Styles, Dialog Boxes, and Menus

Styles

Allow creation of a common format – placed in res/values/styles.xml – file name is incidental Can be applied to multiple widgets, layouts, etc. – When applied to layout, contained widgets are not affected – If applied to different kinds of widgets, attributes that do not apply are simply ignored One style can inherit another – attributes can be overridden Can be used to set a theme at the application or activity level

Example In styles.xml: wrap_content #FF0000 In Activity’s corresponding.xml file: <TextView android:text="I am using a style template" " />

Example of Inheritance Added to styles.xml: #0000FF 20dp In Activity’s corresponding.xml file: <TextView android:text="I am using an inheriting style template" " />

Example of a theme In styles.xml: #0F0F0F In Manifest file (as an attribute of either the Activity or Application): android:theme="myCustomTheme"

Dialog Boxes

Dialog boxes Presents information to the screen – error message – confirmation of a process – other Overlays another Activity – usually translucent and modal

Dialog Boxes Can be created in XML or programmatically – if created in XML: use an Activity with the Dialog theme onPause and onResume of parent fired off advantage: can be as robust as needed disadvantage: relatively unwieldy to pass information back from Dialog – if created programmatically use AlertDialog class no focus events fired off advantage: low overhead and access to all class entities disadvantage: interface is limited

Creating a DialogBox via xml

Creating DialogBox via xml Create an Activity with DialogBox theme – In Manifest file: <activity android:name=".Dialog" android:label="Data Entry Error"

Creating DialogBox via xml Component is technically an Activity, and all requirements remain the same – Manifest file entry,.xml file, and.java file – launched via the startActivity() method in parent Activity intent must be created – Dialog Activity presented modally ‘in front’ of parent activity – Using an Activity with the Dialog theme allows for added functionality

Creating DialogBox via xml openXMLDialog below is an example of a method within the main Activity public void openXMLDialog () { Intent i = new Intent(this, XMLDialog.class); startActivity(i); }

Creating a DialogBox programmatically

Creating DialogBox programmatically Component is created within the current Activity – No Manifest file entry,.xml file, or.java file – launched via the show() method in AlertDialog class (from a method in the parent Activity) – Dialog Activity presented modally ‘in front’ of parent activity setCancelable method determines if user can cancel the Dialog via the back button on the device – Minimal effort, minimal functionality

Creating DialogBox programmatically Can use one, two, or three buttons – all buttons automatically dismiss the dialog after corresponding code is executed – buttons appear right to left in following order positive neutral negative No difference between the three If none are chosen, program will be stuck with the modal dialog box – no build errors

Creating DialogBox programmatically public void inputError() { AlertDialog.Builder builder = new AlertDialog.Builder(this); builder.setCancelable(false); builder.setTitle("Data entry error"); builder.setMessage("Please enter a positive number in the number field"); builder.setPositiveButton("Ok", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { //Functionality goes here } }); ((EditText)findViewById(R.id.etNumField)).requestFocus(); AlertDialog alert = builder.create(); alert.show(); }

Menus

Can be created in xml or programmatically – If created in.xml, placed in res\menu\ folder Menu displayed by means of menu key on phone Must override the following methods in Activity – onCreateOptionsMenu creates the menu ‘inflates’ xml code or programmatically creates menu – onOptionsItemSelected provide the functionality to the menu

Creating a menu via xml

Creating a menu using xml This xml file would reside in the res\menu folder <item android:title="First" android:orderInCategory="1“ android:showAsAction="never" /> <item android:title="Second" android:orderInCategory="2“ android:showAsAction="never" />

Creating a menu using xml onCreateOptionsMenu() overridden in the corresponding Activity – called only once – first time menu is displayed onPrepareOptionsMenu is called every time menu is displayed – here ‘choices’ reflects the name of the menu xml file – a return value of true allows the menu to be public boolean onCreateOptionsMenu(Menu menu) { getMenuInflater().inflate(R.menu.choices, menu); return true; }

onCreateOptionsMenu return value – true menu can displayed – false menu cannot display Scenario – When Activity is displayed, may want the Menu available under certain conditions and not otherwise if (condition met) return true; else return false;

Creating a menu using xml onOptionsItemSelected() overridden in the corresponding Activity – Here ‘miX’ reflects the name of the menu item in the xml public boolean onOptionsItemSelected(MenuItem item) { switch(item.getItemId()) { case (R.id.mi1): //Functionality here case (R.id.mi2): //Functionality here } return true; }

onOptionsMenuItem return value – true consume menu processing here will not call super class’ onOptionsMenuItem – false will call super class’ onOptionsMenuItem Scenario – May have one activity that implements the menu, and others that subclass it if subclass handles subset of cases, handle those and return false in any case that is not handled

Creating a menu programmatically

onCreateOptionsMenu() overridden in the corresponding Activity – Each menu item added via the ‘add’ method in the Menu class parameters are: – group id, item id, order, title – group id useful if actions need to be taken on a group of items » removeGroup(), setGroupVisible(), etc. – item id is the unique id (value returned by getItemId()) – items will appear in numerical order by order parameter public boolean onCreateOptionsMenu(Menu menu) { menu.add(Menu.NONE, 1, 1, "First"); menu.add(Menu.NONE, 2, 2, "Second"); return true; }

Creating a menu programmatically onOptionsItemSelected() overridden in the corresponding Activity – getItemId() matches those set in public boolean onOptionsItemSelected(MenuItem item) { switch(item.getItemId()) { case 1: //Functionality here case 2: //Functionality here } return true; }