add file select preference for media downloads

app/src/main/java/com/dkanada/gramophone/util/PreferenceUtil.java

@@ -130,6 +130,10 @@ public final class PreferenceUtil {
         return instance;
     }
 
+    public SharedPreferences getPreferences() {
+        return mPreferences;
+    }
+
     public void registerOnSharedPreferenceChangedListener(SharedPreferences.OnSharedPreferenceChangeListener sharedPreferenceChangeListener) {
         mPreferences.registerOnSharedPreferenceChangeListener(sharedPreferenceChangeListener);
     }

app/src/main/java/com/dkanada/gramophone/views/settings/FilePreference.java

@@ -0,0 +1,59 @@
+package com.dkanada.gramophone.views.settings;
+
+import android.app.Activity;
+import android.app.FragmentManager;
+import android.content.Context;
+import android.content.SharedPreferences;
+import android.util.AttributeSet;
+import android.view.View;
+
+import androidx.preference.Preference;
+import androidx.preference.PreferenceViewHolder;
+
+import com.codekidlabs.storagechooser.StorageChooser;
+import com.dkanada.gramophone.util.PreferenceUtil;
+
+public class FilePreference extends Preference implements View.OnClickListener, StorageChooser.OnSelectListener {
+    private final SharedPreferences preferences;
+    private final String defaultLocation;
+
+    public FilePreference(Context context, AttributeSet attrs) {
+        super(context, attrs);
+
+        preferences = PreferenceUtil.getInstance(getContext()).getPreferences();
+        defaultLocation = getContext().getCacheDir().toString();
+
+        setSummary(preferences.getString(getKey(), defaultLocation));
+    }
+
+    @Override
+    public void onBindViewHolder(PreferenceViewHolder holder) {
+        super.onBindViewHolder(holder);
+
+        holder.itemView.setOnClickListener(this);
+    }
+
+    @Override
+    public void onSelect(String path) {
+        preferences.edit().putString(getKey(), path).apply();
+        setSummary(path);
+    }
+
+    @Override
+    public void onClick(View v) {
+        Activity activity = (Activity) getContext();
+        FragmentManager fragmentManager = activity.getFragmentManager();
+
+        StorageChooser chooser = new StorageChooser.Builder()
+            .withActivity(activity)
+            .withFragmentManager(fragmentManager)
+            .withPredefinedPath(preferences.getString(getKey(), defaultLocation))
+            .allowCustomPath(true)
+            .allowAddFolder(true)
+            .setType(StorageChooser.DIRECTORY_CHOOSER)
+            .build();
+
+        chooser.setOnSelectListener(this);
+        chooser.show();
+    }
+}