Sometimes while trying to export an APK using Eclipse, it gives the error “Conversion to Dalvik format failed with error 1.” However meanwhile if you try to run the project normally on a debug device, it launches just fine. For example, this often happens when you try to make an APK out of a Cocos2d-x project.

This error is due to the crapball design of Eclipse (let’s pile more crap on a crap to increase functionality), but fortunately, there’s an easy solution to fix this problem: All you need to do to fix this problem is to disable automatic build from the Project menu, clean everything and retry exporting the APK.

This tutorial is compatible with Cocos2d-x 3.0.

Some features of Cocos2d-x such as EditBox and HttpClient are not in the main libCocos2d project and in order to access them, other projects should be imported to the solution first. In this post, I am going to explain how to import and link external projects to the main game project. This post can also help people with general problems regarding referencing C++ projects in Visual Studio.

First, we need to import the libExtensions and libNetwork projects to our solution. To do this, right click on your Solution in the Solution Explorer window, hover over the Add item and press Existing Project….

The libExtensions.vcxproj project file is located at cocos2dextensionsproj.win32 and the libNetwork.vcxproj is located at cocos2dcocosnetworkproj.win32. After importing them, you need to link them to your main project.

To add references to other projects, you need to go to the property pages of your main project. Right click on your project and press Properties.

From Common Propertiesclick on the Add New Reference…button and check the boxes next to libExtensions and libNetwork.

One last thing that you need to do before using libExtensions, is to add $(EngineRoot) to your projects include directories. In Property Pages, open Configuration Properties>C/C++>General, and add $(EngineRoot); to Additional Include Directories.

There is one additional dependency that you probably might need to add to the libNetwork project. It requires the libcurl_imp.lib file to build, and we can set this by opening the Property Pages of libNetwork, locating Additional Dependencies at Configuration Properties>Librarian>General and adding $(EngineRoot)externalcurlprebuiltwin32libcurl_imp.lib; to the beginning of it.

Now you are all set to use libExtensions and libNetwork. For example, to create an EditBox, after adding the #include “extensions/GUI/CCEditBox/CCEditBox.h” line to the top of your file, you can use this code:

nameBox = cocos2d::extension::EditBox::create(Size(width, height), Scale9Sprite::createWithSpriteFrameName(“editBox”));

nameBox->setPosition(CP(0.5f, 0.45f));

nameBox->setFont(“Arial”, 42.0f);

nameBox->setLabelAnchorPoint(Point(-0.1f, 0.5f));

nameBox->setFontColor(Color3B::WHITE);

addChild(nameBox);

Note that the classes in libExtensions are located in the cocos2d::extension namespace, and for libNetwork you’d want to look into the cocos2d::network namespace. As an example for libNetwork, in the next section I will show how to send a simple POST request using the HttpRequest and HttpClient classes.

Sending a POST request with Cocos2d-x

To use HttpRequest and HttpClient, you first need to include their header files:s

#include “network/HttpClient.h”

#include “network/HttpRequest.h”

using namespace cocos2d::network;

Now, let’s assume that we want to send some std::string containing our POST data called data to http://127.0.0.1:1337. We can use the following code snippet to do that:

HttpRequest* request = new HttpRequest();

request->setUrl(“http://127.0.0.1:1337 “);

request->setRequestType(HttpRequest::Type::POST);

request->setRequestData(data.c_str(), data.size());

HttpClient::getInstance()->send(request);

request->release();

It’s that easy. Sending GET, PUT and DELETE requests is also very similar, you just need to pass a different HttpRequest::Type to the setRequestType(…) method.

This tutorial is compatible with Cocos2d-x v3.1.

Repeating textures can be used to make tiled backgrounds, floors, and for many other purposes. The stars in the image shown above are an example of this. The easiest way to repeat a texture is to put it in a separate file with power-of-two dimensions (also known as a POT texture), and display it using a Sprite with its wrapS and wrapT TexParams values set to GL_REPEAT. This is how to do that:

Texture2D::TexParams texParams;

texParams.magFilter = GL_LINEAR;

texParams.minFilter = GL_LINEAR;

texParams.wrapS = GL_REPEAT;

texParams.wrapT = GL_REPEAT;

Sprite* bgwrap = Sprite::create(“stars.png”, Rect(0, 0, visibleSize.width, visibleSize.height));

bgwrap->getTexture()->setTexParameters(texParams);

bgwrap->setPosition(visibleSize.width * 0.5f, visibleSize.height * 0.5f));

In this case, the screen size is larger than the size of the image file, therefore (in line 6) we try to reference points in the image file that do not exist. In situations like this, OpenGL needs to know how we want it to interpret such coordinates. We tell the engine how we want it to react by setting the values of wrapS and wrapT, where S is for the x-axis and T is for the y-axis.

We can either set these values to GL_CLAMP which means we want the texture edges to be repeated, or GL_REPEAT which means we want the whole texture to be repeated.

Animating the background

With a bit of GLSL goodness, we can animate the background and bring it to life. Here’s a fragment shader code that slowly moves the background for us:

precision highp float;

varying vec4 v_fragmentColor;    

varying vec2 v_texCoord;

//CC_Time[1] is time

void main()            

{

    vec2 new_uv = v_texCoord;

    new_uv.x = fract(new_uv.x + CC_Time[1] * 0.03);

    new_uv.y = fract(new_uv.y + CC_Time[1] * 0.01);

    gl_FragColor = v_fragmentColor * texture2D(CC_Texture0, new_uv);    

}

We just need to render our background with this program:

auto p = GLProgram::createWithFilenames(“generic.vsh”, “uv.glsl”);            

bgwrap->setGLProgram(p);

Voila, now we have a moving repeated background!