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javajlistflagsselecteditem

Using Flags to Mark Selected Entries in a JList

I've done some looking into flags but I still don't really understand how I would attach them to and item/use them in general. My goal is to use flags to mark all the selected entries in a JList so that when a search is performed all showing selected items stay selected and when the search is cleared all previously selected items get rehighlighted. Also so that when a term is searched and selected it stays highlighted after the search is cleared. I was told flags was the best way to do this but I just have no idea how I would go about it.

Solution

  • Your question is kind of out of context, as I have no idea how you are refreshing your view, for example.

    But instead of a JList, I might be temptered to use a JTable, as it's editable and has in built rendering for things like JCheckBox

    But, first, I would start with a container object which could carry both the selected state but also the value I want to associate with it...

    SearchTerm

    public class SearchTerm {

    private boolean selected;
    private String text;

    public SearchTerm(boolean selected, String text) {
        this.selected = selected;
        this.text = text;
    }

    public boolean isSelected() {
        return selected;
    }

    public String getText() {
        return text;
    }

    public void setSelected(boolean selected) {
        this.selected = selected;
    }

}

    Pretty simple, now because the state is maintain internally to the object, you can move the object around and it's state (and other content) will remain in tact.

    Nopw, we need some way to model this, which maintains the logic we want to control it (so only the checkbox is editable)

    SearchTermTableModel

    public class SearchTermTableModel extends AbstractTableModel {

    private List<SearchTerm> searchTerms;

    public SearchTermTableModel() {
        searchTerms = new ArrayList<>(25);
    }

    public void add(SearchTerm searchTerm) {
        searchTerms.add(searchTerm);
        fireTableRowsInserted(searchTerms.size() - 1, searchTerms.size() - 1);
    }

    @Override
    public int getRowCount() {
        return searchTerms.size();
    }

    @Override
    public int getColumnCount() {
        return 2;
    }

    @Override
    public String getColumnName(int column) {
        return column == 0 ? "" : "Search Term";
    }

    @Override
    public Class<?> getColumnClass(int columnIndex) {
        return columnIndex == 0 ? Boolean.class : String.class;
    }

    @Override
    public Object getValueAt(int rowIndex, int columnIndex) {
        SearchTerm term = searchTerms.get(rowIndex);
        Object value = null;
        switch (columnIndex) {
            case 0:
                value = term.isSelected();
                break;
            case 1:
                value = term.getText();
                break;
        }
        return value;
    }

    @Override
    public boolean isCellEditable(int rowIndex, int columnIndex) {
        return columnIndex == 0;
    }

    @Override
    public void setValueAt(Object aValue, int rowIndex, int columnIndex) {
        switch (columnIndex) {
            case 0:
                if (aValue instanceof Boolean) {
                    SearchTerm term = searchTerms.get(rowIndex);
                    term.setSelected((Boolean)aValue);
                    super.setValueAt(aValue, rowIndex, columnIndex);
                }
                break;
        }
    }
}

    Okay, now, we just need to put it on the screen for the user to play with...

    model = new SearchTermTableModel();
model.add(new SearchTerm(false, "Bananas"));
model.add(new SearchTerm(false, "Apples"));
model.add(new SearchTerm(false, "Streberries"));
model.add(new SearchTerm(false, "Poines with guns"));
model.add(new SearchTerm(false, "Anime"));
model.add(new SearchTerm(false, "Helicopters"));
model.add(new SearchTerm(false, "Sunny beaches which I'm not on"));

setLayout(new BorderLayout());
table = new JTable(model);
add(new JScrollPane(table));

    enter image description here

    import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.table.AbstractTableModel;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JTable table;
        private SearchTermTableModel model;

        public TestPane() {
            model = new SearchTermTableModel();
            model.add(new SearchTerm(false, "Bananas"));
            model.add(new SearchTerm(false, "Apples"));
            model.add(new SearchTerm(false, "Streberries"));
            model.add(new SearchTerm(false, "Poines with guns"));
            model.add(new SearchTerm(false, "Anime"));
            model.add(new SearchTerm(false, "Helicopters"));
            model.add(new SearchTerm(false, "Sunny beaches which I'm not on"));

            setLayout(new BorderLayout());
            table = new JTable(model);
            add(new JScrollPane(table));
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

    }

    public class SearchTerm {

        private boolean selected;
        private String text;

        public SearchTerm(boolean selected, String text) {
            this.selected = selected;
            this.text = text;
        }

        public boolean isSelected() {
            return selected;
        }

        public String getText() {
            return text;
        }

        public void setSelected(boolean selected) {
            this.selected = selected;
        }

    }

    public class SearchTermTableModel extends AbstractTableModel {

        private List<SearchTerm> searchTerms;

        public SearchTermTableModel() {
            searchTerms = new ArrayList<>(25);
        }

        public void add(SearchTerm searchTerm) {
            searchTerms.add(searchTerm);
            fireTableRowsInserted(searchTerms.size() - 1, searchTerms.size() - 1);
        }

        @Override
        public int getRowCount() {
            return searchTerms.size();
        }

        @Override
        public int getColumnCount() {
            return 2;
        }

        @Override
        public String getColumnName(int column) {
            return column == 0 ? "" : "Search Term";
        }

        @Override
        public Class<?> getColumnClass(int columnIndex) {
            return columnIndex == 0 ? Boolean.class : String.class;
        }

        @Override
        public Object getValueAt(int rowIndex, int columnIndex) {
            SearchTerm term = searchTerms.get(rowIndex);
            Object value = null;
            switch (columnIndex) {
                case 0:
                    value = term.isSelected();
                    break;
                case 1:
                    value = term.getText();
                    break;
            }
            return value;
        }

        @Override
        public boolean isCellEditable(int rowIndex, int columnIndex) {
            return columnIndex == 0;
        }

        @Override
        public void setValueAt(Object aValue, int rowIndex, int columnIndex) {
            switch (columnIndex) {
                case 0:
                    if (aValue instanceof Boolean) {
                        SearchTerm term = searchTerms.get(rowIndex);
                        term.setSelected((Boolean) aValue);
                        super.setValueAt(aValue, rowIndex, columnIndex);
                    }
                    break;
            }
        }
    }

}

    Have a look at How to Use Tables for more details