Save MapView as a Bitmap

Question

I've tried both methods to save a MapView as a bitmap which I've found here and none seem to work for me. The first option,

Bitmap bitMap = mMapView.getDrawingCache();             
mMapView.setDrawingCacheEnabled(true);
bitMap = mMapView.getDrawingCache(true);

and the second,

Canvas offscreencanvas = new Canvas();
Bitmap bmap = Bitmap.createBitmap(mMapView.getWidth(), mMapView.getHeight(),
                    Bitmap.Config.ARGB_8888);
bmap.copy(Config.ARGB_4444, true);
offscreencanvas.setBitmap(bmap);
offscreencanvas.drawBitmap(bmap, 0, 0, null);

both result in a bitmap object with width and height of -1 so when I then try and use the bitmap as a texture, it doesn't show. I call the bitmap saving code in a button click, after the mapview has rendered but it still gives the same result.

Has anyone managed to do this?

Answer 1

I encountered similar problems attempting to make use of the drawing cache. Some items I found that helped me:

• Ensure you copy the drawing cache immediately. Android can and will recycle the bitmap that the cache is drawn too. I have had Android destroy the bitmap cache while I was drawing to a view with it.
• For some reason, destroying the cache before retrieving it gave me more consistent results.

Here is the working code I am using:

// Disable caching, destroy the cache, and force a rebuild
imageView.setWillNotCacheDrawing(false);
imageView.destroyDrawingCache();
imageView.buildDrawingCache();

// Copy the drawing cache before the system recycles it
Bitmap cachedImage = Bitmap.createBitmap(imageView.getDrawingCache());

Also note that I am using an ImageView, but I would expect the code path to be the same for MapView.

Finally in the code sample that you posted, you are creating a bitmap the size of the map view. You copy this bitmap and then throw the result away. Then you set your canvas to be backed by this bitmap, and then you try to draw the bitmap to the bitmap. (Yes I typed that correctly.) Try something like this, in place of your canvas code

Bitmap mapCache = /* Get this using the previous code */
Bitmap bmap = Bitmap.createBitmap(mMapView.getWidth(), mMapView.getHeight(),
                        Bitmap.Config.ARGB_8888);
Canvas offscreencanvas = new Canvas(bmap);
offscreencanvas.drawBitmap(mapCache, 0, 0, null);

Answer 2

i didn't work much with MapView, i'll assume that it exteneding the View class, thus, make sure to specify the layout before you build the cach, and you should do it as follow :

This is how i do it, you can change it or try something different if you preffer :

View v = new View(context)
{   public void onMeasure(int w, int h)
    {  setMeasuredDimension(width, height);//the desired width and height
    }}; //important
v.setDrawingCacheEnabled(true); //important
v.measure(width,height); //important the desired width and height
v.layout(0, 0, v.getMeasuredWidth(), v.getMeasuredHeight()); //important
v.setDrawingCacheQuality(DRAWING_CACHE_QUALITY_HIGH);
v.setLayoutParams(new LayoutParams(width,height)); //important
v.buildDrawingCache(true); //important
Bitmap b = v.getDrawingCache(true);
v.buildDrawingCache(false);

Hope this helps, Best regards.