Android:从活动中输入数据后，刷新查看Pager片段内容

我只是Android的新手，我已经研究了数周，但是我仍然找不到使它起作用的方法。：（

我在主要活动中有4个片段选项卡（动态创建）。我从主要活动中的提示中输入金额，然后将其保存到数据库中。我想在提示中按"确定"按钮后，在第一个选项卡中更新值，以将保存在数据库中的金额并在第一个选项卡片段中显示。

如何在第一个选项卡中刷新值？

在我的片段中，我有此代码以显示数据。但这仅在最初显示数据，而不是在我从主要活动中输入金额后。

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
  final View rootview = inflater.inflate(R.layout.home_tab, container, false);
  super.onCreate(savedInstanceState);
  myDb = new DatabaseHelper(getContext());
  viewBudget(rootview);
  return rootview;
}
public View viewBudget(final View rootview) {
  //get values from database and display in dynamic views
}

我非常感谢您的回答。预先感谢您。

编辑：这是我的完整代码：

public View viewBudget(final View rootview) { //display funds dynamically in config layout | LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState
  //Cursor res = myDb.getAllData();
  //String[] textArray = {"One", "Two", "Three", "Four"};
  Double budget, totalpct, temp_pct;
  Cursor res2 = myDb.getConfigData();
  res2.moveToFirst();
  Cursor res3 = myDb.getLatestIncome();
  res3.moveToFirst();
  //showMessage("Number of rows",Integer.toString(res2.getCount()));
  Cursor res4 = myDb.getTotalExpenes();
  res4.moveToFirst();
  //view contents of config table
  if (res2.getCount() == 0) {
    // show message
    //showMessage("Error","Nothing found");
    //return;
  }
  final ScrollView scrollView = (ScrollView) rootview.findViewById(R.id.scroll_budget);
  LinearLayout linearLayout = (LinearLayout) rootview.findViewById(R.id.ll_budget);
  LinearLayout llh_texts = new LinearLayout(getActivity());
  llh_texts.setOrientation(LinearLayout.HORIZONTAL);
  LinearLayout llh_texts2 = new LinearLayout(getActivity());
  llh_texts2.setOrientation(LinearLayout.HORIZONTAL);
  LinearLayout llh_texts3 = new LinearLayout(getActivity());
  llh_texts3.setOrientation(LinearLayout.HORIZONTAL);
  LinearLayout llh_texts4 = new LinearLayout(getActivity());
  llh_texts4.setOrientation(LinearLayout.HORIZONTAL);
  LinearLayout.LayoutParams lp_llh_texts = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.MATCH_PARENT);
  llh_texts.setLayoutParams(lp_llh_texts);
  //final View linearLayout = getActivity().findViewById(R.id.ll_config);
  linearLayout.removeAllViews(); //clear layout first - LINE WITH ISSUE
  linearLayout.setGravity(Gravity.CENTER);
  //LinearLayout.LayoutParams lp2 = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,ViewGroup.LayoutParams.WRAP_CONTENT);
  //LinearLayout.LayoutParams lp3 = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
  //compute for value of budget
  budget = 0.0;
  totalpct = 0.0;
  linearLayout.addView(llh_texts); //add button h.linearlayout to parent linearlayout inside scrollview
  TextView textBudget = new TextView(getActivity());
  TextView labelBudget = new TextView(getActivity());
  labelBudget.setText("Budget: ");
  llh_texts.addView(labelBudget);
  llh_texts.addView(textBudget);
  TextView textIncome = new TextView(getActivity());
  TextView labelIncome = new TextView(getActivity());
  labelIncome.setText("Income: ");
  linearLayout.addView(llh_texts2);
  llh_texts2.addView(labelIncome);
  llh_texts2.addView(textIncome);
  TextView textTotalFunds = new TextView(getActivity());
  TextView labelFunds = new TextView(getActivity());
  labelFunds.setText("Total Savings Funds: ");
  linearLayout.addView(llh_texts3);
  llh_texts3.addView(labelFunds);
  llh_texts3.addView(textTotalFunds);
  TextView textTotalExpenses = new TextView(getActivity());
  TextView labelExpenses = new TextView(getActivity());
  labelExpenses.setText("Total Scheduled Expenses: ");
  linearLayout.addView(llh_texts4);
  llh_texts4.addView(labelExpenses);
  llh_texts4.addView(textTotalExpenses);
  //create dynamic objects inside scrollview and dynamic linear layout - horizontal
  for (int i = 0; i < res2.getCount(); i++) {
    LinearLayout llh = new LinearLayout(getActivity());
    llh.setOrientation(LinearLayout.HORIZONTAL);
    LinearLayout.LayoutParams lp_llh = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.MATCH_PARENT);
    llh.setLayoutParams(lp_llh);
    //llh.setLayoutParams(lp4,llh.setOrientation(LinearLayout.HORIZONTAL); //for length and width
    linearLayout.addView(llh);
    //LinearLayout.LayoutParams lp_np = new LinearLayout.LayoutParams(70, LinearLayout.LayoutParams.WRAP_CONTENT);
    temp_pct = (Double.valueOf(res2.getString(2)) / 100) * Double.valueOf(res3.getString(3));
    EditText editText = new EditText(getActivity());
    editText.setText(String.valueOf(temp_pct));
    editText.setEnabled(false);
    EditText editText2 = new EditText(getActivity());
    editText2.setText(String.valueOf(res2.getString(2)) + "%");
    editText2.setEnabled(false);
    //get total of funds
    totalpct = totalpct + temp_pct;
    //showMessage("value",res2.getString(3));
    TextView textView = new TextView(getActivity());
    textView.setText(res2.getString(1));
    llh.addView(textView);
    llh.addView(editText);
    llh.addView(editText2);
    res2.moveToNext();
  }
  //return scrollView;
  //create budget text and content
  budget = Double.valueOf(res3.getString(3)) - (totalpct + res4.getDouble(0));
  textBudget.setText(String.valueOf(budget));
  textIncome.setText(String.valueOf(res3.getString(3)));
  textTotalFunds.setText(String.valueOf(totalpct));
  textTotalExpenses.setText(String.valueOf(res4.getDouble(0)));
  return rootview;
}

编辑：基于布瓦内什的答案：

，将代码添加到第三片段选项卡中

@Override
public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setHasOptionsMenu(true); //Make sure you have this line of code.
  setUserVisibleHint(false);
}
//@Override /*<-- this returned  "method does not override method in its superclass" so I commented out*/
public void setUserVisibleHint(final View view, boolean isVisibleToUser) {
  super.setUserVisibleHint(isVisibleToUser);
  if (isVisibleToUser) {
    //get data from database and refresh view.
    viewFunds(view); //this method refreshes the rootview of the 3rd fragment 
  }
}
@Override
public void onViewCreated(final View view, @Nullable Bundle savedInstanceState) {
  super.onViewCreated(view, savedInstanceState);
  ((Main2Activity) getActivity()).setPopupListener(new Main2Activity.PopupListener() {
    @Override
    public void onDialogClick(String value) {
      //After clicking dialog ok button in Activity
      // you will get value here.
      //viewFunds(view);
      setUserVisibleHint(view, true);
    }
  });
}

首先，在片段中定义一种将重新查询数据库的公共方法，然后更新UI：

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
  final View rootview = inflater.inflate(R.layout.home_tab, container, false);
  super.onCreate(savedInstanceState);
  myDb = new DatabaseHelper(getContext());
  viewBudget(rootview);
  return rootview;
}
public View viewBudget(final View rootview) {
  getUpdatedDatabaseData();
}
public void getUpdatedDatabaseData() {
  //get values from database and display in dynamic views
}

然后，将instantiateItem()覆盖在您的fragmentPagerAdapter中，并保留视图中所有片段的一系列片段参考。这是一个简单的例子：

class PagerAdapter extends FragmentPagerAdapter {
        String tabTitles[] = new String[] { "One", "Two", "Three", "Four"};
        Context context;
        //This will contain your Fragment references:
        public Fragment[] fragments = new Fragment[tabTitles.length];
        public PagerAdapter(FragmentManager fm, Context context) {
            super(fm);
            this.context = context;
        }
        @Override
        public int getCount() {
            return tabTitles.length;
        }
        @Override
        public Fragment getItem(int position) {
            switch (position) {
            case 0:
                return new FragmentOne();
            case 1:
                return new FragmentTwo();
            case 2:
                return new FragmentThree();   
            case 3:
                return new FragmentFour();
            }
            return null;
        }
        //This populates your Fragment reference array:
        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            Fragment createdFragment = (Fragment) super.instantiateItem(container, position);
            fragments[position]  = createdFragment;
            return createdFragment;
        }
        @Override
        public CharSequence getPageTitle(int position) {
            // Generate title based on item position
            return tabTitles[position];
        }         
 }

然后，当用户使用对话框将数据添加到数据库中时，您可以在活动中使用此代码来更新第一个选项卡中的片段（如果它是ViewPager中的当前活动选项卡之一）

    Fragment frag = mAdapter.fragments[0];
    if (frag != null && frag instanceof FragmentOne) {
      ((FragmentOne)frag).getUpdatedDatabaseData();
    }

您可以通过接口进行操作。

在您的活动中创建接口对象并从片段中设置对象。

在您的活动中

public class MyActivity extends AppCompatActivity {
    private PopupListener popupListener;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //Your dialog code.
         setPositiveButton("Ok", new DialogInterface.OnClickListener() {
              @Override
              public void onClick(DialogInterface dialog, int which) {
                 popupListener.onDialogClick(your_value);
              }
         })
    }
    public void setPopupListener(PopupListener popupListener) {
        this.popupListener = popupListener;
    }
    public interface PopupListener{
        void onDialogClick(String value);
    }
}

在您的 fragment 您必须这样的侦听器：

public class MyFragment extends Fragment{ @Override public void onViewCreated(View view, @Nullable Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState); ((MyActivity)getActivity()).setPopupListener(new MyActivity.PopupListener() { @Override public void onDialogClick(String value) { //After clicking dialog ok button in Activity // you will get value here. } }); } }
更新viewPager的其他片段内容，覆盖以下所有viewPager片段中的方法。

@Override public void setUserVisibleHint(boolean isVisibleToUser) { super.setUserVisibleHint(isVisibleToUser); if (isVisibleToUser) { //get data from database and refresh view. } }
在此之前，在您片段中添加以下代码onCreate()。

public void onCreate(@Nullable Bundle savedInstanceState) { setUserVisibleHint(false); }
希望它有帮助：）

您可以在片段中使用broadcastreceiver，并通过广播意图从活动发送数据

在MainActivity中保存到数据库时发送此广播

Intent intent = new Intent("key_to_identify_the_broadcast");
intent.putExtra("refresh", true);
context.sendBroadcast(intent);

，然后为您的第一个片段创建广播接收器

private final BroadcastReceiver mHandleMessageReceiver = new 
BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        Boolean refresh = 
            intent.getBooleanExtra("refresh",false);
        if(refresh){
           notifyDataSetChanged();
        }
        //you can call any of your methods for using this value for your use case
  }
};

您需要在Fragment的OnCreateview（）中注册此广播

IntentFilter filter = new 
      IntentFilter("key_to_identify_the_broadcast");
       getActivity().getApplicationContext().
              registerReceiver(mHandleMessageReceiver, filter);

您需要在片段的ondestroy（）中登记

@Override
public void onDestroy() {
    try {
     getActivity().getApplicationContext().
         unregisterReceiver(mHandleMessageReceiver);
   } catch (Exception e) {
      Log.e("UnRegister Error", "> " + e.getMessage());
   }
   super.onDestroy();
}

您可以针对要刷新列表的所有片段实现相同的广播接收器

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