Java – Incompatible type: MainActivity cannot be converted to LifecycleOwner

MainActivity cannot be converted to LifecycleOwner
I used it as a LiveCycle owner, but it was rejected and I got an error as shown in the image.
I’m working on API 25 and I think this issue might be related to this version
This is information about my SDK

compileSdkVersion 25
buildToolsVersion '25.0.2'

Here is my code :

private void retrieveTasks() {
    Log.d(TAG, "Actively retrieving the tasks from the DataBase");
     Extract all this logic outside the Executor and remove the Executor
     Fix compile issue by wrapping the return type with LiveData
    LiveData<List<TaskEntry>> tasks = mDb.taskDao().loadAllTasks();
     Observe tasks and move the logic from runOnUiThread to onChanged
    tasks.observe(this, new Observer<List<TaskEntry>>() {
        @Override
        public void onChanged(@Nullable List<TaskEntry> taskEntries) {
            Log.d(TAG, "Receiving database update from LiveData");
            mAdapter.setTasks(taskEntries);
        }
    });
}

I put the LiveData dependencies into my Gradle

compile "android.arch.lifecycle:extensions:1.0.0"
annotationProcessor "android.arch.lifecycle:compiler:1.0.0"

If anyone knows the cause of the problem, please let me know

Support Library 26.1.0 and later Fragments and Activities already implement the LifecycleOwner interface by default

But in version 25 you need to implement the LifecycleOwner interface
For example

public class MyActivity extends Activity implements LifecycleOwner {
    private LifecycleRegistry mLifecycleRegistry;

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

mLifecycleRegistry = new LifecycleRegistry(this);
        mLifecycleRegistry.markState(Lifecycle.State.CREATED);
    }

@Override
    public void onStart() {
        super.onStart();
        mLifecycleRegistry.markState(Lifecycle.State.STARTED);
    }

@NonNull
    @Override
    public Lifecycle getLifecycle() {
        return mLifecycleRegistry;
    }
}

Source: Handling lifecycles with lifecycle-aware components