drawText draws a text from the providing point. But I need different behaviour.
Let's call the point(x,y) as p.
How drawText works:
pMYTEXT
What I need:
MYTpEXT
So I want to draw text exactly centered with this point. Is this possible?
I think to do it I should measure text and offset the point. But how can I measure it? It has not drawn yet.
Sure. Use the Paint function measureText to get the width of the string you want to the left of point p. Subtract that length from the x position of p, and draw it there.
Set the paint alignment to center.
paint.setTextAlign(Paint.Align.CENTER)
You can also use LEFT and RIGHT.
Related
I have an array of strings and I have drawn those strings on screen using android graphics library (Canvas, Paint). Firstly, a transparent rectangle is drawn then on this rectangle I paint the strings, giving the impression of text with border line and filled.
The problem is some strings are long and some are short, how can I modify the rectangle so that it is as long and as wide as the string is? (Like WRAP_CONTENT in textView)
Currently I am using this method
canvas.drawRect(_x-10, _y-10, _x+620, _y+30, rectanglePaint);
canvas.drawText(placeName, _x, _y, textPaint); //text
If there is a better way then please do let me know.
Note: It will be used in an AR app so the text will be moving from left to right and vice versa as the mobile is moving. _x, _y for place name works perfectly in 2nd line, I want text should remain highlighted, no matter how the mobile is moving.
Paint has a measure text method that will give the width of the text if it were to be drawn with that paint. Its get font metrics will probably give you some data that you can calculate the height from. The sizing, positioning, wrapping and rendering of text is a very complicated problem and I would advise using a child TextView (with a background) in your ViewGroup rather than trying to roll your own if you're doing anything complicated.
I would like to detect collisions between shapes dynamically drawn on a canvas (SurfaceView) for an Android game.
I can easily use intersect method of Rect or RectF objects but the result is not very good (see picture below where I have a "false" detection).
I don't want to use Bitmap so it's impossible to use the "pixel perfect" method.
Do you know a way to do this for circle, rect, triangle and other basic shapes intersection ?
Thx for help ;)
For a good collision detection you have to create your own models behind. In those models you specify the conditions that two objects colide.
For example, a circle is described by the center position and by the radius. A square is described by the left down corner and by the edge length.
You don' t have to describe all possible poligons, you can use the so called bounding boxes, meaning that, for a complex random poligon you can use a square or whathever shape fits it best(also you can use multiple shapes for a single object).
After you have the objects in mind you compute the condition that each one of them will colide with all other shapes including itself.
In your example The sphere and the square colides if the distance between any corner of the square is greater than the circle's radius.
Here you can read more http://devmag.org.za/2009/04/13/basic-collision-detection-in-2d-part-1/
This problem can get very complex, keep it simple if you want something simple.
Here is a directly applicable method I use in my own game to detect circle and rectangle intersection. It takes the ball (which is a view in this case) and the rectangle (also a view) to be checked for collision with the ball as parameters. You can put the method in a Timer and set the interval you want the circle and rectangle to be checked for collision.
Here is the method:
public boolean intersects(BallView ball, Rectangle rect) {
boolean intersects = false;
if (ball.getX() + ball.getR() >= rect.getTheLeft() &&
ball.getX() - ball.getR() <= rect.getTheRight() &&
ball.getY() + ball.getR() <= rect.getTheBottom() &&
ball.getY() - ball.getR() >= rect.getTheTop())
{
intersects = true;
}
return intersects;
}
getR() gets the circle's radius
getX() gets the center of the circle's X position value
getTheLeft() gets the rectangle's left X value
getTheRight() gets the rectangle's right X value
getTheTop() gets the rectangle's top Y value
getTheBottom() gets the rectangle's bottom Y value
If you can't directly use this method in your code you can still conjecture the logic it entails to implement it where it would work for you. It detects all collisions without using pseudo-collision detection like a collision box for the circle.
Good luck! And if you have any questions feel free to ask, I'm here to help!
To know if a polygon in 2d is colliding with a circle, you can test, for each of its lines, where is the point on the line that is closest to the center of the circle (this might help).
Then, check if the point you found is between to two corners that make the line - that is, that the point is actually on the line, and not just on its continuation - and if the distance of that point to the center of the circle is smaller or equal to the radius of the circle. If both are true for any of the lines of the polygon, you have a collusion. You also have to check for the edge cases where the corners of the polygon might be in, or touching the circle.
For two circles, this is easier. Check the distance between the centers, and compare it to the sum of their radiuses. If the distance is smaller or equal to the sum, you have a collusion.
I need use TextView with outline text. I try use it: https://stackoverflow.com/a/10294290/4181010 , but it doesn't work correctly with android:layout_width="wrap_content", because it doesn't increase canvas when add outlines.
I need to increase the canvas to include the value of strokeWidth.
I suggest I have to override onMeasure somehow, but TextView call final method setMeasuredDimension at the end of onMeasure to apply view size and I can not intervene at this point so as not to have to rewrite the whole method.
Scaling the canvas in OnDraw does not work either, because TextView scales draw text with canvas.
My solution is increase canvas and use canvas.translate() to move in right position before draw text.
And my question: How can I increase the size of the canvas with minimal intervention? Or someone know another solution for this problem?
I'm guessing you are drawing the text twice, once with the orange (manually on the canvas) and once with the white (what the TextView is drawing with super.onDraw).
Instead of drawing the larger orange manually, you could instead draw the smaller white text and leave the orange text to TextView's super.onDraw. That way everything should fit within the canvas.
THis is a follow up question to my other one shown here
basically me and my undergraduate project group are creating a 2D graphing application in opengl es 2.0 where the user can enter an equation of a line and have it plot onto the screen. As shown here
So basically I want to add a numerice scale[-10,-9,-8,-7,-6,-5,-4,-3,-2,-1,0,1,2,3,4,5,6,7,8,9,10] onto the x and y axis and also label the x and y axis with an "X" and "Y". Basically I have now determined that a textView on top of my GLSURFACEVIEW may be the simplest way to achieve this. Anyone have a link to a tutorial or could help me start coding this view and setting text in there appropriate positions like this:
How would I code a textView to display the numeric scale and X and Y labels?
I would create a View on top of GLSurfaceView instead of adding textview, which would cover whole GLSurfaceView.
You can use onDraw(Canvas canvas) to draw the scale using drawText method.
I have been trying to work on a simple code for two days now. I have tried all alterations but none seems to be working.
I am trying to draw vertical rectangles with different colors.
In the first one, I am using only one Rect variable and moving the coordinates. Here is the relevant part of the code.
Rect myRect1=new Rect();
Random colorMe=new Random();
for(int j=0;j<5;j++){
myRect1.set(myCanvas.getWidth()/5*j, 0, myCanvas.getWidth()/5*j, myCanvas.getHeight());
paint.setColor(Color.rgb(colorMe.nextInt(255), colorMe.nextInt(255), colorMe.nextInt(255)));
myCanvas.drawRect(myRect1, paint);
}
Other alteration which I tried was through an array.
Here is the code.
Rect[] myRect=new Rect[5];
Random colorMe=new Random();
for(int j=0;j<5;j++){
myRect[j].set(myCanvas.getWidth()/5*j, 0, myCanvas.getWidth()/5*j, myCanvas.getHeight());
paint.setColor(Color.rgb(colorMe.nextInt(255), colorMe.nextInt(255), colorMe.nextInt(255)));
myCanvas.drawRect(myRect[j], paint);
}
Can somebody please help me what is the problem actually there?
The first thing that seems obviously wrong (there might be more):
The minimum x-coordinate of your rectangle is myCanvas.getWidth()/5*j
The maximum x-coordinate of your rectangle is myCanvas.getWidth()/5*j
They are both the same value, so your rectangle is degenerate.
Offtopic, but very relevant: whenever you run into a problem like this, you need to break it down into smaller parts until you get it to do something. This will help you understand what's wrong:
Extract all subexpressions (like the color, and the generated x/y values) into local variables so you can easily inspect them in the debugger
Replace the random color by a predefined color (COLOR.YELLOW), to rule out the random element
Replace the caclulated rectangle by a fixed rectangle (say (10,10) - (20,20)) to rule out the coordinate calculations.
Replace the loop, to rule out the loop.
Your rect has a width of 0px. The parameters of the set() function are, in order, left/top/right/bottom. You use the same value for left and right, so the width is (right-left)=0.
Let's see your coordinates, first:
myRect1.set(myCanvas.getWidth()/5*j, 0, myCanvas.getWidth()/5*j, myCanvas.getHeight());
Top left corner has the same x coordinate as the bottom right corner, so you are drawing a rectangle with 0 width.
Add this line
myRect[j] = new Rect()
before
myRect[j].set(myCanvas.getWidth()/5*j, 0, myCanvas.getWidth()/5*j, myCanvas.getHeight());