DrKLO/Telegram · error · IllegalStateException

{positionDescription}: Unable to find LayoutManager {classNa

Error message

{positionDescription}: Unable to find LayoutManager {className}

What it means

During XML inflation of RecyclerView, the app:layoutManager class name is resolved by Class.forName. ClassNotFoundException produces 'Unable to find LayoutManager <className>'. The class string in the attribute could not be loaded at runtime.

Source

Thrown at TMessagesProj/src/main/java/androidx/recyclerview/widget/RecyclerView.java:871

                    Constructor<? extends LayoutManager> constructor;
                    Object[] constructorArgs = null;
                    try {
                        constructor = layoutManagerClass
                                .getConstructor(LAYOUT_MANAGER_CONSTRUCTOR_SIGNATURE);
                        constructorArgs = new Object[]{context, attrs, defStyleAttr, defStyleRes};
                    } catch (NoSuchMethodException e) {
                        try {
                            constructor = layoutManagerClass.getConstructor();
                        } catch (NoSuchMethodException e1) {
                            e1.initCause(e);
                            throw new IllegalStateException(attrs.getPositionDescription()
                                    + ": Error creating LayoutManager " + className, e1);
                        }
                    }
                    constructor.setAccessible(true);
                    setLayoutManager(constructor.newInstance(constructorArgs));
                } catch (ClassNotFoundException e) {
                    throw new IllegalStateException(attrs.getPositionDescription()
                            + ": Unable to find LayoutManager " + className, e);
                } catch (InvocationTargetException e) {
                    throw new IllegalStateException(attrs.getPositionDescription()
                            + ": Could not instantiate the LayoutManager: " + className, e);
                } catch (InstantiationException e) {
                    throw new IllegalStateException(attrs.getPositionDescription()
                            + ": Could not instantiate the LayoutManager: " + className, e);
                } catch (IllegalAccessException e) {
                    throw new IllegalStateException(attrs.getPositionDescription()
                            + ": Cannot access non-public constructor " + className, e);
                } catch (ClassCastException e) {
                    throw new IllegalStateException(attrs.getPositionDescription()
                            + ": Class is not a LayoutManager " + className, e);
                }
            }
        }
    }

View on GitHub (pinned to 45ab8f4308)

Solutions

1. Verify the fully-qualified class name in app:layoutManager matches a real class on the runtime classpath.
2. If using '.'-relative names, confirm applicationId matches the package containing the class.
3. Add a ProGuard -keep rule for any LayoutManager referenced from XML so obfuscation does not rename it.

Example fix

<!-- before -->
<androidx.recyclerview.widget.RecyclerView
    app:layoutManager="androidx.Recyclerview.widget.GridLayoutManager"/>

<!-- after -->
<androidx.recyclerview.widget.RecyclerView
    app:layoutManager="androidx.recyclerview.widget.GridLayoutManager"/>

static Class<?> resolveLayoutManagerClass(Context ctx, String name) throws ClassNotFoundException {
    String fqn = name.charAt(0) == '.' ? ctx.getPackageName() + name : name;
    return Class.forName(fqn, false, ctx.getClassLoader());
}

null

try {
    Class<?> c = Class.forName(fqn);
    if (!RecyclerView.LayoutManager.class.isAssignableFrom(c)) throw new IllegalStateException();
} catch (ClassNotFoundException e) {
    // log and fall back to a programmatic LayoutManager
    recyclerView.setLayoutManager(new LinearLayoutManager(ctx));
}

When it happens

Trigger: app:layoutManager points to a class that does not exist, is misspelled, uses a wrong package, or has been renamed/removed by ProGuard/R8 obfuscation. A relative name (leading '.') is prefixed with the app package — a wrong package base yields a missing class.

Common situations: Typo in the class FQN in XML. LayoutManager lives in a library that is not on the classpath at runtime (e.g. dynamic-feature module). Obfuscation renamed the class so the XML string no longer matches. Wrong applicationId makes the '.'-relative resolution resolve to a non-existent package.

Related errors

• {positionDescription}: Error creating LayoutManager {classNa
• {positionDescription}: Could not instantiate the LayoutManag
• {positionDescription}: Cannot access non-public constructor
• {positionDescription}: Class is not a LayoutManager {classNa
• view is not a child, cannot hide {}

AI-assisted analysis of DrKLO/Telegram@45ab8f4308 (2026-08-14). Data as JSON: /api/errors/a0df8cd20e249ec2. Report an issue: GitHub.