did some finetuning

app/src/main/java/org/schabi/newpipe/ChannelActivity.java

@@ -91,9 +91,16 @@ public class ChannelActivity extends AppCompatActivity {
         Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
         rootView = findViewById(R.id.rootView);
         setSupportActionBar(toolbar);
-        Intent i = getIntent();
+        if(savedInstanceState == null) {
-        channelUrl = i.getStringExtra(NavStack.URL);
+            Intent i = getIntent();
-        serviceId = i.getIntExtra(NavStack.SERVICE_ID, -1);
+            channelUrl = i.getStringExtra(NavStack.URL);
+            serviceId = i.getIntExtra(NavStack.SERVICE_ID, -1);
+        } else {
+            channelUrl = savedInstanceState.getString(NavStack.URL);
+            serviceId = savedInstanceState.getInt(NavStack.SERVICE_ID);
+            NavStack.getInstance()
+                    .restoreSavedInstanceState(savedInstanceState);
+        }
 
 
         infoListAdapter = new InfoListAdapter(this, rootView);
@@ -136,6 +143,15 @@ public class ChannelActivity extends AppCompatActivity {
         requestData(false);
     }
 
+    @Override
+    public void onSaveInstanceState(Bundle outState) {
+        super.onSaveInstanceState(outState);
+        outState.putString(NavStack.URL, channelUrl);
+        outState.putInt(NavStack.SERVICE_ID, serviceId);
+        NavStack.getInstance()
+                .onSaveInstanceState(outState);
+    }
+
     private void updateUi(final ChannelInfo info) {
         CollapsingToolbarLayout ctl = (CollapsingToolbarLayout) findViewById(R.id.channel_toolbar_layout);
         ProgressBar progressBar = (ProgressBar) findViewById(R.id.progressBar);

app/src/main/java/org/schabi/newpipe/detail/VideoItemDetailActivity.java

@@ -88,6 +88,8 @@ public class VideoItemDetailActivity extends ThemableActivity {
         } else {
             videoUrl = savedInstanceState.getString(NavStack.URL);
             currentStreamingService = savedInstanceState.getInt(NavStack.SERVICE_ID);
+            NavStack.getInstance()
+                    .restoreSavedInstanceState(savedInstanceState);
             addFragment(savedInstanceState);
         }
     }
@@ -150,6 +152,8 @@ public class VideoItemDetailActivity extends ThemableActivity {
         outState.putString(NavStack.URL, videoUrl);
         outState.putInt(NavStack.SERVICE_ID, currentStreamingService);
         outState.putBoolean(VideoItemDetailFragment.AUTO_PLAY, false);
+        NavStack.getInstance()
+                .onSaveInstanceState(outState);
     }
 
     @Override
@@ -164,9 +168,8 @@ public class VideoItemDetailActivity extends ThemableActivity {
 
             // http://developer.android.com/design/patterns/navigation.html#up-vs-back
 
-            Intent intent = new Intent(this, MainActivity.class);
+            NavStack.getInstance()
-            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
+                    .openMainActivity(this);
-            NavUtils.navigateUpTo(this, intent);
             return true;
         } else {
             return super.onOptionsItemSelected(item);

app/src/main/java/org/schabi/newpipe/download/DownloadActivity.java

@@ -242,9 +242,7 @@ public class DownloadActivity extends ThemableActivity implements AdapterView.On
 
         switch (id) {
             case android.R.id.home: {
-                Intent intent = new Intent(this, org.schabi.newpipe.MainActivity.class);
+                onBackPressed();
-                intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
-                NavUtils.navigateUpTo(this, intent);
                 return true;
             }
             case R.id.action_settings: {
@@ -252,14 +250,6 @@ public class DownloadActivity extends ThemableActivity implements AdapterView.On
                 startActivity(intent);
                 return true;
             }
-            case R.id.action_report_error: {
-                ErrorActivity.reportError(DownloadActivity.this, new Vector<Throwable>(),
-                        null, null,
-                        ErrorActivity.ErrorInfo.make(ErrorActivity.USER_REPORT,
-                                null,
-                                "user_report", R.string.user_report));
-                return true;
-            }
             default:
                 return super.onOptionsItemSelected(item);
         }

app/src/main/java/org/schabi/newpipe/util/NavStack.java

@@ -3,6 +3,7 @@ package org.schabi.newpipe.util;
 import android.app.Activity;
 import android.content.Context;
 import android.content.Intent;
+import android.os.Bundle;
 import android.support.v4.app.NavUtils;
 import android.support.v7.app.AppCompatActivity;
 import android.util.Log;
@@ -14,6 +15,7 @@ import org.schabi.newpipe.detail.VideoItemDetailFragment;
 import org.schabi.newpipe.extractor.NewPipe;
 import org.schabi.newpipe.extractor.StreamingService;
 
+import java.util.ArrayList;
 import java.util.Stack;
 
 /**
@@ -45,6 +47,8 @@ public class NavStack {
     public static final String SERVICE_ID = "service_id";
     public static final String URL = "url";
 
+    private static final String NAV_STACK="nav_stack";
+
     private enum ActivityId {
         CHANNEL,
         DETAIL
@@ -74,33 +78,39 @@ public class NavStack {
     }
 
     public void navBack(Activity activity) throws Exception {
+        if(stack.size() == 0) { // if stack is already empty here, activity was probably called
+            // from another app
+            activity.finish();
+            return;
+        }
         stack.pop(); // remove curent activty, since we dont want to return to itself
-        if(stack.size() == 0) {
+        if (stack.size() == 0) {
             openMainActivity(activity); // if no more page is on the stack this means we are home
-        } else {
+            return;
-            NavEntry entry = stack.pop();  // this element will reapear, since by calling the old page
+        }
-            // this element will be pushed on top again
+        NavEntry entry = stack.pop();  // this element will reapear, since by calling the old page
-            try {
+        // this element will be pushed on top again
-                StreamingService service = NewPipe.getService(entry.serviceId);
+        try {
-                switch (service.getLinkTypeByUrl(entry.url)) {
+            StreamingService service = NewPipe.getService(entry.serviceId);
-                    case STREAM:
+            switch (service.getLinkTypeByUrl(entry.url)) {
-                        openDetailActivity(activity, entry.url, entry.serviceId);
+                case STREAM:
-                        break;
+                    openDetailActivity(activity, entry.url, entry.serviceId);
-                    case CHANNEL:
+                    break;
-                        openChannelActivity(activity, entry.url, entry.serviceId);
+                case CHANNEL:
-                        break;
+                    openChannelActivity(activity, entry.url, entry.serviceId);
-                    case NONE:
+                    break;
-                        throw new Exception("Url not known to service. service="
+                case NONE:
-                                + Integer.toString(entry.serviceId) + " url=" + entry.url);
+                    throw new Exception("Url not known to service. service="
-                    default:
+                            + Integer.toString(entry.serviceId) + " url=" + entry.url);
-                        openMainActivity(activity);
+                default:
-                }
+                    openMainActivity(activity);
-            } catch (Exception e) {
-                e.printStackTrace();
             }
+        } catch (Exception e) {
+            e.printStackTrace();
         }
     }
 
+
     public void openChannelActivity(Context context, String url, int serviceId) {
         openActivity(context, url, serviceId, ChannelActivity.class);
     }
@@ -117,9 +127,25 @@ public class NavStack {
         context.startActivity(i);
     }
 
-    private void openMainActivity(Activity a) {
+    public void openMainActivity(Activity a) {
+        stack.clear();
         Intent i = new Intent(a, MainActivity.class);
         i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
         NavUtils.navigateUpTo(a, i);
     }
+
+    public void onSaveInstanceState(Bundle state) {
+        ArrayList<String> sa = new ArrayList<>();
+        for(NavEntry entry : stack) {
+            sa.add(entry.url);
+        }
+        state.putStringArrayList(NAV_STACK, sa);
+    }
+
+    public void restoreSavedInstanceState(Bundle state) {
+        ArrayList<String> sa = state.getStringArrayList(NAV_STACK);
+        for(String url : sa) {
+            stack.push(new NavEntry(url, NewPipe.getServiceByUrl(url).getServiceId()));
+        }
+    }
 }

app/src/main/res/menu/download_menu.xml

@@ -2,12 +2,7 @@
 <menu xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto">
 
-
     <item android:id="@+id/action_settings"
         app:showAsAction="never"
         android:title="@string/settings"/>
-
-    <item android:id="@+id/action_report_error"
-        app:showAsAction="never"
-        android:title="@string/report_error" />
 </menu>