Develop Reference

Simple way to put graphic on the screen in android

I've been looking around for a simple way to put graphic on the screen in android for a while now and I'm really confused.
I've a simple game written in java with swing for graphics and that's all I really need as the graphics doesn't really matter in this project.
Now we want to rewrite it so it works on devices with android and honestly I can't find a simple way to just put a image on the screen.
I'd love to avoid using complex game engine because I just don't need it. All I want is a possibility to draw an image (or 50 images) on x,y given by me and refreshing a screen every 100 milliseconds and I thought I'd be the first thing I'd learn in any android tutorial but well... it's not. Of course I know how to draw an Image with .xml but I need something more automatic - for dozens of images changing all the time.
So what is the best to do this? Isn't there really any way to do it with just some android built in function? If not what engine should I use just for the simplest things I mentioned?

A simple but not necessarily very clean way to do this would be to create an xml layout that is just an empty RelativeLayout.
Then you could create your images like this:
ImageView image = new ImageView(this);
image.setLayoutParams(new RelativeLayout.LayoutParams(IMAGE_WIDTH,IMAGE_HEIGHT));
//Other setup code for your image goes here
myRelativeLayout.addView(image);
This should give you an image of the specified width and height that sits at the origin.
Then you could move the image into position like this:
image.setX(IMAGE_X_POS);
image.setY(IMAGE_Y_POS);
When to do the moving is up to you as it will depend on when you know the positions that need to be moved to.

Android handler for different screen sizes

I need to know how my game can handle all these screen sizes i have seen a few options including:
Re sizing the elements to fit the screen
Making assets in lots of different sizes
I'd like to know which is more efficient ?
What are my other options ?
How would i go about making it work ?
So far i am just making my screen fit to the android device i'm testing on and this could lead to failure in the future if i do not set this handler up
Thanks

well if you are using libgdx then you dont have to worry about screen sizes. just use its camera class and set its viewports accordingly . refer this link for camera
Also you dont need to make android handlers for it.

This website talks about how to handle this problem http://developer.android.com/guide/practices/screens_support.html.
It claims the best practices are:
Use wrap_content, fill_parent, or dp units when specifying dimensions in an XML layout file
Do not use hard coded pixel values in your application code
Do not use AbsoluteLayout (it's deprecated)
Supply alternative bitmap drawables for different screen densities
The problem is not with the dimensions of the screen, rather the density of the screens. Using dp to set the size for elements is the most common way.

Java Picture Processing Framework

1) Load picture from byte array.
2) Verify it's current picture size.
3) Resize Picture according to my needs.
Is there any out of the box Java Framework which can help me to do it?
Thanks in advance.

Actually, java's default packages should be enough:
To load an image use javax.imageio.ImageIO.read(...)
To get it's size use the getWidth() and getHeight() of the returned BufferedImage object
To resize the image, you can: Create a new image (BufferedImage), acquire it's Grahpics objects, set the transformation, and then draw the original image.
Refer to the java working with images tutorial

I found thumbnailator to be very good.

Zoom in Java Swing application

I am looking for ways to zoom in a Java Swing application. That means that I would like to resize all components in a given JPanel by a given factor as if I would take an screenshot of the UI and just applied an "Image scale" operation. The font size as well as the size of checkboxes, textboxes, cursors etc. has to be adjusted.
It is possible to scale a component by applying transforms to a graphics object:
protected Graphics getComponentGraphics(Graphics g) {
Graphics2D g2d=(Graphics2D)g;
g2d.scale(2, 2);
return super.getComponentGraphics(g2d);
}
That works as long as you don't care about self-updating components. If you have a textbox in your application this approach ceases to work since the textbox updates itself every second to show the (blinking) cursor. And since it doesn't use the modified graphics object this time the component appears at the old location. Is there a possibility to change a components graphics object permanently? There is also a problem with the mouse click event handlers.
The other possibility would be to resize all child components of the JPanel (setPreferredSize) to a new size. That doesn't work for checkboxes since the displayed picture of the checkbox doesn't change its size.
I also thought of programming my own layout manager but I don't think that this will work since layout managers only change the position (and size) of objects but are not able to zoom into checkboxes (see previous paragraph). Or am I wrong with this hypothesis?
Do you have any ideas how one could achieve a zoomable Swing GUI without programming custom components? I looked for rotatable user interfaces because the problem seems familiar but I also didn't find any satisfying solution to this problem.
Thanks for your help,
Chris

You could give a try to the JXLayer library.
There are several tools in it, which could help you to make a zoom. Check the examples shown here. I would recommend you to read more about the TransformUI, from this library. From the example, it seems like it could help solving your problem.

Scaling the view is easy enough; transforming mouse coordinates is only slightly more difficult. Here's an elementary example. I'd keep JComponents out, although it might make sense to develop an analogous ScaledComponent that knows about the geometry. That's where #Gnoupi's suggestion of using a library comes in.

hey you can try this if you want to zoom a image like any other image viewer the use a JPanel draw an image using drawImage() method now create a button and when you click the button increase the size of the panel on the frame it appears as if the image is being viewed in Zoom

You might find Piccolo2D.java API useful: http://code.google.com/p/piccolo2d/
It is very simple.
It touts in particular its smooth zooming. You essentially make a "canvas" that can contain various elements, and can then zoom by just holding right-click and panning the mouse back and forth.
I worked on a team that used it to create this: http://sourceforge.net/apps/mediawiki/guitar/index.php?title=WebGuitar#EFG.2FGUI_Visualizer
The nodes you see there are clickable links themselves.

Since Java 9, there are VM arguments (actually meant to be used for high dpi scaling) that can render a application with a higher scaling factor:
java -Dsun.java2d.uiScale=2.0 -jar MyApplication.jar
Or:
java -Dsun.java2d.win.uiScaleX=2.0 -Dsun.java2d.win.uiScaleY=2.0 -jar MyApplication.jar

Can I user a layout on the android to render just part of an image at a time?

I have an image file that has all the character sprites that I will be using in a game, and I want to make a layout that will allow the user to cycle through each image to be able to pick which one they want. So, I have one large image, and I need to render just a small (32 x 32) section of it at a time. Is that possible with the layouts or will I have to use a canvas, and manually do most of this?

Yes Try using scrollX and scrollY. You can set these properties programmatically or in the layout xml.
That said, loading just the small images that the user needs to see is preferred to loading a large image containing all. If your image is really large you might want to consider the first option.