I'm creating an application with Java and SWT, and have a workspace generated on a Canvas. I need to make certain areas (controls) on the canvas trigger an event when mouseover-ed or clicked. Of course this could be done by listening to the MouseMoveEvent and checking the location of the mouse manually, but I would like to know if SWT provides an easier way to do this.
Thanks
As far as I know, there is no facility to automate this. You will need to register mouse listeners and investigate the x & y coordinates manually.
A different approach might be adding individual Canvas objects onto an enclosing Canvas. This way, you could add listeners to the individual controls. This will, however, use more memory (as the underlying object has a buffer, as well as the control on top) and redrawing will be more CPU intensive.
My personal preference goes to the first technique.
Thanks for the answer, Paul. I finally created an ArrayList of Rectangle objects for each control. Whenever the mousemove event triggers, I loop through each Rectangle and call Rectangle.contains() with the mouse coordinates. This solution turned out to be very organized.
In my case, the control events are homogenous (they all do the same thing), but if anyone has multiple control actions, Rectangle.data can be used to contain a Command object.
Related
How do I get the mouse position. I have tried:
int mouseX = MouseInfo.getPointerInfo().getLocation().x;
int mouseY = MouseInfo.getPointerInfo().getLocation().y;
But that does it for the whole screen. Anyway to do it relative to the JPanel/JFrame
If I'm only using Graphics JFrame and JPanel that is being repainted every millisecond, should I have buffers? Or will it be fine?
How do I add a mouseAcionEvent only to the frame so it gets X() and Y() of mouse but only in frame?
Use a MouseListener instead of MouseInfo. MouseListener will trigger events which are contextual to the component which raised them, which means you won't need to translate the events into the component space as the event will already be converted to within the component context.
See How to write a mouse listener for more details
How should I update my game rePaint() every millisecond or another way?
Use a javax.swing.Timer...
See How to use Swing Timers for more details...
Should I use buffers?
That will depend. Swing components are already double buffered, but if you use a more complex timing mechanism (AKA game loop), you might find it useful, even to roll your own.
I, personally, would start simple
How can I improve the way I thought out my code in the first place? Is it right having 10 loops or only all in 1 to reduce lag ect.
There are probably lots of things, but start with broader idea...
Breakdown entities to their own responsibilities, for example, the player should know where it is and how it should be painted. It could even know how it's suppose to move based on the current state of the game. This way you could create any number of entities, all with there own set of rules which are isolated and easily updated.
Devise a controller mechanism which is responsible for taking in keyboard and mouse events and simply updating the current state of the game model. That is, rather than going "the user pressed the 'left' key, move player to the left", it would simply raise a flag in the game model that the "left" state has been triggered (or untriggered) and the engine would, on the next update loop, ensure that each entity knew about the change
Don't use magic or hard coded numbers, instead provide some kind of ability to scale the scene. For example, you could decide what is shown on the screen based on the size of the window...
This program will have an infinite canvas (ie as long as the user scrolls, it becomes bigger) with a tiled background image, and you can drag and drop blocks and draw arrows between blocks. Obviously I won't use a layout manager for placing blocks and lines, since they will be absolutely positioned (any link on this, possibily with a snapping feature?). The problem arises with blocks and lines. Basically I'll have two options:
Using a simple layout for each building block. This is the simplest and clearest approach, but does it scale well when you have hundreds of objects? This may not be uncommon, just imagine a database with 50 tables and dozens of relationships
Drawing everything with primitives (rectangles, bitmaps, etc). This seems too complicated (especially things like text padding and alignment) but may be more scalable if you have a large number of objects. Also there won't be any event handler
Please give me some hints based on your experience. I have never drawn with Java before - well I did something rather basic with PHP and on Android. Here is a simple preview
DISCLAIMER
You are not forced to answer this. I am looking for someone who did something like this before, what's the use of writing I can check an open source project? Do you know how difficult it is to understand someone else's code? I'm talking about implementations details here... Moreover, there is no guarantee that he's right. This project is just for study and will be funny, I don't want to sell it or anything and I don't need your authorization to start it.
Measuring and drawing text isn't such a pain, since java has built in classes for doing that. you may want to take a look at the 2D Text Tutorial for more information. In fact, I did some text drawing computations with a different graphics engine which is much more primitive, and in the end it was rather easy (at least for the single-line drawing, for going multiline see the previous link).
For the infinite canvas problem, that's also something I always wanted to be able to do. A quick search here at stackoverflow gives this which sounds nice, althought I'm not sure I like it. What you can do, is use the way GIMP has a scroll area that can extend as you move - catch the click of the middle mouse button for marking the initial intention to move the viewport. Then, when the mouse is dragged (while the button is clicked) move the viewport of the jscrollpane by the offset between the initial click and the current position. If we moved outside the bounds of the canvas, then you should simply enlarge the canvas.
In case you are still afraid of some of the manual drawing, you can actually have a JPanel as your canvas, with a fixed layout. Then you can override it's paint method for drawing the connectors, while having child components (such as buttongs and text areas) for other interaction (and each component may override it's own paint method in case it wants to have a custom-painted rect).
In my last drawing test in java, I made an application for drawing bezier curves (which are basically curves made of several control points). It was a JPanel with overidden paint method that drew the curve itself, and buttons with custom painting placed on the location of the control points. Clicking on the control point actually was clicking on a button, so it was easy to detect the matching control point (since each button had one control point associated with it). This is bad in terms of efficiency (manual hit detection may be faster) but it was easy in terms of programming.
Anyway, This idea can be extended by having one child JPanel for each class rectangle - this will provide easy click detection and custom painting, while the parent will draw the connectors.
So in short - go for nested JPanels with custom drawing, so that you can also place "on-canvas" widgets (and use real swing widgets such as text labels to do some ready drawing) while also having custom drawing (by overriding the paint method of the panels). Note that the con of this method is that some swing look-and-feel's may interfere with your drawing, so may need to mess a bit with that (as far as I remember, the metal and nimbus look-and-feel's were ok, and they are both cross-platform).
I'm looking to use the java2d API to make a graph in which users can manipulate certain features using their mouse - such as the scale used for an axis or move around the different points plotted on the graph.
So far all I have found is the drawX methods on a Graphics2D object, however there does not seem to be an easy way to capture a user clicking on one of these and moving it so that I can redraw the graph.
Can anyone suggest the best/easiest way to implement this? Just looking for a point in the right direction.
Not reinventing the wheel is always the best way, there are plenty of excellent libraries you can use: http://www.jfree.org/jfreechart/
If you are looking to implement this yourself, you would listen to mouse events on whatever component you're actually using to display your chart (say a JPanel), and then would have to convert between screen and chart coordinates to figure out what you need to change.
I am looking for ways to zoom in a Java Swing application. That means that I would like to resize all components in a given JPanel by a given factor as if I would take an screenshot of the UI and just applied an "Image scale" operation. The font size as well as the size of checkboxes, textboxes, cursors etc. has to be adjusted.
It is possible to scale a component by applying transforms to a graphics object:
protected Graphics getComponentGraphics(Graphics g) {
Graphics2D g2d=(Graphics2D)g;
g2d.scale(2, 2);
return super.getComponentGraphics(g2d);
}
That works as long as you don't care about self-updating components. If you have a textbox in your application this approach ceases to work since the textbox updates itself every second to show the (blinking) cursor. And since it doesn't use the modified graphics object this time the component appears at the old location. Is there a possibility to change a components graphics object permanently? There is also a problem with the mouse click event handlers.
The other possibility would be to resize all child components of the JPanel (setPreferredSize) to a new size. That doesn't work for checkboxes since the displayed picture of the checkbox doesn't change its size.
I also thought of programming my own layout manager but I don't think that this will work since layout managers only change the position (and size) of objects but are not able to zoom into checkboxes (see previous paragraph). Or am I wrong with this hypothesis?
Do you have any ideas how one could achieve a zoomable Swing GUI without programming custom components? I looked for rotatable user interfaces because the problem seems familiar but I also didn't find any satisfying solution to this problem.
Thanks for your help,
Chris
You could give a try to the JXLayer library.
There are several tools in it, which could help you to make a zoom. Check the examples shown here. I would recommend you to read more about the TransformUI, from this library. From the example, it seems like it could help solving your problem.
Scaling the view is easy enough; transforming mouse coordinates is only slightly more difficult. Here's an elementary example. I'd keep JComponents out, although it might make sense to develop an analogous ScaledComponent that knows about the geometry. That's where #Gnoupi's suggestion of using a library comes in.
hey you can try this if you want to zoom a image like any other image viewer the use a JPanel draw an image using drawImage() method now create a button and when you click the button increase the size of the panel on the frame it appears as if the image is being viewed in Zoom
You might find Piccolo2D.java API useful: http://code.google.com/p/piccolo2d/
It is very simple.
It touts in particular its smooth zooming. You essentially make a "canvas" that can contain various elements, and can then zoom by just holding right-click and panning the mouse back and forth.
I worked on a team that used it to create this: http://sourceforge.net/apps/mediawiki/guitar/index.php?title=WebGuitar#EFG.2FGUI_Visualizer
The nodes you see there are clickable links themselves.
Since Java 9, there are VM arguments (actually meant to be used for high dpi scaling) that can render a application with a higher scaling factor:
java -Dsun.java2d.uiScale=2.0 -jar MyApplication.jar
Or:
java -Dsun.java2d.win.uiScaleX=2.0 -Dsun.java2d.win.uiScaleY=2.0 -jar MyApplication.jar
I have made an Ellipse with the help of java.awt.geom.Ellipse2D
Now, I want that whenever user clicks on that ellipse, an event is generated so that I can listen to that event and peform subsequent tasks based on the ellipse which generated that event.
Here is a simple example of an object drawing program that demonstrates click, drag and multiple selection. Also consider JGraph, which is a much more advanced library for graph visualization.
I'm going to assume this is a question asking a way to listen to mouse clicks which are made on an ellipse drawn on some Swing component using Graphics2D.draw.
The simple answer is, there is no way to generate mouse events from graphics drawn on a surface.
However, here's an alternative approach:
Store the Ellipse2D objects from which the ellipses were drawn from in a List.
Register a MouseListener on the Swing component where the user is to click on.
From the MouseEvents generated from the mouse clicks, determine the location at which the mouse was clicked (using MouseEvent.getPoint), and check if the mouse click occurred in any of the Ellipse2Ds contained in the aforementioned List, using the Ellipse2D.contains method.
I don't think this is possible without lots of handcoded stuff (letting the canvas or whatever, listen to mouse events, and calculating yourself if the ellipse was clicked on).
If you want to do more like that consider scenegraph. With that the ellipse would be an object in its own right and you can register event listeners.
Edit as response to comment:
Scenegraph: https://scenegraph.dev.java.net/
google for more resources: scenegraph java
And yes. Scenegraph ist part of the JavaFX stuff, but works nicely with pure Java (no FX)