Develop Reference

Java, If a draggable object touches other object

I have a code for dragging a label width mouse.
lbl_banner.addMouseListener(new MouseAdapter()
{
#Override
public void mousePressed(MouseEvent e) {
//catching the current values for x,y coordinates on screen
x_pressed = e.getX();
y_pressed = e.getY();
}
});
lbl_banner.addMouseMotionListener(new MouseMotionAdapter(){
#Override
public void mouseDragged(MouseEvent e){
//and when the Jlabel is dragged
setLocation(e.getXOnScreen() - x_pressed, e.getYOnScreen() - y_pressed);
}
});
Now, how do I make a function: While I'm dragging this label around the Screen, If the Label by dragging touches other object (label, button,...) to do something.
if(//labelTouchesSomething){//do something}

While this is not technically a dragging but the dynamic move of a component (dragging is the transfer of contents in between components), you can compute the intersection of the current moving component against other components (this may need some navigation inside your hierarchy). May be this can help you: How do I detect the collison of components?. You can also use the methods contains of Component to determine if some coordinates are inside a component or not.

How to change SWT Button background color or make it transparent

I have a transparent image on a Button (no text), which is placed on a Composite. Since the Composite is white (created with FormToolkit#createComposite(parent, SWT.NONE)), I'd like the Button background to be the same color. How do I do it?
The Label does the trick, but doesn't have the shadows like Button does when I'm clicking on it..

The background color of a Button is determined by the OS. In fact, the documentation for Control.setBackground() states that:
Note: This operation is a hint and may be overridden by the platform. For example, on Windows the background of a Button cannot be changed.
That said, one possible way to circumvent this is to override the paint event as shown here: Changing org.eclipse.swt.widgets background color in Windows. When I tried this out the results were a bit wonky.
The safest and most consistent approach would be to use a label like in your second image, but have different images to display on various mouse events to emulate how a button behaves.
Those images can emulate the shadow just by adding whatever shape of shadow you want to the image itself. That shadow can also change for each image to give the impression that the button is being pressed or not.
For example, I'm thinking something along the lines of:
public class MyButton {
private final Label buttonLabel;
public MyButton(final Composite parent, final Theme theme) {
buttonLabel = new Label(parent, SWT.NONE);
buttonLabel.setImage(theme.getUpImage());
buttonLabel.addMouseListener(new MouseAdapter() {
#Override
public void mouseDown(final MouseEvent mouseEvent) {
buttonLabel.setImage(theme.getButtonPressedImage());
}
#Override
public void mouseUp(final MouseEvent mouseEvent) {
buttonLabel.setImage(theme.getButtonUpImage());
}
});
buttonLabel.addMouseTrackListener(new MouseTrackAdapter() {
#Override
public void mouseEnter(final MouseEvent mouseEvent) {
buttonLabel.setImage(theme.getButtonHoverImage());
}
#Override
public void mouseExit(final MouseEvent mouseEvent) {
buttonLabel.setImage(theme.getButtonUpImage());
}
});
}
}
Where the Theme just has all of the images already conveniently loaded.
You'll also need to make sure that the parent Composite has the background mode set to force its background color:
parent.setBackgroundMode(SWT.INHERIT_FORCE);
Obviously the drawback to this approach is that you have to handle the mouse click logic yourself (ie. mouseDown isn't really clicked until the mouse is released, so you'll have to handle the state of the button in each listener method).

Dynamic Line between two points, click, move mouse, then click

I have to draw a Line in Java. I click one point, then release the mouse key, move the mouse (the end of the line should be where the mouse cursor is (a dynamic preview)) then click the mouse key again to make the line.
I see various questions on here, but most deal with holding a mouse button and dragging the mouse.
My question is, how can I draw a line dynamically using the method above. I am concerned about repainting. I had code earlier and it drew all the lines as I moved the mouse. Is there a way to just have a preview.

You need need to create a application implementing both a MouseEventListener and a MouseMotionListener. Use the MouseEventListener method mouseClicked to check whether the mouse has been clicked and subsequently the MouseMotionListener method MouseMoved to update the other end of the line to your mouse's position. Finally you use the MouseEventListener again to pinpoint the end location of the line.
I hope this helps.
Take a look at:
http://docs.oracle.com/javase/tutorial/uiswing/events/mouselistener.html and http://docs.oracle.com/javase/tutorial/uiswing/events/mousemotionlistener.html.

There's a lot of information missing in your post, so it will be difficult to offer an exact solution, but here is the general idea. Assuming that you need a transparent JComponent that receive mouse events and paint your line preview, the code would look something like this.
public class MyLinePreviewComponent extends JComponent {
Point sourcePoint;
Point destinationPoint;
pubic MyLinePreviewComponent() {
this.addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent e) {
if (sourcePoint == null)
sourcePoint = e.getPoint();
else
sourcePoint = null;
repaint();
}
});
this.addMouseMotionListener(new MouseMotionAdapter() {
public void mouseMoved(MouseEvent e) {
if (sourcePoint != null)
targetPoint = e.getPoint();
repaint();
}
});
}
public void paintComponent(Graphics g) {
if (sourcePoint != null && destinationPoint != null) {
g.setColor(Color.red);
g.drawLine(sourcePoint.x, sourcePoint.y, destinationPoint.x, destinationPoint.y);
}
}
}
Note that I did not run this code.
If the line preview feature has to be added to an existing component, then you will have to repaint the regular content in paintComponent() before paiting the line.

Creating my own event for right button click

I have some component on the frame and I need it to respond just on right button click. I have to use my own event. Should I extend MouseEvent? How can I separate right button click from others in my event?

No, you wouldn't extend MouseEvent, rather you would use MouseEvent.
If this is a Swing GUI you could add a MouseListener to the component and then in the MouseListener's mousePressed method, get the MouseEvent object that is passed in to the method, get its modifiersEx and then check if right click has been pressed:
public void mousePressed(MouseEvent mEvt) {
if ((mEvt.getModifiersEx() & MouseEvent.BUTTON3_DOWN_MASK) != 0) {
// right button has been pressed
}
}

The MouseEvent class has a method that allows you to check which mouse button was used. It's called getButton and it returns an int value that you can compare to one of predefined values
On top of that, there's a convenient class called SwingUtilities, which provides a nice layer of abstraction over the use of these fields. Here's a method you'll find particularly interesting: isRightMouseButton
In other words, you don't need to create your own MouseEvent, a MouseListener implementation will suffice. Here's an example of inline implementation, irrelevant details excluded.
new MouseListener(){
#Override
public void mouseClicked(MouseEvent e) {
if(SwingUtilities.isRightMouseButton(e)){
//do what you want on right click
}
}
// other methods required by the interface
};

Move image using keyboard - Java

I wanted to move my image using keyboard arrow keys. when I pressed the arrow keys it moves accordingly to the direction. However, I need to click on the image before able to move it. May I know how to edit the code such that I do not need to click on the image before able to move it? I would also like to know how to make the image appear from the left once it reaches right and vice versa.
My codes are :
Collect.addKeyListener(new KeyAdapter() {
public void keyPressed(KeyEvent ke)
{
if(ke.getKeyCode() == KeyEvent.VK_LEFT)
{
Collect.setLocation(Collect.getX()-8,Collect.getY());
repaint();
}
if(ke.getKeyCode() == KeyEvent.VK_RIGHT)
{
Collect.setLocation(Collect.getX()+8,Collect.getY());
repaint();
}
}
});
Collect.addMouseListener(new MouseAdapter()
{
public void mouseClicked(MouseEvent me)
{
if(me.getClickCount() == 1)
{
boolean dd = Collect.isOptimizedDrawingEnabled();
boolean ff = Collect.requestFocusInWindow();
repaint();
}
}
});

You have look at KeyBindings, otherwise you have to JComponent#setFocusable() that nest the Image, example for Moving Image

Collect.requestFocusInWindow();
requestFocusInWindow()..
Requests that this Component get the input focus, if this Component's top-level ancestor is already the focused Window.
Make sure to call that only after the main window is visible and has the focus.

KeyListeners only work when the component which has the listener has focus. You are giving focus to what appears to be Collect by clicking on it. Then the listener works. You can add the listener to other things or force focus to remain on something like the outer frame by using a focus listener to regain focus whenever it is lost.