{"record":{"id":"1d9da8d09ad321c5","repo":"DrKLO/Telegram","slug":"positiondescription-error-creating-layoutmanage","errorCode":null,"errorMessage":"{positionDescription}: Error creating LayoutManager {className}","messagePattern":"(.+?): Error creating LayoutManager (.+?)","errorType":"exception","errorClass":"IllegalStateException","httpStatus":null,"severity":"error","filePath":"TMessagesProj/src/main/java/androidx/recyclerview/widget/RecyclerView.java","lineNumber":864,"sourceCode":"                        classLoader = this.getClass().getClassLoader();\n                    } else {\n                        classLoader = context.getClassLoader();\n                    }\n                    Class<? extends LayoutManager> layoutManagerClass =\n                            Class.forName(className, false, classLoader)\n                                    .asSubclass(LayoutManager.class);\n                    Constructor<? extends LayoutManager> constructor;\n                    Object[] constructorArgs = null;\n                    try {\n                        constructor = layoutManagerClass\n                                .getConstructor(LAYOUT_MANAGER_CONSTRUCTOR_SIGNATURE);\n                        constructorArgs = new Object[]{context, attrs, defStyleAttr, defStyleRes};\n                    } catch (NoSuchMethodException e) {\n                        try {\n                            constructor = layoutManagerClass.getConstructor();\n                        } catch (NoSuchMethodException e1) {\n                            e1.initCause(e);\n                            throw new IllegalStateException(attrs.getPositionDescription()\n                                    + \": Error creating LayoutManager \" + className, e1);\n                        }\n                    }\n                    constructor.setAccessible(true);\n                    setLayoutManager(constructor.newInstance(constructorArgs));\n                } catch (ClassNotFoundException e) {\n                    throw new IllegalStateException(attrs.getPositionDescription()\n                            + \": Unable to find LayoutManager \" + className, e);\n                } catch (InvocationTargetException e) {\n                    throw new IllegalStateException(attrs.getPositionDescription()\n                            + \": Could not instantiate the LayoutManager: \" + className, e);\n                } catch (InstantiationException e) {\n                    throw new IllegalStateException(attrs.getPositionDescription()\n                            + \": Could not instantiate the LayoutManager: \" + className, e);\n                } catch (IllegalAccessException e) {\n                    throw new IllegalStateException(attrs.getPositionDescription()\n                            + \": Cannot access non-public constructor \" + className, e);\n                } catch (ClassCastException e) {","sourceCodeStart":846,"sourceCodeEnd":882,"githubUrl":"https://github.com/DrKLO/Telegram/blob/45ab8f4308496e1f01026a97fcdb0d58a5274474/TMessagesProj/src/main/java/androidx/recyclerview/widget/RecyclerView.java#L846-L882","documentation":"When a LayoutManager class name is declared in XML (app:layoutManager), RecyclerView reflects to instantiate it. It first tries the (Context, AttributeSet, int, int) constructor; on NoSuchMethodException it falls back to the no-arg constructor. If NEITHER exists, it throws 'Error creating LayoutManager' — the class exists but lacks an invokable constructor.","triggerScenarios":"Declaring app:layoutManager=\"com.example.MyGridManager\" in layout XML where MyGridManager only exposes a constructor like (Context, int) or (int) and has no public default constructor nor the 4-arg signature.","commonSituations":"Custom LayoutManager written with only a (Context) or (int, int) constructor. Constructor was made private for a builder pattern. ProGuard/R8 stripped or renamed a constructor that the reflection path expects.","solutions":["Add a public constructor matching LAYOUT_MANAGER_CONSTRUCTOR_SIGNATURE (Context, AttributeSet, int, int) to your LayoutManager subclass.","Or add a public no-arg constructor as the fallback.","Ensure the class and its constructor are not stripped by ProGuard (add a keep rule for LayoutManager subclasses referenced in XML)."],"exampleFix":"// before\npublic class MyGridManager extends GridLayoutManager {\n    public MyGridManager(Context ctx, int span) { super(ctx, span); }\n}\n\n// after\npublic class MyGridManager extends GridLayoutManager {\n    public MyGridManager() { super(/* defaults */); }\n    public MyGridManager(Context ctx, int span) { super(ctx, span); }\n}","handlingStrategy":"validation","validationCode":"// Verify the LayoutManager subclass has a usable constructor at build time\nstatic boolean hasUsableCtor(Class<?> c) throws NoSuchMethodException {\n    try {\n        c.getConstructor(Context.class, AttributeSet.class, int.class, int.class);\n        return true;\n    } catch (NoSuchMethodException e) {\n        c.getConstructor();\n        return true;\n    }\n}","typeGuard":"static boolean isInstantiableLayoutManager(Class<?> c) {\n    return RecyclerView.LayoutManager.class.isAssignableFrom(c)\n        && !Modifier.isAbstract(c.getModifiers())\n        && !c.isInterface();\n}","tryCatchPattern":"null","preventionTips":["Always provide a public no-arg constructor on custom LayoutManagers referenced in XML.","Keep a -keep rule for LayoutManager subclasses referenced from layouts.","Add an instrumentation test that inflates each layout containing app:layoutManager."],"tags":["recyclerview","layoutmanager","xml-inflation","reflection"],"backgroundTag":null,"analyzedSha":"45ab8f4308496e1f01026a97fcdb0d58a5274474","analyzedAt":"2026-08-14T05:19:30.815Z","schemaVersion":2},"datasetVersion":"2026-08-14T10:17:34.591Z"}