Help: canvas.drawLine(p1.x, p1.y, p2.x, p2.y, paint);

mnish · by **mnish** » Sun Jun 21, 2009 2:03 am

Hello,
I have a problem with drawing lines between two points on google map.
I get nullpointerexception on this line of code:
canvas.drawLine(p1.x, p1.y, p2.x, p2.y, paint);

I know this is a very basic thing, but I don't know not much about it
and I really really need your help.

here is were i call this method:

Syntax: [ Download ] [ Hide ]

Using java Syntax Highlighting

 
        @Override
 
        public void onCreate(Bundle savedInstanceState) {
 
                super.onCreate(savedInstanceState);
 
                setContentView(R.layout.main);
 
                linearLayout = (LinearLayout) findViewById(R.id.zoomview);
 
                mapView = (MapView) findViewById(R.id.mapview);
 
                mapView.setBuiltInZoomControls(on);
 
                mapOverlays = mapView.getOverlays();
 
                drawable = this.getResources().getDrawable(R.drawable.circle);
 
                itemizedoverlay = new HelloItemizedOverlay(drawable);
 
                Projection projection = mapView.getProjection();
 
                Double lat1 = 30.342833*1E6, lon1 = -91.719033*1E6;
 
                Double lat2 = -37.5262180*1E6, lon2 = 175.8060710*1E6;
 
                point1 = new GeoPoint(lat1.intValue(), lon1.intValue());
 
                point2 = new GeoPoint(lat2.intValue(), lon2.intValue());
 
                p1 = new Point();
 
                p2 = new Point();
 
                projection.toPixels(point1, p1);
 
                projection.toPixels(point2, p2);
 
                canvas = new Canvas();
 
                canvas.drawLine(p1.x, p1.y, p2.x, p2.y, paint);
 
        }.
Parsed in 0.035 seconds,  using GeSHi 1.0.8.4

Please tell me what do i do wrong.
Any help is more than welcome

WarrenFaith · by **WarrenFaith** » Sun Jun 21, 2009 10:58 am

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Using java Syntax Highlighting

canvas = new Canvas();
 
canvas.drawLine(p1.x, p1.y, p2.x, p2.y, paint); 
Parsed in 0.031 seconds,  using GeSHi 1.0.8.4

This is not possible in a Activity. You can only draw inside a View.

mnish · by **mnish** » Sun Jun 21, 2009 1:42 pm

WarrenFaith wrote:
Syntax: [ Download ] [ Hide ]
Syntax: [ Download ] [ Show ]
Using java Syntax Highlighting
canvas = new Canvas();

canvas.drawLine(p1.x, p1.y, p2.x, p2.y, paint);

Parsed in 0.034 seconds, using GeSHi 1.0.8.4

This is not possible in a Activity. You can only draw inside a View.

Thanks for your reply. I need to use the MapView and draw lines on it. How can i do this. Could you please show me in a simple way how i can do this?

thank you

Help: canvas.drawLine(p1.x, p1.y, p2.x, p2.y, paint);

Help: canvas.drawLine(p1.x, p1.y, p2.x, p2.y, paint);

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