Question

我在选项卡式布局的选项卡中有一个recyclerview，所以在一个片段中。从recyclerview中添加和删除项目效果很好，但是当我刷新应用程序（打开手机上的最新应用程序并关闭它）时，recyclerview为空，即应用程序重新启动时。请让我知道是否需要查看任何代码。

这是我的片段的代码：

import android.annotation.SuppressLint;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.graphics.Rect;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.provider.AlarmClock;
import android.support.annotation.RequiresApi;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.app.Fragment;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.text.InputType;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.inputmethod.InputMethodManager;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.TimePicker;
import android.widget.Toast;
import android.widget.ToggleButton;

import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.List;

import static rongorai.wakeup.MainActivity.alarms;

public class Tab1 extends Fragment
{
    /**Fragment stuff-------------------------------------------*/
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";
    private String mParam1;
    private String mParam2;
    private OnFragmentInteractionListener mListener;

    /**Actual stuff--------------------------------------------*/
    private FloatingActionButton fab;
    private Button inserttest;
    private Button removetest;

    private RecyclerView rv;
    public static MainAdapter rva;

    public static TextView txtNoAlarms;

    /**Methods-------------------------------------------------*/
    public Tab1()
    {
        // Required empty public constructor
    }

    public static Tab1 newInstance(String param1, String param2)
    {
        Tab1 fragment = new Tab1();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        if (getArguments() != null)
        {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        View view = inflater.inflate(R.layout.fragment_tab1, container, false);
        fab = view.findViewById(R.id.fab);
        rv = view.findViewById(R.id.rv);
        inserttest = view.findViewById(R.id.inserttest);
        removetest = view.findViewById(R.id.removettest);
        txtNoAlarms = view.findViewById(R.id.txtNoAlarm);

        fab.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View view)
            {
                Intent intent = new Intent(getActivity(), NewAlarm.class);
                startActivity(intent);
            }
        });

        removetest.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                /*if (alarms.size() > 0) {
                    alarms.remove(0);
                }
                rva.notifyItemRemoved(0);
                if (alarms.size() == 0 & txtNoAlarms.getVisibility() == View.INVISIBLE) {
                    txtNoAlarms.setVisibility(View.VISIBLE);
                }*/

                Intent intent = new Intent(AlarmClock.ACTION_SET_ALARM);
                intent.putExtra(AlarmClock.EXTRA_HOUR, 21);
                intent.putExtra(AlarmClock.EXTRA_MINUTES, 6);
                startActivity(intent);

            }
        });

        inserttest.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                alarms.add(new Alarm("alarm name", true, true, true, true, new boolean[] {true, false}, 15, 27));
                rva.notifyItemInserted(0);
                if (alarms.size() != 0 & txtNoAlarms.getVisibility() == View.VISIBLE) {
                    txtNoAlarms.setVisibility(View.INVISIBLE);
                }
                updateAlarmVals();
            }
        });

        //Recycler View-----------------------------------------------------------------------------
        rv.setHasFixedSize(true);
        rva = new MainAdapter(alarms, getActivity());
        rv.setAdapter(rva);
        rv.setLayoutManager(new LinearLayoutManager(getActivity()));
        /*rva.setOnItemClickListener(new MainAdapter.OnItemClickedListener() {
            @Override
            public void onItemClick(int position) {
                //Toast.makeText(getActivity(), "clicked " + position, Toast.LENGTH_SHORT).show();
                Intent intent = new Intent(getActivity(), EditAlarm.class);
                startActivity(intent);
            }
        });*/

        return view;
    }

    public static void updateAlarmVals() {
        Tab2.alarmvals.setText("" + alarms.size() + "\n");
        for (Alarm i: alarms) {
            Tab2.alarmvals.setText(Tab2.alarmvals.getText().toString() +
                    i.toString() + "\n");
        }
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item)
    {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onAttach(Context context)
    {
        super.onAttach(context);
        if (context instanceof OnFragmentInteractionListener)
        {
            mListener = (OnFragmentInteractionListener) context;
        } else
        {
            throw new RuntimeException(context.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

    @Override
    public void onDetach()
    {
        super.onDetach();
        mListener = null;
    }

    public interface OnFragmentInteractionListener
    {
        // TODO: Update argument type and name
        void onFragmentInteraction(Uri uri);
    }
}

Answer 1

您可能需要在片段中处理onResume()并更新recyclerview。

 @Override
    protected void onResume() {
        super.onResume();
        adapter.notifyDataSetChanged();

    }

重新启动应用程序时，为什么我的recyclerview清空？

1 个答案: