I'm doing these iTunes Stanford classes, and I've been learning beginning Java. Things are going great, but they recently introduced events-and specifically MouseEvents. I've been reading the chapters in the book, and pouring through the example code, and something is just not clicking right for me...it's always that asynchronous stuff that gives me trouble :-D
Earlier, some people mentioned it was important that I mention that the "addMouseListener" is a class in the Graphics import. As far as I can tell, that just adds a blanket mouse listener to the canvas.
I'm still real new to this, so I may not be describing things as well as I should.
This is a piece of code that I have been trying to simplify in order to better understand it. Currently, it will build a red rectangle, and I can click on it and drag it along the x axis. Great!!!
import java.awt.*;
import java.awt.event.*;
import acm.graphics.*;
import acm.program.*;
/** This class displays a mouse-draggable rectangle and oval */
public class DragObject extends GraphicsProgram {
/* Build a rectangle */
public void run() {
GRect rect = new GRect(100, 100, 150, 100);
rect.setFilled(true);
rect.setColor(Color.RED);
add(rect);
addMouseListeners();
}
/** Called on mouse press to record the coordinates of the click */
public void mousePressed(MouseEvent e) {
lastX = e.getX();
lastY = e.getY();
gobj = getElementAt(lastX, lastY);
}
/** Called on mouse drag to reposition the object */
public void mouseDragged(MouseEvent e) {
if((lastX) > 100){
gobj.move(e.getX() - lastX, 0);
lastX = e.getX();
lastY = e.getY();
}
}
/** Called on mouse click to move this object to the front */
public void mouseClicked(MouseEvent e) {
if (gobj != null) gobj.sendToFront();
}
/* Instance variables */
private GObject gobj; /* The object being dragged */
private double lastX; /* The last mouse X position */
private double lastY; /* The last mouse Y position */
}
If I drag the mouse off the canvas, I want the rectangle to stay within the canvas, and not move off it (the same behavior that a horizontal scroll bar would do if you moved beyond the scroll area with the mouse button still clicked). How can I do that?
I've been trying something along these lines, but it's not working right:
if ( ( lastX > (getWidth() - PADDLE_WIDTH) ) || ( lastX < PADDLE_WIDTH ) ) {
gobj.move(0, 0);
} else {
gobj.move(e.getX() - lastX, 0);
}
Your code is moving the rectangle relative to the last position of the mouse. This works fine when you are simply moving things, but for your needs when you want it to stop at the borders, you need to use absolute positioning.
// When the mouse is pressed, calculate the offset between the mouse and the rectangle
public void mousePressed(MouseEvent e) {
lastX = e.getX();
lastY = e.getY();
gobj = getElementAt(lastX, lastY);
}
public void mouseDragged(MouseEvent e) {
double newX;
// Assuming you can get the absolute X position of the object.
newX = gobj.getX() + e.getX() - lastX;
// Limit the range to fall within your canvas. Adjust for your paddle width as necessary.
newX = Math.max( 0, Math.min( newX, getWidth() ) );
// Set the new position of the paddle, assuming you can set the absolute position.
gobj.setX( newX );
lastX = e.getX();
lastY = e.getY();
}
}
This may not be quite what you want because as soon as you go off the edge, the object will stop moving, but then once you move back toward the canvas, your paddle will move immediately instead of waiting for the mouse to reach the same relative position to the paddle at which it started.
You can probably experiment to get it to do what you want.
In order to do this you will need to know the width of the Canvas object, i'm sure there will be a method that will provide this value. You can then check the current x location of the MouseEvent against the width of the canvas, and not increment the x coordinates of the shape object once you are past the width of the canvas. Depending on how much of the shape you want to remain in the canvas, you may need to take into account the width of the shape object as well.
One thing that helps me when dealing w/ animation and moving objects in a gui is drawing out a few scenarios on paper, and noting how the coordinates change.
Related
I'm working on something that involves clicking specific points on a buffered image in a JPanel. I had issues with this earlier in the project (affine transform translation not working properly), but nothing I found fixed it so I decided I would come back to it later.
I'm not entirely sure how to trouble shoot it since I'm a novice, but I think it's reading my y coordinates too low. I made a mouse input listener that tracks the number of times the user has clicked and gets the mouse pointer's location for functions I haven't made yet. For testing I have it output the coordinates and number of clicks then make a circle centered where the mouse clicks.
#Override
public void mouseClicked(MouseEvent e) {
Point mouseCursor = MouseInfo.getPointerInfo().getLocation();
panel.drawCenteredCircle(mouseCursor.getX(), mouseCursor.getY(), 100);
System.out.println(String.valueOf(mouseCursor));
System.out.println(String.valueOf(clickCount));
clickCount++;
}
Here is drawCenteredCircle in my custom panel class:
public void drawCenteredCircle(double x, double y, int r) {
imgG2 = image.createGraphics();
imgG2.setPaint(Color.RED);
x = (x-r/2.0);
y = (y-r/2.0);
imgG2.fillOval((int)Math.round(x), (int)Math.round(y), r, r);
this.repaint();
imgG2.dispose();
}
I tried taking a screenshot to show what happens, but the circle properly centers on the x coordinate, but not the y coordinate. Instead it draws the circle with the pointer at the top center edge.
I overrided the paintComponent of my JPanel to implement a zoom feature:
#Override
protected void paintComponent(Graphics g) {
//Implimenting zoom
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g.create();
g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
/*Supposed to counter the movement from the scale, not working properly
int imageWidth = image.getWidth();
int imageHeight = image.getHeight();
double x = (w - scale * imageWidth)/2;
double y = (h - scale * imageHeight)/2;*/
AffineTransform at = new AffineTransform()/*.getTranslateInstance(x, y) */;
at.scale(scale, scale);
g2.drawRenderedImage(image, at);
//g2.dispose(); I was told to put this, but I'm not sure if it's necessary or what it does entirely
}
My confused notes are because I got this code from an example someone made and, as I said earlier, the affine translation wasn't working (I took the actual translation out). They're irrelevant to the question.
The reason I put this is because I initially had code that was meant to fit the image to the screen/frame depending if it was fullscreen or not:
int x = image.getWidth();
int y = image.getHeight();
double frameW = frame.getBounds().getWidth();
double frameH = frame.getBounds().getHeight();
//Rectangle winSize = GraphicsEnvironment.getLocalGraphicsEnvironment().getMaximumWindowBounds();
double screenW = Toolkit.getDefaultToolkit().getScreenSize().getWidth();
double screenH = Toolkit.getDefaultToolkit().getScreenSize().getHeight();
if (!isFullScreen) {
if (x/y > frameW/frameH) {
scale = frameW/x;
} else {
scale = frameH/y;
}
} else {
if (x/y > screenW/screenH) {
scale = screenW/x;
} else {
scale = screenH/y;
}
}
It uses my zoom function which scales the image with the double "scale." I noticed that when I zoomed in or out, it would change where the dots would appear relative to the pointer. It wasn't until I removed the code for the image to start fitted to the window and had it start at 100% that I received the result of the pointer being at the top center of the circle.
I also tried removing the part that's supposed to center the circle and the result was the pointer being on the left side and having a gap between it and the top of the circle.
Sorry if this is too much stuff. I'm pretty novice and learned just as much about java (the only coding language I know) working on this project as I knew when I first started it. I'm not sure what information I have that could be helpful in this, so I just threw in everything I thought could help. I appreciate any help, even irrelevant to my question.
I'm trying to make a graphic project where a Ball runs away from my cursor, I already did the other way around where the ball seeks my cursor and when she arrives she loses velocity so it's like she's running fast until she comes around a range of 10 pixels and then she loses velocity until she touches the cursor.
The thing is, I can't find a way to make the ball run away from the cursor in a way that when I enter a diameter(from the ball), she runs slow, if I approach more she starts to run faster to get away but when my cursor leaves the diameter, she runs slow until she stops once again.
I hope I made it clear, I thought about a solution but I don't know if there's a library or some built function in Java that I could use guys:
-have like a percentage from 0 to 100 where the distance between my cursor and the ball fits inside, 0% is velocity=0, 100% is velocity=4 for example, do you have any idea if there is such thing that I could implement?
Thank you in advance!
I've made a Vector class where I change it and access the X and Y coordinates to make the ball move, I used basic trigonometry to make the vector ALWAYS the same length.
code of my ball (Chaser) class:
public class Chaser {
private double x;
private double y;
private double vel = 1;
private double hyp;
private Vector vector = new Vector(0, 0);
private double distance;
public Chaser(int width, int height){
x = width/2;
y = height/2;
}
public void setVel(Point m){
if(m.x != x)
hyp = Math.sqrt(Math.pow(Math.abs(m.x - x), 2) + Math.pow(Math.abs(m.y - y), 2));
else
hyp = Math.abs(m.y - y);
}
public void setDirection(Point m){
if(hyp == 0) return;
vector.change((m.x - x)/hyp, (m.y - y)/hyp);
}
public void draw(Graphics g){
g.setColor(Color.RED);
g.fillOval((int)x - 10, (int)y - 10, 20, 20);
g.setColor(Color.BLACK);
g.drawLine((int)x, (int)y, (int)(vector.getX()*15*vel) + (int)x, (int)(vector.getY()*15*vel) + (int)y);
}
public void move(Point m){
setVel(m);
setDirection(m);
useVector();
}
public void useVector(){
if(vector == null) return;
x -= vector.getX() * vel;
y -= vector.getY() * vel;
}
public void calculateVelocity(Point m){
if(vector == null) return;
// I don't know what to do yet
}
}
If you want to just push the ball around you can do something simple. Let's use vectors to make it easier to understand. Say ball holds the ball's center (x,y) and mouse contains the mouse position (x,y).
You can compute the distance between ball and mouse, that is (mouse - ball).length() to get how far away the mouse is from the ball.
If the distance > ball radius then the mouse is outside.
Otherwise you can do:
tmp = ball - mouse // get the vector from mouse to the ball.
tmp = tmp / tmp.length() * ball_radious // change the vector's length to match the radious of the ball.
ball = mouse + tmp // Move the ball such that the mouse will be on the edge.
As you move the mouse the ball will get pushed by the mouse.
If you want a bit of inertia, so the ball doesn't just stop when you don't push it anymore then you need to keep an additional vector speed and use tmp to get an acceleration.
Something like this:
tmp = ball - mouse // get the vector from mouse to the ball.
force = max(0, ball_radious - tmp.length()) // how strong we push the ball.
acceleration = tmp / tmp.legnth() * f(force) // compute the acceleration vector. f(force) is some function based on force, try k*f or k*f*f and see what looks better for your setup.
speed = speed * kDrag + acceleration // update the speed, kDrag should be between 0 and 1, start with something like 0.8 and try different values.
ball = ball + speed * time_delta // Update the ball's position.
You can play with the constants to get the right feel that you're looking for. time_delta is meant to normalize the speed between frams so you don't need to worry too much if there's some inconsistency between them. You can use a constant as well, but the movement might become jerky at times.
All operations above are vector operations.
I'm trying to create a remote desktop access tool in Java (more of an experiment than anything really), but i'm having trouble converting the point in which is clicked to a location on the main screen. Let me explain.
Here's an example of how the tool looks (for now).
The screen capture window is 1280x720, and the actual screens vary in size, how can I get the location of where the mouse is and change it to the same location on the main screen?
e.g. if I click on the apple logo on the screen capture window, it should move my mouse and click on the apple logo on the main screen. I just can't figure out how to get the point in the window, and translate it to the same point on the main screen!
EDIT: Here is what i'm trying to do atm:
MouseAdapter adapter = new MouseAdapter() {
#Override
public void mouseMoved(MouseEvent e) {
PacketMoveMouse packetMoveMouse = new PacketMoveMouse(address, e.getXOnScreen(), e.getYOnScreen());
sendPacket(address, packetMoveMouse);
}
#Override
public void mousePressed(MouseEvent e) {
Point point = this.getPoint(e.getPoint());
PacketClickMouse packetClickMouse = new PacketClickMouse(address, point.getX(), point.getY(), e.getButton());
sendPacket(address, packetClickMouse);
}
private Point getPoint(Point point) {
SwingUtilities.convertPointFromScreen(point, panel);
return point;
}
};
I also tried without converting the point, i was just trying various things. It moves the mouse correctly, but to the wrong point.
I also tried to convert it to a point on the main screen using some basic math, but i think my logic flawed, here is what i tried:
Rectangle screenRect = new Rectangle(Toolkit.getDefaultToolkit().getScreenSize());
int x = ((PacketMoveMouse) packet).getX();
int y = ((PacketMoveMouse) packet).getY();
double xRatio = (screenRect.getWidth() / 1280);
double yRatio = (screenRect.getHeight() / 720);
Robot robot = new Robot();
robot.mouseMove((int) ((x * xRatio)), (int) ((y * yRatio)));
This is when i just send the regular point to the client then change to to a relative point once it's received. The display screen of the client is 1280x720 currently.
To get your mouse CURRENT coordinates
int mouseX;
int mouseY;
#Override
public void mouseMoved(MouseEvent e) {
mouseX = e.getX();
mouseY = e.getY();
}
I want to make a game where you can build stuff by dragging and dropping objects into place. I think LibGDX only supports DragNDrop on Actors, but I need physics on bricks in order to make them fall down if the construction is not stable.
So far, my approach to drag and drop is:
for(Brick b : map.getList()){
final Image im = new Image(b.ar);
stage.addActor(im);
im.setPosition(b.posX, b.posY);
im.setOrigin(b.posX, b.posY);
im.addListener((new DragListener() {
public void touchDragged (InputEvent event, float x, float y, int pointer) {
im.setOrigin(x, y);
im.setPosition(x, y);
//System.out.println("touchdragged ---> X=" + x + " , Y=" + y);
}
}));
}
where the map.getLists contains all bricks to be painted. b.ar is the texture to be painted.
With this aproach [this] is what happens. I don't know what may be causing it.
#Override
public void render(float delta) {
spritebatch.begin();
map.getWorld().step(1/60f, 6, 2);
renderer.render(map.getWorld(), camera.combined);
if(Gdx.input.justTouched()){
Vector3 touchPoint = new Vector3(Gdx.input.getX(), Gdx.input.getY(),0);
camera.unproject(touchPoint.set(Gdx.input.getX(), Gdx.input.getY(), 0));
System.out.println(touchPoint);
}
stage.draw();
spritebatch.end();
}
Of course i'd like to make the body fell (with the box 2d engine from libgdx) if you drop the object and it has nothing under it.
Thanks in advance
You're setting the origin in your listener callback to a screen coordinate. That is not going to work.
The origin is used to define the "center" of your object, so when you reposition it, Libgdx knows which part of the actor to put where. Generally the origin is either the bottom left corner of the object (I think this is the default) or its the center of the object.
I guess you may want to reset the origin so if someone taps on the left edge of a brick and then you reposition the object you'll reposition that point on the brick (and not reposition the bottom left corner of the brick). To do that you'll need to convert the screen coordinates into coordinates in the actor's space.
That's all somewhat icky though. I think you'd be better off just doing relative repositioning. Instead of trying to position the brick absolutely with setPosition just reposition it relatively:
im.setPosition(im.getX() + dx, im.getY() + dy);
Then it doesn't matter where the "origin" is.
You'll have to compute dx and dy in your listener based on the previous touch point.
It appears that the drag listener gives coordinates relative to the origin of the actor that is raising the event. That is a bit strange when you are moving that actor in response to the drag events, because the origin keeps changing. Essentially, I found that if I just move the actor by the x and y values of the event, it will follow the mouse or finger.
One improvement is to record the position that the drag started at and use it as an offset, so the pointer stays the same distance from the actor's origin.
Another option might be to add the listener to the stage instead of the button. I expect the coordinates would then be relative to the stage's origin, which is not changing. I haven't tried that technique.
Here's the code I used to drag a button horizontally:
DragListener dragListener = new DragListener() {
private float startDragX;
#Override
public void dragStart(
InputEvent event,
float x,
float y,
int pointer) {
startDragX = x;
}
#Override
public void drag(InputEvent event, float x, float y, int pointer) {
insertButton.translate(x - startDragX, 0);
}
};
dragListener.setTapSquareSize(2);
insertButton.addListener(dragListener);
If you want to drag something in two dimensions, just copy the x code for the y position.
I have built a custom component that shows only a line. The line is drawn from the top left corner to the bottom right corner as a Line2D at the paint method. The background is transparent. I extended JComponent. These line components are draggable and change their line color when the mouse pointer is located max. 15 pixels away from the drawn line.
But if I have multiple of these components added to another custom component that extends JPanel they sometimes overlap. I want to implement that if the mouse pointer is more than 15 pixels away from the line the mouse events should fall through the component. How to let it fall through is my problem.
Is that even possible?
Thanks in advance!
I want to implement that if the mouse pointer is more than 15 pixels
away from the line the mouse events should fall through the component.
If your child component has a mouse listener, then it will intercept every mouse event occurring over it. If you want to forward the MouseEvent to the parent Component you should manually do it. For example you can implement your custom mouse listener extending MouseAdapter:
public class yourMouseListener extends MouseAdapter{
//this will be called when mouse is pressed on the component
public void mousePressed(MouseEvent me) {
if (/*do your controls to decide if you want to propagate the event*/){
Component child = me.getComponent();
Component parent = child.getParent();
//transform the mouse coordinate to be relative to the parent component:
int deltax = child.getX() + me.getX();
int deltay = child.getY() + me.getY();
//build new mouse event:
MouseEvent parentMouseEvent =new MouseEvent(parent, MouseEvent.MOUSE_PRESSED, me.getWhen(), me.getModifiers(),deltax, deltay, me.getClickCount(), false)
//dispatch it to the parent component
parent.dispatchEvent( parentMouseEvent);
}
}
}
For my final year project at university I did a whiteboard program and had the same problem. For each shape the user drew on the board I created a JComponent, which was fine when they were drawing rectangles, but more difficult with the free form line tool.
The way I fixed it in the end was to do away with JComponents altogether. I had a JPanel which held a Vector (I think) of custom Shape objects. Each object held its own coordinates and line thicknesses and such. When the user clicked on the board, the mouse listener on the JPanel fired and went through each Shape calling a contains(int x, int y) method on each one (x and y being the coordinates of the event). Because the Shapes were added to the Vector as they were drawn I knew that the last one to return true was the topmost Shape.
This is what I used for a straight line contains method. The maths might be a bit iffy but it worked for me.
public boolean contains(int x, int y) {
// Check if line is a point
if(posX == endX && posY == endY){
if(Math.abs(posY - y) <= lineThickness / 2 && Math.abs(posX - x) <= lineThickness / 2)
return true;
else
return false;
}
int x1, x2, y1, y2;
if(posX < endX){
x1 = posX;
y1 = posY;
x2 = endX;
y2 = endY;
}
else{
x1 = endX;
y1 = endY;
x2 = posX;
y2 = posY;
}
/**** USING MATRIX TRANSFORMATIONS ****/
double r_numerator = (x-x1)*(x2-x1) + (y-y1)*(y2-y1);
double r_denomenator = (x2-x1)*(x2-x1) + (y2-y1)*(y2-y1);
double r = r_numerator / r_denomenator;
// s is the position of the perpendicular projection of the point along
// the line: s < 0 = point is left of the line; s > 0 = point is right of
// the line; s = 0 = the point is along the line
double s = ((y1-y)*(x2-x1)-(x1-x)*(y2-y1) ) / r_denomenator;
double distance = Math.abs(s)*Math.sqrt(r_denomenator);
// Point is along the length of the line
if ( (r >= 0) && (r <= 1) )
{
if(Math.abs(distance) <= lineThickness / 2){
return true;
}
else
return false;
}
// else point is at one end of the line
else{
double dist1 = (x-x1)*(x-x1) + (y-y1)*(y-y1); // distance to start of line
double dist2 = (x-x2)*(x-x2) + (y-y2)*(y-y2); // distance to end of line
if (dist1 < dist2){
distance = Math.sqrt(dist1);
}
else{
distance = Math.sqrt(dist2);
}
if(distance <= lineThickness / 2){
return true;
}
else
return false;
}
/**** END USING MATRIX TRANSFORMATIONS****/
}
posX and posY make up the coordinates of the start of the line and endX and endY are, yep, the end of the line. This returned true if the click is within lineThickness/2 of the centre of the line, otherwise you have to click right along the very middle of the line.
Drawing the Shapes was a case of passing in the JPanel's Graphics object to each Shape and doing the drawing with that.
It's been a while since I touched Swing, but I think you will need to handle your mouse events in the parent component and then loop through the child components with lines and determine which one of them should handle the event (well, the logic of deciding should still remain in the line component, but parent will explicitly invoke that logic until one of the components takes the event).
I believe that the easiest way is to catch the event and call parent.processEvent(). So, you component will be transparent for events because it will propagate them to parent.
I was struggling with this sort of question and tried all the stuff with parents and glasspane until i realised that override of contains method does just what you want. Because when parent fires some sort of getcomponent your 'Line' will reply to it: 'no, its not me, i'm not there!' and the loop will check other components.
Also, when you need to setup a complex depth to your draggable object, you can use JLayeredPane descendant.