tls-psk: add compatibility fragment for android < 5

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/MainActivity.java

@@ -20,6 +20,8 @@
 package org.sufficientlysecure.keychain.ui;
 
 import android.content.Intent;
+import android.os.Build;
+import android.os.Build.VERSION_CODES;
 import android.os.Bundle;
 import android.support.v4.app.Fragment;
 import android.support.v4.app.FragmentManager;
@@ -42,6 +44,7 @@ import org.sufficientlysecure.keychain.operations.results.OperationResult;
 import org.sufficientlysecure.keychain.remote.ui.AppsListFragment;
 import org.sufficientlysecure.keychain.ui.base.BaseSecurityTokenActivity;
 import org.sufficientlysecure.keychain.ui.transfer.view.TransferFragment;
+import org.sufficientlysecure.keychain.ui.transfer.view.TransferNotAvailableFragment;
 import org.sufficientlysecure.keychain.util.FabContainer;
 import org.sufficientlysecure.keychain.util.Preferences;
 
@@ -176,7 +179,6 @@ public class MainActivity extends BaseSecurityTokenActivity implements FabContai
     }
 
     private void setFragment(Fragment fragment, boolean addToBackStack) {
-
         FragmentManager fragmentManager = getSupportFragmentManager();
         fragmentManager.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
 
@@ -221,8 +223,13 @@ public class MainActivity extends BaseSecurityTokenActivity implements FabContai
     private void onTransferSelected() {
         mToolbar.setTitle(R.string.nav_transfer);
         mDrawer.setSelection(ID_TRANSFER, false);
-        Fragment frag = new TransferFragment();
-        setFragment(frag, true);
+        if (Build.VERSION.SDK_INT < VERSION_CODES.LOLLIPOP) {
+            Fragment frag = new TransferNotAvailableFragment();
+            setFragment(frag, true);
+        } else {
+            Fragment frag = new TransferFragment();
+            setFragment(frag, true);
+        }
     }
 
     @Override

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/transfer/view/TransferNotAvailableFragment.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2017 Vincent Breitmoser <look@my.amazin.horse>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.sufficientlysecure.keychain.ui.transfer.view;
+
+
+import android.os.Bundle;
+import android.support.annotation.Nullable;
+import android.support.v4.app.Fragment;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+import org.sufficientlysecure.keychain.R;
+
+
+public class TransferNotAvailableFragment extends Fragment {
+    @Override
+    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
+        return inflater.inflate(R.layout.transfer_not_available_fragment, container, false);
+    }
+}