Question

我的片段类从支持v4导入正确。但是，当我在MainActivity中使用getFragmentManager时，我收到错误“无法强制转换android.app.Fragment ”。不知何故，getFragmentManager使用的是旧片段，而不是supprt.v4.app.Fragment。你知道我应该用什么方法吗？

package example.hfad.fragments_chapter7;

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

public class WorkoutDetailFragment extends Fragment {
    private long workoutId;

    public WorkoutDetailFragment() {
        // Required empty public constructor
    }

    @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);
    }

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

我的MainActicity是这样的：**最后一行

gerFragmentManager（）。findFragmentById

抱怨我无法将android.app.Fragment强制转换为上面定义的自定义片段类。**

package example.hfad.fragments_chapter7;
import android.app.Activity;
import android.os.Bundle;

public class MainActivity extends Activity {
    @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);

    }
}

Answer 1

您的片段继承自android.support.v4.app.Fragment，因此您应该使用getSupportFragmentManager()。如果它继承自android.app.Fragment，则只能使用getFragmentManager()

替换

WorkoutDetailFragment frag = (WorkoutDetailFragment) getFragmentManager().findFragmentById(R.id.detail_frag);

与

WorkoutDetailFragment frag = (WorkoutDetailFragment) getSupportFragmentManager().findFragmentById(R.id.detail_frag);

Answer 2

试试这段代码：

import android.support.v4.app.FragmentActivity;
public class MainActivity extends FragmentActivity {

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

Android Fragment：“无法投射android.app.Fragment”

2 个答案: