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Interface java.awt.image.ImageObserver - JDK 5 Documentation v1.1.8, Java 2 SDK 英文文档

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Interface java.awt.image.ImageObserver

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

Variable Index

o ABORT
An image which was being tracked asynchronously was aborted before production was complete.
o ALLBITS
A static image which was previously drawn is now complete and can be drawn again in its final form.
o ERROR
An image which was being tracked asynchronously has encountered an error.
o FRAMEBITS
Another complete frame of a multi-frame image which was previously drawn is now available to be drawn again.
o HEIGHT
The height of the base image is now available and can be taken from the height argument to the imageUpdate callback method.
o PROPERTIES
The properties of the image are now available.
o SOMEBITS
More pixels needed for drawing a scaled variation of the image are available.
o WIDTH
The width of the base image is now available and can be taken from the width argument to the imageUpdate callback method.

Method Index

o imageUpdate(Image, int, int, int, int, int)
This method is called when information about an image which was previously requested using an asynchronous interface becomes available.

Variables

o WIDTH 
 public static final int WIDTH
The width of the base image is now available and can be taken from the width argument to the imageUpdate callback method.

See Also:
getWidth, imageUpdate
o HEIGHT 
 public static final int HEIGHT
The height of the base image is now available and can be taken from the height argument to the imageUpdate callback method.

See Also:
getHeight, imageUpdate
o PROPERTIES 
 public static final int PROPERTIES
The properties of the image are now available.

See Also:
getProperty, imageUpdate
o SOMEBITS 
 public static final int SOMEBITS
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:
drawImage, imageUpdate
o FRAMEBITS 
 public static final int FRAMEBITS
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:
drawImage, imageUpdate
o ALLBITS 
 public static final int ALLBITS
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:
drawImage, imageUpdate
o ERROR 
 public static final int ERROR
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
o ABORT 
 public static final int ABORT
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

Methods

o imageUpdate 
 public abstract 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.

See Also:
getWidth, getHeight, drawImage 
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