java render()_java中的绘制器Renderer的问题？

======classColorTableCellRendererextendsJPanelimplementsTableCellRenderer{publicComponentgetTableCellRendererComponent(JTabletable,Objectvalue,booleanisSelected,booleanha...

======

class ColorTableCellRenderer extends JPanel implements TableCellRenderer

{

public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected,

boolean hasFocus, int row, int column)

{

setBackground((Color) value);

if (hasFocus) setBorder(UIManager.getBorder("Table.focusCellHighlightBorder"));

else setBorder(null);

return this;

}

}

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class ClassNameTreeCellRenderer extends DefaultTreeCellRenderer

{

public Component getTreeCellRendererComponent(JTree tree, Object value, boolean selected,

boolean expanded, boolean leaf, int row, boolean hasFocus)

{

super.getTreeCellRendererComponent(tree, value, selected, expanded, leaf, row, hasFocus); //这边，为什么这要先调用父类的这个函数，作用是什么，为什么有时候不用

// get the user object

DefaultMutableTreeNode node = (DefaultMutableTreeNode) value;

Class> c = (Class>) node.getUserObject();

// the first time, derive italic font from plain font

if (plainFont == null)

{

plainFont = getFont();

// the tree cell renderer is sometimes called with a label that has a null font

if (plainFont != null) italicFont = plainFont.deriveFont(Font.ITALIC);

}

// set font to italic if the class is abstract, plain otherwise

if ((c.getModifiers() & Modifier.ABSTRACT) == 0) setFont(plainFont);

else setFont(italicFont);

return this;

}

===========================

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