我是Java的初学者，所以我不知道我想要访问的是上层/包装类。基本上，我有三个班，A，B和C.
CLASS A.java
public class A{
private String aName;
private B objectB;
}
CLASS B.java
public class B{
private String bName;
private C objectC;
}
CLASS C.java
public class C{
private String cName;
}
基本上，我有一个A类，它有一个B类对象，后者又有一个C类对象。 我有一个C类对象的实例。如何从对象C的这个instane中访问变量bName和cName？
答案 0 :(得分：1)
你为什么不使用getter＆amp;用于从c的实例访问变量bName的setter方法。你不能直接访问它们，因为它们是私有的。
“CLASS B.java”
public static void generateTooltip(final TableCursor tableCursor,final Table table) {
tableCursor.addTraverseListener(new TraverseListener() {
@Override
public void keyTraversed(TraverseEvent e) {
switch (e.detail)
{
case SWT.TRAVERSE_ARROW_NEXT:
if (tip == null)
break;
tip.dispose();
tip = null;
break;
case SWT.TRAVERSE_ARROW_PREVIOUS:
if (tip == null)
break;
tip.dispose();
tip = null;
break;
}
}
});
tableCursor.addKeyListener(new KeyAdapter() {
public void keyPressed (KeyEvent e)
{
if(((e.stateMask & SWT.ALT) != 0) && e.keyCode == SWT.TAB)
{
System.out.println("Key down ALT +TAB Detact!!");
if (tip != null && !tip.isDisposed()) {
tip.close();
tip.dispose();
}
}
}
public void keyReleased(KeyEvent e)
{
if(((e.stateMask & SWT.ALT) != 0) && e.keyCode == SWT.TAB)
{
System.out.println("Key down ALT +TAB Detact!!");
if (tip != null && !tip.isDisposed()) {
tip.close();
tip.dispose();
}
}
}
});
final Listener labelListener = new Listener() {
public void handleEvent(Event event) {
Text label = (Text) event.widget;
tip = label.getShell();
switch (event.type)
{
case SWT.MouseDown:
label.setFocus();
break;
case SWT.MouseExit:
break;
case SWT.MouseHover:
{
label.setFocus();
break;
}
case SWT.MouseEnter:
{
label.setFocus();
break;
}
}
}
};
Listener tableListener = new Listener() {
Text label = null;
public void handleEvent(Event event) {
if (event.keyCode == SWT.F3)
{
if (tip != null && !tip.isDisposed()) {
tip.setFocus();
label.setFocus();
}
}
switch (event.type)
{
case SWT.Dispose:
{
if (tip == null)
break;
tip.dispose();
tip = null;
label = null;
break;
}
case SWT.MouseExit:
{
System.out.println("Mouse Exit");
if (tip != null && !tip.isDisposed()) {
tip.dispose();
break;
}
}
case SWT.MouseHover: {
// for F1 pressed key focus.
TableItem item = tableCursor.getRow();
if(item==null)
return;
if (tip != null && !tip.isDisposed()) {
if (!tip.isFocusControl()) {
tip.close();
tip.dispose();
}
}
if (tableCursor.getRow().getText(tableCursor.getColumn()).equals("")) {
return;
}
tip = new Shell(tableCursor.getShell(), SWT.ON_TOP| SWT.TOOL | SWT.RESIZE );
tip.addTraverseListener( new TraverseListener() {
@Override
public void keyTraversed( TraverseEvent event ) {
event.doit = true;
}
} );
tip.setLayout(new GridLayout(1, false));
tip.layout(true, true);
tip.setBackground(SWTResourceManager.getColor(255, 250,205));
ScrolledComposite scroll = new ScrolledComposite(tip,SWT.BORDER | SWT.H_SCROLL | SWT.V_SCROLL);
GridData gd_scrolledComposite = new GridData(SWT.FILL,SWT.FILL, true, true, 1, 1);
scroll.setLayoutData(gd_scrolledComposite);
scroll.setExpandHorizontal(true);
scroll.setExpandVertical(true);
scroll.setMinSize(item.getBounds().width,item.getBounds().height);
Composite compo = new Composite(scroll, SWT.RESIZE);
compo.setLayoutData(new GridData(SWT.FILL, SWT.FILL,true, true, 1, 1));
compo.setLayout(new GridLayout(1, false));
compo.layout(true);
scroll.setContent(compo);
label = new Text(compo, SWT.RESIZE | SWT.V_SCROLL | SWT.WRAP | SWT.BORDER | SWT.READ_ONLY);
GridData gd_lblNewLabel_2 = new GridData(SWT.FILL,SWT.FILL, true, true, 1, 1);
gd_lblNewLabel_2.widthHint = 251;
gd_lblNewLabel_2.heightHint = 75;
label.setLayoutData(gd_lblNewLabel_2);
label.setText(tableCursor.getRow().getText(tableCursor.getColumn()));
Label lblNewLabel_1 = new Label(tip, SWT.NONE);
GridData gd_lblNewLabel_1 = new GridData(SWT.LEFT,SWT.RIGHT, true, true, 1, 1);
lblNewLabel_1.setLayoutData(gd_lblNewLabel_1);
lblNewLabel_1.setText("Press F3 to focus");
lblNewLabel_1.setBackground(SWTResourceManager.getColor(255, 250, 205));
Label saveTextLabel = new Label(tip, SWT.NONE);
GridData gd_savetext = new GridData(SWT.LEFT,SWT.RIGHT, true, true, 1, 1);
saveTextLabel.setLayoutData(gd_savetext);
saveTextLabel.setText("Press F3 to Save");
saveTextLabel.setVisible(false);
saveTextLabel.setBackground(SWTResourceManager.getColor(255, 250, 205));
// / Label lisner called
label.addListener(SWT.MouseHover, labelListener);
label.addListener(SWT.MouseEnter, labelListener);
label.addListener(SWT.KeyDown, labelListener);
label.addListener(SWT.MouseMove, labelListener);
label.setBackground(SWTResourceManager.getColor(255,250, 205));
Rectangle rect = item.getBounds();
Point pt = tableCursor.toDisplay(rect.x, rect.y);
tip.setBounds(pt.x - rect.x, pt.y - rect.y+ tableCursor.getSize().y, rect.width,rect.height);
tip.setVisible(true);
tip.pack(true);
break;
}
case SWT.Close:
case SWT.MouseMove:
{
if (tip != null && !tip.isDisposed()) {
tip.dispose();
}
}
}//End switch
}
};
tableCursor.addListener(SWT.MouseHover, tableListener);
tableCursor.addListener(SWT.KeyDown, tableListener);
table.getShell().addListener(SWT.MouseExit, tableListener);
table.addListener(SWT.MouseMove, tableListener);
}
您可以直接访问“cName”变量，因为此变量属于您用于获取bName的c的同一个obejct。
答案 1 :(得分：1)
从 C类访问 B类实例的最简单方法是在C中添加对B的引用：
C类
public class C {
private String cName;
private B bObj;
}
然后在B组中使用getter和setter：
B类
public class B {
private String bName;
private C cObj;
public String getBName() {
return bName;
}
public void setBName(String newName) {
this.bName = newName;
}
}
然而，请记住，这会导致循环依赖，这通常是代码气味（但在这种情况下可能没问题，具体取决于整体类层次结构）。
更好的选择是在类之间实现Observer模式：
C类
public class C {
private String cName;
private List<Observers> observers; //if you only need one instance, then
//switch out for a single interface reference
public void requestWrapperName () {
List<String> names = new ArrayList<>();
for(observer: observers) {
names.add(observer.requestName());
}
// code to do what you want with wrapper name
...
}
public void addObserver(Observer observer) {
observers.add(obsersver);
}
}
观察者界面
public interface Observer {
String requestName();
}
B类
public class B implements Observer {
private String bName;
private C cObj;
// Observer method
public String requestName() {
return bName;
}
}
现在，当您在B类中拥有C的实例时，您可以使用cObj.addObserver(this);将B作为观察者注入C，然后使用方法requestWrapperName();请求B的名称。因此避免双向关联:)