Add attribute show_hidden_files to FilePickerPreference & update README

Author: mrgames13

Readme.md

@@ -68,6 +68,7 @@ Step 2. Add the dependency
         properties.error_dir = new File(DialogConfigs.DEFAULT_DIR);
         properties.offset = new File(DialogConfigs.DEFAULT_DIR);
         properties.extensions = null;
+        properties.show_hidden_files = false;
     ```
 
 3. Next create an instance of `FilePickerDialog`, and pass `Context` and `DialogProperties` references as parameters. Optional: You can change the title of dialog. Default is current directory name. Set the positive button string. Default is Select. Set the negative button string. Defalut is Cancel.
@@ -132,7 +133,8 @@ Marshmallow and above requests for the permission on runtime. You should overrid
            app:root_dir="/sdcard"
            app:selection_mode="multi_mode"
            app:selection_type="dir_select"
-           app:extensions="txt:pdf:"/>
+           app:extensions="txt:pdf:"
+           app:show_hidden_files="false"/>
     ```
 
 2. Implement [Preference.OnPreferenceChangeListener](https://developer.android.com/reference/android/preference/Preference.OnPreferenceChangeListener.html) to class requiring selected values and `Override` `onPreferenceChange(Preference, Object)` method. Check for preference key using [Preference](https://developer.android.com/reference/android/preference/Preference.html) reference.

library/src/main/java/com/developer/filepicker/view/FilePickerPreference.java

@@ -8,10 +8,12 @@
 import android.preference.Preference;
 import android.util.AttributeSet;
 import android.view.View;
+
 import com.developer.filepicker.R;
 import com.developer.filepicker.controller.DialogSelectionListener;
 import com.developer.filepicker.model.DialogConfigs;
 import com.developer.filepicker.model.DialogProperties;
+
 import java.io.File;
 
 /**
@@ -72,7 +74,7 @@ protected Parcelable onSaveInstanceState() {
 
     @Override
     protected void onRestoreInstanceState(Parcelable state) {
-        if (state == null || !(state instanceof SavedState)) {
+        if (!(state instanceof SavedState)) {
             super.onRestoreInstanceState(state);
             return;
         }
@@ -188,6 +190,9 @@ else if (attr == R.styleable.FilePickerPreference_extensions) {
             else if (attr == R.styleable.FilePickerPreference_title_text) {
                 titleText=tarr.getString(R.styleable.FilePickerPreference_title_text);
             }
+            else if (attr == R.styleable.FilePickerPreference_show_hidden_files) {
+                properties.show_hidden_files = tarr.getBoolean(R.styleable.FilePickerPreference_show_hidden_files, false);
+            }
         }
         tarr.recycle();
     }

library/src/main/res/values/attrs.xml

@@ -31,5 +31,9 @@
             name="title_text"
             format="string"/>
 
+        <attr
+            name="show_hidden_files"
+            format="boolean"/>
+
     </declare-styleable>
 </resources>