您能指導我代碼有什么問題嗎？

Question

MainActivity.java中強制轉換WorkoutDetailFragment的行顯示無法完成的錯誤。 請告訴我為什么它不起作用。 我從一本書中復制了代碼。

主要活動

package gangster.workout;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    WorkoutDetailFragment frag = (WorkoutDetailFragment) getFragmentManager().findFragmentById(R.id.detail_frag);
    frag.setWorkout(1);
}
}

鍛煉Java

package gangster.workout;


public class Workout {
private String name;
private String description;

public static final Workout[] workouts = {
        new Workout("The Limb Loosener" , " Pta nhi kya ksgdrna hai isme") ,
        new Workout("The Timb Loosener" , " Pta nhi kya asdfasasfasasdkrna hai isme") ,
        new Workout("The Pimb Loosener" , " Pta nhi kyaasf krna hai isme") ,
        new Workout("The Zimb Loosener" , " Pta nhi kyasfasa krna hai isme") ,
};
private Workout(String name , String description){
    this.name = name;
    this.description = description;
}

public String getDescription(){
    return description;
}
public String getName(){
    return name;
}
public String toString(){
    return this.name;
}
}

WorkoutDetailFragment.java

package gangster.workout;


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


public class WorkoutDetailFragment extends Fragment {
private long workoutId;

public void setWorkout(long id) {

    this.workoutId = id;
}

@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 View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_workout_detail, container, false);
}

}

Answer 1

使用getSupportFragmentManager()而不是getFragmentManager()