add option to abort a scan

res/layout/medialibrary_preferences.xml

@@ -85,5 +85,14 @@ along with this program. If not, see <http://www.gnu.org/licenses/>.
 		android:layout_height="wrap_content"
 		android:text="@string/empty" />
 
+	<Button
+		android:id="@+id/cancel_button"
+		android:layout_width="wrap_content"
+		android:layout_height="wrap_content"
+		android:layout_gravity="end"
+		android:text="@android:string/cancel">
+		<requestFocus />
+	</Button>
+
 
 </LinearLayout>

src/ch/blinkenlights/android/medialibrary/MediaLibrary.java

@@ -83,7 +83,7 @@ public class MediaLibrary  {
 	 * @param forceFull starts a full / slow scan if true
 	 * @param drop drop the existing library if true
 	 */
-	public static void scanLibrary(Context context, boolean forceFull, boolean drop) {
+	public static void startLibraryScan(Context context, boolean forceFull, boolean drop) {
 		MediaLibraryBackend backend = getBackend(context); // also initialized sScanner
 		if (drop) {
 			sScanner.flushDatabase();
@@ -97,6 +97,16 @@ public class MediaLibrary  {
 		}
 	}
 
+	/**
+	 * Stops any running scan
+	 *
+	 * @param context the context to use
+	 */
+	public static void abortLibraryScan(Context context) {
+		MediaLibraryBackend backend = getBackend(context); // also initialized sScanner
+		sScanner.abortScan();
+	}
+
 	/**
 	 * Whacky function to get the current scan progress
 	 *

src/ch/blinkenlights/android/medialibrary/MediaScanner.java

@@ -124,6 +124,15 @@ public class MediaScanner implements Handler.Callback {
 		}
 	}
 
+	/**
+	 * Stops a running scan
+	 */
+	public void abortScan() {
+		mHandler.removeMessages(MSG_SCAN_RPC);
+		mScanPlan.clear();
+		mHandler.sendMessage(mHandler.obtainMessage(MSG_SCAN_RPC, RPC_KICKSTART, 0));
+	}
+
 	/**
 	 * Drops the media library
 	 */
@@ -547,6 +556,14 @@ public class MediaScanner implements Handler.Callback {
 			}
 		}
 
+		/**
+		 * Flushes all progress, turning the object into a fresh state
+		 */
+		void clear() {
+			mSteps.clear();
+			mStats.reset();
+		}
+
 		/**
 		 * Adds the next step in our plan
 		 *

src/ch/blinkenlights/android/vanilla/PreferencesMediaLibrary.java

@@ -41,6 +41,10 @@ public class PreferencesMediaLibrary extends Fragment
 	 * Our start button
 	 */
 	private View mStartButton;
+	/**
+	 * The cancel button
+	 */
+	private View mCancelButton;
 	/**
 	 * The debug / progress text describing the scan status
 	 */
@@ -72,6 +76,7 @@ public class PreferencesMediaLibrary extends Fragment
 		super.onViewCreated(view, savedInstanceState);
 
 		mStartButton = (View)view.findViewById(R.id.start_button);
+		mCancelButton = (View)view.findViewById(R.id.cancel_button);
 		mProgress = (TextView)view.findViewById(R.id.media_stats_progress);
 		mStatsTracks = (TextView)view.findViewById(R.id.media_stats_tracks);
 		mStatsPlaytime = (TextView)view.findViewById(R.id.media_stats_playtime);
@@ -84,6 +89,13 @@ public class PreferencesMediaLibrary extends Fragment
 				startButtonPressed(v);
 			}
 		});
+
+		mCancelButton.setOnClickListener(new View.OnClickListener() {
+			@Override
+			public void onClick(View v) {
+				cancelButtonPressed(v);
+			}
+		});
 	}
 
 	@Override
@@ -120,6 +132,7 @@ public class PreferencesMediaLibrary extends Fragment
 		String scanText = MediaLibrary.describeScanProgress(getActivity());
 		mProgress.setText(scanText);
 		mStartButton.setEnabled(scanText == null);
+		mCancelButton.setVisibility(scanText == null ? View.GONE : View.VISIBLE);
 
 		Integer songCount = MediaLibrary.getLibrarySize(context);
 		mStatsTracks.setText(songCount.toString());
@@ -152,7 +165,17 @@ public class PreferencesMediaLibrary extends Fragment
 	 * @param view the view which was pressed
 	 */
 	public void startButtonPressed(View view) {
-		MediaLibrary.scanLibrary(getActivity(), mFullScanCheck.isChecked(), mDropDbCheck.isChecked());
+		MediaLibrary.startLibraryScan(getActivity(), mFullScanCheck.isChecked(), mDropDbCheck.isChecked());
+		updateProgress();
+	}
+
+	/**
+	 * Called when the user hits the cancel button
+	 *
+	 * @param view the view which was pressed
+	 */
+	public void cancelButtonPressed(View view) {
+		MediaLibrary.abortLibraryScan(getActivity());
 		updateProgress();
 	}