java - 从父 Activity 中获取 fragment 中不同字段的值

Question

我有一个 addActivity 托管 5 个 fragment ，在每个 fragment 上我有一些字段要填充。
我想从 addActivity< 中获取这些字段的值。我试过类似的东西:
AddActivity.java

public class AddActivity extends FragmentActivity {
    ViewPager vp;
    ProgressDialog dialog;

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

        vp = (ViewPager) findViewById(R.id.pager);
        PagerAdapter pa = new FragPagerAdapter(getSupportFragmentManager());
        vp.setAdapter(pa);}

    public class getValueOfFields() {
  //here I'm trying to get the value of differents fields in the different fragments but I get 

always "editText == Null" If the editText is in The fragment 1 or 2 or 3 it will get null
     EditText editTextFromFrag1 = (EditText) findViewById(R.id.visitDateFiled); // this == null
// If the EditText is in Fragment 4 or 5 it will get the value normaly without any issue


             ...}

FragPagerAdapter.java

public class FragPagerAdapter extends FragmentPagerAdapter {
    public FragPagerAdapter(FragmentManager fm) {
        super(fm);}

    @Override
    public Fragment getItem(int index) {
        switch (index) {
            case 0:
                return new FirstFragment();
            case 1:
                return new SecondFragment();
            case 2:
                return new HousingFragment();
            case 3:
                return new FeedingFragment();
            case 4:
                return new OtherFragment();
        }

        return null;
    }

    @Override
    public int getCount() {
        return 5; }

其他 fragment .java公共(public)类 OtherFragment 扩展 fragment { 按钮 btn;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_other, container, false);
    btn = (Button) view.findViewById(R.id.send);
    btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
//Call the getValueOfFields (After filling the differnts fields the user click the send button) 
                ((AddActivity) getActivity()).getValueOfFields();
            }
        });
        return view;
    }
}

已更新
如果它们位于 fragment 1 或 2 或 3 中，我得到的问题总是 EditText(以及要获取的其他字段)等于 null。否则我会得到正确的值

Answer 1

你好 Chlebta 你需要设置 pager.setOffscreenPageLimit(5);。当您在 fragment 之间滑动时， fragment 可能会被破坏。这就是为什么你得到空值。

或者一个简单的解决方案是你设置

pager.setOnPageChangeListener(new OnPageChangeListener() {

                @Override
                public void onPageSelected(int arg0) {
                    // Now here you get your fragment object. 
                   // To get the Fragment Object you need to store them in an ArrayList in your FragPagerAdapter class.
                  //  create a method `getMyFraggment ` which return your Fragment from Arraylist.
                 //   Now create a method in your each Fragment which return your EditText values. Here you can use HashMap to store the values.

                // Here you use switch cases to get your Fragment Object I just wrote 1 here                        
                MyFragment f =  ((FragPagerAdapter)pager.getAdapter()).getMyFraggment(arg0);

                HashMap <String, String> hashMap = f.getValuesFromFragment();
                myValues.putAll(hashMap);    // myValues is global hashmap in your Activity. 
               // Now you get All values in your Global HashMap. But remember here you can get duplicate values if user swipe a fragment more than 1 time. You should do a logic here to remove duplicate values.

                }

                @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

                }
            });