CODEWITHSUNDEEP
javaswingconstructor
Bernheart
Bernheart

Reputation: 637

not understood Java syntax of defined Constructor

I'm Implementing a type of table. To do this, I have used an AbstractTableModel, but I don't know what my code is doing (that's why I get a snippet that did his work, but obviously I want to understand). You can see the code

public class TablePanel extends JPanel
{
    private JTable table;
    public TablePanel()
    {
        setLayout(new BoxLayout(this, BoxLayout.Y_AXIS)); 
        table = new JTable(new MyTableModel());
        table.setFillsViewportHeight(true);     
        table.setPreferredScrollableViewportSize(new Dimension(500, 100));
        JScrollPane jps = new JScrollPane(table);
        add(jps);
        add(new JScrollPane(table));
        table.setCellSelectionEnabled(true);
    }
    private class MyTableModel extends AbstractTableModel {
        private String[] columns = {"","Monday","Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
        private String[][] data = {{"8:30 - 9:30","","","","","",""},
            {"9:30 - 10:30","","","","","",""},
            {"10:30 - 11:30","","","","","",""},
            {"11:30 - 12:30","","","","","",""},
            {"12:30 - 13:30","","","","","",""},
            {"13:30 - 14:30","","","","","",""},
            {"14:30 - 15:30","","","","","",""},
            {"15:30 - 16:30","","","","","",""},
            {"16:30 - 17:30","","","","","",""}};

        public int getColumnCount() {
            return columns.length;
        }

        public int getRowCount() {
            return data.length;
        }

        public String getColumnName(int col) {
            return columns[col];
        }

        public Object getValueAt(int row, int col) {
            return data[row][col];
        }
        public Object myMethod (){
            //do something
        }
    }
}

Well, what does it mean table = new JTable(new MyTableModel());?
I thought that table would be a MyTableModel instance, but that is not true. In fact, if I pass table to another external class, this class won't see the method myMethod defined in the body of MyTableModel.

Upvotes: 1

Views: 97

Answers (3)

trashgod
trashgod

Reputation: 205805

A MyTableModel is a TableModel, but a TableModel is not necessarily a MyTableModel.

As you know your table's model is an instance of MyTableModel, which has the desired myMethod(), you can use a cast:

JTable table = new JTable(new MyTableModel());
MyTableModel model = (MyTableModel) table.getModel();

It may be easier to create and use a reference to your model:

MyTableModel model = new MyTableModel();
JTable table = new JTable(model);

Don't neglect to include the implementation of setValueAt(), shown here.

Upvotes: 1

X39
X39

Reputation: 827

its expected behaviour that other classes cant see the function myMethod because they "think" that your MyTableModel is just a AbstractTableModel (which in fact it isnt) The code and everything else you put into MyTableModel is callen correctly but you just cant see the function myMethod Thats because youre using a OOP language

So no youre wrong. Youre creating a instance of MyTableModel so everything you do inside will be executed if you call

you should read this here which will explain more about the OOP part: http://www.dummies.com/how-to/content/understanding-javas-objectoriented-programming-oop.html

just to say it quick

If you need to access your myMethod function just cast it like so: // Create the MyTableInstance (this is possible because AbstractTableModel is the parent and MyTableModel is the child) AbstractTableModel atmTestVariable = new MyTableModel();

 // Now to be able to call this:
 // atmTestVariable.myMethod();
 // we need to do this:

 if(atmTestVariable isntanceof MyTableModel) //make sure that atmTestVariable is REALY a MyTableModel
 {
    MyTableModel mtmTemp = (MyTableModel)atmTestVariable; //cast to MyTableModel
    mtmTemp.myMethod(); //Call the function
    // and now the short variant:
    ((MyTableModel)atmTestVariable).myMethod(); //cast to MyTableModel AND call the function
 }

Hopefully i was able to help

Ohhh and please move the define of your MyTabelModel class into a seperate file : /

Upvotes: 0

Thirumalai Parthasarathi
Thirumalai Parthasarathi

Reputation: 4671

a JTable constructor accepts any Object of a class that implements the TableModel interface

this will help you learn more.

Upvotes: 0

Related Questions