Java(TM) 2 Platform, Standard Edition, v1.2.2 API Specification: Interface ImageObserver - JDK 5 Documentation v1.2.2, Java 2 SDK 英文文档

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java.awt.image
Interface ImageObserver

All Known Implementing Classes:: Component

public interface ImageObserver

An asynchronous update interface for receiving notifications about Image information as the Image is constructed.

Field Summary

static int ABORT
          This flag in the infoflags argument to imageUpdate indicates that an image which was being tracked asynchronously was aborted before production was complete.

static int ALLBITS
          This flag in the infoflags argument to imageUpdate indicates that a static image which was previously drawn is now complete and can be drawn again in its final form.

static int ERROR
          This flag in the infoflags argument to imageUpdate indicates that an image which was being tracked asynchronously has encountered an error.

static int FRAMEBITS
          This flag in the infoflags argument to imageUpdate indicates that another complete frame of a multi-frame image which was previously drawn is now available to be drawn again.

static int HEIGHT
          This flag in the infoflags argument to imageUpdate indicates that the height of the base image is now available and can be taken from the height argument to the imageUpdate callback method.

static int PROPERTIES
          This flag in the infoflags argument to imageUpdate indicates that the properties of the image are now available.

static int SOMEBITS
          This flag in the infoflags argument to imageUpdate indicates that more pixels needed for drawing a scaled variation of the image are available.

static int WIDTH
          This flag in the infoflags argument to imageUpdate indicates that the width of the base image is now available and can be taken from the width argument to the imageUpdate callback method.

Method Summary

boolean imageUpdate(Image img, int infoflags, int x, int y, int width, int height)
          This method is called when information about an image which was previously requested using an asynchronous interface becomes available.

Field Detail

WIDTH

public static final int WIDTH

This flag in the infoflags argument to imageUpdate indicates that the width of the base image is now available and can be taken from the width argument to the imageUpdate callback method.

See Also:: Image.getWidth(java.awt.image.ImageObserver), imageUpdate(java.awt.Image, int, int, int, int, int)

HEIGHT

public static final int HEIGHT

This flag in the infoflags argument to imageUpdate indicates that the height of the base image is now available and can be taken from the height argument to the imageUpdate callback method.

See Also:: Image.getHeight(java.awt.image.ImageObserver), imageUpdate(java.awt.Image, int, int, int, int, int)

PROPERTIES

public static final int PROPERTIES

This flag in the infoflags argument to imageUpdate indicates that the properties of the image are now available.

See Also:: Image.getProperty(java.lang.String, java.awt.image.ImageObserver), imageUpdate(java.awt.Image, int, int, int, int, int)

SOMEBITS

public static final int SOMEBITS

This flag in the infoflags argument to imageUpdate indicates that more pixels needed for drawing a scaled variation of the image are available. The bounding box of the new pixels can be taken from the x, y, width, and height arguments to the imageUpdate callback method.

See Also:: Graphics.drawImage(java.awt.Image, int, int, java.awt.image.ImageObserver), imageUpdate(java.awt.Image, int, int, int, int, int)

FRAMEBITS

public static final int FRAMEBITS

This flag in the infoflags argument to imageUpdate indicates that another complete frame of a multi-frame image which was previously drawn is now available to be drawn again. The x, y, width, and height arguments to the imageUpdate callback method should be ignored.

See Also:: Graphics.drawImage(java.awt.Image, int, int, java.awt.image.ImageObserver), imageUpdate(java.awt.Image, int, int, int, int, int)

ALLBITS

public static final int ALLBITS

This flag in the infoflags argument to imageUpdate indicates that a static image which was previously drawn is now complete and can be drawn again in its final form. The x, y, width, and height arguments to the imageUpdate callback method should be ignored.

See Also:: Graphics.drawImage(java.awt.Image, int, int, java.awt.image.ImageObserver), imageUpdate(java.awt.Image, int, int, int, int, int)

ERROR

public static final int ERROR

This flag in the infoflags argument to imageUpdate indicates that an image which was being tracked asynchronously has encountered an error. No further information will become available and drawing the image will fail. As a convenience, the ABORT flag will be indicated at the same time to indicate that the image production was aborted.

See Also:: imageUpdate(java.awt.Image, int, int, int, int, int)

ABORT

public static final int ABORT

This flag in the infoflags argument to imageUpdate indicates that an image which was being tracked asynchronously was aborted before production was complete. No more information will become available without further action to trigger another image production sequence. If the ERROR flag was not also set in this image update, then accessing any of the data in the image will restart the production again, probably from the beginning.

See Also:: imageUpdate(java.awt.Image, int, int, int, int, int)

Method Detail

imageUpdate

public boolean imageUpdate(Image img,
                           int infoflags,
                           int x,
                           int y,
                           int width,
                           int height)

This method is called when information about an image which was previously requested using an asynchronous interface becomes available. Asynchronous interfaces are method calls such as getWidth(ImageObserver) and drawImage(img, x, y, ImageObserver) which take an ImageObserver object as an argument. Those methods register the caller as interested either in information about the overall image itself (in the case of getWidth(ImageObserver)) or about an output version of an image (in the case of the drawImage(img, x, y, [w, h,] ImageObserver) call).

This method should return true if further updates are needed or false if the required information has been acquired. The image which was being tracked is passed in using the img argument. Various constants are combined to form the infoflags argument which indicates what information about the image is now available. The interpretation of the x, y, width, and height arguments depends on the contents of the infoflags argument.

The infoflags argument should be bitwise inclusive OR of the following flags: WIDTH, HEIGHT, PROPERTIES, SOMEBITS, FRAMEBITS, ALLBITS, ERROR, ABORT.

See Also:: WIDTH, HEIGHT, PROPERTIES, SOMEBITS, FRAMEBITS, ALLBITS, ERROR, ABORT, Image.getWidth(java.awt.image.ImageObserver), Image.getHeight(java.awt.image.ImageObserver), Graphics.drawImage(java.awt.Image, int, int, java.awt.image.ImageObserver)