text in text box

i am pretty new to the gwt framework and i am using it for building the ui of my web site, i would like to make the text box 开发者_StackOverflow社区have a text in it that once the user clicks on it for the first time, the text disappears. and in the rest of the time it behaves like a normal text box

any ideas on how to do it?

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When you create the textbox, set the default text and add a keyboard listener:

TextBox box = new TextBox();
box.setText("Default Text");
box.addKeyboardListener(this);
defaultValue = true; // this is a global boolean value

Then have your class implement KeyboardListener leaving them all blank except:

public void onKeyPress(Widget arg0, char arg1, int arg2) 
{
    if(defaultValue)
    {
        box.setText = "";
        defaultValue = false;
    }
}

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you can add a clickHandler to the box. Within the handler you do something as easy as:

if(text==DEFAULT_TEXT)
{
text==""
}

If someone is going to write again the same DEFAULT_TEXT it would get wiped out again. If you want to avoid that add boolean variable in the check expression.

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Can't tell it for GWT, but a general approach could be:

1. use a variable to flag, whether the text box is 'initialized' or 'in use'
2. add a listener to the text widget (I'd use a KeyboardListener and make the text disappear when the user starts entering text and not on the first - maybe accidental - mouse click)
3. When the listener receives the first event for the widget (flag = 'initialized'), clear the flag and replace the text inside the text field with the actual keystroke.

(for a click listener: upon the first click on the widget clear the flag and the text box.)