I am drag and dropping an ImageView on to another ImageView.
I am following this http://developer.android.com/guide/topics/ui/drag-drop.html
While I can display a drag shadow and change drop targets with different colors and drawables. I am happy with the article.
But I am looking for a little bit more. I am looking to draw a straight line between my drag shadow and the source. I want this line to be straight and update it's length and direction as I drag the item around. When I finally drop the item in my drop zone I want the line to stay permanently (unless I remove it later).
Like this:
Drag without line, this is my current situation
Drag with a line following, this is what I want
I should also mention that I want to do this with multiple sources and single target (maybe multiple target in future).
Here is the code that I am working on https://github.com/ishanatmuz/HelloDrag
I think you will need to override onDraw( Canvas ) and then when you are dragging call a routine to draw your line.
When you are not dragging draw the lines between the boxes.
both routines as sub-routines of onDraw
If you do this don't forget to call super.onDraw( Canvas ).
I'm struggling with something I would expect to be straight forward with libgdx.
In short this is a "finger paint" app where I want to draw a path of a certain width where the user touches the screen.
I've earlier done this by using a plain Android android.view.View. I had a android.graphics.Path in which I stored the coordinates of the user's current touch. In the onDraw() method of the view I drew the path to the android.graphics.Canvas. Whenever the user released a finger I drew the path to an offline canvas/android.graphics.Bitmap which also was drawn in the onDraw() method. Plain and simple.
How can that be done using libgdx?
I have tried using a com.badlogic.gdx.graphics.Pixmap that I can draw a line to whenever the user moves a finger. This works well except the fact that I'm unable to control the witdh of the line using Gdx.gl.glLineWidth(). I know I can draw a rectangle instead of a line to set the width, but Pixmap doesn't seem to have any means of rotating, so I don't see how this can be done.
I can use a com.badlogic.gdx.graphics.glutils.ShapeRenderer for drawing lines (or rectangles) in com.badlogic.gdx.Screen.render(). As far as I can see I then need to store every single touch point of the current touch, and then draw all lines on render. Whenever the user relases a finger I guess I can store the screen as-is with something like com.badlogic.gdx.utils.ScreenUtils.getFrameBufferPixmap(). Hopefully there is a easier way to achieve what I want.
I ended up drawing circles on a pixmap where the line should be:
One circle on touchDown
Several circles from last touch point to next touch point reported to touchDragged
I'm not very happy with this solution, but it kinda works.
Maybe you can calculate line dot coordinates manually and use triangles to draw them on pixmap? Like use 2 triangles to form (rotated) box?
I'm new to Android (and Java for that matter), and I'm making a simple game. I'm stuck.
My problem is this:
I have 2 png images (a background and foreground) that take up the whole screen on startup. I now want to be able to set the width of the "drawn portion" of the foreground to the x-coordinate of ON_DRAG. My control method works fine; it's used like this:
g.drawRect(0, 0, scene.getLine(), g.getHeight(), Color.GREEN);
where scene.getLine() returns the x-value of the touch. So at this point I can draw a green rectangle above my images. But what I actually want is for those rectangle dimensions to "punch a hole" in my top-layer png (so the background is revealed beneath). I do not want to scale the foreground.
I have tried clipRect, but it doesnt work because I have other images that need to be drawn on top of these two, and clipRect prevents this. I have looked at a bunch of "PorterDuffXfermode" code, but cannot understand how to apply it to my situation, and cannot make it work. i.e. I can make a Paint with the PorterDuff "SRC" mode set, but I dont know how to define "source" and "destination" images so the Paint will work its magic. A final consideration with this is that even if the PorterDuff would work, Im not sure it would be practical given that I want this thing to run at 60fps.
Any suggestions?
Thanks.
You can call canvas.save() before a clip and canvas.restore() after your drawing to return the canvas to the sate it was in before you stared. Then you can draw your additional images.
I am building a paint application for android. Extending the FingerPaint application sample provided with the SDK. However, unlike FingerPaint, I'm using SurfaceView with a separate rendering thread to draw to the surface. All this is very standard and straightforward. Working well. I want to, however, give a White coloured background to the painting surface, so it's like drawing on a white paper. The default background is black coloured.
The thread of my surface view, calls the onDraw() method of the view.
The problem I'm facing here is, if I set a background colour or background resource to my SurfaceView, this background overwrites the previous drawing of the surface, when the view is rendered the next time. I will explain this with an example:
Suppose I set the background to white colour. Now, the application starts, with my SurfaceView having the white colour. Ok, so far good. Now, I draw a red coloured line on this surface, with my finger. The line is now shown on the white surface. Good. Now, this is supposed to be a painting app, and suppose I want to draw a car. So, then, I draw my 2nd red line, with my finger. The 2nd line is drawn on the screen, but the 1st one, which I drew previously, vanishes. That is, because I have set some background to my SurfaceView, the background is drawn again, thus overwriting the 1st line that was drawn. Now the screen shows only the 2nd line drawn.
Obviously, I do not want this to happen. The code works perfectly, when I don't attempt to change the background (that is, both lines are shown, on a default black background, no background effectively). But when I set some desired background, this thing happens. Is there a way to somehow have a static background, that is not drawn every time? I want the background to be drawn only once, all the subsequent drawings should happen on this background. I don't want the android runtime , to draw the background, every time it draws my view, thus overwriting all drawing present on that view, from previous renderings. Any way to work around this?
The things I have tried, to achieve this are:
Setting the background colour of my SurfaceView using android:background in XML.
Doing the above, using the concept of style. (specifying a style value and referencing it in the layout file). The style just defines the background colour as #FFFFFFFF (white).
Setting the style of 2, to the parent view of the SurfaceView (a RelativeLayout).
Setting the style of 2, to the entire application, as a theme,using android:theme in my manifest file.
Setting the background drawable of my SurfaceView to an image which is plain and white-coloured.
Calling the setBackgroundColor for my SurfaceView from the code as, this.setBackgroundColor(Color.WHITE).
Thanks.
according to android's doc:
The surface is Z ordered so that it is behind the window holding its
SurfaceView; the SurfaceView punches a hole in its window to allow its
surface to be displayed. The view hierarchy will take care of
correctly compositing with the Surface any siblings of the SurfaceView
that would normally appear on top of it. This can be used to place
overlays such as buttons on top of the Surface, though note however
that it can have an impact on performance since a full alpha-blended
composite will be performed each time the Surface changes
so if you change the z order of surface view via:
setZOrderOnTop(true);
this will work, but then you cannot put any other view on top of surface view.
Now I also tried overlaying my SurfaceView over another View with a white background, and setting the SurfaceView to be fully transparent. I used FrameLayout for this. That is, a View with a white background, overlayed upon which is my SurfaceView set to fully transparent.
This also failed to work. So now I have come to conclusion that the background colour of SurfaceView cannot be changed. So now I have dropped SurfaceView, and using a normal view, instead for my drawings. So far, there has not been any performance loss observed. But, it feels kind of wrong to drop an efficient implementation , just because SurfaceView doesn't let me change it's background colour.
Question : Is there any better way to implement a function that draws line on the screen other than drawing circles on the input points ?
Details : I am trying to write a function which basically will draw a line.However the line will not be a regular colored line. This line will let user to copy pixels from one image to another trough that line , you can think It like "history brush" or "stamp" on Photoshop . My first thought was just get the points and draw circles on each point. Which is working but not smooth and have some bugs. The first problem is it is not working if user sweep his finger too fast. I thought it would solve problem if i can fill the dots between two points and then draw the line which is kind of work but this time drawing gets very slow. One other problem is that it never looks smooth.
Bresenham's line algorithm
Isn't the BitmapShader what you're looking for?