Extract export database logic into own class

- Separate it from the UI.
- Add happy path unit test.

app/src/main/java/org/schabi/newpipe/settings/ContentSettingsFragment.java

@@ -30,19 +30,15 @@ import org.schabi.newpipe.report.UserAction;
 import org.schabi.newpipe.util.FilePickerActivityHelper;
 import org.schabi.newpipe.util.ZipHelper;
 
-import java.io.BufferedOutputStream;
 import java.io.File;
 import java.io.FileInputStream;
-import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.ObjectInputStream;
-import java.io.ObjectOutputStream;
 import java.text.SimpleDateFormat;
 import java.util.Date;
 import java.util.Locale;
 import java.util.Map;
 import java.util.zip.ZipFile;
-import java.util.zip.ZipOutputStream;
 
 import static org.schabi.newpipe.util.Localization.assureCorrectAppLanguage;
 
@@ -50,6 +46,8 @@ public class ContentSettingsFragment extends BasePreferenceFragment {
     private static final int REQUEST_IMPORT_PATH = 8945;
     private static final int REQUEST_EXPORT_PATH = 30945;
 
+    private ContentSettingsManager manager;
+
     private File databasesDir;
     private File newpipeDb;
     private File newpipeDbJournal;
@@ -131,6 +129,8 @@ public class ContentSettingsFragment extends BasePreferenceFragment {
         newpipeSettings = new File(homeDir + "/databases/newpipe.settings");
         newpipeSettings.delete();
 
+        manager = new ContentSettingsManager(homeDir);
+
         addPreferencesFromResource(R.xml.content_settings);
 
         final Preference importDataPreference = findPreference(getString(R.string.import_data));
@@ -212,33 +212,16 @@ public class ContentSettingsFragment extends BasePreferenceFragment {
             //checkpoint before export
             NewPipeDatabase.checkpoint();
 
-            try (ZipOutputStream outZip = new ZipOutputStream(new BufferedOutputStream(
-                            new FileOutputStream(path)))) {
-                ZipHelper.addFileToZip(outZip, newpipeDb.getPath(), "newpipe.db");
+            final SharedPreferences preferences = PreferenceManager
+                .getDefaultSharedPreferences(requireContext());
+            manager.exportDatabase(preferences, path);
 
-                saveSharedPreferencesToFile(newpipeSettings);
-                ZipHelper.addFileToZip(outZip, newpipeSettings.getPath(),
-                        "newpipe.settings");
-            }
-
-            Toast.makeText(getContext(), R.string.export_complete_toast, Toast.LENGTH_SHORT)
-                    .show();
+            Toast.makeText(getContext(), R.string.export_complete_toast, Toast.LENGTH_SHORT).show();
         } catch (final Exception e) {
             onError(e);
         }
     }
 
-    private void saveSharedPreferencesToFile(final File dst) {
-        try (ObjectOutputStream output = new ObjectOutputStream(new FileOutputStream(dst))) {
-            final SharedPreferences pref
-                    = PreferenceManager.getDefaultSharedPreferences(requireContext());
-            output.writeObject(pref.getAll());
-            output.flush();
-        } catch (final IOException e) {
-            e.printStackTrace();
-        }
-    }
-
     private void importDatabase(final String filePath) {
         // check if file is supported
         try (ZipFile zipFile = new ZipFile(filePath)) {

app/src/main/java/org/schabi/newpipe/settings/ContentSettingsManager.kt

@@ -0,0 +1,45 @@
+package org.schabi.newpipe.settings
+
+import android.content.SharedPreferences
+import org.schabi.newpipe.util.ZipHelper
+import java.io.BufferedOutputStream
+import java.io.File
+import java.io.FileOutputStream
+import java.io.IOException
+import java.io.ObjectOutputStream
+import java.lang.Exception
+import java.util.zip.ZipOutputStream
+
+class ContentSettingsManager(
+    private val newpipeDb: File,
+    private val newpipeSettings: File
+) {
+
+    constructor(homeDir: String) : this(
+        File("$homeDir/databases/newpipe.db"),
+        File("$homeDir/databases/newpipe.settings")
+    )
+
+    /**
+     * Exports given [SharedPreferences] to the file in given outputPath.
+     * It also creates the file.
+     */
+    @Throws(Exception::class)
+    fun exportDatabase(preferences: SharedPreferences, outputPath: String) {
+        ZipOutputStream(BufferedOutputStream(FileOutputStream(outputPath)))
+            .use { outZip ->
+                ZipHelper.addFileToZip(outZip, newpipeDb.path, "newpipe.db")
+
+                try {
+                    ObjectOutputStream(FileOutputStream(newpipeSettings)).use { output ->
+                        output.writeObject(preferences.all)
+                        output.flush()
+                    }
+                } catch (e: IOException) {
+                    e.printStackTrace()
+                }
+
+                ZipHelper.addFileToZip(outZip, newpipeSettings.path, "newpipe.settings")
+            }
+    }
+}