I know that the canvas in android is a lower level drawing surface but currently Im drawing all my objects inside a canvas and I would like a better way to handle clicks for each object on the canvas. Ive tried matching an x and y through the view their drawn in and that only works some of the time.
Is there anyway to make the individual bitmaps Im drawing im my canvas clickable. The objects in my app are moving dynamically...think of a game object where on screen elements are moving. Ive tried creating a class that extended Button but everything got drawn in the upper right hand corner of the screen so Im not sure if you can have moving objects onscreen that extend button however at least when I clicked the image on top of the stack of ones drawn it gave the expected response. Right now I register onscreen clicks through the view that the canvas is drawn in and through the running loop that makes on screen action take place I have an array of all items and when a click is registered I loop through all the items and those that are onscreen are checked for their coordinates. if I get a match i fire an intent to perform an action.....like I said this is unreliable at best and Im momentarily at a loss on how to restructure everything to get reliable responses.
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I wan't to develop game named "Balda".
I have a 2d grid of imageviews (or buttons, maybe).
User should be able move his finger on the grid, and app should know wich images in grid was touched in this move.So, in the picture below is what I'm trying to achieve. A - is start point where user pressed on screen. B is end point where finger leaves the screen. And I need to know what images were touched (There are blue in the picture).
I know that I can do something like this. But I think that this is a wrong solution, because It contradicts the principle of giving functionality by responsibilitys.
I think that it is responsibility of the imageView to know when finger enters its borders and when it is leaving its borders.
I thought, that this would be in android API. And it has MotionEvent like EVENT_HOVER_ENTER and EVENT_HOVER_LEAVE but it's not working with finger. After finger is pressed on some View it will recieve all other MotionEvents, if I get it right.
I think that this is wrong. What can I do to get this functionality? Maybe I could create some custom listeners and custom Views, that supports them?
I think your requirement is slightly similar to custom gridview.
You can try below steps-
1)Create Custom view
2)Attach TouchListener to it.
3)Divide this view into 4*3 matrix.
4)Map your images to this 4*3 matrix
5)Write a function which gives the cell number respective toTouched Co-ordinates
6)After getting cell number;get the mapped image for that cell number
7)Put this image in arraylist
8)When user lifts his finger you will get arraylist of touched images(do whatever you want with it).
9)Remember to put this custom view in your activity
Tell me,if you have any doubt or concern
I have an android app I have written, that basically has a custom overlay, in this overlay I have overwritten the DRAW method to draw something on a canvas and at the end of my DRAW override, I call the super DRAW passing in the canvas I have painted.. the result is, every time the map is modified in anyway my custom overlay is redrawn as expected.
Now, I am trying to accomplish the same thing on iPhone and am getting a little confused.
Basically I need something drawn in the top right corner of the map every time a redraw occurs of the map. The drawin will change change with every update as well so can't simply be put a view over the map and pass touches through etc.
So, I guess the question is, what is the euivalent of the DRAW method in iOS.. how would I roughly accomplish this same thing? There are MKOverlayView in the API, but there seem to be some significant differences.. So, how do I put something say at 10x10 over the map, whos size is variable and make sure every time the map is moved, scaled or otherwised interacted with this object is redrawn at location 10x10 on the screen.
The docs for MKMapView state that you should not subclass MKMapView, so you can't / shouldn't override the drawRect method. You could add a UIView, though, and override drawRect to do your custom drawing.
I'm looking at this example of how to drag things around the screen and my only point of confusion is what exactly IS the Canvas c object being passed in?
Is this View occupying the entire screen? What if it's set as the child to a Layout? Are there multiple canvases (one for each display item) or is there one overall Canvas upon which all things are rendered?
I'm having a hard time picturing what's happening beneath the hood.
The Canvas is the entire drawable area of the screen. You're supposed to stay within the bounds that the view has set, but in reality there's nothing stopping you from drawing all over.
I want to be able to dynamically place image(s) over another image in my app.
Consider the first image as background and the other images to be on top level, I will also need to move those top level images (change their x and y on the screen) by code too.
Imagine, for example, a sea in which the user places fish and sea animals, then those sea animals start to move here and there on the screen: it will be like that.
How can I do this? If you don't know but remember any simple program or demo that does that, it will be also very welcome!
Thank you!
There is, of course, more than one way to do this, but I would say that the best way to do it would be to create a custom View (class that derives from View) and have this handle your bitmap drawing and all of your touch events.
There's a lot of code to write for loading the Bitmaps and keeping track of all of their positions (and then drawing them to the canvas in onDraw), but if you start really small by just allowing one image to be drawn and dragged around the screen, you can build on that and keep your code organized.
You would need to override onDraw(Canvas) and onTouchEvent(MotionEvent) in your custom View. You'll load your bitmaps with BitmapFactory (decodeResource method if you're including your images as resources in your project) and you'll need to remember to call recycle on your bitmaps when you're no longer using them.
In onDraw, you draw your bitmaps to the canvas at a specific location using Canvas.drawBitmap. There are two overloads of this method you can choose from, one that takes the top and left coordinates of the bitmap as floats (and therefore performs no scaling or stretching) and one that takes a destination and source rectangle to perform scaling, stretching and placement.
I always use the latter as it gives me finer tuned control. If you choose this route, you'll want to keep two Rect instances and a Bitmap instance for each image being drawn, update them in the touch events and draw them to the canvas in the draw event.
When something changes inside your view (as in the case of a touch event), call invalidate() method and the framework will know to redraw everything which triggers your onDraw method.
I'm new to Android application development and I'm currently experimenting with various UI ideas. In the image below, you can see a vertically scrolling list of horizontally scrolling galleries (and also textviews as you can see). I'm also doing some matrix and camera transformations which I will come to in a minute.
For the background of the list elements, I use green. Blue is the background of the galleries, and red is the background for the images. These are just for my benefit of learning.
The galleries being used are extended classes where I overrode the drawChild method to perform a canvas scale operation in order for the image closest to the center (width) to be larger than the others.
The list view going vertically, I overrode the drawChild method and used the camera rotations from lack of depth dimension in the canvas functionality. The items in the list are scaled down and rotated relative to their position's proximity to the center (height).
I understood that scrolling and clicking would not necessarily follow along with the image transforms, but it appears as though the parent Gallery class's drawing is constrained to the original coordinates as well (see photo below).
I would love to hear any insight any of you have regarding how I can change the coordinates of the galleries in what is rendered via gallery scroll and the touch responsiveness of said gallery.
Images in the gallery are not same dimensions, so don't let that throw you in looking at the image below
Thanks in advance!
Ben
link to image (could not embed)
-- Update:
I was using my test application UI and noticed that when I got the UI to the point of the linked image and then I touched the top portion of the next row in the list, the gallery updated to display the proper representation. So, I added a call to clearFocus() in the drawChild method and that resulted in more accurate drawing. It does seem a tad slower, and since I'm on the Incredible, I'm worried it is a bloated solution.
In any event, I would still appreciate any thoughts you have regarding the best way to have the views display properly and how to translate the touch events in the gallery's new displayed area to its touchable coordinates so that scrolling on the actual images works when the gallery has moved.
Thanks!
As I updated earlier, the issue of the graphics of the gallery not fully refreshing was resolved by calling clearFocus in drawChild method for the ListView extending class.
The problem with registering the touch events turned out to be where I had used an example for the basis of my experimental program which called a pre-translation on the matrix used for painting. Once I removed that call and adjusted the post-translate call to compensate not having the pre-translate call any longer, I was able to scroll through the galleries regardless of their position, size or rotation (around x axis).