Question

我的代码有轻微的问题，我在这个网站搜索但仍未找到最佳答案我将数据发送到我的标签片段，这是我的代码

我的活动课

public class MainActivity extends AppCompatActivity 

    private ViewPager pager;
    private Toolbar toolbar;
    private TabLayout tabs;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        pager=(ViewPager) findViewById(R.id.pager);
        tabs=(TabLayout) findViewById(R.id.tabs);

        pager.setAdapter(new TabFragmentPagerAdapter(getSupportFragmentManager()));
        tabs.setupWithViewPager(pager);
        tabs.setTabGravity(TabLayout.GRAVITY_FILL);

        Bundle bundle = new Bundle();
        bundle.putString("edttext", "data From Activity");
        // set Fragmentclass Arguments
        tab1Fragment fragobj = new tab1Fragment();
        fragobj.setArguments(bundle);

    }
}

这是我的tab1类

public class tab1Fragment extends Fragment 

    public tab1Fragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment

        View view= inflater.inflate(R.layout.fragment_tab1, container, false);
        TextView tes=(TextView) view.findViewById(R.id.testtab1);
        String strtext = getArguments().getString("edttext");

        tes.setText("tes :"+ strtext);
        return  view;
    }
}

和我的页面片段适配器

public class TabFragmentPagerAdapter extends FragmentPagerAdapter 

    String[] title = new String[]{
            "Tab 1", "Tab 2", "Tab 3"
    };

    public TabFragmentPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position){
        Fragment fragment=null;
        switch (position){
            case 0:
                fragment=new tab1Fragment();
                break;
            case 1:
                fragment=new tab2Fragment();
                break;
            case 2:
                fragment=new tab3Fragment();
                break;
            default:
                fragment=null;
                break;
        }
        return  fragment;
    }
    @Override
    public  CharSequence getPageTitle(int position){
        return  title[position];
    }
    @Override
    public  int getCount(){
        return  title.length;
    }
}

当我运行错误

显示java.lang.NullPointerException

请帮助

Answer 1

在您发送的AppCompatActivity

中

tab1Fragment fragobj = new tab1Fragment();
fragobj.setArguments(bundle);

但在您的TabFragmentPagerAdapter

中

fragment=new tab1Fragment();
            break;

它有空参数

内部开关

switch (position){
    case 0:
      fragment=new tab1Fragment();               
      Bundle bundle = new Bundle();
      bundle.putString("edttext", "data From Activity");
      fragment.setArguments(bundle);
    break;

Answer 2

可能是你得到了NullPointerException，因为你的片段在getItem内没有参数再次初始化。

试试这种方式。

@Override
public Fragment getItem(int position){
    Fragment fragment=null;

    Bundle bundle = new Bundle();
    bundle.putString("edttext", "data From Activity");

    switch (position){
        case 0:
            fragment=new tab1Fragment();
            fragment.setArguments(bundle);
            break;
        case 1:
            fragment=new tab2Fragment();
            break;
        case 2:
            fragment=new tab3Fragment();
            break;
        default:
            fragment=null;
            break;
    }
    return  fragment;
}

注意：确保在MainActivity和tab1Fragment中导入相同版本的Fragment。

Answer 3

我认为你首先使用Youractivity的On调用启动Tab1Frament（）你可以这样做......

用过这个..

   if (savedInstanceState == null) {

 FragmentTransaction ft = this.getSupportFragmentManager().beginTransaction();

tab1Fragment fragobj = new tab1Fragment();

  Bundle bundle = new Bundle();
  bundle.putString("edttext", "data From Activity");
 // set Fragmentclass Arguments

 fragobj.setArguments(bundle);


    ft.replace(R.id.frame, fragobj);
    ft.addToBackStack(null);
    ft.commit();
  }

而不是

 Bundle bundle = new Bundle();
 bundle.putString("edttext", "data From Activity");
 // set Fragmentclass Arguments
 tab1Fragment fragobj = new tab1Fragment();
 fragobj.setArguments(bundle);

Answer 4

在片段中创建一个函数以传递活动中的数据，就像在getters和setters中为对象类所做的那样：

// Fragment
class TabFragment extends Fragment{

    public String myDataString;

    ...

    public void setTabInfo(String myActivityString){
        this.myDataString = myActivityString;
    }
}

// Activity

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    ...

    TabFragment frag = new TabFragment();
    frag.setTabInfo("data From Activity");

}

我更喜欢这种方法，因为对于对象，在使用Bundle的情况下无需直接序列化对象即可直接传递数据

Answer 5

也许它的答案很晚，但是有些东西对我有用：

将捆绑包发送到适配器：

  Bundle bundle = new Bundle();
  bundle.putString("edttext", "data From Activity");
  pager.setAdapter(new TabFragmentPagerAdapter(getSupportFragmentManager(), bundle));

在适配器中扩展构造函数：

Bundle bundle;

  public TabFragmentPagerAdapter(FragmentManager fm, Bundle bundle) {
    super(fm);
    this.bundle=bundle;
}

并将其发送到片段：

switch (position){
        case 0:
            fragment=new tab1Fragment();
            fragment.setArguments(bundle);
            break;

希望它会有所帮助。 }

将数据从Activity发送到Tab Fragment

5 个答案: