World's Fastest Java Netbeans 5.5 Tutorial

World's Fastest NetBeans 5.5 Beta 2 Tutorial

Above: Projects view on left, files view on right. Use tabs to selet each view.

Above: on left is the view during step 1, on right is view after finishing steps 1 to 3.

In the right side of the above figure, NetBeans has created the tpw.ecgr6118a package containing the Ecgr6118aUI.java JFrame (top level window frame of the graphic interface) In addition, NetBeans opens up the Ecgr6118aUI JFrame in GUI Builder as shown below.

Above: Ecgr6118aUI opened in the GUI builder.

Experiment by clicking the "Design" and "Source" buttons over the GUI builder to toggle between the source code view and graphical view of the Ecgr6118aUI graphical user interface.

Above: JPanel added to GUI .

Above: widgets added in JPanel .

Above: changing the variable name of the JLabel widget .

To preview your GUI design, click the "Design Preview" icon:

.

Also, look in the ProjectPane to see the full hierarchy of your GUI with the renamed widgets JLabelFilename, JTextfieldFilename, and JButtonFilename as shown below:

Above: ProjectPane hierarchy showing renamed widgets JLabelFilename,
JTextfieldFilename, and JButtonFilename .

Above: Running project window.

Above: making a backup with CopyProject.

So far, our window has a button, but nothing happens when the button is pressed. To make something happen, we need to add an event handler. To do this, right-click the read button and select Events>Mouse>MouseClicked, as shown below.

Above: Adding mouseClicked eevnt handler to read button.

Once the event handler is added, the source code editor should appear with a blank function named "jButtonFileNameMouseClicked" and a "TODO" comment where you are to add your code. For our example, we will do seevral things. First, we will add code to pop-up a new window that contains the filename that was typed into the parent window. Second, we will print an informational line to the standard system output area (bottom of NetBeans). Finally, we will print a message "Button Pressed!" to the text area of the parent window, where the fileame originally appeared.

To do this, first edit the function as follows:

    private void jButtonFileNameMouseClicked(java.awt.event.MouseEvent evt) {
         // TODO add your handling code here:

        //Create a new pop-up window.
        JFrame frame = new JFrame("HelloWorldSwing");
        frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
        //read filename and print it in pop-up window
        String filename;
        filename = jTextFieldFileName.getText();
        JLabel label = new JLabel("File Name = " + filename);
        frame.getContentPane().add(label);

        //Display the window.
        frame.pack();
        frame.setVisible(true);

        //print out a line
        System.out.println("jButtonFileNameMouseClicked");
        //in the original window, print a message in the filename area
        jTextFieldFileName.setText("Button Pressed!");

    }

You must also go to the top of the source code file Ecgr6118aUI.java, and add the line "import javax.swing.*;" right after the line "package xyz.ecgr6118a;" to add the needed swing library components. Without adding this line, you should get the error "cannot find symbol, class JFrame." When you have added this, the top of your Ecgr6118aUI.java file should have:

package tpw.ecgr6118a;
import javax.swing.*;

Rebuild and run the project. Type "zzz.txt" in the textfield for the file name, then press the read button. The output should appear as follows:

Above: output after pressing read button.

The output pane at the bottom of netbeans should also show the printed output line "jButtonFileNameMouseClicked" as shown below. This line was printed from the command "System.out.println("jButtonFileNameMouseClicked");" added above.

init:
deps-jar:
compile:
run:
jButtonFileNameMouseClicked

Next, we will add a simple drawing area and draw an oval. First, add a new JPanel for the drawing area below our old JPanel. Set the border property of the panel to TitledBorder, with Title=DrawingArea. For the new panel, also right-click to edit properties, click the code button in the properties editor, and change the variable name of the panel from JPanel1 to "JPanelDrawingArea." Then, add a JScrollPane to the new JPanel, filling up almost all of the panel. (Note, by sizing the JScrollPane to occupy nearly all of the DrawingPanel, this affects the behavior of the scrolling when the window is resized. If the JScrollPane is much smaller than the enclosing JPanel, then the scrolling area will not resize itself when the window resizes.) Similarly, rename the JScrollPane Right-click>Properties>Code>VariableName and rename it "JScrollPaneDrawingArea." The final design should appear as below (also note the class hierarchy in the project pane and navigator pane).

Above: JScrollPane added inside JPanel drawing area.

Next, we need to manually add another panel that will be actual drawing that will be scrolled by the JScrollPane. To add this new
class, right click the properties window class icon Ecgr6118aUI and PropertiesPane>RightClick>Add>InnerClass as shown on the left below. Name the class "InnerClassDrawingPanel" with SuperClass javax.swing.JPanel as shown on the right below.

Above: InnerClass "InnerClassDrawingPanel added insideEcgr6118aUI .

When you have added the new class, the hieracrchy in the ProjectPane should look like:

Above: InnerClass in hierarchy .

Now add "import java.awt.*;" to the top of your Ecgr6118aUI.java source code to allow us to access the Graphics class in Java, and insert the following code so that your new class InnerClassDrawingPanel definition becomes:

//at the top of your code, you should have the following imports
package tpw.ecgr6118a;
import javax.swing.*;
import java.awt.*; //needed for Graphics class inclusion

//edit your new class as follows
public final class InnerClassDrawingPanel extends javax.swing.JPanel {
          protected void paintComponent(Graphics g) {
            super.paintComponent(g);

        g.setColor( ovalColor );
        g.fillOval(oval.x,oval.y,oval.width,oval.height);
        drawpanel.setAutoscrolls(true);
          }
    }

The above painting function for our new InnerClassDrawingPanel draws one oval at coordinates set by variable "oval" and with color "ovalcolor." So, we need to add these variables to the Ecgr6118aUI class for our drawing. Double click the Ecgr6118aUI >Fields>JButtonFileName item in the projects pane, and the auto-generated variables source code should appear in the source-code pane. Do not modifiy the auto-generated variables! Manually add new variables above this area as shown below:

//begin our manually added variables

    private InnerClassDrawingPanel drawpanel;
    private Dimension area;
    private Rectangle oval;
    private Color ovalColor;
    //end our manually added variables


    // Variables declaration - do not modify
    private javax.swing.JButton jButtonFileName;
    private javax.swing.JLabel jLabelFileName;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanelDrawingArea;
    private javax.swing.JScrollPane jScrollPaneDrawingArea;
    private javax.swing.JTextField jTextFieldFileName;
    // End of variables declaration

The new variables must be initialized when the program runs, so edit the Ecgr6118aUI() constructor function as follows:

    /** Creates new form Ecgr6118aUI */
    public Ecgr6118aUI() {
        initComponents();

        //set up default drawing
        oval = new Rectangle(20,30,10,20); //topleft-x,y-ccord, wid, height
        ovalColor = new Color(0,0,0);
        area = new Dimension(400,200); //(width,height)

        //Set up the drawing area.
       drawpanel = new InnerClassDrawingPanel();
       jScrollPaneDrawingArea.setViewportView(drawpanel);

        drawpanel.setBackground(Color.white);
        drawpanel.setPreferredSize(area);
        drawpanel.revalidate();
        drawpanel.repaint();
        drawpanel.setAutoscrolls(true); //allows dragging?

    }

Add a new button "Draw" to the old JPanel area, name it JButtonDrawMouseClick and add the event for mouseClick and call it JButtonDrawMouseClick. The project design should look like:

Above: Draw button added .

Next, edit the source code for the event handler as follows:

   private void JButtonDrawMouseClick(java.awt.event.MouseEvent evt) {
// TODO add your handling code here:

        ovalColor=Color.RED;
        drawpanel.setBackground(Color.YELLOW);
        jScrollPaneDrawingArea.setBackground(Color.BLUE);
        drawpanel.setForeground(ovalColor);
        oval.setBounds(60, 30, 20, 10);
        area.setSize(500,200); //width,height

    }

Finally, clean and rebuild the project, then run the project. The initail window when run should appear as below:

Above: initial window appearance when project is run .

After clicking the Draw button and resuizing the window until the scroll bars appear, the window should change to the format shown below.

Above: window appearance after Draw button is pressed, and after resizing window several times .

Next, we will add another scrollable panel where we can display image files. In this, we will make use of the javax.imageio library for the ImageIO class, the java.awt.image library for the BufferedImage class, and the java.io for the File class. Create a new JPanel with BorderTilte "ImageArea" and Naamed jPanelImageArea. Add a JScrollPane to the new JPanel, named jScrollPaneImageArea (size the scroll pane to nearly fill the panel, so window resizing will work correctly). This new design is shown below.

Above: window appearance after new ImageArea is added .

Next, manually add the following variables for the new image area. Double click the Ecgr6118aUI >Fields>JButtonFileName item in the projects pane, and the auto-generated variables source code area of your Ecgr6118a.java should appear in the source-code pane. Do not modifiy the auto-generated variables! Manually add new variables above this area as shown below.

      //begin our second set of manually added variables
    private InnerClassImagePanel imagepanel;
    private String imgFileName;
    private ImageIO imgIo;
    private BufferedImage buffImg;
    private File imgFile;
    private JLabel iconLabel;
    private ImageIcon imageIcon;
    //end our second set manually added variables

    // Variables declaration - do not modify

Then add the following import statemets, as necessary, to the top of your Ecgr6118a.java source code:

package xyz.ecgr6118a;
import javax.swing.*;
import java.awt.*; //needed for Graphics class inclusion
import javax.imageio.*; //needed for ImageIO
import java.awt.image.*; //needed for BufferedImage
import java.io.*; //needed for File

Next, we need to manually add another panel that will be actual drawing that will be scrolled by the ImageArea JScrollPane. To add this new class as before, right click the properties window class icon Ecgr6118aUI and PropertiesPane>RightClick>Add>InnerClass as shown on the left below. Name the class "InnerClassImagePanel" with SuperClass javax.swing.JPanel as shown on the right below.

Above: adding inner class for image area, InnerClassImagePanel.

Now insert the following code so that your new class InnerClassImagePanel definition becomes:

//edit your new class as follows
public final class InnerClassImagePanel extends javax.swing.JPanel {

           protected void paintComponent(Graphics g) {
            super.paintComponent(g);
                /*   //following not used .. may be helpful for debug
                    drawpanel.revalidate();
                    drawpanel.repaint();
                */
            drawpanel.setAutoscrolls(true); //allows dragging?
            }

    }

The above painting function for our new InnerClassImagePanel simply draws the existing graphics context "g," and so we next need to add the functionality needed to load an image into this graphics context. To load an image, we will take advantage of the built-in functionality of JLabels to display image icons. An image file will first be read into a BufferedImage object using an ImageIO object to access the file. The BufferedImage will then be converted to an Icon which is then displayed through a JLabel object.

Next, add thefollowing initialization code to the public Ecgr6118aUI() constructor, below the Ecgr6118aUI() code added previously to initialize the drawingpanel for drawing the ovals in the drawing area.

//below added for image panel area
//---------------------------------------------------------
        //initialize variables to null to hopefully suppress rendering
            imgFileName = null;
            imgIo = null;
            buffImg = null;
            imgFile = null;
            iconLabel = null;
            imageIcon = null;

        //Set up the drawing area.
            imagepanel = new InnerClassImagePanel();
            jScrollPaneImageArea.setViewportView(imagepanel);
            iconLabel = new JLabel(); //this label will contain the image
            imagepanel.add(iconLabel); //attach the label to the drawing panel
            imagepanel.revalidate();
            imagepanel.repaint();
            imagepanel.setAutoscrolls(true); //allows dragging?

//end added for image panel area
//---------------------------------------------------------

Finally, we will make better use of the read button that was previously added, and use the existing read button to read our image file. However, first downlad the following test images in imgs.zip or as a tar-file imgs.tar (you might have to press shift or ctrl key on your browser to download), and save them in the directory of your project, ecgr6118a. These will be used as the test image files. The directory structure of theproject should be as shown below:

Above: image directory "imgs" added to project.

Edit the read-button function "jButtonFileNameMouseClicked" that was created previously, and add the code as follows (deleting the previous code in the function):

    private void jButtonFileNameMouseClicked(java.awt.event.MouseEvent evt) {
// TODO add your handling code here:

        //BufferedImage and ImageIO method
        imgFileName = jTextFieldFileName.getText();
        jTextFieldFileName.setText("Read Button Pressed!");
        imgFileName=new String("imgs/image512x512.gif");
        imgFile = new File(imgFileName);
        int ioflag = 0;

        try { buffImg = imgIo.read(imgFile) ; }
          catch (IOException e) {
              System.out.println("public jButtonFileNameMouseClicked::imgIo.read IOException");
              ioflag=1;
             }

        if(ioflag == 0)
        {
            System.out.println("file width=" + buffImg.getWidth()
                    +" length=" + buffImg.getHeight() );

            //why not draw a line on the image
            Graphics gg = buffImg.createGraphics();
            gg.setColor(Color.MAGENTA);
            gg.drawLine(10,10,buffImg.getWidth()-buffImg.getWidth()/10,
                    buffImg.getHeight()-buffImg.getHeight()/2);

            //save the file after drawing the line on it
            File outfile = new File("imgs/out.jpg");
            try {ImageIO.write(buffImg,"JPG",outfile); }
              catch (IOException e) {
                  System.out.println("jButtonFileNameMouseClicked::"
                          +"outfilewrite IOException");
                 }

            //examples of reading and writing pixel data
            int rgb =0;
            int alpha=0 , red=0 , green=0 , blue=0;
            int a=255 , r=0 , g=200 , b=0;
            int xx=20;

            for(int yy=0; yy<30; yy++) //read and write some pixels
                {
                   rgb = buffImg.getRGB(xx, yy) ; //read pixel
                   alpha = ((rgb >> 24) & 0xff);
                   red = ((rgb >> 16) & 0xff);
                   green = ((rgb >> 8) & 0xff);
                   blue = ((rgb ) & 0xff);
                   System.out.println("yy="+ yy +" pix=" + buffImg.getRGB(xx, yy)
                        + " red=" + red + " green=" + green + " blue=" + blue
                        +" alpha=" +alpha );
                   //change the pixels to green
                   a=255; r=0; g=200; b=0;
                   rgb = (a << 24) | (r << 16) | (g << 8) | b;
                   buffImg.setRGB(xx, yy, rgb);    //write pixel
                  }

            imageIcon=new ImageIcon(buffImg);
            iconLabel.setIcon(imageIcon);
            iconLabel = new JLabel(imageIcon);
            imagepanel.removeAll();
            imagepanel.add(iconLabel,0);
            imagepanel.setBackground(Color.YELLOW);
            jScrollPaneImageArea.setBackground(Color.BLUE);

            imagepanel.revalidate();
            imagepanel.repaint();
            imagepanel.setAutoscrolls(true); //allows dragging?
        }

    }

Build and run the program. Press rhe read and draw buttons, and if all goes well, you shoud observe an output as follows:

Above: adding inner class for image area, InnerClassImagePanel.

Also, the program should have created a new image file "imgs/out.jpg" that has the magenta line drawn across the original image file "imgs/image512x512.gif." Use another image viewer tool to see that the original file does not have the magenta line. The green line appears because of the pixel-writing that occurs at the bottom of the pixel-reading loop in the In the jButtonFileNameMouseClicked(java.awt.event.MouseEvent evt) method above. Because the file is writtten before the green line is drawn, "out.jpg" will not contain the green line.

Sometimes you may encounter graphics color map problems, if you try to read a file with a color table, and then write to it. To avoid such problems, you may need to allocate a buffer as follows:

// do this to make sure there is no color mapping problem
buffImg=new BufferedImage(outIclass.getxdim(),
outIclass.getydim(),
BufferedImage.TYPE_INT_ARGB);

When the read button is clicked, the OutputPane at the bottom of NetBeans contains the printeout of the pixel data from the pixel-reading loop. The output should appear something like the following:

yy=25 pix=-196868 red=252 green=254 blue=252 alpha=255
yy=26 pix=-196868 red=252 green=254 blue=252 alpha=255
yy=27 pix=-592900 red=246 green=243 blue=252 alpha=255
yy=28 pix=-196868 red=252 green=254 blue=252 alpha=255
yy=29 pix=-196868 red=252 green=254 blue=252 alpha=255

In the jButtonFileNameMouseClicked(java.awt.event.MouseEvent evt) method above, also try commenting out the line "imgFileName=new String("imgs/image512x512.gif");" and rebuilding the program. In this case, you will now have to enter the file name "imgs/image512x512.gif" in the window text area for the file to be loaded.

The entire project up to this point may be downloaded as ecgr6118a_4.zip or as a tar-file ecgr6118a_4.tar for convenience.

Another example Java project using Java/Netbeans-4.1 is available on :
imgProjv41 or
tpwJavaNtebeansTutorial/imgProjv41/

Note: if the windows-click-and-run is installed incorrectly, you will need to open a command-prompt window and type "java -jar myjarfile.jar" to run myjarfile.jar. The jar files are most commonly in the "dist" subdirectories of Netbeans projects. Or, you may just run your application from within Netbeans.

Unfortunately, this does not work: you will get error: javac: source release 1.5 requires target release 1.5
BUILD FAILED
On occasion, the project may not run on a machine that is running an older version of Java. You may get error messages such as "Unsupported major.minor version 49.0." You can check the version of Java on the machine with the "java -version" command. This tutorial used version 1.5 of Java. To compile your project for an older machine, use compiler options "-source 1.5 -target 1.4" or similar. To set these compile options, right-click your project in the ProjectPane in NetBeans and select properties and edit as shown below. The v1.4 version of the project is ecgr6118a_4_v14.zip or as a tar-file ecgr6118a_4_v14.tar

Unfortunately, this does not work: you will get error: javac: source release 1.5 requires target release 1.5
BUILD FAILED

The above tutorial was written for NetBeans 5.5 Beta 2, and tested on a system with the following installed items :

NetBeans IDE 5.5 Beta 2 Installer: netbeans-5_5-beta2-windows.exe (42.1 MB)
NetBeans Mobility 5.5 Beta 2 Installer: netbeans_mobility-5_5-beta2-win.exe (22.49 MB)
NetBeans Profiler 5.5 Beta 2 Installer: profiler-5_5-beta2-win.exe (9.06 MB)
NetBeans C/C++ Pack 5.5 EA Installer: cnd-060615-windows.exe (7.49 MB)

To obtain the above (or newer releases), please visit the NetBeans site: http://www.netbeans.org/

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