Question

在我的活动A中，它有一个listView。单击listView时，它会将 ID 传递给Activity B，后者使用适配器显示与所选选项卡对应的数据。

活动A

 listViewEdit.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> listView, View view,
                                    int position, long id) {
                // Get the cursor, positioned to the corresponding listview_item_row in the result set
                Cursor cursor = (Cursor) listView.getItemAtPosition(position);

                // Get the state's capital from this listview_item_row in the database.
                 ID =
                        cursor.getLong(cursor.getColumnIndexOrThrow("_id"));
                Intent intent=new Intent(getApplicationContext(),ActivityB.class);
                intent.putExtra("ID",ID);
                startActivity(intent);


            }
        });
    }

活动B

 protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_b);
        id=getIntent().getExtras().getString("ID");
        viewPager = (ViewPager) findViewById(R.id.viewPager);
        tabsAdapter = new TabsFragmentPagerAdapter(getSupportFragmentManager());
        viewPager.setAdapter(tabsAdapter);
        actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        for(int i=0; i<3; i++){
            actionBar.addTab(actionBar.newTab().setText(item[i]).setTabListener(this));
        }
        viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

            @Override
            public void onPageSelected(int arg) {
                // TODO Auto-generated method stub
                actionBar.setSelectedNavigationItem(arg);
            }

            @Override
            public void onPageScrolled(int arg0, float arg1, int arg2) {
                // TODO Auto-generated method stub

            }

            @Override
            public void onPageScrollStateChanged(int arg0) {
                // TODO Auto-generated method stub

            }
        });

    }

TabsFragmentPagerAdapter

  @Override
    public Fragment getItem(int index) {
        // TODO Auto-generated method stub
        Fragment fragment=null;

        if(index == 0) {

            Bundle bundle = new Bundle();
            bundle.putLong("ID", Edit.ID);
            Log.e("ID", Edit.ID+"");
            fragment.setArguments(bundle);
            return new EditInformation();

        }

        if(index == 1)
            return new Edit_WorkForce();
        if(index == 2)
            return new Edit_WorkDetails();


        return null;
    }

EditInformation

 public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View edit_info = inflater.inflate(R.layout.edit_information, container, false);
        Name=(EditText)edit_info.findViewById(R.id.Edit_name);
        Status=(EditText)edit_info.findViewById(R.id.Edit_status);
        Weather=(EditText)edit_info.findViewById(R.id.Edit_weather);
        Date=(EditText)edit_info.findViewById(R.id.Edit_date);
        ts = new com.example.project.myapplication.API.InfoAPI(getActivity());
        Bundle bundle = this.getArguments();
        if(getArguments()!=null)
        {
            ID=bundle.getLong("ID");
        }
        RetrieveInformation(ID);

        return edit_info;
    }

当我点击活动A中的列表时，应用程序崩溃并显示如下错误。

  Process: com.example.project.myapplication, PID: 3103
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.Fragment.setArguments(android.os.Bundle)' on a null object reference
            at com.example.project.myapplication.Adapter.TabsFragmentPagerAdapter.getItem(TabsFragmentPagerAdapter.java:35)
            at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:97)
            at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:870)

我可以从活动A获取ID，这是错误引用fragment.setArguments(bundle);

的行

Answer 1

在 TabsFragmentPagerAdapter 中，更改

Fragment fragment=null;
if(index == 0) {
    Bundle bundle = new Bundle();
    bundle.putLong("ID", Edit.ID);
    Log.e("ID", Edit.ID+"");
    fragment.setArguments(bundle);
    return new EditInformation();
}
...

到

@Override
public Fragment getItem(int index) {
    // TODO Auto-generated method stub
    Fragment fragment=null;
    if(index == 0) {
        fragment = new EditInformation();
        Bundle bundle = new Bundle();
        bundle.putLong("ID", Edit.ID);
        Log.e("ID", Edit.ID+"");
        fragment.setArguments(bundle);
        return fragment;
    }
    ...
}

在设置参数之前，您需要初始化 EditInformation片段。

尝试在空对象引用上调用虚方法'void android.app.Fragment.setArguments（android.os.Bundle）'

1 个答案: