Question

你好我的情况是我正在创建一个列表，一旦单击列表中的项目，它必须将用户发送到另一个片段，该片段将在我的应用程序中的谷歌地图中有占位符。我的问题是，当我点击列表中项目上的按钮时，应用程序立即崩溃。我的日志告诉我我有一个空例外。我知道我已经在我的观点和听众之间建立了一个参考，但希望对这个问题有更深入的了解。任何帮助将不胜感激，谢谢！

fragment_countries.xml

public class Foo extends HashMap<Class, List>{

    @Override
    public List put(Class clazz, List list){
        ...
        // make sure every thing in list is of type clazz here
        return super.put(clazz, list);
    }

    @Override
    public List get(Object clazz){
        return super.get(clazz);
    }

}

row.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" tools:context="myapps.countryapp.Countries"
>

  <ListView
      android:layout_width="fill_parent"
      android:layout_height="fill_parent"
      android:id="@+id/MyListView">
  </ListView>

</FrameLayout>

Countries.java

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal" android:layout_width="match_parent"
    android:layout_height="match_parent">

<ImageView
    android:layout_width="50dp"
    android:layout_height="50dp"
    android:id="@+id/ImageViewPicasso"
    android:layout_marginLeft="10dp"
    android:src="@drawable/ic_launcher"/>
<TextView
    android:layout_width="fill_parent"
    android:layout_height="50dp"
    android:textStyle="bold"
    android:gravity="center_vertical"
    android:id="@+id/textAreaList"
    android:padding="10dp"/>

</LinearLayout>

MyMapFragment.java

package myapps.countryapp;

import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.support.v4.app.Fragment;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import com.parse.FindCallback;
import com.parse.ParseObject;
import com.parse.ParseQuery;
import com.squareup.picasso.Picasso;

import java.text.ParseException;
import java.util.ArrayList;
import java.util.List;


/**
 * A simple {@link Fragment} subclass.
 */
public class Countries extends Fragment {
private ListView mListView;


private List<CountriesRetrieved> retrievedCountriesList;


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

    @Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View fragmentview = inflater.inflate(R.layout.fragment_countries, container, false);

    mListView = (ListView) fragmentview.findViewById(R.id.MyListView);


        retrievedCountriesList = new ArrayList<>(); //Array of objects.
        ParseQuery<ParseObject> query = ParseQuery.getQuery("Countries"); //name of the database from parse.com
        query.findInBackground(new FindCallback<ParseObject>() {
            //                @Override
            public void done(List<ParseObject> countriesList, com.parse.ParseException e) {
                if (e == null) {
                    for (ParseObject parseObject : countriesList) {
                        String titleOfCountry = (String) parseObject.get("Title");
                        String imageLink = (String) parseObject.get("Image_URL");
                        String latitude = (String) parseObject.get("Latitude");
                        String longitude = (String) parseObject.get("Longitude");
                        CountriesRetrieved countries = new CountriesRetrieved(titleOfCountry, imageLink, latitude, longitude);
                        retrievedCountriesList.add(countries);
                    }
                    mListView.setAdapter(new CountriesAdapterList());
                } else {
                    Log.d("Cannot Parse", "Error: " + e.getMessage());
                }
            }
        });

        mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                CountriesRetrieved crl = retrievedCountriesList.get(position);
                Double lat = Double.parseDouble(crl.getLatitude());
                Double lon = Double.parseDouble(crl.getLongitude());
                MyMapFragment mp = new MyMapFragment();
                mp.setLocation(lat, lon);
            }
        });

    return fragmentview;
}


private class CountriesAdapterList extends BaseAdapter{

    @Override
    public int getCount() {
        return retrievedCountriesList.size(); //This is how the adaptor keeps going, because of the size of list.
    }

    @Override
    public Object getItem(int position) {
        return  retrievedCountriesList.get(position);
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        View rowView = getActivity().getLayoutInflater().inflate(R.layout.row, null);//Instantiates a layout XML file into its corresponding View objects.

        CountriesRetrieved rowCountries = retrievedCountriesList.get(position);

        TextView textViewRow = (TextView) rowView.findViewById(R.id.textAreaList); //Find text view on every row.

        textViewRow.setText(rowCountries.getTitle());

        ImageView imageView = (ImageView) rowView.findViewById(R.id.ImageViewPicasso);
        Picasso.with(getActivity()).load(rowCountries.getImageLink()).into(imageView);

        return rowView;
    }
}

}

我的日志猫：

package myapps.countryapp;

import android.os.Bundle;

import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

/**
 * Created by user on 8/25/2015.
 */
public class MyMapFragment extends SupportMapFragment {
    GoogleMap googleMap = getMap();

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

}

public void setLocation(Double latitude, Double longitude){
    MarkerOptions markerOptions = new MarkerOptions();

    markerOptions.position(new LatLng(latitude, longitude));
    markerOptions.icon(BitmapDescriptorFactory.fromResource(R.drawable.set_marker));
    googleMap.addMarker(markerOptions);
}

}

ListView上的OnitemClick侦听器崩溃

0 个答案: