'S paint(Graphics).
- public void drawRect(int x,int y,int width,int height);
- public abstract void fillRect(int x,int y,int width,int height);
. x, y - indicates is the top-left of the rectangle.
- public abstract void drawRoundRect(int x,int y,int width,int height
,int arcWidth,int arcHeight);
- public abstract void fillRoundRect(int x,int y,int width,int height
,int arcWidth,int arcHeight);
- public abstract void drawPolygon(int[] xPoints,int[] yPoints,int nPoints);
- public abstract void fillPolygon(int[] xPoints,int[] yPoints,int nPoints);
. Compiler error results if, nPoints does not match, number points in x and y arrays.
. Tip: If xAy is an array, then xAy.length returns an int array length.
. Before Java version 2, drawPolygon() worked like drawPolyline() does now.
- public void drawPolygon(Polygon p);
- public void fillPolygon(Polygon p);
. Polygon objects allows, adding points individually.
- public abstract void drawPolyline(int[] xPoints,int[] yPoints,int nPoints);
. Does not conect the last point to the first point.
- public abstract void drawOval(int x,int y,int width,int height);
- public abstract void fillOval(int x,int y,int width,int height);
. Draws circles and ovals.
. x, y - indicates is the top-left of area where oval is drawn.
- public abstract void drawArc(int x,int y,int width,int height,int startAngle,int arcAngle);
- public abstract void fillArc(int x,int y,int width,int height,int startAngle,int arcAngle);
. int startAngle, - Starting place of arc. In arc's plane (not display's)
90 even for slanted circles (ie, ovals).
+------+------+
| | | . int arcAngle - Degree length of arc.
| | | If negative (0 to 359) --> clockwise direction.
| | | If positive (0 to -359) --> counter-clockwise.
180 + + + 0 | . See: element.html for good arc test code.
| | degrees |
| | |
| |
+------+------+
270 degrees
===Copy and Clear (pg.310)
- public abstract void copyArea(int x,int y,int width,int height,int dx,int dy);
. Copies an area of the window to another of the window. (must be visible, (probably))
- public abstract void clearRect(int x,int y,int width,int height);
- public Dimension getSize();
. "Returns the size of this component in the form of a Dimension object."
. int height - "The height dimension; negative values can be used."
. int width - "The width dimension; negative values can be used." (Sun docs)
. In Java 1.0, getSize() is called size().
===Text and Fonts (pg.311)
- java.awt.Font is the class used to store font name, style, and point size.
. The class FontMetrics has methods to find exact dimensions of different fonts. This
info would help better format text placement, etc.
- Java's built in fonts: TimesRoman, Helvetica, Courier, Dialog, and DialogInput.
- With Java 2, it is better to use generic names for the fonts, incase font not there:
. Before: TimesRoman, Helvetica , and Courier .
. Java 2: serif , sanserif , and monospaced.
- Font styles: Font.PLAIN, Font.BOLD, and Font.ITALIC. (Can be added together)
- setFont(java.awt.Font) method can be used on several object types.
- public abstract void drawString(String str,int x,int y);
. y - baseline of text output.
===Color (pg.314)
- Classes of interest: Color and ColorSpace.
- Constructor Color(r,g,b) - r,g,b can be either (int: 0 to 255) or (float: 0.0 to 1.0).
- The class java.awt.color.ColorSpace "contains methods that transform colors
in a specific color space to/from sRGB and to/from a well-defined
CIEXYZ color space. The purpose ... is to support conversions between any
two color spaces at a reasonably high degree of accuracy." (Sun docs)
. Use of sRGB is usually adequate.
- Call setColor() on the Graphics or Graphics2D object that represents area drawing to.
- RBG values: black(0,0,0), red(255,0,0), yellow(255,255,0), magenta(255,0,255), cyan(0,255,255),
pink(255,175,175), gray(128,128,128), orange(255,200,0), white(255,255,255).
- setForeground() - (like setColor()) called on user-interface components to change their color,
such as buttons or a window.
- void setBackground(Color c); - "Sets the background color of this component."
. Change background color attribute of applet window, frame, etc.
- void setForeground(Color c); - "Sets the foreground color of this component."
. Called on user-interface components to change their color, such as buttons or a window.
(similar to setColor())
. Can be used (or setColor()) in applet's init() method, to set color for drawing methods.
- public abstract Color getColor(); - Gets Graphics obj's current color.
- public Color getForeground(); - Gets Component's obj's Foreground color.
- public Color getBackground(); - Gets Component's obj's Background color.
- Classes that setBackground() AND setForeground() methods are both found in:
java.awt.Component.
java.awt.Component.AccessibleAWTComponent.
java.awt.List.AccessibleAWTList.AccessibleAWTListChild.
java.awt.MenuComponent.AccessibleAWTMenuComponent.
javax.accessibility.AccessibleComponent.
javax.swing.JComponent.
javax.swing.JList.AccessibleJList.AccessibleJListChild.
javax.swing.JTable.AccessibleJTable.AccessibleJTableCell.
javax.swing.JTree.AccessibleJTree.AccessibleJTreeNode.
javax.swing.table.DefaultTableCellRenderer.
javax.swing.table.JTableHeader.AccessibleJTableHeader.AccessibleJTableHeaderEntry.
javax.swing.text.StyleConstants.
- Classes that the setBackground() method is found in, but not setForeground():
java.awt.Graphics2D.
java.awt.TextComponent.
javax.swing.tree.DefaultTreeCellRenderer.
org.w3c.dom.css.CSS2Properties.
org.w3c.dom.html.HTMLBodyElement.
===Advanced Graphics (of Java 2D) (pg.317)
- Java2D features include:
. "Special fill patterns such as gradients and patterns"
. "Strokes that define the width and style of a drawing stroke"
. "Anti-aliasing to smooth edges of drawn objects" B19.pg317.
===Coordinate Spaces (pg.317)
- New Term: Coordinate space - Any 2D area describable by x,y coordinates.
- Before Java 2, only the devices coordinate space was used. Java 2 requires another
called the user coordinate space.
. In Java 2, when creating an object to be drawn on, you refer to the user's
coordinate space. Its origion can be moved. And rotation can be done at the
origion.
===Setting Rendering Attributes (pg.318)
- Non-2D drawing only have one attribute that is adjustable. It is color.
- With 2D, you can set color, line width, fill patterns, transparency, and many more.
- Fill Paterns. - Java 2D fill methods can use: solid color, gradient fill, texture, or
a pattern of your own.
- public abstract void setPaint(Paint paint);
. Can use Graphics2D setPaint() to define the fill pattern used for fill methods.
- New Term: Gradient fill - A gradual shift of color, from point to point.
. Acyclic gradient - The gradual color shift occurs once, pt to pt.
. Cyclic gradient - The gradual color shift occurs pt to pt and repeats.
- GradientPaint(float x1,float y1,Color c1,float x2,float y2,Color c2,boolean cyclic);
"Constructs either a cyclic or acyclic GradientPaint object ..." (Sun docs)
- // Example: How to select a custom fill pattern.
GradientPaint myAcyclicGP = new GradientPaint(0F,0F,Color.white,100F,45F,Color.blue);
comp2D.setPaint(myAcyclicGP);
- // Example: How to change the pen width, endcap style, and junture style.
BasicStroke pen = BasicStroke(2.0F,BasicStroke.CAP_BUTT,BasicStroke.JOIN_ROUND);
setStroke(pen);
===Creating Objects and Drawing Them (pg.321)
- ??? See Book and read intro to this subject. It looks like you the rendering may not
apply to the draw and fill methods covered up to this point. ???
- "Drawn ojs in Java2D are created by defining them as geometric shapes using the
java.awt.geom package classes." B19.pg.321
- Lines (pg.321), Rectangles (pg.321), Ellipses (pg.321), Arcs (pg.322), Polygons (pg.322).
. Example: Line2D.Float ln = new Line2D.Float(60F,5F,13F,28F);
. Example: Rectangle2D.Float ln = new Rectangle2D.Float(60F,5F,13F,28F);
- Drawing: "After you have defined the rendering... and created the object to be drawn,
you're ready to draw something in all its 2D glory." B19.pg.323
. All shapes use Graphics2D's draw(Shape s) and fill(Shape s).
. Strings use drawString(String str,float x,float y).
- A 2D Drawing example (in an applet): Map2D.java. B19.pg.324.
===Summary and QA (pg.326)
- Non-2D drawing require use of Graphics class methods that describe the shape.
- Java2D uses two methods, draw() and fill(), to output.
- Java does not keep track of any "current point". You need to know the x,y of each output.
*************************************************************************************
B19 - Teach Yourself Java 2 in 21 Days. 2nd ed. Lemay and Cadenhead. © 2001.
*************************************************************************************
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