java - Android Google Maps Api v2 fragment : NullPointerException error

Question

当我在 Fragment 中使用 MapFragment 时，出现 NullPointerException 错误。

我无法发布图片，这是 LogCat:

• java.lang.NullPointerException
• com.ps.admin.EventsFragment.onCreateView(EventsFragment.Java:103)

基本上当 Activity 开始两次时就已经停止了!!

    package com.ps.admin;

@SuppressLint("NewApi")
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    v = inflater.inflate(R.layout.fragment_events, container, false);

    app = getActivity();
    month = Calendar.getInstance();
    prevMonth = (Calendar) month.clone();
    prevMonth.roll(Calendar.MONTH, false);

    try{
    map = ((MapFragment) app.getFragmentManager().findFragmentById(R.id.map)).getMap();
    map.setMyLocationEnabled(true);
    map.setMapType(GoogleMap.MAP_TYPE_SATELLITE);
    }catch (Exception e){
        Toast.makeText(app, e.toString(), Toast.LENGTH_LONG).show();
    }

    int lastDay = month.getActualMaximum(Calendar.DAY_OF_MONTH);
    if(Integer.valueOf(getDayOfMonth())>1){
        for (int i = 0; i < Integer.valueOf(getDayOfMonth())-1; i++) {
            days.add("");
        }
        space = Integer.valueOf(getDayOfMonth())-1;
    }
       for (int i = 1; i <= lastDay; i++) {

        days.add(String.valueOf(i));
    }
    tx = (TextView)v.findViewById(R.id.textView1);

    cCalendar = (GridView)v.findViewById(R.id.gridView1);

    cCalendar.setAdapter(new ProductAdapter(app, android.R.layout.simple_expandable_list_item_1, days));
    readCalendarEvent(app);
    cCalendar.setOnTouchListener(gestureListener);
    cCalendar.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                long arg3) {
            RelativeLayout rld = (RelativeLayout)arg1.findViewById(R.id.rld);
            try{
            popupHoney(rld.getTag().toString(),getRelativeLeft(arg1),getRelativeTop(arg1));
            }catch (Exception e){

            }
        }

    });
    cCalendar.setOnItemLongClickListener(new OnItemLongClickListener() {

        @Override
        public boolean onItemLongClick(AdapterView<?> arg0, View view,
                int arg2, long arg3) {
            RelativeLayout mn = (RelativeLayout)view.findViewById(R.id.main);
            TextView tx = (TextView)view.findViewById(R.id.textView1);

                addCalendarEvent(arg2);
                tx.setText("+");
                mn.setBackgroundResource(R.color.Green);


            return false;
        }
    });
    return v;

}
private int getRelativeLeft(View myView) {
    if (myView.getParent() == myView.getRootView())
        return myView.getLeft();
    else
        return myView.getLeft() + getRelativeLeft((View) myView.getParent());
}

private int getRelativeTop(View myView) {
    if (myView.getParent() == myView.getRootView())
        return myView.getTop();
    else
        return myView.getTop() + getRelativeTop((View) myView.getParent());
}
private String getDayOfMonth() {
    Calendar c = Calendar.getInstance();  
    c.set(Calendar.DAY_OF_MONTH, 1);
    String date = c.getTime().toString().substring(0, 3).toString();
    if (date.equals("Mon")){
        return "1";
    }else
        if (date.equals("Tue")){
            return "2";
        }else
            if (date.equals("Wed")){
                return "3"; 
            }else
                if (date.equals("Thu")){
                    return "4";
                }else
                    if (date.equals("Fri")){
                        return "5";
                    }else
                        if (date.equals("Sat")){
                            return "6";
                        }else
                            if (date.equals("Sun")){
                                return "7";
                            }
    return date;
}



public String getFirstDay(int day, int month, int year)
{
    Calendar cal = new GregorianCalendar();
    cal.set(Calendar.DATE, day);
    cal.set(Calendar.MONTH, month);
    cal.set(Calendar.YEAR, year);
    cal.set(Calendar.DAY_OF_MONTH, 1);
    switch (cal.get(Calendar.DAY_OF_WEEK)) {
        case Calendar.SUNDAY:
            return "SUNDAY";
        case Calendar.MONDAY:
            return "MONDAY";
        case Calendar.TUESDAY:
            return "TUESDAY";
        case Calendar.WEDNESDAY:
            return "WEDNESDAY";
        case Calendar.THURSDAY:
            return "THURSDAY";
        case Calendar.FRIDAY:
            return "FRIDAY";
        case Calendar.SATURDAY:
            return "SATURDAY";
    }
    return null;
}
public static ArrayList<String> readCalendarEvent(Context context) {
    Cursor cursor = context.getContentResolver()
            .query(
                    Uri.parse("content://com.android.calendar/events"),
                    new String[] { "calendar_id", "title", "description",
                            "dtstart", "dtend", "eventLocation" }, null,
                    null, null);
    cursor.moveToFirst();

    String CNames[] = new String[cursor.getCount()];

    nameOfEvent.clear();
    startDates.clear();
    endDates.clear();
    descriptions.clear();

    for (int i = 0; i < CNames.length; i++) {

        nameOfEvent.add(cursor.getString(1));
        startDates.add(getDate(Long.parseLong(cursor.getString(3))));
        endDates.add(getDate(Long.parseLong(cursor.getString(4))));
        descriptions.add(cursor.getString(2));

        CNames[i] = cursor.getString(1);
        cursor.moveToNext();

    }
    return nameOfEvent;
}

@SuppressLint("SimpleDateFormat")
public static String getDate(long milliSeconds) {
    SimpleDateFormat formatter = new SimpleDateFormat(
            "dd/MM/yyyy hh:mm:ss a");
    Calendar calendar = Calendar.getInstance();
    calendar.setTimeInMillis(milliSeconds);
    return formatter.format(calendar.getTime());
}
private void addCalendarEvent(int day){
    long startTime = 0;

    Calendar calendar = Calendar.getInstance();
    String startDate = calendar.get(Calendar.YEAR)+"-"+(calendar.get(Calendar.MONTH)+1)+"-"+(day-space+1);
    try {
        Date date = new SimpleDateFormat("yyyy-MM-dd").parse(startDate);
        startTime=date.getTime();
    }catch (Exception e){

    }
    Intent intent = new Intent(Intent.ACTION_EDIT);
    intent.setType("vnd.android.cursor.item/event");
    intent.putExtra("beginTime",startTime);
    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    app.startActivity(intent);
}

private void editCalendarEvent(int calendarEventID){

    Intent intent = new Intent(Intent.ACTION_EDIT);
    intent.setData(Uri.parse("content://com.android.calendar/events/" + String.valueOf(calendarEventID)));
    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    app.startActivity(intent);
}
public class ProductAdapter extends ArrayAdapter<String> {
    ArrayList<String> items;
    LayoutInflater vi;
    public ProductAdapter(Context context, int textViewResourceId,
            ArrayList<String> objects) {
        super(context, textViewResourceId, objects);
        this.items = objects;
        vi = (LayoutInflater)context.getSystemService(context.LAYOUT_INFLATER_SERVICE);
    }
            @SuppressLint({ "NewApi", "SimpleDateFormat" })
            @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView == null) {

            convertView = vi.inflate(R.layout.product_event, null);
        }
        try {
        RelativeLayout bg = (RelativeLayout)convertView.findViewById(R.id.rld);
        RelativeLayout mn = (RelativeLayout)convertView.findViewById(R.id.main);
        TextView name = (TextView)convertView.findViewById(R.id.textView1);
        name.setText(items.get(position).toString());
        SimpleDateFormat format1 = new SimpleDateFormat("dd/MM/yyyy");
        String localTime = format1.format(month.getTime());
        System.out.println(localTime);
        if (Integer.valueOf(days.get(position))<10) {
            if (("0"+days.get(position)+""+localTime.substring(2, localTime.length())).equals(localTime)){
                mn.setBackgroundResource(R.color.Blue_Trans);
            }   
            }else{
                if ((days.get(position)+""+localTime.substring(2, localTime.length())).equals(localTime)){
                    mn.setBackgroundResource(R.color.Blue_Trans);
                }
          }
            for (int j = 0; j < startDates.size(); j++) {
                if (days.get(position).equals("")){
                System.out.println(days.get(position)); 
                }else{
                if (Integer.valueOf(days.get(position))<10) {
                    if (("0"+days.get(position)+""+localTime.substring(2, localTime.length())).equals(startDates.get(j).substring(0, 10))){
                        bg.setBackgroundResource(R.color.Green);
                        bg.setTag(j);
                    }   
                    }else{
                        if ((days.get(position)+""+localTime.substring(2, localTime.length())).equals(startDates.get(j).substring(0, 10))){
                            bg.setBackgroundResource(R.color.Green);
                            bg.setTag(j);
                        }
                  }
                }
            }

        } catch (Exception e) {

        }finally{
            app.setProgressBarIndeterminateVisibility(false);
        }
        return convertView;
    }

}

class MyGestureDetector extends SimpleOnGestureListener {
    @SuppressLint("NewApi")
    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        try {
            if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH)
                return false;
            // right to left swipe
            if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                month.set(month.get(Calendar.YEAR), month.get(Calendar.MONTH)+1,month.get(Calendar.DAY_OF_MONTH),month.get(Calendar.HOUR),month.get(Calendar.MINUTE));

                int lastDay = month.getActualMaximum(Calendar.DAY_OF_MONTH);
                days.clear();
                if(Integer.valueOf(getDayOfMonth())>1){
                    for (int i = 0; i < Integer.valueOf(getDayOfMonth())-1; i++) {
                        days.add("");
                    }
                    space = Integer.valueOf(getDayOfMonth())-1;
                }
                   for (int i = 1; i <= lastDay; i++) {

                    days.add(String.valueOf(i));
                }
                   cCalendar.startAnimation(AnimationUtils.loadAnimation(app, R.anim.righttoleft));
                   cCalendar.setAdapter(new ProductAdapter(app, android.R.layout.simple_expandable_list_item_1, days));
                   SimpleDateFormat format1 = new SimpleDateFormat("dd-MM-yyyy");
                   app.getActionBar().setTitle(format1.format(month.getTime()));

            }  else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                month.set(month.get(Calendar.YEAR), month.get(Calendar.MONTH)-1,month.get(Calendar.DAY_OF_MONTH),month.get(Calendar.HOUR),month.get(Calendar.MINUTE));

                int lastDay = month.getActualMaximum(Calendar.DAY_OF_MONTH);
                days.clear();
                if(Integer.valueOf(getDayOfMonth())>1){
                    for (int i = 0; i < Integer.valueOf(getDayOfMonth())-1; i++) {
                        days.add("");
                    }
                    space = Integer.valueOf(getDayOfMonth())-1;
                }
                   for (int i = 1; i <= lastDay; i++) {

                    days.add(String.valueOf(i));
                }
                   cCalendar.startAnimation(AnimationUtils.loadAnimation(app, R.anim.lefttoright));
                   cCalendar.setAdapter(new ProductAdapter(app, android.R.layout.simple_expandable_list_item_1, days));
                   SimpleDateFormat format1 = new SimpleDateFormat("dd-MM-yyyy");
                   app.getActionBar().setTitle(format1.format(month.getTime()));

            }

        } catch (Exception e) {
            // nothing
        }
        return false;
    }
}
@Override
public void onResume(){
    super.onResume();

    int lastDay = month.getActualMaximum(Calendar.DAY_OF_MONTH);
    days.clear();
    if(Integer.valueOf(getDayOfMonth())>1){
        for (int i = 0; i < Integer.valueOf(getDayOfMonth())-1; i++) {
            days.add("");
        }
        space = Integer.valueOf(getDayOfMonth())-1;
    }
       for (int i = 1; i <= lastDay; i++) {

        days.add(String.valueOf(i));
    }
       cCalendar.setAdapter(new ProductAdapter(app, android.R.layout.simple_expandable_list_item_1, days));
    }
@SuppressLint("NewApi")
private void popupHoney(final String builded,float f,float g) {
     try {

    LayoutInflater inflater = (LayoutInflater) app
    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View layout = inflater.inflate(R.layout.toast_popup,
    (ViewGroup) v.findViewById(R.id.popup_element));

    pwindow = new PopupWindow(layout,WindowManager.LayoutParams.WRAP_CONTENT,
            WindowManager.LayoutParams.WRAP_CONTENT,true);

    pwindow.showAtLocation(layout, Gravity.NO_GRAVITY, Math.round(f)-40, Math.round(g)-30);
    TextView tx = (TextView)layout.findViewById(R.id.textView2);
    TextView tx1 = (TextView)layout.findViewById(R.id.textView1);
    RelativeLayout close = (RelativeLayout)layout.findViewById(R.id.popup);

    tx.setText(" "+nameOfEvent.get(Integer.valueOf(builded))+" ");
    tx1.setText(" "+nameOfEvent.get(Integer.valueOf(builded))+" ");

    tx.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            try{
            String loca = descriptions.get(Integer.valueOf(builded));
            String[] separated = loca.split(",");
            setLatLang(Double.valueOf(separated[0]),Double.valueOf(separated[1]),nameOfEvent.get(Integer.valueOf(builded)),startDates.get(Integer.valueOf(builded)).substring(0, startDates.get(Integer.valueOf(builded)).length()-6)+"\n"+
                    endDates.get(Integer.valueOf(builded)).substring(0, endDates.get(Integer.valueOf(builded)).length()-6));

            pwindow.dismiss();
        }catch(Exception e){
            Toast.makeText(app, "Bu bir harita notu değildir!", Toast.LENGTH_LONG).show();
        }}
    });
    close.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            pwindow.dismiss();
        }
    });

    } catch (Exception e) {

    }
     app.setProgressBarIndeterminateVisibility(false);
     }
    public void setLatLang(final double lat,final double lon,final String tit,String date){
        sydney = new LatLng(lat, lon);

        //map.moveCamera(CameraUpdateFactory.newLatLngZoom(sydney, 13));
        map.animateCamera(CameraUpdateFactory.newLatLngZoom(sydney, 16));
        //map.addCircle(new CircleOptions().center(sydney).fillColor(Color.TRANSPARENT).radius(100).strokeColor(Color.BLUE));
        map.addMarker(new MarkerOptions()
                .title(tit)
                .snippet(date)
                .flat(true)
                .icon(BitmapDescriptorFactory.fromResource(R.drawable.ic_action_mic))
                .visible(true)
                .anchor(0.5f, 1)
                .position(sydney));
        map.addPolyline(new PolylineOptions().geodesic(true)
                        .add(new LatLng(lat, lon))  // Sydney
                        /*.add(new LatLng(-18.142, 178.431))  // Fiji
                        .add(new LatLng(21.291, -157.821))  // Hawaii
                        .add(new LatLng(37.423, -122.091)) */ // Mountain View
                );
        map.setOnInfoWindowClickListener(new OnInfoWindowClickListener() {

            @Override
            public void onInfoWindowClick(Marker arg0) {

                /*String label = tit;
                String uriBegin = "geo:" + lat + "," + lon;
                String query = lat + "," + lon + "(" + label + ")";
                String encodedQuery = Uri.encode(query);
                String uriString = uriBegin + "?q=" + encodedQuery + "&z=16";
                Uri uri = Uri.parse(uriString);
                Intent intent = new Intent(android.content.Intent.ACTION_VIEW, uri);
                startActivity(intent);*/

            }
        });
    }
}

Answer 1

问题是您在 onCreateView 中保存了 Activity 引用，并且还尝试取消引用它。

错误可能来自代码中的以下几行:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
        //your code ...
        app = getActivity(); //getActivity() can return null, so app will be null
        //your code ...
        map = ((MapFragment) app.getFragmentManager().findFragmentById(R.id.map)).getMap(); //possible NPE

正确的方法是将 Activity 引用保存在 onAttach 中，并取消引用它。

@Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
    app = activity; //correct place to get activity reference
    //your code ...
    map = ((MapFragment) app.getFragmentManager().findFragmentById(R.id.map)).getMap();
    }