Next Generation B / S Development Framework - Echo Tutorial (5)
Editable drop-down list
We know that the drop-down list on the HTML page is invisible. Echo can make us easily achieve. Let's take a look at this ComboBox how to use:
// drop-down list data string [] member = new string [] {"steeven", "stella"}; selectfieldmodel model = new defaultselectfieldModel (Member); // can be reused: ComboBOX Combo = New ComboBox ("default text" , SelectFieldModel;
Simple? Let's take a look at the specific implementation:
/ ************ComboBOX.java***********
* Editable drop-down list
* /
Import nextApp.echo. *;
Import nextapp.echo.event. *;
Public class comboBOX EXTENDS Panel Implements ActionListener {
Private textfield input = new textfield (); // input box
Private selectfield select = new selectfield (); // pull-down box
Private checkbox check = new checkbox (); // switch button
Public ComboBox (String text, selectfieldmodel model) {
Select.SetModel (Model); // Set the content of the drop-down list
Settext; // Set the default text
Select.setVisible (false); // Default
Add (Input);
Add (SELECT);
Add (CHECK);
Check.addactionListener (this); // Listening to switching action
}
Public void setText (string text) {
this.input.settext (text); // Set text box text
/ / Set the drop-down frame selected value
This.select.getmodel (). setSelectedItem (Text);
}
Public string gettext () {
Return check.isselected ()? select.getSelectedItem (). Tostring (): Input.getText ();
}
Public Void ActionPerformed (ActionEvent E) {
Input.setvisible (! check.isselected ());
Select.setvisible (Check.isSelected ());
//Synchronous Data
Check.isselected ())
Select.getmodel (). setSelectedItem (Input.getText ());
Else
INPUT.SETTEXT (Select.getSelectedItem (). TOSTRING ());
}
}
The principle is simple:
Simultaneously construct the input box and drop-down box, alternately appear according to the state of the check box. Synchronize the data in the switch, according to the value of the drop-down box, or copy the selected value in the drop-down box to the input box. GetText () and getText () methods similar to TextField are provided.
Is it a full desktop programming style? No HTML and scripts are written.
This implemented ComboBox needs to interact with the server, slightly insufficient speed. Such interaction can be used to completely complete it on the browser. Don't worry, Echo allows you to write your own controls to achieve special needs, later chapters will have an introduction .
