ViewPager 使用 CursorLoader 托管两个片段，仅加载一个加载程序

Question

我正在尝试使用游标加载器将数据加载到托管在 viewpager 中的两个片段中。每次启动 activity 时，只有一个 fragment1 cursorloader 加载数据。 Fragment2 在方向发生变化时加载，此时 fragment1 不加载 data.The fragment1 的代码是：

public class TransactionFragment extends Fragment 
implements LoaderManager.LoaderCallbacks<Cursor>{
private static final int TRANSACTION_LOADER = 0;
private int walletId;
private RecyclerView transactionRecycler;
TransactionCursorAdapter adapter;
public TransactionFragment() {
    // Required empty public constructor
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    walletId=WalletViewDashboardActivity.walletId;
    getActivity().getSupportLoaderManager().initLoader(TRANSACTION_LOADER, null, this);
}

@Override
public void onResume() {
    super.onResume();
    getActivity().getSupportLoaderManager().restartLoader(TRANSACTION_LOADER, null, this);

}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
  View rootView=inflater.inflate(R.layout.fragment_transaction, container, false);
    transactionRecycler = (RecyclerView) rootView.findViewById(R.id.recycler_transactions);
    transactionRecycler.setLayoutManager(new LinearLayoutManager(getActivity()));
    return rootView;
}

@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
    String sTransactionSelection =
            CarepayContract.InvoiceEntry.TABLE_NAME +
                    "." + CarepayContract.InvoiceEntry.COLUMN_WALLET_ID + " = ? ";

    String[] sArguments = {String.valueOf(walletId)};
    return new CursorLoader(
            getActivity(),
            CarepayContract.InvoiceEntry.CONTENT_URI,
            null,
            sTransactionSelection,
            sArguments,
            null
    );
}

@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
    Log.e("Transactions", String.valueOf(data.getCount()));
    adapter = new TransactionCursorAdapter(getActivity(), data);
    transactionRecycler.setAdapter(adapter);
}

@Override
public void onLoaderReset(Loader<Cursor> loader) {

}}

第二个片段的代码是：

public class DependantFragment extends Fragment implements      LoaderManager.LoaderCallbacks<Cursor> {
private RecyclerView recyclerView;
private static final int DEPENDANT_LOADER = 0;
private int walletId;
private DependantCursorAdapter adapter;
public DependantFragment() {}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    walletId=WalletViewDashboardActivity.walletId;
    recyclerView.setAdapter(adapter);
    getActivity().getSupportLoaderManager().initLoader(DEPENDANT_LOADER, null, this);
}
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

}
@Override
public void onResume() {
    super.onResume();
    recyclerView.setAdapter(adapter);
   getActivity().getSupportLoaderManager().restartLoader(DEPENDANT_LOADER, null, this);

}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_dependant, container, false);
    recyclerView = (RecyclerView) rootView.findViewById(R.id.recycler_dependants);
    recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));

    return rootView;
}

@Override
public android.support.v4.content.Loader<Cursor> onCreateLoader(int id, Bundle args) {
    String sDependantSelection =
            CarepayContract.UserEntry.TABLE_NAME +
                    "." + CarepayContract.UserEntry.COLUMN_TYPE + " = ? AND " + CarepayContract.UserEntry.TABLE_NAME +
                    "." + CarepayContract.UserEntry.COLUMN_WALLET_ID + " = ?";

    String[] sArguments = {"1", String.valueOf(walletId)};
    return new CursorLoader(
            getActivity(),
            CarepayContract.UserEntry.DEPENDANT_URI,
            null,
            sDependantSelection,
            sArguments,
            null
    );
}

@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
    Log.e("Dependant", String.valueOf(data.getCount()));
    adapter = new DependantCursorAdapter(getActivity(), data);
    recyclerView.setAdapter(adapter);
}

@Override
public void onLoaderReset(Loader<Cursor> loader) {

} }

主机代码 activity 是：

public class WalletViewDashboardActivity extends AppCompatActivity  {
public static int walletId;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_wallet_view_dashboard);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    walletId = Integer.parseInt(getIntent().getStringExtra("wallet_id"));
    TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);
    tabLayout.addTab(tabLayout.newTab().setText("Transactions"));
    tabLayout.addTab(tabLayout.newTab().setText("Dependants"));
    tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
    final ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
    final WalletViewPagerAdapter adapter = new WalletViewPagerAdapter(getSupportFragmentManager(), tabLayout.getTabCount());
    viewPager.setAdapter(adapter);
    viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
        @Override
        public void onTabSelected(TabLayout.Tab tab) {
            viewPager.setCurrentItem(tab.getPosition());
        }

        @Override
        public void onTabUnselected(TabLayout.Tab tab) {

        }

        @Override
        public void onTabReselected(TabLayout.Tab tab) {

        }
    });
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

}



public class WalletViewPagerAdapter extends FragmentStatePagerAdapter {
    int mNumOfTabs;

    public WalletViewPagerAdapter(FragmentManager fm, int NumOfTabs) {
        super(fm);
        this.mNumOfTabs = NumOfTabs;
    }

    @Override
    public Fragment getItem(int position) {

        switch (position) {
            case 0:
                return new TransactionFragment();
            case 1:
                return new DependantFragment();
            default:
                return null;
        }
    }

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

Answer 1

private static final int TRANSACTION_LOADER = 0;
private static final int DEPENDANT_LOADER = 0;

你用了getActivity()，所以你用了一个loadermanager，两个loader的id都设置为0，只要把其中一个常量改成1就可以了

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