Develop Reference

Box2d creates specific body and fixture seemingly at random

I have created an android application similar to Not Tetris 2 using Libgdx with Box2d.
It can successfully remove a slice from the world, which obviously involves duplicating several bodies and destroying/creating fixtures. However, seemingly at random, a body with a 2x2 fixture will appear. The body and fixture are displayed using information related to the objects around it when it is created, so I narrowed its creation down to the following function:
Body duplicateBody(Body original){
BodyDef d = new BodyDef();
d.position.set(original.getPosition());
d.angle = original.getAngle();
d.linearVelocity.set(original.getLinearVelocity());
d.angularVelocity = original.getAngularVelocity();
Body dup = world.createBody(d);
dup.setType(BodyDef.BodyType.DynamicBody);
return dup;
}
I use this function in 2 different contexts:
Making a copy of the body if a "slice" cuts one in two -- I then transfer the fixtures which are below to it.
When a fixture is below the line then it is added to a body created for ones below
Making a copy of the body when groups of fixtures are separated
I commented out the code responsible for the third instance and still had the 2x2 boxes spawning, so here are the functions relevant to the others:
...
if (below && !above) {
//copy fixture, add copy to lower body and remove original
Body top = fixture.getBody();
FixtureDef n = new FixtureDef();
PolygonShape s = new PolygonShape();
s.set(getLocalVerticesOfFixture(fixture));
n.shape = s;
n.density = fixture.getDensity();
//create lower body if a lower one doesn't already exist
if (!topBottomPairs.containsKey(top)) {
Body dup = duplicateBody(top);
topBottomPairs.put(top, dup);
}
//delete fixture
remove.add(fixture);
Fixture f = topBottomPairs.get(top).createFixture(n);
s.dispose();
}
...
if (below && above) {
//copy fixture, add copy to lower body, but keep original on upper as it needs to split
FixtureDef n = new FixtureDef();
PolygonShape s = new PolygonShape();
s.set(getLocalVerticesOfFixture(fixture));
n.shape = s;
n.density = fixture.getDensity();
Body top = fixture.getBody();
//create lower body if a lower one doesn't already exist
if (!topBottomPairs.containsKey(top)) {
Body dup = duplicateBody(top);
topBottomPairs.put(top, dup);
}
Fixture second = topBottomPairs.get(top).createFixture(n);
s.dispose();
}
....
private Vector2[] getLocalVerticesOfFixture(Fixture fixture) {
PolygonShape shape = ((PolygonShape) fixture.getShape());
Vector2[] localVertices = new Vector2[shape.getVertexCount()];
for (int i = 0; i < shape.getVertexCount(); i++) {
localVertices[i] = new Vector2();
shape.getVertex(i, localVertices[i]);
}
return localVertices;
}
I also have this remove fixture function which runs on all fixtures I want to remove:
private void smartDeleteFixture(Fixture f){
f.getBody().destroyFixture(f);
if(f.getBody().getFixtureList().size == 0){
world.destroyBody(f.getBody());
}
}
Nowhere do I create vertices, let alone a fixture of a 2x2 shape. I was wondering if this duplication function has any flaws, or if I stumbled upon some "default shape" that box2d uses.
Edit: I have removed anything not related to the manipulation of box2d bodies. Hope that helps

Deleted this question as I decided to perform a major recode and hoped that would fix my problem. It did not, but I figured out the cause.
I looked through box2d and found a couple instances of code similar to this in the polygon shape class:
if (n < 3)
{
// Polygon is degenerate.
b2Assert(false);
SetAsBox(1.0f, 1.0f);
return;
}
These instances check the number of vertices after various operations and turn the shape into a 2x2 box if there are fewer than 3. One of these operations makes the shape convex. Another checks if vertices are close together (closer than 0.0025f), deleting one if so.
In my case, the problem was simple. Some of my vertices were less than 0.0025f from each other, resulting in them being deleted, the vert count dropping below 3, an assertion being ignored, and then my shape being turned into a 2x2 box. I hope this helps someone out.

how to show null graph

I am using jjoe64 Graph View in my android application.
and I am trying to show dynamic values in graph but first time it contains no values but graph is not appearing.
give me solution.
http://www.android-graphview.org/
https://github.com/jjoe64/GraphView

Can you show us your code?
Have you tried something like
graph = (GraphView) findViewById(R.id.graph);
LineGraphSeries<DataPoint> series = new LineGraphSeries<DataPoint>();
graph.addSeries(series);
graph.getViewport().setXAxisBoundsManual(true);
graph.getViewport().setYAxisBoundsManual(true);
graph.getViewport().setMinX(0);
graph.getViewport().setMaxX(0);
graph.getViewport().setMinY(0);
graph.getViewport().setMaxY(4);
graph.onDataChanged(true, true);

There's a bug report logged for this one, and it appears the issue will be fixed in the next release (4.0.1).Anyway I simply coded around the issue, by displaying some text, indicating there's no data at that point eg.
// If there is no data, let the user know, else blank the textBox.
TextView fragmentText = (TextView) v.findViewById(R.id.history_text);
if ( xLabels.size() < 2 ){
fragmentText.setTextSize(24);
fragmentText.setText(getString(R.string.history_graph_no_data));
} else {
// Remove the "No Data" text
fragmentText.setText("");
LinearLayout layout = (LinearLayout) v.findViewById(R.id.history_graph);
addGraphToLayout(layout);
}

Remove a lengend from an XYPlot

Am using AndroidPlot on my project and it's just great so far. This is what i got.
Now am trying to remove one of the series indicators from the legend. Actually i want to keep only the first one (the blue one) cause the others are self explanatory.
Am not asking how to remove the legend it self (see https://stackoverflow.com/a/13413758/665823 for that issue).
If someone can help me i'll be great. Thanks in advance.

I finally found a tweek that allows me to do what i need. To achieve this the series that i need to be shown must be added to the plot first over the ones i need to hide :
// I add the blue serie first
LineAndPointFormatter mFormat = new LineAndPointFormatter();
mFormat.configure(context, R.xml.plot_blue);
graphView.addSeries(serieMesures, mFormat);
// I add the other colors after
for (XYSeries serie : seriesSeuils) {
LineAndPointFormatter sFormat = new LineAndPointFormatter();
if (serie.getTitle().equals("RED") {
sFormat.configure(context, R.xml.plot_red);
}
else if (serie.getTitle().equals("ORANGE")) {
sFormat.configure(context, R.xml.plot_orange);
}
else if (serie.getTitle().equals("YELLOW")) {
sFormat.configure(context, R.xml.plot_yellow);
}
graphView.addSeries(serie, sFormat);
}
Then i just created a legend where there is only enough space to show the series i need (in my case just the first one).
// This is what does the trick! A Table with 1 line and 1 column
// so the other series can't be rendered in the LegendWidget
graphView.getLegendWidget().setTableModel(new DynamicTableModel(1, 1));
// Other customizations (size and position)
graphView.getLegendWidget().setSize(new SizeMetrics(55, SizeLayoutType.ABSOLUTE, legendWith, SizeLayoutType.ABSOLUTE));
graphView.getLegendWidget().setPositionMetrics(
new PositionMetrics(20,
XLayoutStyle.ABSOLUTE_FROM_RIGHT,
20,
YLayoutStyle.ABSOLUTE_FROM_TOP,
AnchorPosition.RIGHT_TOP));
graphView.getLegendWidget().setBackgroundPaint(bgPaint);
graphView.getLegendWidget().setTextPaint(txPaint);
graphView.getLegendWidget().setBorderPaint(brPaint);
graphView.getLegendWidget().setPadding(10, 1, 10, 1);
And voila!

Displaying Images(numbers) to screen

I am working on a project that will display math problems to the screen such as:
10 + 5 =
and then the user will need to guess the answer. I am doing this as more of way for me to learn how android ticks.
I have images from 0 to 9 saved in the drawable folder for each of the dpi setting I need to account. I also have the operators (+,-,*,/,=) also saved.
My questions:
How easy is this to do?
How would I go about doing the above dynamically?
Thanks
--EDIT--
The images and operators are stored as .9.png files in my drawable folder. I have string-array contain my problems that I will randomly pull from and then display them to the screen.
In the past I would do the following:
public View buildProblem()
{
LinearLayout rtnView = new LinearLayout(ctx);
rtnView.setOrientation(LinearLayout.HORIZONTAL);
rtnView.setLayoutParams(new GridLayout.LayoutParams());
// Build LeftSide
Iterator<Integer> itor = buildLeftSide();
ImageView iv;
// loop through of iterator
while(itor.hasNext())
{
iv = new ImageView(ctx);
iv.setScaleType(ImageView.ScaleType.FIT_CENTER);
iv.setImageResource(itor.next());
itor.remove();
rtnView.addView(iv);
}
// Space
rtnView.addView(space);
// Operator
rtnView.addView(plusSign);
// Build LeftSide
itor = buildRightSide();
// another loop
while(itor.hasNext())
{
iv = new ImageView(ctx);
iv.setScaleType(ImageView.ScaleType.FIT_CENTER);
iv.setImageResource(itor.next());
itor.remove();
rtnView.addView(iv);
}
// Space
rtnView.addView(space);
// Equal Sign
rtnView.addView(equalSign);
// Space
rtnView.addView(space);
// return the view
return rtnView;
}
I was thinking of using ImageViews for the numbers to be displayed to the screen which I have used in the past but not sure if that is the best way to do it.
https://github.com/barakisbrown/MathTest -- Is one attempt at doing the above but I have now started to rewrite it from scratch so which is why I am asking for help.

Starling Feathers - Available features 101

New to Starling-Feathers, before I start to develop my mobile app, I would like to know what are the best practice to develop the following features using Feathers:
Partial view slide - A part of the next view is shown and the user can drag to see it all. Could this be done with Feathers ScreenNavigator?
Sliding menu from the top
Dragging text elements with title pushing the last items
Since it is hard to describe I've added an animated gif to describe my goals. Thanks for all your advices
I would like to maximize the use of Feathers built in widgets and will appreciate code examples :)

I think these are not that much hard to do in core flash or you can also do it in Starling feathers too. YOu can use list item to do the third point (Dragging text elements with title pushing the last items) .
First and second you can use it with tweening effect i think.
For the third one using feathers list.
(re formated post)
private function addFeatherList():void{
Flist = new List();
Flist.width = 250;
Flist.height = 300;
Flist.x = GAME_W/2 - Flist.width/2;
Flist.y = sampText.height + 5;
this.addChild( Flist );
fontArr = Font.enumerateFonts(true);
for (var i:int=0; i<fontArr.length; i++){
ListArr[i] = { text:Font(fontArr[i]).fontName }
}
var groceryList:ListCollection = new ListCollection( ListArr );
Flist.dataProvider = groceryList;
Flist.itemRendererProperties.labelField = "text";
FeathersControl.defaultTextRendererFactory=function():ITextRenderer{
var render:TextFieldTextRenderer=new TextFieldTextRenderer();
render.textFormat = new TextFormat("Verdana",8,0xFFFFFF,false);
return render;
}
Flist.itemRendererFactory = function():IListItemRenderer //list.itemRendererProperties.accessorySourceField list.itemRendererFactory
{
var renderer:DefaultListItemRenderer = new DefaultListItemRenderer();
renderer.addEventListener(Event.TRIGGERED, onListTriggered);
return renderer;
}
}