Java Reflection on Android Studio unable to find public static method to invoke

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The Java reflection code in my Android application invokes a public static method in a package B, from a package A.

Recently, after some Gradle upgrades, I am unable to invoke the same method. My implementation fails with a NoSuchMethodFound exception. How can I get the implementation to be able to find this method?

I've tried printing all the available methods from the class. The result is all public non-static methods. No static methods are available to be invoked. The method I want to invoke is a static "getInstance" method which initializes the class and returns a singleton instance.

Calling Code:

implementationClass = Class.forName(CLIENT_CLASS_NAME, false, ClientProvider.class.getClassLoader());
final Method method = implementationClass.getMethod("getInstance", (Class[]) null);
result = method.invoke(null, (Object[]) null);

Called Code:

/**
* Public static method to be reflected.
*/
public static ClientImpl getInstance() {
    return ClientImplHolder.INSTANCE;
}

/**
 * Private class used to hold the lazily initialized singleton instance.
 */
private static class ClientImplHolder {
    private static final ClientImpl INSTANCE = new ClientImpl();
}

When attempting to 'getMethod', I receive a NoSuchMethodException.

Not sure what I am doing wrong here, appreciate any help. Thanks!

If i understood correctly, you used reflection API wrong

just try this.

public class Test {

    public static void main(String[] args) {
        try {
            ClientImpl client = (ClientImpl) Class.forName(ClientImpl.class.getCanonicalName())
                    .getMethod("getInstance")
                    .invoke(null);

            System.out.println(client.toString() + " with some -> " + client.getSome());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

/**
 * Public static method to be reflected.
 */

class ClientImpl {

    private final int some;

    public int getSome() {
        return some;
    }

    private ClientImpl(int some) {
        this.some = some;
    }

    public static ClientImpl getInstance() {
        return ClientImplHolder.INSTANCE;
    }

    /**
     * Private class used to hold the lazily initialized singleton instance.
     */
    private static class ClientImplHolder {
        private static final ClientImpl INSTANCE = new ClientImpl(123);
    }
}

and it will put correctly result

ClientImpl@<hashcode> with some -> 123

When you use static methods in reflection API, you don't need to call it ClassLoader explicitly, you have to put it's canonicalName in argument, then you can call it's methods.

Java Reflection Example Tutorial, Using java reflection we can inspect a class, interface, enum, get their We can also use reflection to instantiate an object, invoke it's methods, change field values. Get Class Object; Get Super Class; Get Public Member Classes; Get This can cause you application to fail at runtime because of security manager. Security� Java is an object-oriented programming language. So, as an Android app developer, your primary goal is to describe objects. Your closely related goal is to describe objects’ close cousins — namely, classes. A class is the idea behind a certain kind of thing. An object is a concrete instance of a class. Here, a small …

Try to replace it,maybe it's a parameter problem.

    final Method method = implementationClass.getMethod("getInstance");
    result = method.invoke(null);

Calling Kotlin from Java, public remains public . KClass. Sometimes you need to call a Kotlin method with a parameter of type KClass . There is no automatic conversion from Class� Invoking a method that accepts array parameters using java reflection is a little bit tricky. The following code shows how to do it the right way and the possible errors you may see if you get it wrong. –Class with a method that accepts an array — public class Dao {public void Method2(String[] params){//do something}}

Starting in Android 9 (API level 28), the platform restricts which non-SDK interfaces your app can use. These restrictions apply whenever an app references a non-SDK interface or attempts to obtain its handle using reflection.

How do you unit test private methods?, You should then test the new class and call the public interface of it in your old class. In Java, you can simply give the method "default" access and put the unit test in still use pure standard JDK API to access private methods using reflection. Using TestNG your unit tests must be public static inner classes annotated� Reflection is a very useful approach to deal with the Java class at runtime, it can be use to load the Java class, call its methods or analysis the class at runtime. In this example, you will load a class called “ AppTest ” and call each of its methods at runtime.

Turns out Proguard was removing the method from the build since it was not being used elsewhere. Added an exception for the class and the issue went away.

How to make the perfect Singleton? | by Keval Patel, The Singleton is one of the Creational Design Patterns in Java. Instead, you are creating one public static method (commonly name as for You can see that both the instances are having the same hash code. API is, Java Reflection is a process of examining or modifying the run-time behavior of a class at run time. IllegalArgumentException from Method.invoke() Method.invoke() has been retrofitted to be a variable-arity method. This is an enormous convenience, however it can lead to unexpected behavior. The MethodTroubleToo example shows various ways in which Method.invoke() can produce confusing results.

Using Java Reflection, public class DumpMethods { public static void main(String args[]) { try { Class c The second step is to call a method such as getDeclaredMethods , to get a list� The same way as you invoke a method with arguments - Method.invoke(). From the Javadoc. If the number of formal parameters required by the underlying method is 0, the supplied args array may be of length 0 or null.

Typically, this would only be necessary if it is not possible to cast an instance of the class to the desired type in non-reflective code. Methods are invoked with java.lang.reflect.Method.invoke(). The first argument is the object instance on which this particular method is to be invoked. (If the method is static, the first argument should be

Object Reflection: invoke methods: 6. To get the calling method: 7. Get the class name in a static method: 8. Call a method dynamically (Reflection) 9. Call a class method with 2 arguments: 10. Using reflection to show all the methods of a class, 11. Invoke method through Java Reflection API: 12. Get a given method, and invoke it: 13.

Comments
  • if you are using latest version, access denied to non sdk interfaces and reflections
  • Did not work for me. I still get the same exception.
  • When I run implementationClass.getMethods() I get other methods from the same class which are available to use. Only getInstance (which is the only static method) is not available to use.
  • try getDeclaredMethod() instead of getMethod()