package javax.swing.filechooser;import java.io.File; import javax.swing.*;/** * <code>FileView</code> defines an abstract class that can be implemented * to provide the filechooser with UI information for a <code>File</code>. * Each L&F <code>JFileChooserUI</code> object implements this * class to pass back the correct icons and type descriptions specific to * that L&F. For example, the Microsoft Windows L&F returns the * generic Windows icons for directories and generic files. * Additionally, you may want to provide your own <code>FileView</code> to * <code>JFileChooser</code> to return different icons or additional * information using {@link javax.swing.JFileChooser#setFileView}. * * <p> * * <code>JFileChooser</code> first looks to see if there is a user defined * <code>FileView</code>, if there is, it gets type information from * there first. If <code>FileView</code> returns <code>null</code> for * any method, <code>JFileChooser</code> then uses the L&F specific * view to get the information. * So, for example, if you provide a <code>FileView</code> class that * returns an <code>Icon</code> for JPG files, and returns <code>null</code> * icons for all other files, the UI's <code>FileView</code> will provide * default icons for all other files. * * <p> * * For an example implementation of a simple file view, see * <code><i>yourJDK</i>/demo/jfc/FileChooserDemo/ExampleFileView.java</code>. * For more information and examples see * <a href="http://java.sun.com/docs/books/tutorial/uiswing/components/filechooser.html">How to Use File Choosers</a>, * a section in <em>The Java Tutorial</em>. * * @see javax.swing.JFileChooser * * @author Jeff Dinkins * */ public abstract class FileView { /** * The name of the file. Normally this would be simply * <code>f.getName()</code>. */ public String getName(File f) { return null; }; /** * A human readable description of the file. For example, * a file named <i>jag.jpg</i> might have a description that read: * "A JPEG image file of James Gosling's face". */ public String getDescription(File f) { return null; } /** * A human readable description of the type of the file. For * example, a <code>jpg</code> file might have a type description of: * "A JPEG Compressed Image File" */ public String getTypeDescription(File f) { return null; } /** * The icon that represents this file in the <code>JFileChooser</code>. */ public Icon getIcon(File f) { return null; } /** * Whether the directory is traversable or not. This might be * useful, for example, if you want a directory to represent * a compound document and don't want the user to descend into it. */ public Boolean isTraversable(File f) { return null; }}这是 FileView 的源代码 虽然 FileView 是抽象类,但是里面并没有抽象方法 抽象类不一定要有抽象方法,但是包含了抽象方法的类一定是抽象类
import javax.swing.*;/**
* <code>FileView</code> defines an abstract class that can be implemented
* to provide the filechooser with UI information for a <code>File</code>.
* Each L&F <code>JFileChooserUI</code> object implements this
* class to pass back the correct icons and type descriptions specific to
* that L&F. For example, the Microsoft Windows L&F returns the
* generic Windows icons for directories and generic files.
* Additionally, you may want to provide your own <code>FileView</code> to
* <code>JFileChooser</code> to return different icons or additional
* information using {@link javax.swing.JFileChooser#setFileView}.
*
* <p>
*
* <code>JFileChooser</code> first looks to see if there is a user defined
* <code>FileView</code>, if there is, it gets type information from
* there first. If <code>FileView</code> returns <code>null</code> for
* any method, <code>JFileChooser</code> then uses the L&F specific
* view to get the information.
* So, for example, if you provide a <code>FileView</code> class that
* returns an <code>Icon</code> for JPG files, and returns <code>null</code>
* icons for all other files, the UI's <code>FileView</code> will provide
* default icons for all other files.
*
* <p>
*
* For an example implementation of a simple file view, see
* <code><i>yourJDK</i>/demo/jfc/FileChooserDemo/ExampleFileView.java</code>.
* For more information and examples see
* <a
href="http://java.sun.com/docs/books/tutorial/uiswing/components/filechooser.html">How to Use File Choosers</a>,
* a section in <em>The Java Tutorial</em>.
*
* @see javax.swing.JFileChooser
*
* @author Jeff Dinkins
*
*/
public abstract class FileView {
/**
* The name of the file. Normally this would be simply
* <code>f.getName()</code>.
*/
public String getName(File f) {
return null;
}; /**
* A human readable description of the file. For example,
* a file named <i>jag.jpg</i> might have a description that read:
* "A JPEG image file of James Gosling's face".
*/
public String getDescription(File f) {
return null;
} /**
* A human readable description of the type of the file. For
* example, a <code>jpg</code> file might have a type description of:
* "A JPEG Compressed Image File"
*/
public String getTypeDescription(File f) {
return null;
} /**
* The icon that represents this file in the <code>JFileChooser</code>.
*/
public Icon getIcon(File f) {
return null;
} /**
* Whether the directory is traversable or not. This might be
* useful, for example, if you want a directory to represent
* a compound document and don't want the user to descend into it.
*/
public Boolean isTraversable(File f) {
return null;
}}这是 FileView 的源代码
虽然 FileView 是抽象类,但是里面并没有抽象方法
抽象类不一定要有抽象方法,但是包含了抽象方法的类一定是抽象类