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java.lang.NullPointerException at com.xpn.xwiki.web.XWikiServletURLFactory.findAttachmentForDocRevision(XWikiServletURLFactory.java:876) at com.xpn.xwiki.web.XWikiServletURLFactory.createAttachmentURL(XWikiServletURLFactory.java:644) at com.xpn.xwiki.XWiki.getAttachmentURL(XWiki.java:5571) at com.xpn.xwiki.XWiki.getAttachmentURL(XWiki.java:5582) at com.xpn.xwiki.XWiki.getAttachmentURL(XWiki.java:5619) at com.xpn.xwiki.doc.DefaultDocumentAccessBridge.getAttachmentURL(DefaultDocumentAccessBridge.java:767) at org.xwiki.rendering.internal.wiki.XWikiWikiModel.getLinkURL(XWikiWikiModel.java:155) at org.xwiki.rendering.internal.wiki.XWikiWikiModel.getImageURL(XWikiWikiModel.java:185) at org.xwiki.rendering.internal.renderer.xhtml.image.AttachmentXHTMLImageTypeRenderer.getImageSrcAttributeValue(AttachmentXHTMLImageTypeRenderer.java:68) at org.xwiki.rendering.internal.renderer.xhtml.image.AbstractXHTMLImageTypeRenderer.onImage(AbstractXHTMLImageTypeRenderer.java:91) at org.xwiki.rendering.internal.renderer.xhtml.image.DefaultXHTMLImageRenderer.onImage(DefaultXHTMLImageRenderer.java:76) at org.xwiki.rendering.internal.renderer.xhtml.XHTMLChainingRenderer.onImage(XHTMLChainingRenderer.java:582) at org.xwiki.rendering.listener.chaining.AbstractChainingListener.onImage(AbstractChainingListener.java:559) at org.xwiki.rendering.listener.chaining.AbstractChainingListener.onImage(AbstractChainingListener.java:559) at org.xwiki.rendering.listener.chaining.EmptyBlockChainingListener.onImage(EmptyBlockChainingListener.java:450) at org.xwiki.rendering.listener.chaining.AbstractChainingListener.onImage(AbstractChainingListener.java:559) at org.xwiki.rendering.listener.chaining.BlockStateChainingListener.onImage(BlockStateChainingListener.java:662) at org.xwiki.rendering.listener.chaining.AbstractChainingListener.onImage(AbstractChainingListener.java:559) at org.xwiki.rendering.block.ImageBlock.traverse(ImageBlock.java:96) at org.xwiki.rendering.block.AbstractBlock.traverse(AbstractBlock.java:542) at org.xwiki.rendering.block.AbstractBlock.traverse(AbstractBlock.java:542) at org.xwiki.rendering.block.AbstractBlock.traverse(AbstractBlock.java:542) at org.xwiki.rendering.block.AbstractBlock.traverse(AbstractBlock.java:542) at org.xwiki.rendering.internal.renderer.AbstractBlockRenderer.render(AbstractBlockRenderer.java:63) at org.xwiki.rendering.internal.renderer.AbstractBlockRenderer.render(AbstractBlockRenderer.java:55) at com.xpn.xwiki.doc.XWikiDocument.renderXDOM(XWikiDocument.java:8689) at com.xpn.xwiki.doc.XWikiDocument.display(XWikiDocument.java:1218) at com.xpn.xwiki.doc.XWikiDocument.getRenderedContent(XWikiDocument.java:1356) at com.xpn.xwiki.doc.XWikiDocument.displayDocument(XWikiDocument.java:1305) at com.xpn.xwiki.doc.XWikiDocument.displayDocument(XWikiDocument.java:1272) at com.xpn.xwiki.api.Document.displayDocument(Document.java:786) at jdk.internal.reflect.GeneratedMethodAccessor579.invoke(Unknown Source) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.doInvoke(UberspectImpl.java:565) at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:548) at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:219) at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:369) at org.apache.velocity.runtime.parser.node.ASTReference.value(ASTReference.java:701) at org.apache.velocity.runtime.parser.node.ASTExpression.value(ASTExpression.java:72) at org.apache.velocity.runtime.parser.node.ASTSetDirective.render(ASTSetDirective.java:240) at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:144) at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:423) at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:191) at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:144) at org.xwiki.velocity.internal.directive.TryCatchDirective.render(TryCatchDirective.java:86) at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:301) at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:423) at org.apache.velocity.Template.merge(Template.java:358) at org.apache.velocity.Template.merge(Template.java:262) at org.xwiki.velocity.internal.DefaultVelocityEngine.evaluate(DefaultVelocityEngine.java:284) at com.xpn.xwiki.render.DefaultVelocityManager.evaluate(DefaultVelocityManager.java:316) at com.xpn.xwiki.internal.template.VelocityTemplateEvaluator.evaluateContent(VelocityTemplateEvaluator.java:95) at com.xpn.xwiki.internal.template.TemplateAsyncRenderer.evaluateContent(TemplateAsyncRenderer.java:217) at com.xpn.xwiki.internal.template.TemplateAsyncRenderer.renderVelocity(TemplateAsyncRenderer.java:180) at com.xpn.xwiki.internal.template.TemplateAsyncRenderer.render(TemplateAsyncRenderer.java:137) at com.xpn.xwiki.internal.template.TemplateAsyncRenderer.render(TemplateAsyncRenderer.java:53) at org.xwiki.rendering.async.internal.DefaultAsyncRendererExecutor.lambda$syncRender$0(DefaultAsyncRendererExecutor.java:267) at com.xpn.xwiki.internal.security.authorization.DefaultAuthorExecutor.call(DefaultAuthorExecutor.java:98) at org.xwiki.rendering.async.internal.DefaultAsyncRendererExecutor.syncRender(DefaultAsyncRendererExecutor.java:267) at org.xwiki.rendering.async.internal.DefaultAsyncRendererExecutor.render(DefaultAsyncRendererExecutor.java:250) at org.xwiki.rendering.async.internal.block.DefaultBlockAsyncRendererExecutor.render(DefaultBlockAsyncRendererExecutor.java:154) at com.xpn.xwiki.internal.template.InternalTemplateManager.render(InternalTemplateManager.java:772) at com.xpn.xwiki.internal.template.InternalTemplateManager.renderFromSkin(InternalTemplateManager.java:745) at com.xpn.xwiki.internal.template.InternalTemplateManager.renderFromSkin(InternalTemplateManager.java:725) at com.xpn.xwiki.internal.template.InternalTemplateManager.render(InternalTemplateManager.java:711) at com.xpn.xwiki.internal.template.DefaultTemplateManager.render(DefaultTemplateManager.java:78) at com.xpn.xwiki.XWiki.evaluateTemplate(XWiki.java:2505) at com.xpn.xwiki.XWiki.parseTemplate(XWiki.java:2483) at com.xpn.xwiki.api.XWiki.parseTemplate(XWiki.java:983) at jdk.internal.reflect.GeneratedMethodAccessor252.invoke(Unknown Source) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.doInvoke(UberspectImpl.java:565) at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:548) at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:219) at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:369) at org.apache.velocity.runtime.parser.node.ASTReference.render(ASTReference.java:490) at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:144) at org.apache.velocity.runtime.directive.VelocimacroProxy.render(VelocimacroProxy.java:215) at org.apache.velocity.runtime.directive.RuntimeMacro.render(RuntimeMacro.java:328) at org.apache.velocity.runtime.directive.RuntimeMacro.render(RuntimeMacro.java:258) at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:301) at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:423) at org.apache.velocity.Template.merge(Template.java:358) at org.apache.velocity.Template.merge(Template.java:262) at org.xwiki.velocity.internal.DefaultVelocityEngine.evaluate(DefaultVelocityEngine.java:284) at com.xpn.xwiki.render.DefaultVelocityManager.evaluate(DefaultVelocityManager.java:316) at com.xpn.xwiki.internal.template.VelocityTemplateEvaluator.evaluateContent(VelocityTemplateEvaluator.java:95) at com.xpn.xwiki.internal.template.TemplateAsyncRenderer.evaluateContent(TemplateAsyncRenderer.java:217) at com.xpn.xwiki.internal.template.TemplateAsyncRenderer.renderVelocity(TemplateAsyncRenderer.java:180) at com.xpn.xwiki.internal.template.TemplateAsyncRenderer.render(TemplateAsyncRenderer.java:137) at com.xpn.xwiki.internal.template.TemplateAsyncRenderer.render(TemplateAsyncRenderer.java:53) at org.xwiki.rendering.async.internal.DefaultAsyncRendererExecutor.lambda$syncRender$0(DefaultAsyncRendererExecutor.java:267) at com.xpn.xwiki.internal.security.authorization.DefaultAuthorExecutor.call(DefaultAuthorExecutor.java:98) at org.xwiki.rendering.async.internal.DefaultAsyncRendererExecutor.syncRender(DefaultAsyncRendererExecutor.java:267) at org.xwiki.rendering.async.internal.DefaultAsyncRendererExecutor.render(DefaultAsyncRendererExecutor.java:250) at org.xwiki.rendering.async.internal.block.DefaultBlockAsyncRendererExecutor.render(DefaultBlockAsyncRendererExecutor.java:154) at com.xpn.xwiki.internal.template.InternalTemplateManager.render(InternalTemplateManager.java:772) at com.xpn.xwiki.internal.template.InternalTemplateManager.renderFromSkin(InternalTemplateManager.java:745) at com.xpn.xwiki.internal.template.InternalTemplateManager.renderFromSkin(InternalTemplateManager.java:725) at com.xpn.xwiki.internal.template.InternalTemplateManager.render(InternalTemplateManager.java:711) at com.xpn.xwiki.internal.template.DefaultTemplateManager.render(DefaultTemplateManager.java:78) at com.xpn.xwiki.XWiki.evaluateTemplate(XWiki.java:2505) at com.xpn.xwiki.XWiki.parseTemplate(XWiki.java:2483) at com.xpn.xwiki.api.XWiki.parseTemplate(XWiki.java:983) at jdk.internal.reflect.GeneratedMethodAccessor252.invoke(Unknown Source) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.doInvoke(UberspectImpl.java:565) at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:548) at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:219) at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:369) at org.apache.velocity.runtime.parser.node.ASTReference.render(ASTReference.java:490) at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:144) at org.apache.velocity.runtime.directive.VelocimacroProxy.render(VelocimacroProxy.java:215) at org.apache.velocity.runtime.directive.RuntimeMacro.render(RuntimeMacro.java:328) at org.apache.velocity.runtime.directive.RuntimeMacro.render(RuntimeMacro.java:258) at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:301) at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:144) at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:172) at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:144) at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:423) at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:191) at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:423) at org.apache.velocity.Template.merge(Template.java:358) at org.apache.velocity.Template.merge(Template.java:262) at org.xwiki.velocity.internal.DefaultVelocityEngine.evaluate(DefaultVelocityEngine.java:284) at com.xpn.xwiki.render.DefaultVelocityManager.evaluate(DefaultVelocityManager.java:316) at com.xpn.xwiki.internal.template.VelocityTemplateEvaluator.evaluateContent(VelocityTemplateEvaluator.java:95) at com.xpn.xwiki.internal.template.TemplateAsyncRenderer.evaluateContent(TemplateAsyncRenderer.java:217) at com.xpn.xwiki.internal.template.TemplateAsyncRenderer.renderVelocity(TemplateAsyncRenderer.java:180) at com.xpn.xwiki.internal.template.TemplateAsyncRenderer.render(TemplateAsyncRenderer.java:137) at com.xpn.xwiki.internal.template.TemplateAsyncRenderer.render(TemplateAsyncRenderer.java:53) at org.xwiki.rendering.async.internal.DefaultAsyncRendererExecutor.lambda$syncRender$0(DefaultAsyncRendererExecutor.java:267) at com.xpn.xwiki.internal.security.authorization.DefaultAuthorExecutor.call(DefaultAuthorExecutor.java:98) at org.xwiki.rendering.async.internal.DefaultAsyncRendererExecutor.syncRender(DefaultAsyncRendererExecutor.java:267) at org.xwiki.rendering.async.internal.DefaultAsyncRendererExecutor.render(DefaultAsyncRendererExecutor.java:250) at org.xwiki.rendering.async.internal.block.DefaultBlockAsyncRendererExecutor.render(DefaultBlockAsyncRendererExecutor.java:154) at com.xpn.xwiki.internal.template.InternalTemplateManager.render(InternalTemplateManager.java:772) at com.xpn.xwiki.internal.template.InternalTemplateManager.renderFromSkin(InternalTemplateManager.java:745) at com.xpn.xwiki.internal.template.InternalTemplateManager.renderFromSkin(InternalTemplateManager.java:725) at com.xpn.xwiki.internal.template.InternalTemplateManager.render(InternalTemplateManager.java:711) at com.xpn.xwiki.internal.template.DefaultTemplateManager.render(DefaultTemplateManager.java:78) at com.xpn.xwiki.XWiki.evaluateTemplate(XWiki.java:2505) at com.xpn.xwiki.web.Utils.parseTemplate(Utils.java:179) at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:576) at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:250) at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:425) at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:228) at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913) at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:449) at javax.servlet.http.HttpServlet.service(HttpServlet.java:626) at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at com.xpn.xwiki.web.ActionFilter.doFilter(ActionFilter.java:122) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.xwiki.wysiwyg.filter.ConversionFilter.doFilter(ConversionFilter.java:109) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.xwiki.container.servlet.filters.internal.SetHTTPHeaderFilter.doFilter(SetHTTPHeaderFilter.java:63) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.xwiki.container.servlet.filters.internal.SavedRequestRestorerFilter.doFilter(SavedRequestRestorerFilter.java:208) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.xwiki.container.servlet.filters.internal.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:111) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.xwiki.resource.servlet.RoutingFilter.doFilter(RoutingFilter.java:132) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:543) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:615) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:818) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1626) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.base/java.lang.Thread.run(Thread.java:834)
This page provides general resources about Catrobat's apps. They enable you to develop games and animations directly from your phone. You just have to stick bricks together!
Brick Documentation
Programming with the ease of playing with Lego? The coding blocks do just that. With their help, it's very easy to build your own programs.
Formula Editor
Without formulas, programs would be unthinkable. They help express what you actually want from the computer.
How-Tos
Have you ever thought about how to create clones or how to program a quiz? The How-To's show you how to program these things and more.
Feature Tutorials
Do you want to program your own game and would like to have some components for it? Here you can find program parts that you can use in your game.
Starter Projects
Do you want to see some finished projects? Here you can find some projects for the categories "Games", "Animation", "Interactive Art and Stories" and "Music and Dance". Download these starter projects, take a look at the code and modify it to your taste.
Beginners Course
Work through three units to get started with Pocket Code with our beginner course.
Check out this beginners course to immerse into the world of programing >>
Game Design
You want to improve your game and want to learn more about game mechanics?
Education
Do you teach with Catrobat apps? Want to find out about educational resources?
Chat & Forums
You need help and want to ask us a question?
Web Requests
Having trouble with the "Get web request" and "Get image from" bricks?
Download App
Download from Google Play Store
Download the iOS version from App Store
Download from Huawei AppGallery
Step By Step: Jungle Juggling
New to programming but want to develop your game? Check out this step-by-step guide and start creating your first game: