Android, How to check collision between two rotated views - android

I am trying to randomize the position of a few textviews inside a frameview. The textviews will also have a randomized rotation between 0 and 360 degrees. The textViews is not allowed to be on top of eachother which means I need to check for collisions (or at least know which points that are valid/not valid). I do not know how to check for collision between two textviews when they are rotated. I have tried to use Rect intersects but this does not really work because this function only works if there is no rotation to the view.
Here is an example on what i want:
TEXT1 is placed first. When TEXT2 is placed the green border around the TEXT1 and TEXT2 is colliding which means that TEXT2 should not be allowed to be placed there. TEXT3 does however not collide with anything and should be allowed to be placed. So I want to check the collision for the green border and not the blue rectangle. How do I do this?
Edit
To rotate the view I am using View.setRotation(float)
To position the textview I am using setX(float) and setY(float).

I ended up with the following solution where I create 4 points, one for each corner of the textView, which I then rotate at the same angle as the textView. With these points I then create a Path which I am using to create a region.
private Region createRotatedRegion(TextView textView){
Matrix matrix = new Matrix();
matrix.setRotate(textView.getRotation(), textView.getX() + textView.getMeasuredWidth() / 2, textView.getY() + textView.getMeasuredHeight() / 2);
Path path = new Path();
Point LT = rotatePoint(matrix, textView.getX(), textView.getY());
Point RT = rotatePoint(matrix, textView.getX() + textView.getMeasuredWidth(), textView.getY());
Point RB = rotatePoint(matrix, textView.getX() + textView.getMeasuredWidth(), textView.getY() + textView.getMeasuredHeight());
Point LB = rotatePoint(matrix, textView.getX(), textView.getY() + textView.getMeasuredHeight());
path.moveTo(LT.x, LT.y);
path.lineTo(RT.x, RT.y);
path.lineTo(RB.x, RB.y);
path.lineTo(LB.x, LB.y);
Region region = new Region();
region.setPath(path, new Region(0, 0, textViewParent.getWidth(), textViewParent.getHeight()));
return region;
}
private Point rotatePoint(Matrix matrix, float x, float y){
float[] pts = new float[2];
pts[0] = x;
pts[1] = y;
matrix.mapPoints(pts);
return new Point((int)pts[0], (int)pts[1]);
}
When I have two regions which now have the same position and rotation as two textViews I can then use the following code to check for collision:
if (!region1.quickReject(region2) && region1.op(region2, Region.Op.INTERSECT)) {
return true; //There is a collision
}
Probably not the best solution but it gets the job done.

Related

MPAndroidChart set center vertical line

I want to set a vertical line in center of LineChart like this:
When scrolling to each point, it can notify to change the date below (the orange date field). And it can move left or right programmatically by click on arrow button.
Currently, I can set viewport and allow moving to center with this code:
LineData data = new LineData(xVals, dataSets);
mChart.setScaleMinima((float) data.getXValCount() / 7f, 1f);
mChart.moveViewTo(0, 7, YAxis.AxisDependency.LEFT);
And get the result:
How can I draw and set a vertical line like above?
Update:
For the listener, I think OnChartGestureListener onChartTranslate(MotionEvent me, float dX, float dY) may help. What I need is the distance between 2 points and how to calculate how many points are in current view port. Does anyone know that?
Have you tried using getEntryByTouchPoint on your chart supplying the x and y coordinates of the center of the chart?
public Entry getEntryByTouchPoint(float x, float y)
returns the Entry object displayed at the touched position of the chart
Take a look at the method
protected void drawGridBackground(Canvas c) {
in the BarLineChartBase class (parent for a LineChart). In that method you have all data to draw your line right in the middle.
Something like this
RectF rectF = mViewPortHandler.getContentRect();
float xMiddle = (rectF.right - rectF.left)/2;
Paint p = new Paint();
p.setColor(Color.BLACK);
c.drawLine(xMiddle, rectF.bottom, xMiddle, rectF.top, p);
Maybe it's too late but here is my answer. It's encoded in Swift using Charts (MPAndroidCharts port for iOS) but API is 99% the same ;)
let verticalPointEntry = ChartDataEntry(x: xValue, y: yValue)
let dataSet = LineChartDataSet(values: [verticalPointEntry], label: "")
dataSet.drawCirclesEnabled = false
dataSet.drawValuesEnabled = false
dataSet.setDrawHighlightIndicators(true)
dataSet.drawHorizontalHighlightIndicatorEnabled = false
dataSet.highlightColor = UIColor.white
dataSet.highlightLineWidth = 1
let highlightPoint = Highlight(x: xValue, y: yValue, dataSetIndex: datasetIndex)
self.highlightValues([highlightPoint])
// "yourNormalDataSet" is your regular dataSet in which you want to display vertical line over it
let chartData = LineChartData(dataSets: [yourNormalDataSet, dataSet])
self.data = chartData
self.data?.notifiyDataChanged()
self.notifyDataSetChanged
This will display a vercital line over the point defined by your xValue variable.
Hope it helps!

Draw a segmented circle in Android: OpenGL vs Cavans?

I need to draw something like this:
I was hoping that this guy posted some code of how he drew his segmented circle to begin with, but alas he didn't.
I also need to know which segment is where after interaction with the wheel - for instance if the wheel is rotated, I need to know where the original segments are after the rotation action.
Two questions:
Do I draw this segmented circle (with varying colours and content placed on the segment) with OpenGL or using Android Canvas?
Using either of the options, how do I register which segment is where?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
EDIT:
Ok, so I've figured out how to draw the segmented circle using Canvas (I'll post the code as an answer). And I'm sure I'll figure out how to rotate the circle soon. But I'm still unsure how I'll recognize a separate segment of the drawn wheel after the rotation action.
Because, what I'm thinking of doing is drawing the segmented circle with these wedges, and the sort of handling the entire Canvas as an ImageView when I want to rotate it as if it's spinning. But when the spinning stops, how do I differentiate between the original segments drawn on the Canvas?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I've read about how to draw a segment on its own (here also), OpenGL, Canvas and even drawing shapes and layering them, but I've yet to see someone explaining how to recognize the separate segments.
Can drawBitmap() or createBitmap() perhaps be used?
If I go with OpenGL, I'll probably be able to rotate the segmented wheel using OpenGL's rotation, right?
I've also read that OpenGL might be too powerful for what I'd like to do, so should I rather consider "the graphic components of a game library built on top of OpenGL"?
This kind of answers my first question above - how to draw the segmented circle using Android Canvas:
Using the code found here, I do this in the onDraw function:
// Starting values
private int startAngle = 0;
private int numberOfSegments = 11;
private int sweepAngle = 360 / numberOfSegments;
#Override
protected void onDraw(Canvas canvas) {
setUpPaint();
setUpDrawingArea();
colours = getColours();
Log.d(TAG, "Draw the segmented circle");
for (int i = 0; i < numberOfSegments; i++) {
// pick a colour that is not the previous colour
paint.setColor(colours.get(pickRandomColour()));
// Draw arc
canvas.drawArc(rectF, startAngle, sweepAngle, true, paint);
// Set variable values
startAngle -= sweepAngle;
}
}
This is how I set up the drawing area based on the device's screen size:
private void setUpDrawingArea() {
Log.d(TAG, "Set up drawing area.");
// First get the screen dimensions
Point size = new Point();
Display display = DrawArcActivity.this.getWindowManager().getDefaultDisplay();
display.getSize(size);
int width = size.x;
int height = size.y;
Log.d(TAG, "Screen size = "+width+" x "+height);
// Set up the padding
int paddingLeft = (int) DrawArcActivity.this.getResources().getDimension(R.dimen.padding_large);
int paddingTop = (int) DrawArcActivity.this.getResources().getDimension(R.dimen.padding_large);
int paddingRight = (int) DrawArcActivity.this.getResources().getDimension(R.dimen.padding_large);
int paddingBottom = (int) DrawArcActivity.this.getResources().getDimension(R.dimen.padding_large);
// Then get the left, top, right and bottom Xs and Ys for the rectangle we're going to draw in
int left = 0 + paddingLeft;
int top = 0 + paddingTop;
int right = width - paddingRight;
int bottom = width - paddingBottom;
Log.d(TAG, "Rectangle placement -> left = "+left+", top = "+top+", right = "+right+", bottom = "+bottom);
rectF = new RectF(left, top, right, bottom);
}
That (and the other functions which are pretty straight forward, so I'm not going to paste the code here) draws this:
The segments are different colours with every run.

Mapping A "Touch Region" to a Bitmap

I am trying to gain some more familiarity with the Android SurfaceView class, and in doing so am attempting to create a simple application that allows a user to move a Bitmap around the screen. The troublesome part of this implementation is that I am also including the functionality that the user may drag the image again after it has been placed. In order to do this, I am mapping the bitmap to a simple set of coordinates that define the Bitmap's current location. The region I am mapping the image to, however, does not match up with the image.
The Problem
After placing an image on the SurfaceView using canvas.drawBitmap(), and recording the coordinates of the placed image, the mapping system that I have set up misinterprets the Bitmap's coordinates somehow and does not display correctly. As you can see in this image, I have simply used canvas.drawLine() to draw lines representing the space of my touch region, and the image is always off and to the right:
The Code
Here, I shall provide the relevant code excerpts to help answer my question.
CustomSurface.java
This method encapsulates the drawing of the objects onto the canvas. The comments clarify each element:
public void onDraw(Canvas c){
//Simple black paint
Paint paint = new Paint();
//Draw a white background
c.drawColor(Color.WHITE);
//Draw the bitmap at the coordinates
c.drawBitmap(g.getResource(), g.getCenterX(), g.getCenterY(), null);
//Draws the actual surface that is receiving touch input
c.drawLine(g.left, g.top, g.right, g.top, paint);
c.drawLine(g.right, g.top, g.right, g.bottom, paint);
c.drawLine(g.right, g.bottom, g.left, g.bottom, paint);
c.drawLine(g.left, g.bottom, g.left, g.top, paint);
}
This method encapsulates how I capture touch events:
public boolean onTouchEvent(MotionEvent e){
switch(e.getAction()){
case MotionEvent.ACTION_DOWN:{
if(g.contains((int) e.getX(), (int) e.getY()))
item_selected = true;
break;
}
case MotionEvent.ACTION_MOVE:{
if(item_selected)
g.move((int) e.getX(), (int) e.getY());
break;
}
case MotionEvent.ACTION_UP:{
item_selected = false;
break;
}
default:{
//Do nothing
break;
}
}
return true;
}
Graphic.java
This method is used to construct the Graphic:
//Initializes the graphic assuming the coordinate is in the upper left corner
public Graphic(Bitmap image, int start_x, int start_y){
resource = image;
left = start_x;
top = start_y;
right = start_x + image.getWidth();
bottom = start_y + image.getHeight();
}
This method detects if a user is clicking inside the image:
public boolean contains(int x, int y){
if(x >= left && x <= right){
if(y >= top && y <= bottom){
return true;
}
}
return false;
}
This method is used to move the graphic:
public void move(int x, int y){
left = x;
top = y;
right = x + resource.getWidth();
bottom = y + resource.getHeight();
}
I also have 2 methods that determine the center of the region (used for redrawing):
public int getCenterX(){
return (right - left) / 2 + left;
}
public int getCenterY(){
return (bottom - top) / 2 + top;
}
Any help would be greatly appreciated, I feel as though many other StackOverflow users could really benefit from a solution to this issue.
There's a very nice and thorough explanation of touch/multitouch/gestures on Android Developers blog, that includes free and open source code example at google code.
Please, take a look. If you don't need gestures -- just skip that part, read about touch events only.
This issue ended up being much simpler than I had thought, and after some tweaking I realized that this was an issue of image width compensation.
This line in the above code is where the error stems from:
c.drawBitmap(g.getResource(), g.getCenterX(), g.getCenterY(), null);
As you can tell, I manipulated the coordinates from within the Graphic class to produce the center of the bitmap, and then called canvas.drawBitmap() assuming that it would draw from the center outward.
Obviously, this would not work because the canvas always drops from the top left of an image downwards and to the right, so the solution was simple.
The Solution
Create the touch region with regards to the touch location, but draw it relative to a distance equal to the image width subtracted from the center location in the x and y directions. I basically changed the architecture of the Graphic class to implement a getDrawX() and getDrawY() method that would return the modified x and y coordinates of where it should be drawn in order to have the center_x and center_y values (determined in the constructor) actually appear to be at the center of the region.
It all comes down to the fact that in an attempt to compensate for the way the canvas draws bitmaps, I unfortunately incorporated some bad behaviors and in the end had to handle the offset in a completely different way.

Sprite collisions in android andengine

I'm developing a simple game by andengine.
I have 10 balls which are moving randomly on screen.i'm importing the balls as picture in sprites.if they move at the same coordinate , they pass though their own insides.but i want: if they move at the same coodirnates ,they should change their directions.so they cannot pass through their insides.how can i do that?
private Runnable mStartCircle = new Runnable() {
public void run() {
int i = circleNumber++;
Scene scene = Level1Activity.this.mEngine.getScene();
float startY = -64.0f;
float startX = randomNumber.nextFloat()*(CAMERA_WIDTH-70.0f);
float a= randomNumber.nextFloat()*(CAMERA_WIDTH-70.0f);
circles[i] = new Sprite(startX, startY, textRegCircle[i]);
circles[i].registerEntityModifier(
(IEntityModifier) new SequenceEntityModifier (
new MoveModifier(10.0f, circles[i].getX(), a,
circles[i].getY(),CAMERA_HEIGHT+64.0f)));
}
scene.getLastChild().attachChild(circles[i]);
if (circleNumber < 10){
mHandler.postDelayed(mStartCircle,1000);
}
}
};
Each object(ball) requires a bounding box, or in your case a bounding circle, which is equal to the size of your sprite.
When the game updates and any balls position changes, you have to test for collisions.
Circle to circle collision testing is the simplest type to do.
if distance between (ball1.pos + ball2.pos) is less than (ball1.radius + ball2.radius) = collision.
You then handle the collision by reversing the velocities or calculating new momentums or something. (You also need to move the objects apart so they are no longer colliding)
Just apply a physical connector between balls:
so it will collide and bounce back.
final FixtureDef boxFixtureDef = PhysicsFactory.createFixtureDef(0.1f, 0.5f, 0.5f);
final Body ballBody = PhysicsFactory.createBoxBody(this.mPhysicsWorld, circles[i],BodyType.DynamicBody, boxFixtureDef);
this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(circles[i], ballBody, true, true));
this.mScene.attachChild(circles[i]);

Android: onDraw method using DrawPoint() causing jitter and distortion on canvas

I am developing an app which draws more or less a two-dimensional matrix of values to a canvas. The values of this matrix are scaled to Alpha levels to illustrate intensity, and the coordinates for the matrix are simply extrapolated from row and column indexes. Below is my onDraw routine.
public void onDraw(Canvas canvas, float [][] spectrum, float nsegs,int seglen) {
//canvas.translate(0,0);
//alpha = 0;
int canHeight = canvas.getHeight();
int canWidth = canvas.getWidth();
//float[] array = generateData(512);
float [] spec = new float[seglen];
final float bw = (float)(canWidth-2)/nsegs;
final float bh = (float)(canHeight-2)/(float) seglen;
for (int i = 0;i<seglen;i++){
spec[i] = spectrum[i][index]; // One column at a time
}
float max = maxVal(spec);
float min = minVal(spec);
xcoor = index;
for (int n = 0; n < seglen; n++){
//Scale value to alpha (0-255)
alpha =(int)Math.round((((spec[n] - min)/max)*255.0));
ycoor = n;
paint.setAlpha(alpha);
canvas.drawPoint(xcoor,ycoor, paint);
}
index = (int) (index +1);
if (index == nsegs-1){
index = 0;
}
}
Here paint configuration is pre-defined as:
Paint paint = new Paint();
paint.setStyle(Paint.Style.FILL);
paint.setColor(Color.WHITE);
paint.setStrokeWidth(2);
This program draws one pixel at a time, fills one column of pixels equal to the number of elements in a column of the matrix. Then it starts on the next column, where the previous column is still displayed and so forth. At this stage when all columns are full it stars from the first column again, drawing on top of previous elements.
The Problem: The tailing columns although already drawn appear to flicker and jump around, as does the Alpha. I have attempted to canvas.save() and canvas.restore() to capture the entire canvas and restore it after a column is printed. I have double checked all my row and column indexing and alpha vales to ensure the coordinates increment as per desired (and they do). This is very similar to the sample APIdemo DrawPoints.java, however there are three primary differences.
I am using DrawPoint not DrawPoints, and
I don't use "canvas.setColour" as it removes the tailing columns from the canvas.
This onDraw function is operating in a Thread which extends SurfaceView
Any idea's would be much appreciated, thank you for your time.
In the case above, I was using a SurfaceView instead of a View. Out of the Android dev docs
Note: On each pass you retrieve the Canvas from the SurfaceHolder, the previous state of the Canvas will be retained. In order to properly animate your graphics, you must re-paint the entire surface. For example, you can clear the previous state of the Canvas by filling in a color with drawColor() or setting a background image with drawBitmap(). Otherwise, you will see traces of the drawings you previously performed.
The Solution, re-draw the entire canvas each time to prevent the jitter.

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