Cast object to interface when created via reflection
- by Al
I'm trying some stuff out in Android and I'm stuck at when trying to cast a class in another .apk to my interface. I have the interface and various classes in other .apks that implement that interface. I find the other classes using PackageManager's query methods and use Application#createPackageContext() to get the classloader for that context. I then load the class, create a new instance and try to cast it to my interface, which I know it definitely implements.
When I try to cast, it throws a class cast exception. I tried various things like loading the interface first, using Class#asSubclass, etc, none of which work. Class#getInterfaces() shows the interface is implemented. My code is below:
PackageManager pm = getPackageManager();
List<ResolveInfo> lr = pm.queryIntentServices(new Intent("com.example.some.action"), 0);
ArrayList<MyInterface> list = new ArrayList<MyInterface>();
for (ResolveInfo r : lr) {
try {
Context c = getApplication().createPackageContext(r.serviceInfo.packageName, Context.CONTEXT_IGNORE_SECURITY | Context.CONTEXT_INCLUDE_CODE);
ClassLoader cl = c.getClassLoader();
String className = r.serviceInfo.name;
if (className != null) {
try {
Class<?> cls = cl.loadClass(className);
Object o = cls.newInstance();
if (o instanceof MyInterface) { //fails
list.add((MyInterface) o);
}
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} // some exceptions removed for readability
}
} catch (NameNotFoundException e1) {
e1.printStackTrace();
}
