The status screen of the ongoing configuration is leavable

app/src/main/java/de/tu_chemnitz/wlan/MainActivity.java

@@ -160,21 +160,25 @@ public class MainActivity extends AppCompatActivity {
         if (inInstall) {
 
             Helper.getInstallStatus(this);
+            synchronized (this) {
+                if (timer == null) {
 
-            timer = new Timer(true);
-            timer.schedule(new TimerTask() {
-                @Override
-                public void run() {
-                    MainActivity.this.runOnUiThread(new Runnable() {
+                    timer = new Timer(true);
+                    timer.schedule(new TimerTask() {
                         @Override
                         public void run() {
-                            redrawLayoutInstall();
-                            if (Helper.ticks_install.size() >= 4)
-                                timer.cancel();
+                            MainActivity.this.runOnUiThread(new Runnable() {
+                                @Override
+                                public void run() {
+                                    redrawLayoutInstall();
+                                    if (Helper.ticks_install.size() >= 4)
+                                        timer.cancel();
+                                }
+                            });
                         }
-                    });
+                    }, 1000, 2000);
                 }
-            }, 1000, 2000);
+            }
 
         } else {
 
@@ -289,6 +293,12 @@ public class MainActivity extends AppCompatActivity {
 
     private void btn_exit_click() {
         inInstall = false;
+        synchronized (this) {
+            if (timer != null) {
+                timer.cancel();
+                timer = null;
+            }
+        }
         recomputeLayout();
     }