Stop drawing when paused

Because the (drawing) surface isn't destroyed when the activity
is paused.

app/src/main/java/de/markusfisch/android/wavelines/activity/ThemeActivity.java

@@ -95,12 +95,14 @@ public void onClick(View v) {
 	public void onResume() {
 		super.onResume();
 		queryThemesAsync();
+		themesView.startDrawing();
 	}
 
 	@Override
 	public void onPause() {
 		super.onPause();
 		themesView.closeCursor();
+		themesView.stopDrawing();
 	}
 
 	@Override

app/src/main/java/de/markusfisch/android/wavelines/widget/ThemesView.java

@@ -68,6 +68,7 @@ public void run() {
 	private int currentIndex;
 	private int idColumn;
 	private int pointerId;
+	private boolean initialized = false;
 	private boolean swiping = false;
 	private boolean drawing = false;
 	private float swipeThreshold;
@@ -97,6 +98,20 @@ public ThemesView(
 		initView(context);
 	}
 
+	public void startDrawing() {
+		if (initialized && !drawing) {
+			drawing = true;
+			postDelayed(drawRunnable, 16L);
+		}
+	}
+
+	public void stopDrawing() {
+		if (drawing) {
+			drawing = false;
+			removeCallbacks(drawRunnable);
+		}
+	}
+
 	public void closeCursor() {
 		if (cursor != null) {
 			cursor.close();
@@ -237,8 +252,8 @@ public void surfaceChanged(
 					int width,
 					int height) {
 				renderer.setSize(width, height);
-				drawing = true;
-				postDelayed(drawRunnable, 16L);
+				initialized = true;
+				startDrawing();
 			}
 
 			@Override
@@ -247,8 +262,7 @@ public void surfaceCreated(SurfaceHolder holder) {
 
 			@Override
 			public void surfaceDestroyed(SurfaceHolder holder) {
-				drawing = false;
-				removeCallbacks(drawRunnable);
+				stopDrawing();
 			}
 		});
 	}