Use PassCode static values instead of literal strings

src/com/owncloud/android/ui/activity/PassCodeActivity.java

@@ -59,6 +59,7 @@ public class PassCodeActivity extends AppCompatActivity {
     // NOTE: PREFERENCE_SET_PASSCODE must have the same value as preferences.xml-->android:key for passcode preference
     public final static String PREFERENCE_SET_PASSCODE = "set_pincode";
 
+    public final static String PREFERENCE_PASSCODE_D = "PrefPinCode";
     public final static String PREFERENCE_PASSCODE_D1 = "PrefPinCode1";
     public final static String PREFERENCE_PASSCODE_D2 = "PrefPinCode2";
     public final static String PREFERENCE_PASSCODE_D3 = "PrefPinCode3";

src/com/owncloud/android/ui/activity/Preferences.java

@@ -616,9 +616,9 @@ public class Preferences extends PreferenceActivity
                         .getDefaultSharedPreferences(getApplicationContext()).edit();
 
                 for (int i = 1; i <= 4; ++i) {
-                    appPrefs.putString("PrefPinCode" + i, passcode.substring(i-1, i));
+                    appPrefs.putString(PassCodeActivity.PREFERENCE_PASSCODE_D + i, passcode.substring(i-1, i));
                 }
-                appPrefs.putBoolean("set_pincode", true);
+                appPrefs.putBoolean(PassCodeActivity.PREFERENCE_SET_PASSCODE, true);
                 appPrefs.commit();
                 Toast.makeText(this, R.string.pass_code_stored, Toast.LENGTH_LONG).show();
             }
@@ -627,7 +627,7 @@ public class Preferences extends PreferenceActivity
 
                 SharedPreferences.Editor appPrefs = PreferenceManager
                         .getDefaultSharedPreferences(getApplicationContext()).edit();
-                appPrefs.putBoolean("set_pincode", false);
+                appPrefs.putBoolean(PassCodeActivity.PREFERENCE_SET_PASSCODE, false);
                 appPrefs.commit();
 
                 Toast.makeText(this, R.string.pass_code_removed, Toast.LENGTH_LONG).show();