Develop Reference

Sprites flicker in Andengine

I want to move some sprites from left to right with a constant slow speed. I have first tried RatioResolutionPolicy but I saw sprites were flickering a lot. Then I have changed resolutionpolicy to FixedResolutionPolicy, defined sprite textures as bitmap, scaled them and made sprites by these textures (for more detail: click here). This is better than first method but not completely good. I use setx() for moving sprites. When I change x positon for example by 2 pixels for each frame there is no problem. But for different devices that have different resolutions I must multiply 2 by a ratio. In this case sprites are flickering again, not much but it is annoying for me.

code for camera is below
#Override
public EngineOptions onCreateEngineOptions() {
WindowManager w = getWindowManager();
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR2) {
Point size = new Point();
w.getDefaultDisplay().getSize(size);
V.CAMERA_WIDTH = size.x;
V.CAMERA_HEIGHT = size.y;
} else {
Display d = w.getDefaultDisplay();
V.CAMERA_WIDTH = d.getWidth();
V.CAMERA_HEIGHT = d.getHeight();
}
if (V.CAMERA_HEIGHT/V.CAMERA_WIDTH>480f/860f){
V.CAMERA_HEIGHT=V.CAMERA_WIDTH*480f/860f;
}
else {
V.CAMERA_WIDTH=V.CAMERA_HEIGHT*860f/480f;
}
V.ratio=V.CAMERA_HEIGHT/480f;
this.mCamera = new Camera(0, 0, V.CAMERA_WIDTH, V.CAMERA_HEIGHT);
final EngineOptions engineOptions = new EngineOptions(true,
ScreenOrientation.LANDSCAPE_FIXED, new FixedResolutionPolicy((int)V.CAMERA_WIDTH, (int)V.CAMERA_HEIGHT),
this.mCamera);
return engineOptions;
}
for moving sprites:
this.wallPosX -= this.speed;
this.setX(Math.round(this.wallPosX));
speed is a floating point varibale and it gets 4.4651165 for 1280x720 screen resolution. If I set it as an integer than there is no flickering, but this time sprite speed differs from device to device.

There are too many screen sizes and screen ratio's for android phones.
Use the Cropped Resolution Policy created by jgibbs. Follow Martin Varga's tutorial to get an understanding on how it works and how to implement it.
It works wonders.
Original from jgibbs
I recommend Martin's Tutorial
You shouldn't be worried about micro managing entities positional co-ordinates to suit every and any possible screen size.
I'm not sure this will fix the flickering though, that may be some other problem not related to your camera

I have noticed that this wasn't about Andengine, it was about opengl. Solution for this problem is this wonderful tool:
https://github.com/gemserk/imageprocessing

LibGDX problems rotating sprite

OK so I'm really confused I've rotated sprites before and had no problem such as rotating a boat as it moves through an ocean, but for some reason I'm having a really big problem this time. So I create a texture in an assets file, but not static textures. I load the texture using the following:
class Assets{
Texture img;
public Assets(){
img = new Texture(Gdx.files.internal("images/PNG.png")
And then I call the assets in the main class by calling:
Assets assets = new Assets()
And then I have a class that is an animator just for this main character because his animation is so different and varied from other characters.
class Animations{
Guy MYGUY;
Texture firstTexture;
ArrayList<Texture> running;
Sprite CurrentSprite;
public Animations(Texture standingStill, Guy myGuy){
MYGUY = myGuy;
firstTexture = standingStill;
running = new ArrayList<Texture>();
running.add(firstTexture);
CurrentSprite = new Sprite(firstTexture);
public void update (int direction, int state){
CurrentSprite.setPosition(MYGUY.X, MYGUY.Y)
// I have a switch here, but it does nothing yet because I haven't added in different actions for the character.
//However I do have a switch for direction, because that is important right now
switch(state){
case Guy.LEFT:
CurrentSprite.set rotation(180);
//yes there are more, but even rotating 180 won't work correctly
}
Then I have a renderer class to draw everything, i have the object MyGuy in an object for the world called myLand and I draw it with:
myLand.GUY.animation.CurrentSprite(batch);
So my problem arises on the rotation, whenever it rotates 180 degrees it seems to always rotate around the coordinates (0, 0) instead of the center of the sprite. So it usually ends up where I move like five to the right, but then if I try to go left it does double the distance backwards, but the camera position stays the same, and the guy usually disappears off the left or right side of the screen.

Try use rotate(...)method instead of setRotation(...).
With setOrigin(widthSprite\2, heightSprite\2)
That action rotate sprite itself.

Try
sprite.setOriginCenter();
This should help

Instead of rotating the sprite, just flip it with this single line:
CurrentSprite.flip(true, false);
the first boolean is X flip (that's what you want to set as true when going left) and the second is the Y flip.

Android game developing - dynamic bounds definition

I am currently developing a game for android using libgdx library .
Lets say we have a lizard, now the user creates paths by sliding fingers on the screen, on which the lizard can walk on.
The question is , how do restrict the lizard to walk on only where the finger touched the screen( on the path - between the bounds).
public class Block {
static final float SIZE = 1f;
Vector2 position = new Vector2();
Rectangle bounds = new Rectangle();
public Block(Vector2 pos) {
this.position = pos;
this.bounds.width = SIZE;
this.bounds.height = SIZE;
}
}
In this example we can see a block, the bounds of the block is a rectangle on which the lizard can walk on.
how do I make some similar bounds only using a circle?
Here is what i got so far:
I have created a doubled layer bitmap that overlap each other. When the user touches the screen , he erases the first bitmap reveling the second bitmap underneath the first one ( only the part where the user touched get removed).
here is the function that erases the first bitmap.
public void onDraw(Canvas canvas){
super.onDraw(canvas);
canvas.drawColor(Color.TRANSPARENT);
canvas.drawBitmap(bgr, 0, 0, null);
c2.drawCircle(X, Y, 40, pTouch);
Paint new_paint = new Paint(/*Paint.ANTI_ALIAS_FLAG*/);
new_paint.setXfermode(new PorterDuffXfermode(Mode.SRC_ATOP));
//new_paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
canvas.drawBitmap(overlay, 0, 0, new_paint);
}
Notice#
the bitmap is removed using a circle shape.
It would be great if i could add to the circle that's removing the bitmap, a property of bound, on which the lizard can walk on.
Any ideas?

u should update the cordinates of bounds as per the lizard position
bounds.x=position.x;
bounds.y=position.y;
So that your bounds follow the lizard
Also instead of using recatangle for bounds try to use
sprite.getBoundingRectangle()
this method gives u the exact rectangular bounds of the image so no need to maintain bounds.
Provided you use AtlasSprite or Sprite for your image.

I shared my game Bomberman early. You can find code you needed in GameScreen class
p.s. also you can find different interesting samples of LibGDX usage here

Android Finger Painting stretch on rotate

I am making a finger painting app. Using Paths I have created a canvas for users to draw lines on as if finger painting. I have saved the paths and reload them when the device is rotated to landscape mode. However with the new screen dimensions part of the drawing is now off screen.
What is the best way of adjusting the points in my path to stretch the image across the new screen dimensions so the user doesn't loose any of their drawing off screen?

I solved my issue like this:
if(getWidth() > getHeight())
{
Matrix scaleMatrix = new Matrix();
RectF rectF = new RectF();
p.computeBounds(rectF, true);
scaleMatrix.setScale(1.6f, .6f,0,0);
p.transform(scaleMatrix);
}
canvas.drawPath(p, paint);
Where p is the path.

AndEngine GLES 2 - black screen, no errors

I am writing a game for Android using AndEngine GLES 2. Everything was working properly - I had a background image, there were sprites moving around and even some music - until recently I tried something new (I wanted to be able to switch between two different scenes) when the display turned black.
I could still execute the game and there were no error shown. All log entries I made during the game were shown, even the music was playing so I knew the game was running "properly", but I couldn't see any image. Nothing. All black.
So I thought, changing everything back to before this "error" appeared, would do the trick. But still the screen is black.
I even tried commenting everything out but the background image - nothing.
Now if it is not too much to ask, could anyone please look over this short piece of code and tell me what is wrong there?
This are the variables I use:
private SmoothCamera camera;
private BitmapTextureAtlas bitmapTextureAtlas;
private Scene scene;
private Sprite background;
The EngineOptions I never changed, so they should be alright.
#Override
public EngineOptions onCreateEngineOptions() {
float positionX = 80f; // horizontal (x) position of the camera
float positionY = 280f; // vertical (y) position of the camera
float velocityX = 200f; // velocity of the horizontal camera movement
float velocityY = 200f; // velocity of the vertical camera movement
float zoomFactor = 1f; // the camera's zoom Factor (standard := 1)
this.camera = new SmoothCamera(positionX, positionY, this.getWindowManager().getDefaultDisplay().getWidth(), this.getWindowManager().getDefaultDisplay().getHeight(), velocityX, velocityY, zoomFactor);
EngineOptions options = new EngineOptions(true, ScreenOrientation.LANDSCAPE_SENSOR, new RatioResolutionPolicy(this.camera.getWidth(), this.camera.getHeight()), this.camera);
return options;
}
Here I create the TextureAtlas and load a background image.
#Override
protected void onCreateResources() {
// create the TextureAtlas
BitmapTextureAtlasTextureRegionFactory.setAssetBasePath("gfx/");
this.bitmapTextureAtlas = new BitmapTextureAtlas(this.getTextureManager(), 1024, 1600, TextureOptions.NEAREST);
// background
this.background = new Sprite(0, 0, BitmapTextureAtlasTextureRegionFactory.createTiledFromAsset(this.bitmapTextureAtlas, this, "background.png", 0, 0, 1, 1), this.getVertexBufferObjectManager());
this.mEngine.getTextureManager().loadTexture(this.bitmapTextureAtlas);
}
And finally the Scene is instantiated and the background gets attached.
#Override
protected Scene onCreateScene() {
this.scene = new Scene();
this.scene.attachChild(this.background);
return this.scene;
}
Now why would this small Activity not show? I forgot: its a SimpleBaseGameActivity.
Well, since AndEngine GLES2 is not running on the emulator, I have to use my phone (Samsung Galaxy GIO) and can't test the app on another machine.
Did anyone stumble upon a similar problem?
Any help is really much appreciated and thank you for your time !
Christoph

I think the problem is here:
this.bitmapTextureAtlas = new BitmapTextureAtlas(this.getTextureManager(), 1024, 1600, TextureOptions.NEAREST);
The dimensions of the Atlas are supposed to be powers of 2.