网站建设委托外包协议网站权重查询

除了最后一节有几个方法，如，GeneralPath(), moveTo(), rotate(), closePath()及translate()没有理解外，其他基本都能理解。

不能理解的部分，权当今后的作业了，因为我要继续前行！Keep moving!

Section 13.1Introduction

• Java’s coordinatesystem (p. 556) is a scheme for identifying every point (p. 567) on the screen.

• A coordinate pair (p.556) has an x-coordinate (horizontal) and a y-coordinate(vertical).

• Coordinates are used toindicate where graphics should be displayed on a screen.

• Coordinate units are measuredin pixels (p. 556). A pixel is a display monitor’s smallest unit of resolution.

Section 13.2Graphics Contexts and Graphics Objects

• A Java graphics context(p. 558) enables drawing on the screen.

• Class Graphics (p. 558)contains methods for drawing strings, lines, rectangles and other shapes.

Methods are also includedfor font manipulation and color manipulation.

• A Graphics objectmanages a graphics context and draws pixels on the screen that represent text andother graphical objects, e.g., lines, ellipses, rectangles and other polygons(p. 558).

• Class Graphics is an abstract class. EachJava implementation has a Graphics subclass that provides drawing capabilities. This implementationis hidden from us by class Graphics, which supplies theinterface that enables us to use graphics in a platform-independent manner.

• Method paintComponentcan be used to draw graphics in any JComponentcomponent.

• Method paintComponentreceives a Graphics object that is passed to the method by the system when alightweight Swing component needs to be repainted.

• When an applicationexecutes, the application container calls method paintComponent. For paintComponentto be called again, an event must occur.

• When a JComponentis displayed, its paintComponent method iscalled.

• Calling method repaint (p. 559) on acomponent updates the graphics drawn on that component.

Section 13.3 ColorControl

• Class Color (p. 559)declares methods and constants for manipulating colors in a Java program.

• Every color is createdfrom a red, a green and a blue component. Together these components are calledRGB values (p. 560). The RGB components specify the amount of red, green andblue in a color, respectively. The larger the value, the greater the amount ofthat particular color.

• Color methods getRed, getGreen and getBlue (p. 560)return int values from 0 to 255 representing the amount of red, green andblue, respectively.

• Graphics method getColor (p. 560)returns a Color object with the current drawing color.

• Graphics method setColor (p. 560) setsthe current drawing color.

• Graphics method fillRect (p. 560)draws a rectangle filled by the Graphics object’s current color.

• Graphics method drawString(p. 562) draws a String in the current color.

• The JColorChooserGUI component (p. 563) enables application users to selectcolors.

• JColorChooserstatic method showDialog (p. 564) displays a modal JColorChooser dialog.

Section 13.4Manipulating Fonts

• Class Font (p. 566)contains methods and constants for manipulating fonts.

• Class Font’sconstructor takes three arguments—the font name (p. 567), font styleand font size.

• A Font’s font stylecan be Font.PLAIN, Font.ITALIC or Font.BOLD (each is a static field of class Font). Font styles can beused in combination (e.g., Font.ITALIC + Font.BOLD).

• The font size ismeasured in points. A point is 1/72 of an inch.

• Graphics method setFont (p. 567) setsthe drawing font in which text will be displayed.

• Font method getSize (p. 567)returns the font size in points.

• Font method getName (p. 567)returns the current font name as a string.

• Font method getStyle (p. 569)returns an integer value representing the current Font’s style.

• Font method getFamily (p. 569)returns the name of the font family to which the current font belongs. The nameof the font family is platform specific.

• Class FontMetrics(p. 569) contains methods for obtaining font information.

• Font metrics (p. 569)include height, descent and leading.

Section 13.5Drawing Lines, Rectangles and Ovals

• Graphics methods fillRoundRect(p. 573) and drawRoundRect (p. 573) drawrectangles with rounded corners.

• Graphics methods draw3DRect(p. 575) and fill3DRect (p. 575) drawthree-dimensional rectangles.

• Graphics methods drawOval (p. 575) and fillOval (p. 575) drawovals.

Section 13.6Drawing Arcs

• An arc (p. 575) isdrawn as a portion of an oval.

• Arcs sweep from astarting angle by the number of degrees specified by their arc angle (p. 575).

• Graphics methods drawArc (p. 575) and fillArc (p. 575) areused for drawing arcs.

Section 13.7Drawing Polygons and Polylines

• Class Polygon containsmethods for creating polygons

• Polygons are closedmultisided shapes composed of straight-line segments.

• Polylines (p. 578) aresequences of connected points.

• Graphics method drawPolyline(p. 580) displays a series of connected lines.

• Graphics methods drawPolygon(p. 580) and fillPolygon (p. 581) are used to drawpolygons.

• Polygon method addPoint (p. 581) addspairs of x- and y-coordinates to the Polygon.

Section 13.8 Java2D API

• The Java 2D API (p.581) provides advanced two-dimensional graphics capabilities.

• Class Graphics2D(p. 581)—a subclass of Graphics—is used fordrawing with the Java 2D API.

• The Java 2D API’sclasses for drawing shapes include Line2D.Double, Rectangle2D.Double, RoundRectangle2D.Double, Arc2D.Doubleand Ellipse2D.Double (p. 581).

• Class GradientPaint(p. 584) helps draw a shape in gradually changing colors—calleda gradient(p. 584).

• Graphics2Dmethod fill (p. 584) draws a filled object of any type that implementsinterface Shape (p. 584).

• Class BasicStroke(p. 584) helps specify the drawing characteristics of lines.

• Graphics2Dmethod draw (p. 584) is used to draw a Shape object.

• Classes GradientPaint(p. 584) and TexturePaint (p. 585) help specify thecharacteristics for filling shapes with colors or patterns.

• A general path (p. 586)is a shape constructed from straight lines and complex curves and isrepresented with an object of class GeneralPath (p. 586).

• GeneralPathmethod moveTo (p. 587) specifies the first point in a general path.

• GeneralPathmethod lineTo (p. 588) draws a line to the next point in the path. Each newcall to lineTo draws a line from the previous point to the current point.

• GeneralPathmethod closePath (p. 588) draws a line from the last point to the point specifiedin the last call to moveTo. This completes the general path.

• Graphics2Dmethod translate (p. 588) is used to move the drawing origin to a new location.

• Graphics2D method rotate (p. 588) is used to rotate the next displayed shape.