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Getting help
The libgdx community is glad to help you when you get stuck or encounter a bug, but first you must make it as easy to help you as possible.
Instead of reading this guide, you can use the libgdx Problem Wizzard which walks you through composing a forum post step by step:
- Helping Yourself
- Topic Title
- Context
- Relevance
- Problem Statement
- Exceptions
- Code Snippets
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Executable Example Code
- Example Resources
- [Application](#Barebones_Application Barebones)
- [SpriteBatch](#Barebones_SpriteBatch Barebones)
- Barebones Stage
- Actually Executable
- Attitude
- Formatting
Please go through this short checklist to be sure you haven't missed an easy to find solution.
- Are you using the latest nightly build? Please try that first, as issues are being fixed every single day.
- Have you read the documentation on the Table of Contents)? It can also be very helpful to look at the Javadocs and source code (don't be shy!). Search the tests for a specific class to find example code.
- Have you searched the forum for your problem?
- Have you searched the issue tracker for your problem? Be sure to search "All issues", not just "Open issues".
If you still have a problem, often the fastest way to get help is the libgdx chat room. Usually it has ~100 people, any one of which could answer your question right now. The chat room is #libgdx on irc.freenode.net. You can also access the chat room right through your browser.
Otherwise, if you wish to post on the forum or post a new issue on the tracker, keep reading.
If you believe your issue, error, or suspected bug is related to a specific backend, please present the following information with your issue. If you are on IRC have the following information on hand.
For Android backend issues
- Note: Android issues can sometimes be more difficult do to device manufactures breaking things or buggy drivers.
- Please have the device name and Android version in the bug report. Providing things won't be broken, we will make an attempt to fix the issue or implement a workaround for the device.
For Desktop backend issues (jglfw, lwjgl)
- Please list the operating system and version, architecture, and if necessary OpenGL version.
- Also mark specifically which of those backends have this issue.
For iOS (RoboVM) backend issues
- Please list the iOS version, and device the issue occurs on
For GWT (WebGL) backend issues
- Please list the operating system and version, and architecture.
- Please list the browser and browser version Listing this information can greatly reduce the workload on us and can greatly increase the chances your issue will be resolved or an available fix or workaround implemented.
Write a clear and short topic title. Titles that do not describe the topic (such as "please help") or contain all caps, exclamation marks, etc make it much less likely that your post will be read.
Describe what you are trying to achieve. If it might help your question get answered, also explain the reasons why. If specific solutions are unacceptable, list them and why.
Try to keep the information relevant. If you aren't sure, include the extra information but if your text gets very long, provide an executive summary separate from the rest.
Concisely describe the problem. Describe each approach you have tried and, for each of those, explain what you expected and what actually happened.
If you fail to do this, likely you will be ignored. No one wants to guess what your problem is and often they don't have the time or patience to ask for the information you should have included from the start.
If an exception occurred, include the full exception message and stack-trace.
Often the first line number just after the deepest (nearest to the bottom) exception message is most relevant. If this line is in your code, along with the full exception message and stack-trace you should include your code for this line and 1-2 surrounding lines.
Exception in thread "LWJGL Application" com.badlogic.gdx.utils.GdxRuntimeException: java.lang.NullPointerException
at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:111)
Caused by: java.lang.NullPointerException
at com.badlogic.gdx.scenes.scene2d.ui.Button.setStyle(Button.java:155) <- **MOST IMPORTANT LINE**
at com.badlogic.gdx.scenes.scene2d.ui.TextButton.setStyle(TextButton.java:55)
at com.badlogic.gdx.scenes.scene2d.ui.Button.<init>(Button.java:74)
at com.badlogic.gdx.scenes.scene2d.ui.TextButton.<init>(TextButton.java:34)
at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:125)
at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:108)
Code snippets are most often not very useful. Unless you are blatantly misusing the API, most problems cannot be solved just by looking at a code snippet. Code snippets mostly lead to vague guesses at what might be wrong instead of a real answer to your question. Instead, include executable example code.
Example code that can be copied, pasted, and run is the best way to get help. It saves those helping you time because they can see the problem right away. They can quickly fix your code or fix the bug, verify the fix, and show you the result. No matter what, an executable example has to be written to properly test, fix, and verify the fix. If you can't debug and fix the problem yourself, you can still help by providing the executable example.
Creating executable example code does take some time. You need to take apart your application and reconstruct the relevant parts in a new, bare-bones application that shows the problem. Quite often just by doing this you will figure out the problem. If not, you will get help very quickly and the people helping you will have more time to help more people.
Example code should be contained entirely in a single class (use static member classes if needed) and executable, meaning it has a main method and can simply be copied, pasted, and run. Do not use a GdxTest, as that cannot be copy, pasted, and run.
Often executable examples need some resources, such as an image or sound file. It is extra work for those trying to help if they must download your specific resources. Instead, it is ideal to use resources from the libgdx tests. This enables your example code to be simply pasted into the gdx-tests-lwjgl
project and run.
The easiest way to write an executable example is to paste one of the bare-bones applications below into the gdx-tests-lwjgl
project and then modify it to show your problem, using only the test resources. Note the test resources are pulled in by gdx-tests-lwjgl
from the gdx-tests-android
project.
Below is a simple, bare-bones, executable application. This can be used as a base for creating your own executable example code.
import com.badlogic.gdx.*;
import com.badlogic.gdx.backends.lwjgl.LwjglApplication;
import com.badlogic.gdx.graphics.GL10;
public class Barebones extends ApplicationAdapter {
public void create () {
// your code here
}
public void render () {
Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
// your code here
}
public static void main (String[] args) throws Exception {
new LwjglApplication(new Barebones());
}
}
This bare-bones application uses SpriteBatch to draw an image from the gdx-tests-lwjgl
project.
import com.badlogic.gdx.*;
import com.badlogic.gdx.backends.lwjgl.LwjglApplication;
import com.badlogic.gdx.graphics.*;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
public class BarebonesBatch extends ApplicationAdapter {
SpriteBatch batch;
Texture texture;
public void create () {
batch = new SpriteBatch();
texture = new Texture(Gdx.files.internal("data/badlogic.jpg"));
}
public void render () {
Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
batch.begin();
batch.draw(texture, 100, 100);
batch.end();
}
public static void main (String[] args) throws Exception {
new LwjglApplication(new BarebonesBatch());
}
}
This bare-bones application has a scene2d Stage and uses scene2d.ui to draw a label and a button. It uses the Skin from the gdx-tests-lwjgl
project.
import com.badlogic.gdx.*;
import com.badlogic.gdx.backends.lwjgl.LwjglApplication;
import com.badlogic.gdx.graphics.GL10;
import com.badlogic.gdx.scenes.scene2d.Stage;
import com.badlogic.gdx.scenes.scene2d.ui.*;
public class BarebonesStage extends ApplicationAdapter {
Stage stage;
public void create () {
stage = new Stage();
Gdx.input.setInputProcessor(stage);
Skin skin = new Skin(Gdx.files.internal("data/uiskin.json"));
Label label = new Label("Some Label", skin);
TextButton button = new TextButton("Some Button", skin);
Table table = new Table();
stage.addActor(table);
table.setFillParent(true);
table.debug();
table.defaults().space(6);
table.add(label);
table.add(button);
}
public void render () {
Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
stage.draw();
Table.drawDebug(stage);
}
public static void main (String[] args) throws Exception {
new LwjglApplication(new BarebonesStage());
}
}
If your executable example cannot be pasted into the gdx-tests-lwjgl
project and run, then it is not actually an executable example. Others should not have to fix up your code to run it, not even to add a main method.
Begging for help or a quick answer tends to turn people off and makes it less likely you will receive help at all. Just be polite and your question will get answered politely as time allows. If you are rude, you will be ignored or met with rudeness in return. The people helping you are busy and providing you help for free simply because they are nice. They don't owe you anything and they don't have to care about you or your problems.
If you spend a little bit of your time to format your post nicely, it is more likely others will spend their time responding to your post. This means capital letters where appropriate, paragraphs to separate ideas, use actual words (rather than "u", "bcoz", etc), put code in code blocks, etc. If English is not your first language, we understand. No need to apologize, just do your best to make an effort.
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Developer's Guide
- Introduction
- Goals & Features
- Community & Support
- Contributing
- Games Built with Libgdx
- Prerequisites
- Gradle Project Setup, Running, Debugging and Packaging
- Project Setup, Running & Debugging
- Third Party Services
- Working from Source
- Using libgdx with other JVM languages
- The Application Framework
- A Simple Game
- File Handling
- Networking
- Preferences
- Input Handling
- Memory Management
- Audio
-
Graphics
- Configuration & Querying Graphics ??
- Fullscreen & VSync
- Continuous & Non-Continuous Rendering
- Clearing the Screen
- Take a Screenshot
- OpenGL ES Support * Configuration & Querying OpenGL ?? * Direct Access ?? * Utility Classes * Rendering Shapes * Textures & TextureRegions * Meshes * Shaders * Frame Buffer Objects
- 2D Graphics * SpriteBatch, TextureRegions, and Sprite * 2D Animation * Clipping, with the use of ScissorStack * Orthographic camera * Mapping Touch Coordinates ?? * Viewports * NinePatches * Bitmap Fonts * Distance field fonts * Using TextureAtlases * Pixmaps * Packing Atlases Offline * Packing Atlases at Runtime * 2D Particle Effects * Tile Maps * scene2d * scene2d.ui * Skin
- 3D Graphics * Quick Start * Models * Material and environment * 3D animations and skinning * Importing Blender models in LibGDX * Perspective Camera ?? * Picking ??
- Managing Your Assets
- Utilities
-
Math Utilities
- Interpolation
- Vectors, Matrices, Quaternions
- Circles, Planes, Rays, etc.
- Path interface & Splines
- Bounding Volumes ??
- Intersection & Overlap Testing ??
- Physics
- Tools
- Extensions
- Deploying your Application
- Building Libgdx ??
- Known Issues
- Articles
- Deprecated (May be outdated)