Android map NullPointerException ItemizedOverlay

Question

这根本没有引用我代码中的任何地方。我该如何深入了解它？

java.lang.NullPointerException
at com.google.android.maps.OverlayBundle.draw(OverlayBundle.java:42)
at com.google.android.maps.MapView.onDraw(MapView.java:494)
at android.view.View.draw(View.java:6739)
at android.view.ViewGroup.drawChild(ViewGroup.java:1648)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1375)
at android.view.ViewGroup.drawChild(ViewGroup.java:1646)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1375)
at android.view.View.draw(View.java:6742)
at android.widget.FrameLayout.draw(FrameLayout.java:352)
at android.view.ViewGroup.drawChild(ViewGroup.java:1648)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1375)
at android.view.View.draw(View.java:6742)
at android.widget.FrameLayout.draw(FrameLayout.java:352)
at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1872)
at android.view.ViewRoot.draw(ViewRoot.java:1422)
at android.view.ViewRoot.performTraversals(ViewRoot.java:1167)
at android.view.ViewRoot.handleMessage(ViewRoot.java:1744)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:144)
at android.app.ActivityThread.main(ActivityThread.java:4937)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
at dalvik.system.NativeStart.main(Native Method)

这里是ItemizedOverlay的draw方法

public void draw(Canvas canvas, MapView mapView, boolean shadow) {

            try {
            super.draw(canvas, mapView, false);

            if (getMainOverlayArray().size() != 0){

            pfOverlayItem tempOver = null;
            for (int i = 0; i < getMainOverlayArray().size(); i++) {

                tempOver = getMainOverlayArray().get(i);

            boolean isMatch = false;

            if (tempOver.getTitle().equals(selectedName))
            {
                isMatch = true;
            }

            if (isMatch){

            Projection projection = mapView.getProjection();
            Point point = new Point();
            projection.toPixels(tempOver.getPoint(), point);

            Paint background = new Paint();
            background.setColor(Color.WHITE);
            background.setAlpha(150);
            RectF rect = new RectF();
            rect.set(point.x - 55, point.y +15,
                    point.x + 100, point.y + 65);
            canvas.drawRoundRect(rect, 5, 5, background);


            Paint text = new Paint();
            text.setAntiAlias(true);
            text.setColor(Color.BLUE);
            text.setTextSize(14);
            text.setTypeface(Typeface.MONOSPACE);

            canvas.drawText(tempOver.getTitle() , point.x -50 , point.y + 30, text);
            canvas.drawText(tempOver.getTypeTextOut(), point.x -50 , point.y + 45, text);
            canvas.drawText(tempOver.getdestination(), point.x -50 , point.y + 60, text);
            }
            }
            }
            }catch (Exception e){
                Log.e("Error", "Problem drawing view", e);
                e.printStackTrace();
            }
        }

我现在打印出堆栈跟踪，没有区别! :-(

有没有人有任何想法可以帮助查明这个问题？

编辑 - 最新代码 28/11 全类

    private class SitesOverlay extends ItemizedOverlay<pfOverlayItem> {
        private List<pfOverlayItem> items = new ArrayList<pfOverlayItem>();

        private PopupPanel panel=new PopupPanel(R.layout.popup);
        private MapLocation selectedMapLocation;  
        private static final int CIRCLERADIUS = 2;
        private ArrayList<pfOverlayItem> mOverlays = new ArrayList<pfOverlayItem>();



        public SitesOverlay() {

            super(null);
            //super(boundCenter(defaultMarker));
            //items = getMainOverlayArray();
            //items = mOverlays;
            populate();

        }



public void finishedLoading(){

    populate();

}

        @Override
        protected pfOverlayItem createItem(int i) {
            // Log.i("CREATE","MARKER");
            return (items.get(i));

        }

        public void addItem(OverlayItem overlay) {
            overlay.setMarker(boundCenter(overlay.getMarker(0)));
            items.add((pfOverlayItem) overlay);
            //populate();
        }

        public void clearItems(){
            runOnUiThread(new Runnable() {
                public void run() {
                    items.clear();
                    myMapView.invalidate();
                }
            });


        }

        public void clear() {
            mOverlays.clear();
            myMapView.removeAllViews();
            //numItems = 0;
            // Workaround for another bug with this class:
            // http://groups.google.com/group/android-developers/browse_thread/thread/38b11314e34714c3
            setLastFocusedIndex(-1);
            populate();
        }

        @Override
        public void draw(Canvas canvas, MapView mapView, boolean shadow) {
            super.draw(canvas, mapView, false);

            try {


            if (getMainOverlayArray().size() != 0){

            pfOverlayItem tempOver = null;
            for (int i = 0; i < getMainOverlayArray().size(); i++) {

                tempOver = getMainOverlayArray().get(i);

            boolean isMatch = false;

            //Log.i("Selected Name",selectedName);

            if (tempOver.getTitle().equals(selectedName))
            {
                isMatch = true;
            }

            if (isMatch){

            Projection projection = mapView.getProjection();
            Point point = new Point();
            projection.toPixels(tempOver.getPoint(), point);

            Paint background = new Paint();
            background.setColor(Color.WHITE);
            background.setAlpha(150);
            RectF rect = new RectF();
            rect.set(point.x - 50, point.y +15,
                    point.x + 90, point.y + 50);
            canvas.drawRoundRect(rect, 5, 5, background);


            Paint text = new Paint();
            text.setAntiAlias(true);
            text.setColor(Color.BLUE);
            text.setTextSize(14);
            text.setTypeface(Typeface.MONOSPACE);

            //canvas.drawRoundRect(rect, 2, 2, background);
            canvas.drawText(tempOver.getTitle() + " " + tempOver.getcallsign(), point.x -50 , point.y + 30, text);
            canvas.drawText(tempOver.getdestination() + " " + tempOver.getdraft(), point.x -50 , point.y + 45, text);
            }
            }
            }
            }catch (Exception e){
                Log.e("Error", "Problem drawing view", e);
                 e.printStackTrace();

            }
        }

        @Override
        protected boolean onTap(int i) {

            pfOverlayItem item = getItem(i);

            if (selectedName.equals(item.getTitle())){

                //Toast.makeText(PlaneFinderMain.this, "SECOND MOFO PRESS", 3000).show();
                try{    
                Intent myIntent = new Intent(PlaneFinderMain.this, DetailActivity.class);
                myIntent.putExtra( "int", i);
                myIntent.putExtra( "string", selectedName );
                PlaneFinderMain.this.startActivity(myIntent);
                }catch (Exception e){
                    Log.e("Error", "Cannot launch", e);
                }
            }

            currentadshex = item.getmmsi();
            new GetRouteTask(item.getmmsi()).execute();

            selectedItem = i;
            selectedName = item.getTitle();
            selectedPlanePoint = item.getPoint();

            GeoPoint geo=item.getPoint();
            Point pt=myMapView.getProjection().toPixels(geo, null);

            View view=panel.getView();

            ((TextView)view.findViewById(R.id.reg)).setText(item.getTitle());
            ((TextView)view.findViewById(R.id.flightno)).setText(item.getcallsign());
            ((TextView)view.findViewById(R.id.route)).setText(item.getdestination());
            ((TextView)view.findViewById(R.id.height)).setText(item.getdraft());

            return (true);
        }

        @Override
        public boolean onTouchEvent(MotionEvent event, MapView mapView) {

             if (event.getAction() == MotionEvent.ACTION_DOWN){

                 if (selectedPlanePoint != null){
                     Projection projection = mapView.getProjection();
                     Point point = new Point();
                     projection.toPixels(selectedPlanePoint, point);

                     Point pointHit = new Point();
                     pointHit.x=(int)event.getX();
                     pointHit.y=(int)event.getY();

                     if ((point.x - pointHit.x) >-100 && (point.x - pointHit.x) <70  && (point.y - pointHit.y) < -25  && (point.y - pointHit.y) > -95){

                            try{    
                                 Intent myIntent = new Intent(PlaneFinderMain.this, DetailActivity.class);

                                    myIntent.putExtra( "int", selectedItem);
                                    myIntent.putExtra( "string", selectedName );
                                    PlaneFinderMain.this.startActivity(myIntent);

                                }catch (Exception e){
                                    Log.e("Error", "Cannot launch", e);
                                }

                     }else{

                     }


                 }


             }



            return false;


        }



        @Override
        public int size() {
            return (items.size());
        }

        public void addOverlay(OverlayItem o){
            setLastFocusedIndex(-1);
            populate();
        }



    }

Answer 1

实际上问题不在于您的 ItemizedOverlay 的实现，而在于您的 MapActivity 的实现。从类似的堆栈跟踪中可以看出 here在第 42 行，OverlayBundle 正在调用 Overlay 的 draw() 方法。这指向您在某处添加到 mapView 的空叠加层。

一些有用的提示:你绝对应该通过取消注释你已经拥有的第一行代码来将一个 drawable 传递给你的 super 构造函数(用于 HitTest ):

     public SitesOverlay() {

        //super(null);
        super(boundCenter(defaultMarker));
        //items = getMainOverlayArray();
        //items = mOverlays;
        populate();

    }

并且可能不会在您的 draw() 方法中调用 super.draw()。

    @Override
    public void draw(Canvas canvas, MapView mapView, boolean shadow) {
        // why do you do this if you paint it yourself later on.
        super.draw(canvas, mapView, false

很可能您实际上必须同时执行这两项操作。

编辑: 想一想，您绝对应该将可绘制对象传递给您的 super 构造函数，因为它用于 HitTest 。修改了上面的文本以反射(reflect)这一点。