title: How to fix native SIGABRT using Mapsforge on Android
body: <p>I'm using Mapsforge 0.6.1 and I can reproduce the issue with the following reduced example, which is basically a copy of this tutorial: <a href="https://github.com/mapsforge/mapsforge/blob/master/docs/Getting-Started-Android-App.md" rel="nofollow noreferrer">https://github.com/mapsforge/mapsforge/blob/master/docs/Getting-Started-Android-App.md</a></p>
  
  <p>I've made some minor changes to match the new version.</p>
  
  <pre><code>package org.test.mapsforgeexample;
  
  import java.io.File;
  
  import org.mapsforge.core.model.LatLong;
  import org.mapsforge.map.android.graphics.AndroidGraphicFactory;
  import org.mapsforge.map.android.util.AndroidUtil;
  import org.mapsforge.map.android.view.MapView;
  import org.mapsforge.map.layer.cache.TileCache;
  import org.mapsforge.map.layer.renderer.TileRendererLayer;
  import org.mapsforge.map.datastore.MapDataStore;
  import org.mapsforge.map.reader.MapFile;
  import org.mapsforge.map.rendertheme.InternalRenderTheme;
  
  import android.app.Activity;
  import android.os.Bundle;
  import android.os.Environment;
  
  public class MainActivity extends Activity {
  
      private static final String MAP_FILE = "berlin.map";
  
      private MapView mapView;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
  
          AndroidGraphicFactory.createInstance(this.getApplication());
  
          this.mapView = new MapView(this);
          setContentView(this.mapView);
  
          this.mapView.setClickable(true);
          this.mapView.getMapScaleBar().setVisible(true);
          this.mapView.setBuiltInZoomControls(true);
          this.mapView.getMapZoomControls().setZoomLevelMin((byte) 10);
          this.mapView.getMapZoomControls().setZoomLevelMax((byte) 20);
  
          TileCache tileCache = AndroidUtil.createTileCache(this, "mapcache",
                  mapView.getModel().displayModel.getTileSize(), 1f,
                  this.mapView.getModel().frameBufferModel.getOverdrawFactor());
  
          MapDataStore mapDataStore = new MapFile(new File(Environment.getExternalStorageDirectory(), MAP_FILE));
          TileRendererLayer tileRendererLayer = new TileRendererLayer(tileCache, mapDataStore,
                  this.mapView.getModel().mapViewPosition, AndroidGraphicFactory.INSTANCE);
          tileRendererLayer.setXmlRenderTheme(InternalRenderTheme.OSMARENDER);
  
          this.mapView.getLayerManager().getLayers().add(tileRendererLayer);
  
          this.mapView.setCenter(new LatLong(52.517037, 13.38886));
          this.mapView.setZoomLevel((byte) 12);
      }
  
      @Override
      protected void onDestroy() {
          this.mapView.destroyAll();
          AndroidGraphicFactory.clearResourceMemoryCache();
          super.onDestroy();
      }
  }
  </code></pre>
  
  <p>To run the app, I have to download <a href="http://download.mapsforge.org/maps/europe/germany/berlin.map" rel="nofollow noreferrer">http://download.mapsforge.org/maps/europe/germany/berlin.map</a> to the external storage of my device and grant the permission to read it. The app works fine, but after some screen rotations, it crashes.</p>
  
  <pre><code>12-16 11:43:34.055 1496-1496/? A/DEBUG: *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
  12-16 11:43:34.056 1496-1496/? A/DEBUG: Build fingerprint: 'google/bullhead/bullhead:7.1.1/NMF26F/3425388:user/release-keys'
  12-16 11:43:34.056 1496-1496/? A/DEBUG: Revision: 'rev_1.0'
  12-16 11:43:34.056 1496-1496/? A/DEBUG: ABI: 'arm64'
  12-16 11:43:34.056 1496-1496/? A/DEBUG: pid: 1425, tid: 1449, name: pool-4-thread-1  &gt;&gt;&gt; org.test.mapsforgeexample &lt;&lt;&lt;
  12-16 11:43:34.056 1496-1496/? A/DEBUG: signal 6 (SIGABRT), code -6 (SI_TKILL), fault addr --------
  12-16 11:43:34.058 1496-1496/? A/DEBUG: Abort message: 'Error, cannot access an invalid/free'd bitmap here!'
  12-16 11:43:34.058 1496-1496/? A/DEBUG:     x0   0000000000000000  x1   00000000000005a9  x2   0000000000000006  x3   0000000000000008
  12-16 11:43:34.058 1496-1496/? A/DEBUG:     x4   0000000000000000  x5   0000000000000000  x6   00000078e82a2000  x7   0000000000000000
  12-16 11:43:34.058 1496-1496/? A/DEBUG:     x8   0000000000000083  x9   ffffffffffffffdf  x10  0000000000000000  x11  0000000000000001
  12-16 11:43:34.058 1496-1496/? A/DEBUG:     x12  0000000000000018  x13  0000000000000000  x14  0000000000000000  x15  003627f486f8cd75
  12-16 11:43:34.058 1496-1496/? A/DEBUG:     x16  00000078e72d5ee0  x17  00000078e727faac  x18  0000000007e0f81f  x19  00000078c97ff4f8
  12-16 11:43:34.058 1496-1496/? A/DEBUG:     x20  0000000000000006  x21  00000078c97ff450  x22  000000000000000b  x23  00000000138bedd0
  12-16 11:43:34.058 1496-1496/? A/DEBUG:     x24  00000000138c1300  x25  00000078d79047e0  x26  00000078c8e4c720  x27  0000000013b99b98
  12-16 11:43:34.058 1496-1496/? A/DEBUG:     x28  00000000138c12f0  x29  00000078c97fe320  x30  00000078e727ced8
  12-16 11:43:34.058 1496-1496/? A/DEBUG:     sp   00000078c97fe300  pc   00000078e727fab4  pstate 0000000060000000
  12-16 11:43:34.549 1496-1496/? A/DEBUG: backtrace:
  12-16 11:43:34.549 1496-1496/? A/DEBUG:     #00 pc 000000000006bab4  /system/lib64/libc.so (tgkill+8)
  12-16 11:43:34.549 1496-1496/? A/DEBUG:     #01 pc 0000000000068ed4  /system/lib64/libc.so (pthread_kill+64)
  12-16 11:43:34.549 1496-1496/? A/DEBUG:     #02 pc 0000000000023f58  /system/lib64/libc.so (raise+24)
  12-16 11:43:34.549 1496-1496/? A/DEBUG:     #03 pc 000000000001c810  /system/lib64/libc.so (abort+52)
  12-16 11:43:34.549 1496-1496/? A/DEBUG:     #04 pc 0000000000010c24  /system/lib64/libcutils.so (__android_log_assert+224)
  12-16 11:43:34.549 1496-1496/? A/DEBUG:     #05 pc 00000000001073e4  /system/lib64/libandroid_runtime.so (_ZNK7android6Bitmap11assertValidEv+40)
  12-16 11:43:34.549 1496-1496/? A/DEBUG:     #06 pc 00000000001074c8  /system/lib64/libandroid_runtime.so (_ZN7android6Bitmap11getSkBitmapEP8SkBitmap+20)
  12-16 11:43:34.550 1496-1496/? A/DEBUG:     #07 pc 000000000010359c  /system/lib64/libandroid_runtime.so
  12-16 11:43:34.550 1496-1496/? A/DEBUG:     #08 pc 0000000001a9a3a0  /system/framework/arm64/boot-framework.oat (offset 0x1686000) (android.graphics.Canvas.nativeDrawBitmapMatrix+172)
  12-16 11:43:34.550 1496-1496/? A/DEBUG:     #09 pc 0000000001a9e9b8  /system/framework/arm64/boot-framework.oat (offset 0x1686000) (android.graphics.Canvas.drawBitmap+148)
  12-16 11:43:34.550 1496-1496/? A/DEBUG:     #10 pc 000000000000135c  /data/data/org.test.mapsforgeexample/cache/slice-mapsforge-map-android-0.6.0_24fb6ab0ab8de752356b68dd9111194aa0b25568-classes.dex (offset 0x1c000)
  </code></pre>
  
  <p>The problem is, when you rotate the screen, <code>onDestroy()</code> is called, followed by <code>onCreate()</code>. I can reproduce this with more complex apps with multiple activities by switching between the map activity and a different one. Sometimes, resources free'd in <code>AndroidGraphicFactory.clearResourceMemoryCache()</code> (<code>onDestroy()</code>) cannot be reused immediately to redraw the map in <code>onCreate()</code>.</p>
  
  <p>A possible solution is to delete the call         <code>AndroidGraphicFactory.clearResourceMemoryCache()</code> from <code>onDestroy()</code>. As I figured out, this didn't make any sense at all in Mapsforge 0.6.0, since it has been called in <code>destroyAll()</code> too, deleting that call either would have caused a massive memory leak.</p>
  
  <p>In the current version 0.6.1, using to following method, the error does indeed not occure, because <code>AndroidGraphicFactory.clearResourceMemoryCache()</code> is never called.</p>
  
  <pre><code>@Override
  protected void onDestroy() {
      this.mapView.destroyAll();
      super.onDestroy();
  }
  </code></pre>
  
  <p>Although my app seems to work fine, I'm still not convinced, because I think there's still a resource leak. Is this true or is the solution just fine? Is there a better one, maybe a different point in code to open/close AndroidGraphicFactory? Any hints will be highly appreciated.</p>
  
  <p>I'm testing with a Nexus 5X and Android 7.1.1, but I can reproduce this issue on multiple devices and OS versions.</p>