I'm developing for Android and am a little confused about what is the best way to write 2d full-screen games. On my desktop PC version of my game I create a class which extends the Canvas class and go from there, overloading the update() method to draw to the screen. My intention is to port it to Android.
However I've noticed some online tutorials don't use Canvas, and use View instead. I'm used to using Canvas and drawing with Graphics objects using drawImage(), for example.
Is there a best (i.e. fastest, most accepted) choice out of the two (Canvas or View) or doesn't it matter. Perhaps one extends the other anyway?
A view is your base widget, think of it sort of like a blank panel to which other widgets can be added, or with which you can implement your own widgets. A view has a draw method you can override which takes a canvas as a parameter. You do your rendering in that method. The draw operators you are looking for should be available from the Paint class, which draws to a Canvas.
Related
I'm trying to create a new view that would:
load an image
allow the user to zoom and rotate the image with two fingers while a "cropping box" stays translucent over the top while the image extends beyond the "cropping box"
with the end goal of being able to mark the rotation and position of the main image (so that later i could crop out or show the area within the cropping box)
I'm wondering if I can do this with an ImageView holding the image in the background and another ImageView holding the crop box on top of it, then using TouchEvents to move the image, would this work?
Or do I need to use some drawing API on a 2D surface?
I'm just really new to creating custom objects in Android that aren't just customized out-of-the-box Views.
What's the standard way of creating something like this?
Thanks!
Create a Compound View by extending RelativeLayout with two overlapping ImageViews in it. Then override onTouch event or override onGestureDetector interface in that newly created View.
Official Documentation: http://developer.android.com/guide/topics/ui/custom-components.html
Another Tutorial: http://www.vogella.com/tutorials/AndroidCustomViews/article.html
I've been searching many sources yet I still cannot find a decent explanation. Why should I use it, what is its' purpose and why does it differ from JPanels and such?
The speciality of Canvas is that, like Window, it can provide customized hardware-accelerated double-buffering and page-flipping. See BufferStrategy.
A canvas is for drawing on, basically. It also serves like a Panel for creating a custom AWT-based component, but unlike Panel it can't contain other components.
From my understanding, Canvas is just the AWT version of Swing's JComponent. You shouldn't use it directly, unless you're making a pure AWT app. You can find more info here.
public class Canvas
extends Component
implements Accessible
A Canvas component represents a blank rectangular area of the screen onto which the application can draw or from which the application can trap input events from the user.
An application must subclass the Canvas class in order to get useful functionality such as creating a custom component. The paint method must be overridden in order to perform custom graphics on the canvas.
A canvas is for drawing on, basically. It also serves like a Panel for creating a custom AWT-based component, but unlike Panel it can't contain other components.
I have an app that uses a Class with an extension SurfaceView to draw to a canvas, but i'm looking at moving over to openGL. I noticed that if I merely change the SurfaceView extension to a GLSurfaceView, the app still runs the same. I've also been able to start basic drawing in another app using openGL ES.
I took it the next step and instantiated another class for the renderer in GLSurfaceView, and I instruct the render to draw a triangle. This all compiles and runs fine, but it runs exactly like the original App, with no triangle rendered, but the rest of the canvas draws properly.
I can't think of why it's not rendering, or why it wouldn't render. Or maybe it is rendering, but it's simply being overridden by the canvas?
I know it seems odd to try to use both methods, Since my app is live, I would rather implement switching the rendering over to GL at my own pace so that it doesn't take me a month to get the next update out.
So Anybody ever tried do do this? Run a Gl renderer OVER a canvas?
You cannot use both OpenGL and a Canvas to render on a single SurfaceView. You can however put another View on top of the SurfaceView to achieve the desired effect.
Try the following:
addContentView(SurfaceView);
addContentView(GLSurfaceView);
or create a relative layout with both views.
Here my sample code when adding canvas over the OpenGL view, thanks to #Audrius Butkevicius !
mGLView = new MyOpenGLSurfaceView;
// SET OpenGL View
setContentView(myOpenGLView);
mCanvasOverlayView = new View(context)
mOverlayViewParams = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
// ADD Canvas view overlay
addContentView(mCanvasOverlayView, mOverlayViewParams );
I'm creating a simple 2D game in java. I've only done this in C++ with the Windows API so far. In java, I'm getting a Graphics object by extending JFrame and calling this.getContentPane().getGraphics(). With this object, I'm drawing everything to the screen, every frame. This raises a few questions:
Backbuffer: I'm not getting any flickering effects, while I'm not using a backbuffer (I'm drawing directly on the Graphics object). Why is this? Does java has a built-in backbuffer or something?
Animations: I'm used to put all animation parts in a single sprite sheet, like in this example:
http://www.envygames.com/share/sample_animation.jpg
Now, someone has told me that you can just draw animated .gif's and java will draw these independent of the game loop. I've tried this out and it doesn't seem to work. Is this true or am I also supposed to use these sprite sheets in java?
Thanks
Yes, Java has a double buffer rendering strategy that can be switched on and off...
Java: how to do double-buffering in Swing?
About the animated gifs, I think it is right, but you may have to put them in the appropriate container (maybe as the icon of a JLabel?).
getting a Graphics object by extending JFrame and
calling this.getContentPane().getGraphics().
don't painting directly to the JFrame for Custom Painting you have to look for JLabel that allows painting everything, another choise will be extending JCompoments, or JPanel for that
for painting in the Swing you have to look for paintComponent(Graphics g), not paint(Graphics g), because this method are lots of time used in examples and ditributed on some of Java ExamplesDepots, that's wrong method with possible lacks
Implementing "Kings' Corners" (glorified multiplayer Solitaire) in Java.
I'm trying to allow a player to drag a card (image) from their hand to somewhere else on the table. The problem is that the player's hand is "fanned" so the images of the cards are rotated and they overlap.
Here is an example of a hand:
I've considered making each card a JPanel, but the issue then is that I'd have to paint the card rotated inside its rectangular JPanel, as they themselves can't be rotated. Ideally I'd like to avoid mouse-x,y formulas to determine which card is being chosen.
Using an event-driven approach, how can I determine which card is chosen from the hand?
AWT (and Swing) components are normally rectangular (aligned to the axes).
But this does not have to be the case - while the real bounds must be rectangular, the actual area which a component uses can be smaller. Component supports a contains(Point) method, which will get called by the event dispatch mechanism whenever the question arises to which component a point belongs - for example, for mouse clicks. (Overlapping of different components will be handled by the z-order inside the parent container.)
You can implement this method based on the Shape.contains() method, using a affine transformed rectangle as your shape. Each of your rotated components would know its own shape (or generate it on the fly from its AffineTransform, the same one which would also be used for painting itself).
Have a custom LayoutManager which arranges your cards, too. (Don't use CardLayout, despite the name.)
I'm not sure I would follow the way of having separate components for each card, but you certainly need some objects which represent the rotated rectangles.