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Image didn't load in JPanel

I have a JPanel name "imagePanel" and a button name "browseBtn". All contained in a JFrame class. When pressing the browseBtn, a file chooser will open up and after choosing a PNG image file, the image will appear directly in the imagePanel.
This is the action event for the browseBtn
private void browseBtnActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
JFileChooser fc = new JFileChooser();
int result = fc.showOpenDialog(null);
if (result == JFileChooser.APPROVE_OPTION) {
File file = fc.getSelectedFile();
if (accept(file)) {
try {
ImageIcon image = new ImageIcon(file.getPath());
JLabel l = new JLabel(image);
imagePanel.add(l);
} catch (Exception e) {
JOptionPane.showMessageDialog(this, "Error reading file !");
}
}
else {
JOptionPane.showMessageDialog(this, "Choose png file only !");
}
}
}
public boolean accept(File file) {
return file.isDirectory() || file.getAbsolutePath().endsWith(".png");
}
I have choose the correct .png file but i don't understand why the image didn't show up in the imagePanel. Can you guy explain on that ?
Cheers.

You should avoid creating new objects everytime you want to display your image, imagine if you change it 5 times, you're creating 5 times an object while you display only one !
Like said in the comments, your best shot would be to create your label when you create your panel, add it to said panel, then simply change the icon of this label when you load your image.
browseBtn.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
JFileChooser fc = new JFileChooser();
int result = fc.showOpenDialog(null);
if (result == JFileChooser.APPROVE_OPTION) {
File file = fc.getSelectedFile();
if (accept(file)) {
try {
ImageIcon image = new ImageIcon(file.getPath());
label.setIcon(image);
} catch (Exception ex) {
JOptionPane.showMessageDialog(this, "Error reading file !");
}
}
else {
JOptionPane.showMessageDialog(this, "Choose png file only !");
}
}
}
public boolean accept(File file) {
return file.isDirectory() || file.getAbsolutePath().endsWith(".png");
}
});
Assuming label is the reference to said JLabel, created on components initialisation.

Or you might try this :
browseBtn.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
JFileChooser fc = new JFileChooser();
int result = fc.showOpenDialog(null);
if (result == JFileChooser.APPROVE_OPTION) {
File file = fc.getSelectedFile();
if (accept(file)) {
try {
ImageIcon imageIcon = new ImageIcon(new ImageIcon(file.getPath()).getImage().getScaledInstance(20, 20, Image.SCALE_DEFAULT)); //resizing
label.setIcon(imageIcon);
/*try { // or try this
InputStream inStream = this.getClass().getClassLoader().getResourceAsStream(file.getPath());
BufferedImage img = ImageIO.read(inStream);
Image rimg = img.getScaledInstance(width, height, Image.SCALE_STANDARD);
label.setIcon(rimg);
} catch (IOException e) {}*/
} catch (Exception ex) {JOptionPane.showMessageDialog(this, "Error reading file !");}
} else {JOptionPane.showMessageDialog(this, "Choose png file only !");}
}
}
public boolean accept(File file) {
return file.isDirectory() || file.getAbsolutePath().endsWith(".png");
}
});

Java JNA- Jar application hangs in 32 bit windows system

Here's a screenshot application. Compiled with 1.8 JDK, works perfectly well in 64 bit systems, but lags and hangs in two iterations in 32 bit systems.
Basically this application takes a screenshot using robot class, takes the file name from user which is a URL. Truncates and removes all illegal characters from it and saves it using a save as dialog box with time-stamp as the prefix.
I am using Windows Low Level KeyHook to initiate the screenshot with PrtSc key.
Error in 32 bit systems:
It only takes 2 screenshots and then does not respond when I press PrtSc for the 3rd time. Can JFrame cause any problems, it certainly loads up slow. Should I use any alternate text box than JFrame or is it because I have complied in java 1.8 jdk 64 bit environment, which wont work in lower versions of jdk or 32 bit systems.
public class KeyHook {
private static HHOOK hhk;
private static LowLevelKeyboardProc keyboardHook;
static JFileChooser fileChooser = new JFileChooser();
public static void main(String[] args) {
final User32 lib = User32.INSTANCE;
HMODULE hMod = Kernel32.INSTANCE.GetModuleHandle(null);
keyboardHook = new LowLevelKeyboardProc() {
public LRESULT callback(int nCode, WPARAM wParam, KBDLLHOOKSTRUCT info) {
if (nCode >= 0) {
switch(wParam.intValue()) {
case WinUser.WM_KEYUP:
case WinUser.WM_KEYDOWN:
case WinUser.WM_SYSKEYUP:
case WinUser.WM_SYSKEYDOWN:
if (info.vkCode == 44) {
try {
Robot robot = new Robot();
// Capture the screen shot of the area of the screen defined by the rectangle
BufferedImage bi=robot.createScreenCapture(new Rectangle(0,25,1366,744));
JFrame frame = new JFrame();
JFrame.setDefaultLookAndFeelDecorated(true);
frame.toFront();
frame.requestFocus();
frame.setAlwaysOnTop(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// prompt the user to enter their name
String name = JOptionPane.showInputDialog(frame, "Enter file name");
// frame.pack();
frame.dispose();
String fileName= dovalidateFile(name);
FileNameExtensionFilter filter = new FileNameExtensionFilter("PNG", ".png");
fileChooser.setFileFilter(filter);
fileChooser.setSelectedFile(new File (fileName));
int returnVal = fileChooser.showSaveDialog(null);
if ( returnVal == JFileChooser.APPROVE_OPTION ){
File file = fileChooser.getSelectedFile();
file = validateFile(file);
System.out.println(file);
ImageIO.write(bi, "png", file);
}
}
catch (NullPointerException e1)
{e1.printStackTrace(); }
catch (AWTException e1) {
e1.printStackTrace();
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
}
return lib.CallNextHookEx(hhk, nCode, wParam, info.getPointer());
}
private File validateFile(File file) {
DateFormat dateFormat = new SimpleDateFormat("HH.mm.ss.ddMMMMMyyyy");
//get current date time with Calendar()
Calendar cal = Calendar.getInstance();
// System.out.println(dateFormat.format(cal.getTime()));
String filePath = file.getAbsolutePath();
if (filePath.indexOf(".png") == -1) {
filePath += "." + dateFormat.format(cal.getTime()) + ".png";
}
//System.out.println("File Path :" + filePath);
file = new File(filePath);
if (file.exists()) {
file.delete();
}
try {
file.createNewFile();
} catch (Exception e) {
e.printStackTrace();
}
return file;
}
private String dovalidateFile(String name) {
String input = name.replace("https://www.","");
input = input.replaceAll("http://www.","");
input = input.replaceAll("https://","");
input = input.replace("http://","");
input = input.replace("/?",".");
input = input.replace("/",".");
input = input.replace("|",".") ;
input = input.replace("%",".");
input = input.replace("<",".");
input = input.replace(">",".");
input = input.replaceAll("\\?",".");
input = input.replaceAll("\\*",".");
input = input.replace(":",".");
input = input.replace("\\",".");
input = Character.toUpperCase(input.charAt(0)) + input.substring(1);
return input;
}
};
hhk = lib.SetWindowsHookEx(WinUser.WH_KEYBOARD_LL, keyboardHook, hMod, 0);
if(!SystemTray.isSupported()){
return ;
}
SystemTray systemTray = SystemTray.getSystemTray();
Image image = Toolkit.getDefaultToolkit().getImage(KeyHook.class.getResource("/images/icon.png"));
//popupmenu
PopupMenu trayPopupMenu = new PopupMenu();
MenuItem close = new MenuItem("Exit");
close.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
System.err.println("unhook and exit");
lib.UnhookWindowsHookEx(hhk);
System.exit(0);
}
});
trayPopupMenu.add(close);
//setting tray icon
TrayIcon trayIcon = new TrayIcon(image, "captur", trayPopupMenu);
//adjust to default size as per system recommendation
trayIcon.setImageAutoSize(true);
try{
systemTray.add(trayIcon);
}catch(AWTException awtException){
awtException.printStackTrace();
}
int result;
MSG msg = new MSG();
while ((result = lib.GetMessage(msg, null, 0, 0)) != 0) {
if (result == -1) {
System.err.println("error in get message");
break;
}
else {
System.err.println("got message");
lib.TranslateMessage(msg);
lib.DispatchMessage(msg);
}
}
lib.UnhookWindowsHookEx(hhk);
}
}

I don't have any experience with JNA, but there are several things that are wrong about your code - I don't think I got them all, but here are some:
close.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
System.exit(0);
quit=true;
}
});
The quit=true will never be reached because your program exit()s before it ever goes there.
2.
new Thread() {
public void run() {
while (!quit) {
try { Thread.sleep(10); } catch(Exception e) { }
}
System.err.println("unhook and exit");
lib.UnhookWindowsHookEx(hhk);
System.exit(0);
}
}.start();
doesn't make any sense since quit will never be true. Also spinning on a variable to detect a change will severly slow down your application (espacially with sleep-times of 10 ms). Why not do the unhook in your ActionListener?
3.
while ((result = lib.GetMessage(msg, null, 0, 0)) != 0) {
Here I'm not too sure because I don't have experience with JNA and the windows event system. The method waits for messages sent to the specified window, but since you don't specify any (second parameter is null) I don't think you will ever get one.
For each callback you are creating a new JFrame but at the end of the method you are only hiding it using frame.setVisible(false);. Since it is still referenced from various Swing-classes it will never be garbage-collected. This creates a memory-leak which will slow down your application. You will have to call frame.dispose() to get rid of it.

Opening a file without the extension - Java

Im doing a project for my college, my save/opening file are working all right, but I need them to save as my desired extension, and open like that as well.
For example: When I click on Save File, I write the name testFile as file name and hit save, now the my code must save as my desired extension. Same works for opening file, if I write testFile and hit open, it must locate the testFile.txt. Anyone can give me a hand how I should do this? follow my code below.
private class SalvaDesenho implements ActionListener {
private Component parent;
SalvaDesenho(Component parent) {
this.parent = parent;
}
public void actionPerformed(ActionEvent e) {
try {
final JFileChooser fc = new JFileChooser();
fc.setFileFilter(new FileNameExtensionFilter("Arquivo de Texto (.txt)", "txt"));
fc.setAcceptAllFileFilterUsed(false);
int returnVal = fc.showSaveDialog(parent);
if (returnVal != JFileChooser.APPROVE_OPTION)
return;
int op = 0;
if (fc.getSelectedFile().exists()) {
Object[] options = { "Sim", "Não" };
op = JOptionPane.showOptionDialog(null, "O arquivo já existe deseja substituilo?", "Warning",
JOptionPane.DEFAULT_OPTION, JOptionPane.WARNING_MESSAGE,
null, options, options[1]);
}
if (op != 0) return;
System.out.println("Salvando: " + fc.getSelectedFile().getPath());
FileOutputStream fout = new FileOutputStream(fc.getSelectedFile());
ObjectOutputStream oos = new ObjectOutputStream(fout);
oos.writeObject(figuras);
isSaved = true;
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
private class AbreDesenho implements ActionListener {
private Component parent;
AbreDesenho(Component parent) {
this.parent = parent;
}
public void actionPerformed(ActionEvent e) {
try {
final JFileChooser fc = new JFileChooser();
FileNameExtensionFilter txtFilter = new FileNameExtensionFilter("Arquivo de texto (.txt)", "txt");
fc.setFileFilter(txtFilter);
int returnVal = fc.showOpenDialog(parent);
if (returnVal != JFileChooser.APPROVE_OPTION)
System.out.println("File error!");
System.out.println("Abrindo: " + fc.getSelectedFile().getPath());
FileInputStream fin = new FileInputStream(fc.getSelectedFile());
ObjectInputStream ois = new ObjectInputStream(fin);
figuras = (Vector<Figura>) ois.readObject();
} catch (Exception ex) {
ex.printStackTrace();
return;
}
pnlDesenho.getGraphics().clearRect(0 , 0, parent.getHeight(), parent.getWidth());
for (int i=0 ; i<figuras.size(); i++)
figuras.get(i).torneSeVisivel(pnlDesenho.getGraphics());
}
}
Thanks.

You have to do this manually:
Get the File object from the JFileChooser
Get its absolute path as a String, using getAbsolutePath().
Check whether it has an extension or not: Check file extension in Java
If not, add your extension to the path: path = path+".txt";
Create a new File object from the path: File file = new File(path)
Open/Save the file (your code)

Drag and drop TXT file into TextArea

Here I have text area called sourceTx in which I drag and drop files, then I read content of that file with BufferedReader. As you can see from bellow code I set file from which I am reading content with absolutepath.
So, when I drag an drop some .txt file it works, it reads content and put it in text area, but when I also drag and drop some folder for example it also reads some content and put it in text area.
So I want set this drag and drop to read only .txt files? How I can get that?
Here is code of that method:
public void dragDrop(){
sourceTx.setOnDragOver(new EventHandler <DragEvent>() {
#Override
public void handle(DragEvent event) {
Dragboard db = event.getDragboard();
if(db.hasFiles()){
event.acceptTransferModes(TransferMode.ANY);
for(File file:db.getFiles()){
String absolutePath = file.getAbsolutePath();
BufferedReader br = null;
try {
br = new BufferedReader(new InputStreamReader(new FileInputStream(absolutePath)));
String line = null;
String text = "";
String nl = System.getProperty("line.separator", "\n");
while((line = br.readLine()) != null)
text += line + nl;
sourceTx.setText( text.trim() );
} catch (Exception e) {
MessageBox.show(MessageBoxType.ERROR, I18n.localize("File Error"), I18n.localize("Error while reading content from selected file"));
} finally{
if(br != null)
try {
br.close();
} catch (Exception e) {}
}
}
}else{
event.setDropCompleted(false);
}
event.consume();
}
});
}

Hi there try to read your file with recursion
...
for (File file : db.getFiles()) {
sourceTx.setText(handleFile(file));
}
...
private String handleFile(File file) {
String ret = "";
if (file.isDirectory()) {
for (File f : file.listFiles()) {
ret.concat(handleFile(f));
}
} else {
/*this is your filereader*/
String absolutePath = file.getAbsolutePath();
BufferedReader br = null;
try {
br = new BufferedReader(new InputStreamReader(new FileInputStream(absolutePath)));
String line = null;
String text = "";
String nl = System.getProperty("line.separator", "\n");
while ((line = br.readLine()) != null)
text += line + nl;
ret.concat(text.trim());
} catch (Exception e) {
MessageBox.show(MessageBoxType.ERROR, I18n.localize("File Error"), I18n.localize("Error while reading content from selected file"));
} finally {
if (br != null)
try {
br.close();
} catch (Exception e) {
}
}
}
return ret;
}

I found a good resource online on using drag and drop.
Here are some classes/things that you might want to investigate:
java.awt.dnd.*
I practically copied this from a tutorial online but here is some code (not mine, but tested and it works):
public class MyFrame extends JFrame
{
// insert other code here
JLabel myLabel = new JLabel("My stuff here");
// Create the drag and drop listener
MyDragDropListener myDragDropListener = new MyDragDropListener(this);
// Connect the label with a drag and drop listener
new DropTarget(myLabel, myDragDropListener);
// then just add the label
// also have a method something like "get" which will be used so that the listener can send
// the list of files dropped here, and you can process it here
}
Now for the MyDragDropListener.
import java.awt.dnd.*;
import java.awt.datatransfer.*;
import java.io.File;
import java.util.List;
public class MyDragDropListener implements DropTargetListener
{
MyFrame frame; // initialize in a constructor that takes in the frame
#Override
public void dragEnter(DropTargetDragEvent event) {
}
#Override
public void dragExit(DropTargetEvent event) {
}
#Override
public void dragOver(DropTargetDragEvent event) {
}
#Override
public void dropActionChanged(DropTargetDragEvent event) {
}
#Override
public void drop(DropTargetDropEvent event)
{
// This is the main chunk of the drag and drop.
event.acceptDrop(DnDConstants.ACTION_COPY);
Transferable transferable = event.getTransferable();
DataFlavor[] flavors = transferable.getTransferDataFlavors();
for(DataFlavor flavor : flavors)
{
if(flavor.isFlavorJavaFileListType())
{
List myFiles = (List) transferable.getTransferData(flavor);
frame.get(myFiles);
}
}
}
}
You can use this to create a JFrame to drag and drop the files, then check if the filename contains ".txt" ( I am not sure if Java has methods of determining the type of file even if it has no extensions .) If it contains ".txt" then you can open it in the TextArea.
If anyone can please help me find the original tutorial/site, I would really appreciate it. Also sorry for the formatting of the answer.

Java JTextPane RTF Save

i have the following code trying to save the contents of a JTextPane as RTF. although a file is created in the following code but it is empty!
any tips regarding what am i doing wrong? (as usual dont forget im a beginner!)
if (option == JFileChooser.APPROVE_OPTION) {
////////////////////////////////////////////////////////////////////////
//System.out.println(chooser.getSelectedFile().getName());
//System.out.println(chooser.getSelectedFile().getAbsoluteFile());
///////////////////////////////////////////////////////////////////////////
StyledDocument doc = (StyledDocument)textPaneHistory.getDocument();
RTFEditorKit kit = new RTFEditorKit();
BufferedOutputStream out;
try {
out = new BufferedOutputStream(new FileOutputStream(chooser.getSelectedFile().getName()));
kit.write(out, doc, doc.getStartPosition().getOffset(), doc.getLength());
} catch (FileNotFoundException e) {
} catch (IOException e){
} catch (BadLocationException e){
}
}
EDIT: HTMLEditorKit if i use HTMLEditorKit it works and thats what i really wanted. SOLVED!

if (textPaneHistory.getText().length() > 0){
JFileChooser chooser = new JFileChooser();
chooser.setMultiSelectionEnabled(false);
int option = chooser.showSaveDialog(ChatGUI.this);
if (option == JFileChooser.APPROVE_OPTION) {
StyledDocument doc = (StyledDocument)textPaneHistory.getDocument();
HTMLEditorKit kit = new HTMLEditorKit();
BufferedOutputStream out;
try {
out = new BufferedOutputStream(new FileOutputStream(chooser.getSelectedFile().getAbsoluteFile()));
kit.write(out, doc, doc.getStartPosition().getOffset(), doc.getLength());
} catch (FileNotFoundException e) {
} catch (IOException e){
} catch (BadLocationException e){
}
}
}
here is the solution. it works if HTMLEditorKit is used.

Here is a solution for RTF and not HTML.
As RTF is not standardized, I needed some additional tags like \sb and \sa to force my Wordpad to display the file properly.
protected void exportToRtf() throws IOException, BadLocationException {
final StringWriter out = new StringWriter();
Document doc = textPane.getDocument();
RTFEditorKit kit = new RTFEditorKit();
kit.write(out, doc, doc.getStartPosition().getOffset(), doc.getLength());
out.close();
String rtfContent = out.toString();
{
// replace "Monospaced" by a well-known monospace font
rtfContent = rtfContent.replaceAll("Monospaced", "Courier New");
final StringBuffer rtfContentBuffer = new StringBuffer(rtfContent);
final int endProlog = rtfContentBuffer.indexOf("\n\n");
// set a good Line Space and no Space Before or Space After each paragraph
rtfContentBuffer.insert(endProlog, "\n\\sl240");
rtfContentBuffer.insert(endProlog, "\n\\sb0\\sa0");
rtfContent = rtfContentBuffer.toString();
}
final File file = new File("c:\\temp\\test.rtf");
final FileOutputStream fos = new FileOutputStream(file);
fos.write(rtfContent.toString().getBytes());
fos.close();
}

This is how I did when I faced the same problem.
public void actionPerformed(ActionEvent e) {
text = textPane.getText();
JFileChooser saveFile = new JFileChooser();
int option = saveFile.showSaveDialog(null);
saveFile.setDialogTitle("Save the file...");
if (option == JFileChooser.APPROVE_OPTION) {
File file = saveFile.getSelectedFile();
if (!file.exists()) {
try {
BufferedWriter writer = new BufferedWriter(
new FileWriter(file.getAbsolutePath() + ".rtf"));
writer.write(text);
writer.close();
} catch (IOException ex) {
ex.printStackTrace();
System.out.println(ex.getMessage());
JOptionPane.showMessageDialog(null,
"Failed to save the file");
}
}
else if (file.exists()) {
int confirm = JOptionPane.showConfirmDialog(null,
"File exists do you want to save anyway?");
if (confirm == 0) {
try {
BufferedWriter writer = new BufferedWriter(
new FileWriter(file.getAbsolutePath()
+ ".rtf"));
writer.write(text);
writer.close();
} catch (IOException ex) {
ex.printStackTrace();
System.out.println(ex.getMessage());
JOptionPane.showMessageDialog(null,
"Failed to save the file");
}
}
else if (confirm == 1) {
JOptionPane.showMessageDialog(null,
"The file was not saved.");
}
}
}
if (option == JFileChooser.CANCEL_OPTION) {
saveFile.setVisible(false);
}
}// End of method

The only problem I've seen in your code is that you're not closing the output stream (when content is actually written to disk).
Try out.close().
It should solve your problem.