Inconvertable类型Android

Question

我收到了一个奇怪的错误。在我的代码中，我试图将WorkoutDetailFragment强制转换为WorkoutDetailFragment类型的对象。以下是WorkoutDetailFragment的代码：

package com.hfad.workout;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.app.Fragment;

public class WorkoutDetailFragment extends Fragment {
    private long workoutId;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        if(savedInstanceState != null)
        {
            workoutId = savedInstanceState.getLong("workoutId");
        }
        android.support.v4.app.FragmentTransaction ft = getChildFragmentManager().beginTransaction();
        com.hfad.workout.StopwatchFragment stopwatchFragment = new com.hfad.workout.StopwatchFragment();
        ft.replace(R.id.stopwatch_container, stopwatchFragment);
        ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
        ft.commit();
        return inflater.inflate(R.layout.fragment_workout_detail, container, false);
    }
    @Override
    public void onStart(){
        super.onStart();
        View view = getView();
        if(view != null)
        {
            TextView title = (TextView) view.findViewById(R.id.textTitle);
            Workout workout = Workout.workouts[(int) workoutId];
            title.setText(workout.getName());
            TextView description = (TextView) view.findViewById(R.id.textDescription);
            description.setText(workout.getDescription());
        }
    }

    @Override
    public void onSaveInstanceState(Bundle savedInstanceState)
    {
        savedInstanceState.putLong("workoutId", workoutId);
    }

    public void setWorkout(long id)
    {
        this.workoutId = id;
    }
}

此类名为DetailActivity的错误发生在：＆＃34; Inconvertable类型;无法投射＆＃39; android.app.Fragment＆＃39; to＆＃39; com.hfad.workout.WorkoutDetailFragment＆＃39;。这是DetailActivity的代码，我在有错误的代码片段顶部发表评论：

    package com.hfad.workout;

    import android.app.Activity;
    import android.os.Bundle;

    public class DetailActivity extends Activity
    {
        public static final String EXTRA_WORKOUT_ID = "id";

        @Override
        protected void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_detail);
            //This is where the error occurs: 
WorkoutDetailFragment workoutDetailFragment = (WorkoutDetailFragment) getFragmentManager().findFragmentById(R.id.detail_frag);
            int workoutId = (int) getIntent().getExtras().get(EXTRA_WORKOUT_ID);
            workoutDetailFragment.setWorkout(workoutId);
        }
    }

非常感谢任何帮助，如果需要任何其他代码或进一步说明，请告诉我们。）

Answer 1

如果您使用支持ActivityCompat，则需要使用Fragment而不是普通的旧活动。常规Activity对支持片段一无所知，并且它们不共享任何共同的祖先 - 只是符合相同的接口（不是实际的Interface）。