I am trying to make a function in my program that will read a string, and then set every jlabel on my page to that string. I am aware of .setText(); but I am intending to do this to 100's of labels at once. Using the below code I intended to use a for loop and call the method for as many times as I will have labels and send the label name within the function. i.e.
button.pressed() {
updateLabel(labelName);
}
public void updateLabel(String name) {
…
}
But to test the code initially I just hardcoded the name of one label in and ran it. the first time it worked but now I get a null pointer exception every time. please someone help. The actual code below:
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
labeltest();
}
public void labeltest() {
for (Component c : this.getContentPane().getComponents()) {
if (c.getName().equals("Jlabel")) {
// do the modifications...
((JLabel) c).setText("Updated");
}
}
}
By default, Component.name is null, therefore to select only label, you should use instance of:
private void updateLabels(String str) {
for (Component component : getContentPane().getComponents())
if (component instanceof JLabel)
((JLabel)component).setText(str);
}
I think in general case, there're many component on the panel and a few labels. Therefore
using for (Component component : getComponents()) {} is not the best solution.
In case you want to set the same text to all the labels, then is is better to create a List<JLabel> with all labels that should be updated and us it to set a text:
private final List<JLabel> labels = new ArrayList<>();
private void init() {
add(createLabel());
}
// hide add to labels within create method
private JLabel createLabel() {
JLabel label = new JLabel():
labels.add(label);
return label;
}
In case you want to set different text to the labels, then it is better to set correct name for the labels and use Map<String, JLabel> with all labels:
private final Map<String, JLabel> labels = new HashMap<>();
private final static String NAME_ACCOUNT = "account";
private final static String NAME_SCORE = "score";
private void int() {
add(createLabel(NAME_ACCOUNT));
add(createLabel(NAME_SCORE);
}
// hide add to labels within create method
private JLabel createLabel(String name) {
JLabel label = new JLabel():
label.setName(name);
labels.put(name, label);
return label;
}
Here's a potential problem:
if (c.getName().equals("Jlabel")) {
as most Swing components don't have the name property set unless you, the coder, explicitly set it, and I have to wonder if this is the source of your NullPointerException.
Better to do:
if (c instanceof JLabel) {
// ....
}
So yes, you could recursively iterate through all components held in all Containers on your GUI, checking each if instanceof JLabel, and then casting and setting, but ... no, this is not clean, not good.
Why not simply put the JLabels into a collection such as
List<JLabel> labels = new ArrayList<>();
and then use a for loop, iterate over the list and change the state of the labels.
.... or I wonder if you're looking to use other components to display your Strings, such as a JList<String> perhaps?
Related
I am programming an application that deals with orders from a database. It has several pages, a navigation, a header that always should show information about the actual order you are working with and a content area, in which the details of said order get shown:
My MainProgram extends a JFrame and contains a CardLayout, in which the other pages are hosted, so when the user clicks on the page in the navigation, only the view of the content-area changes. Logo, header and the navigation stay the same. The header keeps displaying the order number.
As there are several different pages that contain details about the same order, I need to "send / transfer" information about the order from one page to the other so I can show some information in the header and in the content area from the order object.
But I am not getting this to work as intended, mostly to my misunderstand of static and when to use it, where objects get created exactly and also the complexity of my program: I am using a class that is intended for the navigation and therefore should also handle
the information transfer from one page to the other.
Since I am using a database, creating a MVCE will be hard, so instead I will show the important parts of my program.
MainProgram.java
Here the navigation and the content panel (centerPanel) get created, also the CardLayout. centerPanel and the CardLayout are static, so I can call this from other classes and switch the page that is shown (probably not a good idea?):
NavigationPanel navigationPanel = new NavigationPanel();
public static JPanel centerPanel = new JPanel();
public static CardLayout contentCardsLayout = new CardLayout();
I create the pages and put them into my CardLayout:
OverviewPage overviewPage = new OverviewPage();
BasicDataPage basicDataPage = new BasicDataPage();
centerPanel.setLayout(contentCardsLayout);
overviewPage.setName("overviewPage");
basicDataPage.setName("basicDataPage");
centerPanel.add(overviewPage, "overviewPage");
centerPanel.add(basicDataPage, "basicDataPage");
The main method, where I create a MainProgram object:
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
MainProgram window = new MainProgram();
window.setVisible(true);
window.initialize();
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
OverviewPage.java
The overview page contains a JTable which gets populated from a database. If the user double-clicks an entry, he gets transfered to the BasicDataPage where he can see the details of the order.
But in order to show the details, I need to somehow transfer the information of the order object into the target class and thats the point I am struggling with!
// I tried several things like object into constructor, static object, creating a method etc...
if (mouseEvent.getClickCount() == 2 && row != -1) {
String workNumberOfOrderObject = (String) table.getValueAt(row, 0);
OrderObject orderObject = GetOrderObject.getOrderObjectFromDatabase(workNumberOfOrderObject);
BasicDataPage basicDataPage = new BasicDataPage();
basicDataPage.recieveOrderObject(orderObject);
workNumberPanel.recieveOrderObject(orderObject);
workNumberPanel.setTxtWorkNumber(workNumberOfOrderObject);
MainProgram.contentCardsLayout.show(MainProgram.centerPanel, "basicDataPage");
}
I tried "sending" the order object to the BasicDataPage via the constructor and set the text in the JTextFields in the BasicDataPage accordingly. This did not work, the textfields simply stayed empty altough I can System.out.println(orderObject.toString()) the recieved object.
BasicDataPage.java
I also tried creating a method receiveOrderObject that I use in the OverviewPage, which should set the textfields of the basicDataPage AND the workNumberPanel, but the fields stay empty:
WorkNumberPanel workNumberPanel = new WorkNumberPanel();
JTextField txtCarWidth = new JTextField(TEXTFIELD_LENGTH);
JTextField txtCarDepth = new JTextField(TEXTFIELD_LENGTH);
JTextField txtCarHeight = new JTextField(TEXTFIELD_LENGTH);
public void recieveOrderObject(OrderObject orderObject){
txtCarDepth.setText(orderObject.getCar_depth());
}
Before posting my question I've read several Q/As here on SO like this:
Accessing UUID from another class in Java ... suggesting to use static for global variables.
I know that static variables are class variables, that all instances can use and only one version exists of. So I tried to send a static object from one class to the other.
But since I am using JTextFields, I had to mix static and non-static content, which either did not work at all or the textfields disappeared.
I have the feeling that I am getting a very basic concept in java wrong, so any help, no matter in which direction, is appreciated!
EDIT:
Based on Reşit Dönüks answer, I was able to fill the textfields by making BasicDataPage and loadBasicData(orderObject) in MainProgram static. Now I can do MainProgram.loadBasicData(orderObject); ... and the textfields in the BasicDataPage get filled as intended.
Is this a valid approach or do I get problems for using static for GUI-Elements? ..... Don't!
I realized that, your are creating BasicDataPage in each double click.
if (mouseEvent.getClickCount() == 2 && row != -1) {
String workNumberOfOrderObject = (String) table.getValueAt(row, 0);
OrderObject orderObject = GetOrderObject.getOrderObjectFromDatabase(workNumberOfOrderObject);
BasicDataPage basicDataPage = new BasicDataPage();
This is the main problem. Do not create BasicDataPage there, just reach the created instance and set the order object to that. My solution is below.
public class MainProgram implements OrderView{
//remove statics here
private JPanel centerPanel = new JPanel();
private CardLayout contentCardsLayout = new CardLayout();
private BasicDataPage basicPage;
public MainProgram() {
//other codes
OverviewPage overviewPage = new OverviewPage();
basicPage = new BasicDataPage();
centerPanel.setLayout(contentCardsLayout);
overviewPage.setName("overviewPage");
basicDataPage.setName("basicDataPage");
centerPanel.add(overviewPage, "overviewPage");
centerPanel.add(basicPage, "basicDataPage");
//oher codes
}
#Override
public void loadOrder(OrderObject order) {
basicPage.recieveOrderObject(orderObject);
contentCardsLayout.show(centerPanel, "basicDataPage");
}
}
public interface OrderView {
public void loadOrder(OrderObject order);
}
public class OverviewPage {
OrderView orderView;
public OverviewPage(OrderView orderView) {
this.orderView = orderView;
}
//in ActionPerformed
if (mouseEvent.getClickCount() == 2 && row != -1) {
String workNumberOfOrderObject = (String) table.getValueAt(row, 0);
OrderObject orderObject = GetOrderObject.getOrderObjectFromDatabase(workNumberOfOrderObject);
orderView.loadOrder(orderObject);
workNumberPanel.recieveOrderObject(orderObject);
workNumberPanel.setTxtWorkNumber(workNumberOfOrderObject);
}
}
As pointed already, Singleton is the way to go. I would just like to point out a mistake in the code provided in the answer before.
private static MainFrameinstance = null;
Rename MainFrameinstance to instance or vice-versa; because the same variable is checked by the getInstance() method.
I have jTextField named "p0_1000"
And i use below methods can call it by name;
Creating Hashmap in class.
private HashMap componentMap;
Fill hashmap with components name.
private void createComponentMap() {
componentMap = new HashMap<String,Component>();
Component[] components = jDesktopPane1.getComponents();
for (int i=0; i < components.length; i++) {
componentMap.put(components[i].getName(), components[i]);
}
}
For call components by their names.
public Component getComponentByName(String name) {
if (componentMap.containsKey(name)) {
return (Component) componentMap.get(name);
}
else return null;
}
If i use directly p0_1000.setToolTipText("trying"); succesfully appear tooltiptext when mouse on releated textfield.
But if i use getComponentByName("p0_1000").setToolTipText("trying"); setToolTipText not recognized.
getComponentByName("p0_1000") succesfully working i tested. Because if i type "." after method name, avaliable action list come and i can use them (example .setVisible(false) working succesfully)
Some add, set or get commands not in avaliable action list when i call componen by name.
Any advice, idea, comments are appreciated.
Regards.
---SOLVED---
public JComponent getComponentByName(String name) {
if (componentMap.containsKey(name)) {
return (JComponent) componentMap.get(name);
}
else return null;
}
Above changes solve my problem.
You probably should be using JComponent which is has setToolTipText. If that's not what you want, you can check if the java.awt.Component is a JComponent and cast:
if (components[i]) instanceof JComponent) {
JComponent jc = (JComponent) components[i];
// now you can use setToolTipText
}
Your problem is that your method is declared to return Component type, and if you look in the API for this class, you'll see that it does not have a setToolTipText(...) method. This method begins in the JComponent class. One solution is to have the Map only collect JComponents and have the method declared to return this type. Incidentally, if you declare your Map with generic parameters, you won't have to do your cast.
i.e., rather than this declaration,
private HashMap componentMap;
use,
private HashMap<String, Component> componentMap;
or if again if this will work for you:
private HashMap<String, JComponent> componentMap;
I was asking about the right way to make a component that holds some state. Like a Jbutton that saves a color in it, or a list item that saves a certain object. So when those GUI components fire an event I can use the saved states to do something with it.
My way was like that:
1- Make a subclass of the required component, like a subclass from Jbutton.
2- Make a Listener for this new subclass : in the listener check if the event source is the subclass, convert it then use the stored data.
Example:
class ColorButton extends JButton
{
static class Listener implements ActionListener{
#Override
public void actionPerformed(ActionEvent actionEvent) {
Object source = actionEvent.getSource();
if( source.getClass() == ColorButton.class)
{
ColorButton t = (ColorButton) source;
t.getComponent().setBackground(t.getColor());
}
}
}
//states i want to be saved
private Color c;
private Component comp;
ColorButton(Component comp, Color c) {
setColorChanger(comp, c);
}
/* ......
......
rest of constructors added with those additions
......
*/
private void setColorChanger(Component comp, Color c)
{
this.comp = comp;
this.c = c;
}
Color getColor() {
return c;
}
Component getComponent() {
return comp;
}
}
And I use it this way:
JPanel panel = new JPanel();
ColorButton.Listener l = new ColorButton.Listener();
JButton b = new ColorButton("Blue", panel, Color.BLUE);
JButton r = new ColorButton("Red", panel, Color.RED);
r.addActionListener(l);
b.addActionListener(l);
panel.add(b);
panel.add(r);
add(panel);
So I was wondering if this way is okay or what, I feel it is very boring to make this for every component that should hold a certain states, is there a better way?
Yes, there is a better way. Every single component object should have its own separate ActionListener, so that you don't have to check if( source.getClass() == ColorButton.class), and you can directly access the fields of the component by name, without having to go through the source at all. For that to work, you have to use a non-static inner class, or an anonymous inner class. That if statement is a very old-fashioned and non-OOP way of doing things.
In fact, the component object itself can be its own ActionListener - but that style only allows you to have one ActionListener, and is a bit less well-organised.
The better way is dependent on what kind of state you want to hold and what use you want to make of it. Without thinking that through so that you can state it, it isn't possible to make an overall plan for a better way to do it. Is setting color the only thing you want to do? Do you need to mix regular JButtons with ColorButtons in your application?
I have a List, that included JPA Entity objects of a certain type. Their reference String values are displayed in a JList for the user to see.
I want my user to be able to select filters as JCheckBoxes in the UI such as 'only from Client x', or 'only of Type x' and dynamically filter the Entity List.
I had thought to just keep a copy of static List completeList; and static List filteredList; and then just run individual filter methods each time a new filter is selected in the UI to update filteredList, which would work fine until you have to un-select a single filter and leave the others selected (at which point it all falls apart).
Every situation I think through fall apart at one point or another, usually when trying to select multiple filters of from one Menu.
An example of my thought pattern that checks all the filters to determine what needs to go in the new JList;
public static void filterList(){
List filteredList = new ArrayList<Job>(StoredDataClass.completeList);
if(clientSmithsCheckBox.isSelected()){
for(Job job : filteredList){
if(!job.getClient.equals(clientSmithsCheckBox.getText())){
filteredList.remove(job);
}
}
}
....... // Check other filters here etc.
if(clientBobAndCoCheckBox.isSelected()){
for(Job job : filteredList){
if(!job.getClient.equals(clientBobAndCoCheckBox.getText())){
filteredList.remove(job);
}
}
}
Even if clientBobAndCoCheckBox is selected, no jobs with that client will show in the final list, because we already removed them all because another client was already selected. Now, we could add to the list instead but we would face similar problems of having add stuff that shouldn't be there etc.
This is obviously possible, because this type of filtering system is common practice (example, excel). Although this is more of a design question, how can I achieve this?
Here's a short (and raw!) example of how you could organize your logic. It's in the context of SwingX (which supports sorting/filtering of a JList just the same way as a JTable) because I'm lazy - but you can apply it to your own environment easily.
Think of your criteria as a collection of filters which can be on or off, and then combine them with OR (if one or more is selected) or turn off if none is selected. The sole "trick" is to evaluate all of the checkboxes' states wheneven one of them is changed:
final JXList list = new JXList(new DefaultComboBoxModel(Locale.getAvailableLocales()));
list.setAutoCreateRowSorter(true);
final List<RowFilter> filters = new ArrayList<>();
filters.add(new MyRowFilter("de"));
filters.add(new MyRowFilter("ar"));
final List<JCheckBox> boxes = new ArrayList<>();
ActionListener l = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
List<RowFilter<Object, Object>> orCandidates = new ArrayList<>();
for (int i = 0; i < boxes.size(); i++) {
if (boxes.get(i).isSelected())
orCandidates.add(filters.get(i));
}
RowFilter<Object, Object> or = orCandidates.isEmpty() ? null :
RowFilter.orFilter(orCandidates);
list.setRowFilter(or);
}
};
JCheckBox first = new JCheckBox("de");
first.addActionListener(l);
boxes.add(first);
JCheckBox second = new JCheckBox("ar");
second.addActionListener(l);
boxes.add(second);
JComponent content = new JPanel();
content.add(new JScrollPane(list));
for (JCheckBox box : boxes) {
content.add(box);
}
showInFrame(content, "filters");
// just for completeness, the custom RowFilter
public static class MyRowFilter extends RowFilter {
private String text;
public MyRowFilter(String text) {
this.text = text;
}
#Override
public boolean include(Entry entry) {
Locale locale = (Locale) entry.getValue(0);
return locale.getLanguage().contains(text);
}
}
Im using a JPanel with propertyChangeListener and want it to rerender itself based on whenever a particular variable model changes. My code for the same is as follows --
public class LabelMacroEditor extends JPanel implements PropertyChangeListener {
private static final long serialVersionUID = 1L;
private LabelMacroModel model;
public LabelMacroEditor(LabelMacroModel bean) {
this.model = bean;
model.addPropertyChangeListener(this);
setupComponents();
validate();
setVisible(true);
}
public void setupComponents()
{
Box allButtons = Box.createVerticalBox();
JScrollPane macroModelScroller = new JScrollPane(allButtons);
macroModelScroller.setPreferredSize(new Dimension(300, 200));
for(MacroModel macroModel : model.getMacroModelList())
{
LabelMacroEditorEditableEntity macroEditorEntity = new LabelMacroEditorEditableEntity(macroModel);
Box entityBox = Box.createHorizontalBox();
entityBox.add(macroEditorEntity.getUpButton());
entityBox.add(Box.createHorizontalStrut(15));
entityBox.add(macroEditorEntity.getMacroDetailsButton());
entityBox.add(Box.createHorizontalStrut(15));
entityBox.add(macroEditorEntity.getDownButton());
allButtons.add(entityBox);
}
add(macroModelScroller);
}
#Override
public void propertyChange(PropertyChangeEvent arg0) {
revalidate();
repaint();
}
}
When i use the debug mode in eclipse i can see that whenever there is a change to model it triggers off the call propertyChange and it also runs over revalidate and repaint but only the JPanel display remains the same. It does not seem to be rerendering itself.
Anything fundamental that I'm missing here ?
EDIT :
An example snippet of a property im changing is as follows --
labelMacroModel.addMacroModel(addedMacroModel);
where labelMacroModel is of the type LabelMacroModel and addedMacroModel is of the type Macro
Now the relevant part of LabelMacroModel class that fires off the property change is as follows --
private List<MacroModel> macroModelList;// this is the list of all MacroModels
public void addMacroModel(MacroModel macroModel) {
macroModelList.add(macroModel);
pcs.fireIndexedPropertyChange("LabelMacroModel", macroModelList.size(), null, macroModel);
}
Its not clear how you are changing the components in the panel. If panel is not updated then repaint/revalidate will have no effect. I think you should not need revalidate/repaint to be called explicitly if you are not modifying the way components are laid out. JButton.setText should for example change the label of the button without need of calling repaint.
To expand on the answer by AKJ above, I think you should be reconstructing your components on property change. So doing a remove all then readding is one way to do this. Once you get this working you could be more selective about pushing the model update into the GUI eg if a new entry has been added then just add a new component to reflect this. The remove all / readd is fine for a lot of cases though. HTH.