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## com.google.gwt.user.client
Class History

    java.lang.Object
      com.google.gwt.user.client.History

    public class History

extends java.lang.Object

This class allows you to interact with the browser's history stack. Each "item" on the stack is represented by a single string, referred to as a "token". You can create new history items (which have a token associated with them when they are created), and you can programmatically force the current history to move back or forward.

In order to receive notification of user-directed changes to the current history item, implement the `HistoryListener` interface and attach it via `addHistoryListener(com.google.gwt.user.client.HistoryListener)`.

### Example

>     public class HistoryExample implements EntryPoint, HistoryListener {

>       private Label lbl = new Label();

>       public void onModuleLoad() {
>         // Create three hyperlinks that change the application's history.
>         Hyperlink link0 = new Hyperlink("link to foo", "foo");
>         Hyperlink link1 = new Hyperlink("link to bar", "bar");
>         Hyperlink link2 = new Hyperlink("link to baz", "baz");

>         // If the application starts with no history token, start it off in the
>         // 'baz' state.
>         String initToken = History.getToken();
>         if (initToken.length() == 0)
>           initToken = "baz";

>         // onHistoryChanged() is not called when the application first runs. Call
>         // it now in order to reflect the initial state.
>         onHistoryChanged(initToken);

>         // Add widgets to the root panel.
>         VerticalPanel panel = new VerticalPanel();
>         panel.add(lbl);
>         panel.add(link0);
>         panel.add(link1);
>         panel.add(link2);
>         RootPanel.get().add(panel);

>         // Add history listener
>         History.addHistoryListener(this);
>       }

>       public void onHistoryChanged(String historyToken) {
>         // This method is called whenever the application's history changes. Set
>         // the label to reflect the current history token.
>         lbl.setText("The current history token is: " + historyToken);
>       }
>     }

Constructor Summary
`History()`

Method Summary
`static void` | `addHistoryListener(HistoryListener listener)` Adds a listener to be informed of changes to the browser's history stack.
`static void` | `back()` Programmatic equivalent to the user pressing the browser's 'back' button.
`static void` | `forward()` Programmatic equivalent to the user pressing the browser's 'forward' button.
`static java.lang.String` | `getToken()` Gets the current history token.
`static void` | `newItem(java.lang.String historyToken)` Adds a new browser history entry.
`static void` | `onHistoryChanged(java.lang.String historyToken)`
`static void` | `removeHistoryListener(HistoryListener listener)` Removes a history listener.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### History

    public History()

Method Detail

### addHistoryListener

    public static void addHistoryListener(HistoryListener listener)

  Adds a listener to be informed of changes to the browser's history stack.

  Parameters:
    `listener` - the listener to be added

### back

    public static void back()

  Programmatic equivalent to the user pressing the browser's 'back' button.

### forward

    public static void forward()

  Programmatic equivalent to the user pressing the browser's 'forward' button.

### getToken

    public static java.lang.String getToken()

  Gets the current history token. The listener will not receive an onHistoryChanged() event for the initial token; requiring that an application request the token explicitly on startup gives it an opportunity to run different initialization code in the presence or absence of an initial token.

  Returns:
    the initial token, or the empty string if none is present.

### newItem

    public static void newItem(java.lang.String historyToken)

  Adds a new browser history entry. In hosted mode, the 'back' and 'forward' actions are accessible via the standard Alt-Left and Alt-Right keystrokes. Calling this method will cause `onHistoryChanged(java.lang.String)` to be called as well.

  Parameters:
    `historyToken` - the token to associate with the new history item

### onHistoryChanged

    public static void onHistoryChanged(java.lang.String historyToken)

### removeHistoryListener

    public static void removeHistoryListener(HistoryListener listener)

  Removes a history listener.

  Parameters:
    `listener` - the listener to be removed

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