Alright so I'm trying to create a combo box that will update it's contents during runtime except I have no clue how to do this without receiving a bunch of errors. Is there some sort of method that I can use in order to accomplish this? For example, I have a vector that might start out with the name in drawers 1 and 2 be hi and bye. Then during runtime the program will change drawer one and two to eggs, sausage and add a third drawer with the name being computer. How can I go about changing the name on a JComboBox during runtime?
You want to clear the combobox of all entries using removeAllItems(), then re-add the items from the Vector using addItem().
The data shown in the ComboBox actually lives in its model - some subclass of ComboBoxModel.
DefaultComboBoxModel has methods for adding and removing elements. If you want to completely replace the combo box's contents at runtime, the simplest way might be to just build a new model and call theComboBox.setModel(theNewModel) with it. Also see setSelectedItem() for setting the selection.
Related
For some reason, even though JList is, by default, a multi-select list, when one clicks another option, any choices you previously clicked get erased. Also, for some reason, one would have to hold down Ctrl and click, to make otherSelection
I tried to override this, by making custom ListModel that has selectedIndices stored to it, and adding MouseListener to my JList that, when activated, will append list.getSelectedIndices() to listModel.selectedIndices. However, there is unexpected problem with this approach: when stress-testing my solution (I made damn sure I was working out all of the inevitable programming mistakes before proceeding!), I found out that, for example, I could have the second list option selected, but click on the first, and list.getSelectedIndices() would return the index for the second option (and thus, my algorithm would fail).
Is there any way to make it so that every click would actually add (or remove) the index of the clicked list option to list.getSelectedIndices(), without my workaround?
Here is JAR file for testing (DEBUG == true so debug output is visible from command line).
I use JCheckBox as the ListCellRenderer
Then maybe you should be using a single column JTable with Boolean values. The state of the checkbox will be toggled every time you click on the cell.
Program Outline:
I plan to make a simple Java program that will load Vehicle objects (Vehicle being the superclass, EnginedVehicle and GoodsVehicle being the subclasses) from an XML file into an ArrayList which will then be displayed on a JList. The user will be able to show/hide the different Vehicle types using check boxes, add a new vehicle type or press the selected item in the JList and edit or delete it. The program will then put the Objects back into the ArrayList where it can be then saved back to the XML file.
Question: So, I am completely fine with the loading of the XML file into the ArrayList and putting that object onto the JList but the thing that is hurting my head is thinking about how I am going to:
What is the best way of getting the object back from the JList ready for it to be modified or deleted and put back into the ArrayList?
How would I show/hide the different types of Vehicles in the JList using the check boxes?
I understand this may seem a lot but, this is my first post and I am new to the community and I have fairly good knowledge of Java and OOP programming but I have just finished writing a fairly big website and going back to Java is a headache.
Since your ArrayList should be equal in size (item count) to your JList, your JList will have the index you're interested based on selection. Regardless if you want to modify or delete the item, store what index it was at and remove the item from the JList (You should be using a DefaultListModel). Use this index value to get the object from your ArrayList. If you're modifying, modify your object as needed, you shouldn't have to remove the object from the ArrayList for modifications, and place it back into your DefaultListModel. If it's a delete, then just remove the object from your ArrayList using the index value you stored.
As far as displaying (show/hide), clear your DefaultListModel (which will clear your JList), iterate through your ArrayList and add the items to the DefaultListModel that match your checkbox selection criteria.
EDIT:
I didn't take into consideration of possibly modifying/deleting items when items are hidden. For this, may want your objects to have a field that stores what index they are at in the ArrayList. This way when you do your filter, I would copy the items from your "Master" ArrayList into a sub list that you can populate your DefaultListModel. Then you apply the same logic to this sublist when selecting an item from you JList, then take your changes from your sublist and apply them to the "Master" ArrayList.
Keep in mind that when you remove an item, you'll have to reassign all items index location from that point on down.
I'm sure there is probably a cleaner way of doing this, but this is what first comes to mind for me.
I don't know if I'm horribly mistaken, but why change to a JList at all? Do you use your JList as a parameter to visualize the information in it? If yes, why dont you use your ArrayList instead? Then the checkboxes only change the visibility ot the Items of the List. So you dont have to care about indices, because they stay the same. And new entries, can be made as well... maybe im wrong but i guess you got kind of a GUI for the user to browse/alter/add new vehicles?
I've been trying to freshen up on my Java knowledge and I've been building a small GUI program and I've been running into a bit of a problem.
Basically, I have a JList which I'm currently populating with strings from an object from one of my classes which implement AbstractListModel which we can call my ItemList class. It contains an ArrayList of objects of the type Item which implements Serializable.
But, what I'd like to do is rather than populate my JList with a bunch of strings I'd like to populate it with some kind of string + JTextField combination so I can see one property of each Item object while also being able to update another property by changing the JTextField.
Now, what I'm looking for is the simplest possible way of doing this, and I am assuming there is a (relatively) simple way to do this since it's such a common thing to want to do in a GUI application (although I wouldn't put it past Java and Swing to make it convoluted and complicated).
So, what is the correct way of doing this?
No need to ever use String objects. Instead:
Put Item objects in the JList.
Add a ListCellRenderer to the list, to show the Item object the most user friendly way.
When the user selects an item, show the details in a different place (I'm thinking a panel with 2 columns of labels and text fields, and two rows - one for each attribute, and perhaps a button to Save)
The edit controls would best be encapsulated in a panel that can then hidden when not required, & put in a variety of places, e.g.
Below the list
In the main part of the GUI
displayed in a JOptionPane or a (modal or not) JDialog
Here is an example of placing the 'view/edit panel' (the file details) below the selection component (the table).
I'm trying to create list that shows contacts, each list item shows the name on a line, and the phone number on a second line, and maybe an image or icon. I was thinking of using two labels for that, but i can figure out how to use a custom list model to implement this.
My first attempt was to add a Panel object that contained the info i wanted in the list, then add it to an instance of the defualt list model, but that only turned up the class name in the list.
DefaultListModel Clistmodel = new DefaultListModel();//
Clistmodel.addElement(Contact);//Contact is an JPanel object
GroupList.setModel(Clistmodel);//GroupList is the List object
this didn't work out at all then i learnt that the default list model only knows how to render strings i think, so i have to create a custom list model, or a custom ListCellRenderer, i don't really know which will solve the problem.
Your question asks how to create a custom list model, however, that's not what you need (I don't think) as a DefaultListModel will work nicely for you. Rather you will need to work on the renderer. You need to create a non-GUI class to hold your information that each item will display, probably your Contact class, and then create a JList that holds this in its DefaultListModel.
The key for you will be to then create a custom list cell renderer to display the information on multiple lines -- perhaps a JTextArea, or a JPanel that holds two JLabels in a GridLayout. Please understand that the renderer does not display the actual underlying components, but something more akin to a stamped image of whatever components you're trying to display, so it will not have the full behaviors available to it as the actual component would. It will take work, but the writing a renderer section of the tutorial linked to by user714965 will show you how to do this.
Please give it a try, and then if you still are stuck, come on back with your code, your errors, and your questions, and we'll be better able to give you specific help.
I have two Jlist in the same class each with DnD drop enable.
The problem is whatever file I DnD from my desktop to the JLists either number of or number 2 will populate ( and appear ) in JList1. Jlist2 accepts the drag and drop but it is like the content is going to Jlist1 automatically.
Any idea on how to solve that ?
Maybe by cleaning your code ;-)
Take a look at the DropTargetListener you created to enable DnD operations. i think that either it
adds elements to list 1 datamodel wherever you drop them
is the same instance for list 1 and list 2, but configured to drop in list 1