Question

您好我尝试将ArrayList发送到Fragment并且我遇到了这个问题（问题是在获取ArrayList时引起的）并且我在发送之前已经测试过它不是null，我发送了

arg.putStringArrayList("lp", li);

并通过

接收

ArrayList<String> lil = getArguments().getStringArrayList("lp");

这就是StackTrace：

04-18 20:43:55.153  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.ArrayList android.os.Bundle.getStringArrayList(java.lang.String)' on a null object reference
04-18 20:43:55.153  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ at com.pfe.elmokhtar.domotique.DetailFragment.onCreateView(DetailFragment.java:31)
04-18 20:43:55.158  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ at android.app.Fragment.performCreateView(Fragment.java:2053)
04-18 20:43:55.158  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:894)
04-18 20:43:55.158  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
04-18 20:43:55.158  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ at android.app.BackStackRecord.run(BackStackRecord.java:833)
04-18 20:43:55.158  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1452)
04-18 20:43:55.160  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ at android.app.FragmentManagerImpl$1.run(FragmentManager.java:447)
04-18 20:43:55.160  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ at android.os.Handler.handleCallback(Handler.java:739)
04-18 20:43:55.160  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ at android.os.Handler.dispatchMessage(Handler.java:95)
04-18 20:43:55.160  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ at android.os.Looper.loop(Looper.java:135)
04-18 20:43:55.160  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ at android.app.ActivityThread.main(ActivityThread.java:5254)
04-18 20:43:55.160  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ at java.lang.reflect.Method.invoke(Native Method)
04-18 20:43:55.160  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ at java.lang.reflect.Method.invoke(Method.java:372)
04-18 20:43:55.160  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:898)
04-18 20:43:55.160  17577-17577/com.pfe.elmokhtar.domotique W/System.err﹕ at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693)

这就是我实例化片段

的方式

public void onItemClick(AdapterView<?> arg0, View v, int position, long id) {
            dLayout.closeDrawers();
            Bundle arg = new Bundle();
            arg.putString("Menu", menu[position]);
            Fragment detail = new DetailFragment();
            FragmentManager fragmentManager = getFragmentManager();
            fragmentManager.beginTransaction().replace(R.id.content_frame, detail).commit();
            if (position == 0) {
            /*
            Pieces
             */
                InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
                invokeWS();  //WebService Invocation it run fine

                arg.putStringArrayList("lp", li);
                if(li.isEmpty())
                    System.out.println("null Catched !");
            }
                /*
            Pieces
             */


            if (position == 5) {

                Intent intent = new Intent(Home.this, CheckLoginActivity.class);
                intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(intent);

            }

        }
    });

这是Class detailfragment

package com.pfe.elmokhtar.domotique;

/**
 * Created by elmokhtar on 3/11/15.
 */

import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;

import java.util.ArrayList;


public class DetailFragment extends Fragment {


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle args) {
        View view = inflater.inflate(R.layout.detailfragment, container, false);
        //        TextView text= (TextView) view.findViewById(R.id.detail);
        ListView list = (ListView) view.findViewById(R.id.list);
        Bundle test = getArguments();
        //        String menu = getArguments().getString("Menu");
        try {

            ArrayList < String > lil = test.getStringArrayList("lp");
            System.out.println("done!");


            ArrayAdapter < String > adapter;
            adapter = new ArrayAdapter < String > (this.getActivity(), android.R.layout.simple_list_item_1, lil);
            list.setAdapter(adapter);
        } catch (Exception e) {
            e.printStackTrace();
        }
        //text.setText("test");
        return view;
    }
}

Answer 1

Fragment detail = new DetailFragment();
Bundle arg = new Bundle();
arg.putStringArrayList("lp", li);
detail.setArguments(arg);
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.content_frame, detail).commit();

Answer 2

将参数传递给片段，正如我在评论中所建议的那样：

public void onItemClick(AdapterView <? > arg0, View v, int position, long id) {
    dLayout.closeDrawers();
    Bundle arg = new Bundle();
    arg.putString("Menu", menu[position]);
    arg.putStringArrayList("lp", li);
    Fragment detail = new DetailFragment();
    detail.setArguments(arg);
    FragmentManager fragmentManager = getFragmentManager();
    fragmentManager.beginTransaction().replace(R.id.content_frame, detail).commit();
    //...
}

Answer 3

创建片段实例并向其传递值的首选方法

活动：像这样创建片段实例

Fragment detail=DetailFragment.newInstace(li);
fragmentManager.beginTransaction().replace(R.id.content_frame, detail).commit();

片段：始终为片段创建默认构造函数

Fragment的所有子类都必须包含公共无参数构造函数。

 public class DetailFragment extends Fragment {

        public DetailFragment() {
        }

        public static Fragment newInstace(ArrayList<String> items) {
            Fragment fragment = new DetailFragment();
            Bundle bundle = new Bundle();
            bundle.putStringArrayList("key", items);
            fragment.setArguments(bundle);
            return fragment;
        }

        //your stuff

    }

尝试使用片段中的Bundle调用虚方法java.util.ArrayList

3 个答案: