I'm trying to use the Robot class to move the mouse pointer based on accelerometer readings I'm getting from my android device via bluetooth. The problem is that the mouse cursor moves in steps. I need a way to move it smoothly, like physically dragging the pointer. Here's what I have so far
#Override
public void serialEvent(SerialPortEvent serialPortEvent) {
if(serialPortEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
try {
String inputLine = input.readLine();
String[] values = inputLine.split(",");
int x = Integer.parseInt(values[0])*(-1);
int y = Integer.parseInt(values[1])*(-1);
mouse.moveMouse(x, y);
//System.out.println(inputLine);
} catch (IOException e) {
System.err.println(e.toString());
}
}
}
Here the mouse pointer moves in smaller or bigger steps depending on how much the phone is tilted. But I want it to move faster or slower.
What you're looking for is called interpolation, and there are probably a bunch of results on google for it. But the basics are that you need to figure out which positions are between your start and end positions, and move through them over time.
Alternatively, it looks like you might be able to simply scale your input values down.
Related
I'm trying to write a logic in memory game that when I click on cards and they are not a pair (different ID), program should swap them back after 1s. If they are same, then leave them as they are.
The problem is that when I first click and the card appears, after second clicking on another (different) card it doesn't appear and swap the first card after 1s. someone knows why the second card does not appear after clicking?
Btw when the pair is correct, everything works fine, here is my fragment of the code responsible for that logic in listener:
final int copy = i;
card2.addActionListener((e) -> {
card2.setIcon(new ImageIcon(icons[copy].getAbsolutePath()));
if(firstClick == null)
{
firstClick = (Card)e.getSource();
}
else
{
Card secondClick = (Card)e.getSource();
if(firstClick.getID() != secondClick.getID())
{
try
{
Thread.sleep(1000);
} catch (InterruptedException e1)
{
//e1.printStackTrace();
}
firstClick.setIcon(new ImageIcon(background.getAbsolutePath()));
secondClick.setIcon(new ImageIcon(background.getAbsolutePath()));
firstClick = null;
}
else
firstClick = null;
}
});
While method actionPerformed is executing, the GUI cannot react to mouse and keyboard events, so basically your code is "freezing" your GUI for one second. I believe that the class javax.swing.Timer is what you need and at first glance it looks like the duplicate question that MadProgrammer referred to may help you.
First of all, check this out (link): it's an example program taken from the Processing Box2D library on github, which displays a box at the center of the screen (it can be moved around with the mouse) while a cascade of little balls fall on it; whenever a ball hits the box, that ball turns red. I copypasted the four .pde files into a single .pde sketch, run it, and it works perfectly.
Now, onto my problem. I'm currently making a game in Processing: you have a ball, a player 1 and a player 2 (both of which can be moved around using the keyboard). Box2D is in charge of the physical interactions between each player and the ball, and I must say it handles them pretty well. Each of the three main objects has its own class. Now, I want stuff to happen as soon as player 1 makes contact with the ball. And that example code seems perfect for this scope, right? It works on my computer, after all.
So, I started copying the relevant parts:
I copypasted all the 'import's at the beginning of my code;
I added box2d.listenForCollisions(); inside setup();
I also added these two functions at the very bottom of my sketch:
void beginContact(Contact cp) {
Fixture f1 = cp.getFixtureA();
Fixture f2 = cp.getFixtureB();
Body b1 = f1.getBody();
Body b2 = f2.getBody();
Object o1 = b1.getUserData();
Object o2 = b2.getUserData();
if (o1.getClass() == Box.class) {
Particle p = (Particle) o2;
p.change();
}
else if (o2.getClass() == Box.class) {
Particle p = (Particle) o1;
p.change();
}
}
void endContact(Contact cp) {
}
Which I promptly changed into this (I basically renamed the classes, and substituted p.change(), the method that turned the balls red in that sketch, with what I want to happen when contact is being made):
(... same ...)
if (o1.getClass() == Player.class) {
Ball p = (Ball) o2;
//do stuff when contact happens
}
else if (o2.getClass() == Player.class) {
Ball p = (Ball) o1;
//do stuff when contact happens
}
}
void endContact(Contact cp) {
}
But guess what? I get a 'Could not invoke the "beginContact()" method for some reason' error! I don't think I'm lacking any crucial files or libraries, since that example worked fine in my computer and all I did was just copypaste and run the code.
I cannot paste here my whole code because it's huge, but I swear the Player class (player 1 class), the Enemy class (player 2 class) and the Ball class all have their fixtures, and there's literally nothing in my classes that differs in a substantial way from those from the example sketch. The bodies are all of dynamic type, the players are rectangular boxes like the box in the example, and the ball is a pure circle like the little balls that turned red there.
What is happening? Did I miss an important line from that code? Even though the example code runs perfectly without needing any additional files, I should mention that the console also prints an 'at shiffman.box2d.Box2DContactListener.beginContact(Box2DContactListener.java:54)' error: now, like I said, I don't need that Box2DContactListener.java file in my computer to run the example sketch... but anyway, if I read it up online (link), I can see this is what it's referring to:
public void beginContact(Contact c) {
if (beginMethod != null) {
try {
beginMethod.invoke(parent, new Object[] { c });
} catch (Exception e) {
System.out.println("Could not invoke the \"beginContact()\" method for some reason.");
e.printStackTrace();
beginMethod = null;
}
}
}
Do you have any idea what's going on here?
Basically, before the if statement, you have to check if either of the objects is 'null'.
In case it is, you just have to break.
You can just simply paste this:
if (o1==null || o2==null)
return;
I am trying to make a NXT Robot that has attached the Ultrasonic Sensor. It has to drive until the distance is 15, and then the engines have to stop. After it stops it has to turn, but it doesn't work.
import lejos.nxt.*;
public class test {
public static void main(String [] args) throws InterruptedException {
UltrasonicSensor ultra = new UltrasonicSensor(SensorPort.S1);
for (int i = 0; i < 5; i++) {
try {
Motor.B.rotate(-1500 , true);
Motor.C.rotate(-1500 , true);
} catch (Exception E){}
while ( ultra.getDistance() < 15 ) {
Motor.B.backward();
Motor.C.backward();
}
LCD.clear();
LCD.drawString("Distance : "+ultra.getDistance(), 0, 0);
}
Button.waitForAnyPress();
}
}
My old code, which also didn't work:
import lejos.nxt.*;
public class test {
public static void main(String [] args) throws InterruptedException {
UltrasonicSensor ultra = new UltrasonicSensor(SensorPort.S1);
try {
Motor.B.rotate(-720);
Motor.C.rotate(-720);
} catch (Exception E){}
for (int i = 0; i < 5; i++)
{
LCD.drawString("Distance : "+ultra.getDistance(), 0, i);
Thread.sleep(2000);
int maxDistance = ultra.getDistance();
if (maxDistance < 15){
Motor.B.stop();
Motor.C.stop();
}
}
Button.waitForAnyPress();
}
}
Assumptions
Okay, from the looks of things, your code is probably not doing what you want. (In the future, when writing a question on Stack Overflow, please clarify in detail what the expected behavior is, as well as what erroneous behavior you're seeing. Those are usually the first two questions we would ask of you, anyway.)
First of all, you're going to want to ensure that your NXT kit has been set up properly, with your two motors on B and C, and your sensor on S1. If this is so, continue reading.
Code Interpretation
The motor commands:
try {
Motor.B.rotate(-1500, true);
Motor.C.rotate(-1500, true);
} catch (Exception E) {}
look like they're valid motor commands... but wait! You're using a two-wheeled robot, with the motors connected to two wheels that point in opposite directions? But you're using the same distance and direction for your motor's limit angle! If your wheels oppose each other, then this will do nothing but make the robot spin in a circle.
NOTE: Since your motors are configured properly, as written in your comments, ignore this part.
If you change the direction of one of the motors by changing the positive to a negative, then you'll have them both working in unison to move your robot forward (or backwards, if you change the wrong one!)
Also, keep in mind that passing true as the second argument in
Motor.B.rotate(-1500, true);
Motor.C.rotate(-1500, true);
makes this function in a very specific fashion, according to the Javadoc (emphasis mine):
If immediateReturn is true, method returns immediately and the motor stops by itself.
If any motor method is called before the limit is reached, the rotation is canceled.
The first sentence means that this does what we want it to: It tells our motor to find the right limit angle by itself, but don't make our program wait for it. However, the second sentence means that if any other motor commands are called, it will stop moving to the given limit angle. Yeah, that's right. Those next few lines make us stop moving the motors and do what they say instead.
Now, this code is problematic for two reasons:
while (ultra.getDistance() < 30) {
Motor.B.backward();
Motor.C.backward();
}
First, these commands will IMMEDIATELY stop our previous two motor commands from executing, which basically means the motors will jump straight to going "backwards" and looping until the distance sensor reads greater than or equal to 30. This is actually what we want, but we need a bit more...
Second, after your sensor reads the distance greater than 30, your motors are never told to stop! So even when your program is showing you the distance, and waiting for your button to be pressed, it'll still be moving!
A Solution
Okay, there's a few things that need to change:
Your initial motor command is being blocked out by the later commands that tell it to move to the correct position.
Your motors don't stop when they're supposed to.
Below is your code, edited to address each of these issues. I've included notes where I've made changes to show you what I've changed.
import lejos.nxt.*;
public class test {
public static void main(String [] args) throws InterruptedException {
UltrasonicSensor ultra = new UltrasonicSensor(SensorPort.S1);
for (int i = 0; i < 5; i++) {
// No initial motor movement (because it did nothing anyway)
// We change this to approach from either direction.
while (ultra.getDistance() != 30) {
// Check whether it's behind or ahead of it.
// Assuming that B- and C- increase distance, and B+ and C+ decrease it (depends on robot configuration).
// This is called a feedback loop, by the way.
if (ultra.getDistance() < 30) { // Move forward (distance+)
Motor.B.backward();
Motor.C.backward();
} else { // Move backward (distance-)
Motor.B.forward();
Motor.C.forward();
}
}
// We only get here when the distance is right, so stop the motors.
Motor.B.stop();
Motor.C.stop();
LCD.clear();
LCD.drawString("Distance : "+ultra.getDistance(), 0, 0);
}
Button.waitForAnyPress();
}
}
Now, this code isn't perfect; it may have a tendency to oscillate between forward and backward on slippery surfaces (which may turn it slightly to the left or right due to differences in applied torque), or if the sensor misses the correct position and the robot overshoots it.
This code also doesn't wait until the robot stabilizes at the given position, just until the sensor first reports the correct one. Again, this may result in sliding around a bit if the wheels don't have decent traction, the motors are set to smooth acceleration, or if the motors run at too high of a speed.
To correct these flaws, you'd need a more advanced type of feedback loop which accounts for acceleration and slip, and you'd need to wait until the robot stabilizes at the correct position for a short period of time before stopping the motors.
However, this should get you moving in the right direction, so to speak.
EDIT Corrected drive motor directionality, as specified in the comments.
So I've been trying to write a simple game where a character is moving using the statement
character1.x+=0.1f*delta
where delta is the time (in milliseconds) between frames. This works well when I want to move it every frame, but I want to be able to move it a set distance (50 pixels, or a single tile in my game) at that speed. Using for() loops makes it move the sprite at maximum speed, so I can't do that. It has to work on a single keypress, so they don't have to hold the key down.
Of course, I've barely done anything ever in Java, so there's probably a really stupidly simple solution that I'm missing. For now, I can just change it to instantaneous movement, but it looks really jerky. Can someone help?
In this case, you might want to add a keyListener yo your component.
yourComponent.addKeyListener(new KeyAdapter () { // Possibly your Frame
#Override // Overrides the keyPressed event
public void keyPressed(KeyEvent e) {
if ( e == YOUR_KEY_CODE ) {
for( int var = 0; var < yourDistance; var ++ ){
yourSpriteComponent.x += 1;
try{
Thread.sleep(yourTimeInMilliSec);
} catch( Exception e ){
// Your catch block here
}
}
}
}
});
Where YOUR_KEY_CODE is the key that the user needs to be pressed in order to execute the for() loop. Key Codes can be found in javadoc
I'm doing some Swing GUI work with Java, and I think my question is fairly straightforward; How does one set the position of the mouse?
As others have said, this can be achieved using Robot.mouseMove(x,y). However this solution has a downfall when working in a multi-monitor situation, as the robot works with the coordinate system of the primary screen, unless you specify otherwise.
Here is a solution that allows you to pass any point based global screen coordinates:
public void moveMouse(Point p) {
GraphicsEnvironment ge =
GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice[] gs = ge.getScreenDevices();
// Search the devices for the one that draws the specified point.
for (GraphicsDevice device: gs) {
GraphicsConfiguration[] configurations =
device.getConfigurations();
for (GraphicsConfiguration config: configurations) {
Rectangle bounds = config.getBounds();
if(bounds.contains(p)) {
// Set point to screen coordinates.
Point b = bounds.getLocation();
Point s = new Point(p.x - b.x, p.y - b.y);
try {
Robot r = new Robot(device);
r.mouseMove(s.x, s.y);
} catch (AWTException e) {
e.printStackTrace();
}
return;
}
}
}
// Couldn't move to the point, it may be off screen.
return;
}
You need to use Robot
This class is used to generate native system input events for the purposes of test automation, self-running demos, and other applications where control of the mouse and keyboard is needed. The primary purpose of Robot is to facilitate automated testing of Java platform implementations.
Using the class to generate input events differs from posting events to the AWT event queue or AWT components in that the events are generated in the platform's native input queue. For example, Robot.mouseMove will actually move the mouse cursor instead of just generating mouse move events...
Robot.mouseMove(x,y)
Check out the Robot class.
The code itself is the following:
char escCode = 0x1B;
System.out.print(String.format("%c[%d;%df",escCode,row,column));
This code is incomplete by itself, so I recommend placing it in a method and calling it something like 'positionCursor(int row, int column)'.
Here is the code in full (method and code):
void positionCursor(int row, int column) {
char escCode = 0x1B;
System.out.print(String.format("%c[%d;%df",escCode,row,column));
}