fix start/pause buttons disappear when screen goes off

* fix start/pause buttons disappear, issued by RecyclerView re-draw
* show start/pause buttons in pair to avoid confusions

app/src/main/java/us/shandian/giga/service/DownloadManager.java

@@ -666,9 +666,9 @@ public class DownloadManager {
                         continue;
 
                     if (mission.running)
-                        paused = true;
-                    else
                         running = true;
+                    else
+                        paused = true;
                 }
             }
 

app/src/main/java/us/shandian/giga/ui/adapter/MissionAdapter.java

@@ -122,14 +122,8 @@ public class MissionAdapter extends Adapter<ViewHolder> {
                         break;
                 }
 
-                if (mStartButton != null && mPauseButton != null) switch (msg.what) {
+                if (mStartButton != null && mPauseButton != null)
-                    case DownloadManagerService.MESSAGE_DELETED:
-                    case DownloadManagerService.MESSAGE_ERROR:
-                    case DownloadManagerService.MESSAGE_FINISHED:
-                    case DownloadManagerService.MESSAGE_PAUSED:
                     checkMasterButtonsVisibility();
-                        break;
-                }
             }
         };
 
@@ -163,8 +157,7 @@ public class MissionAdapter extends Adapter<ViewHolder> {
             mPendingDownloadsItems.remove(h);
             if (mPendingDownloadsItems.size() < 1) {
                 setAutoRefresh(false);
-                if (mStartButton != null) mStartButton.setVisible(false);
+                checkMasterButtonsVisibility();
-                if (mPauseButton != null) mPauseButton.setVisible(false);
             }
         }
 
@@ -664,11 +657,11 @@ public class MissionAdapter extends Adapter<ViewHolder> {
         if (mEmptyMessage.getVisibility() != flag) mEmptyMessage.setVisibility(flag);
     }
 
-    private void checkMasterButtonsVisibility() {
+    public void checkMasterButtonsVisibility() {
         boolean[] state = mIterator.hasValidPendingMissions();
 
-        mStartButton.setVisible(state[0]);
+        mPauseButton.setVisible(state[0]);
-        mPauseButton.setVisible(state[1]);
+        mStartButton.setVisible(state[1]);
     }
 
     public void ensurePausedMissions() {

app/src/main/java/us/shandian/giga/ui/fragment/MissionsFragment.java

@@ -7,6 +7,7 @@ import android.content.Context;
 import android.content.Intent;
 import android.content.ServiceConnection;
 import android.content.SharedPreferences;
+import android.content.res.Configuration;
 import android.os.Bundle;
 import android.os.IBinder;
 import android.preference.PreferenceManager;
@@ -138,6 +139,7 @@ public class MissionsFragment extends Fragment {
      * deprecated in API level 23,
      * but must remain to allow compatibility with api<23
      */
+    @SuppressWarnings("deprecation")
     @Override
     public void onAttach(Activity activity) {
         super.onAttach(activity);
@@ -169,6 +171,15 @@ public class MissionsFragment extends Fragment {
 
         if (mAdapter != null) setAdapterButtons();
 
+        int max = getMaxActionButtons() - 1 /* grid button */;
+        if (max >= 2) {
+            // show start/pause downloads buttons in pair to avoid confusions
+            mStart.setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS);
+            mPause.setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS);
+
+            if (max > 3) mClear.setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS);
+        }
+
         super.onPrepareOptionsMenu(menu);
     }
 
@@ -249,6 +260,23 @@ public class MissionsFragment extends Fragment {
         );
     }
 
+    public int getMaxActionButtons() {
+        Configuration configuration = mContext.getResources().getConfiguration();
+        int widthDp = configuration.screenWidthDp;
+        int heightDp = configuration.screenHeightDp;
+        int smallest = configuration.smallestScreenWidthDp;
+
+        if (smallest > 600 || widthDp > 600) {
+            return 5;
+        } else if (widthDp >= 500 || widthDp > 480 && heightDp > 640) {
+            return 4;
+        } else if (widthDp >= 360) {
+            return 3;
+        } else {
+            return 2;
+        }
+    }
+
     @Override
     public void onSaveInstanceState(@NonNull Bundle outState) {
         super.onSaveInstanceState(outState);
@@ -273,6 +301,7 @@ public class MissionsFragment extends Fragment {
             }
 
             mBinder.addMissionEventListener(mAdapter.getMessenger());
+            mAdapter.checkMasterButtonsVisibility();
         }
         if (mBinder != null) mBinder.enableNotifications(false);
     }

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

@@ -1,29 +1,31 @@
 <?xml version="1.0" encoding="utf-8"?>
-<menu xmlns:android="http://schemas.android.com/apk/res/android"
+<menu xmlns:tools="http://schemas.android.com/tools"
+    xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto">
 
     <item android:id="@+id/switch_mode"
         android:icon="?attr/ic_grid"
         android:title="@string/grid"
-        app:showAsAction="ifRoom" />
+        tools:ignore="AlwaysShowAction"
+        app:showAsAction="always" />
 
     <item android:id="@+id/start_downloads"
         android:visible="false"
         android:icon="?attr/play"
         android:title="@string/start_downloads"
-        app:showAsAction="ifRoom" />
+        app:showAsAction="never" />
 
     <item android:id="@+id/pause_downloads"
         android:visible="false"
         android:icon="?attr/pause"
         android:title="@string/pause_downloads"
-        app:showAsAction="ifRoom" />
+        app:showAsAction="never" />
 
     <item android:id="@+id/clear_list"
         android:visible="false"
         android:icon="?attr/ic_delete"
         android:title="@string/clear_finished_download"
-        app:showAsAction="ifRoom" />
+        app:showAsAction="never" />
 
     <item android:id="@+id/action_settings"
         android:title="@string/settings"