Mobile Programming Lecture 3. Resources, Selection, Activities, Intents

Transcription

1 Mobile Programming Lecture 3 Resources, Selection, Activities, Intents

2 Lecture 2 Review What widget would you use to allow the user to enter a yes/no value a range of values from 1 to 100 What's the benefit of a TableLayout over LinearLayout? How many ways can you set an event listener?

3 Lecture 2 Review How do you make the android:inputtype attribute of an EditText both textcapwords and textmultiline? Why should you use resource for TextViews instead of hardcoding the string? If you use the same android:onclick value for multiple views, how do you determine which one was clicked?

4 Agenda resources Setters and Getters Selection Views Android Components - Activity Intents More on the Android Manifest File

5 String Resources Three types of string resources String String Array Quantity Strings

6 String Resources Three types of string resources String String Array Quantity Strings

7 String Resources - String Used to store a single string resource <string name= sample_string >Sample String</string> Referenced - in XML Resources res = getresources(); res.getstring() / gettext() //gettext() retains any text styling

8 String Resources Three types of string resources String String Array Quantity Strings

9 String Resources - String Array Used to provide an array of strings <string-array name= array_name > <item>item 1</item> <item>item 2</item> <item>item 3</item> </string-array> Referenced in XML Resources res = getresources(); res.getstringarray();

10 String Resources Three types of string resources String String Array Quantity Strings

11 String Resources - Quantity Strings Used to provide different string outputs for plurals <plurals name= plural_name > <item quantity= one >%d student has an A</item> <item quantity= other >%d students have an A</item> </plurals> Referenced using: Resource res = getresources(); res.getquantitystring(r.plurals.plural_name, count, count);

12 Resources Resources are stored in res/values/strings.xml You reference them in XML as

13 Resources You can also reference them in Java String buttontext = ""; Resources res = getresources(); buttontext = res.getstring(r.string.string_name);

14 Referencing Resources You can store an array of strings if you need a collection instead of just a single string. This makes it resource instead resource! Open res/values/strings.xml and create the new entry You can also get some assistance by Right-click the body of the strings.xml file Select Generate > XML Tag Select the appropriate resource type (string-array) Provide your resource with a name, e.g. "countries" Add an <item> entry for each item in the array

15 Setters and Getters for Views Most of a View's attributes can be set and get programmatically Example widget XML attribute set method get method EditText android:text settext(string) gettext() Button android:onclick setonclicklistener( OnClickListener) - CheckBox android:checked setchecked(boolean) ischecked() SeekBar android:progress setprogress(int) getprogress() SeekBar android:max setmax(int) getmax()

16 Selection Widgets - Spinner Similar to a drop-down list android:spinnermode "dialog" or "dropdown" android:prompt e.g. "Select an option" message to display when the spinner dialog is shown only when android:spinnermode="dialog" android:entries e.g. "@array/countries" populate the spinner using this array

17 Selection Widgets - Spinner Similar to a drop-down list android:prompt e.g. "Select If the list is static, an option" you message can again to display avoid Java when the spinner dialog is shown by specifying the android:spinnermode "dialog" or "dropdown" android:entries entries in XML! e.g. "@array/countries" populate the spinner using this array

18 Selection Widgets - Spinner Similar to a drop-down list android:prompt e.g. "Select an option" message to display when the spinner dialog is shown android:spinnermode you can set the entries "dialog" or "dropdown" android:entries If you don't like XML, in Java also. e.g. "@array/countries" populate the spinner using this array

19 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Spinner myspinner = (Spinner) findviewbyid(r.id.my_spinner); ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.countries, android.r.layout.simple_spinner_item); myspinner.setadapter(adapter);

20 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Spinner myspinner = (Spinner) findviewbyid(r.id.my_spinner); This is the Java code. If you choose to do this, then you don't need to set the android:entries attribute ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.countries, android.r.layout.simple_spinner_item); myspinner.setadapter(adapter);

21 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); You should already know what this does. setcontentview(r.layout.main); Spinner myspinner = (Spinner) findviewbyid(r.id.my_spinner); ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.countries, android.r.layout.simple_spinner_item); myspinner.setadapter(adapter);

22 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Since you don't like XML, to do it programmatically, you need to use an Adapter. Spinner spinner = (Spinner) findviewbyid(r.id.my_spinner); ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.countries, android.r.layout.simple_spinner_item); myspinner.setadapter(adapter);

23 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); This is Java stuff. If you don't know what it is, try Spinner myspinner = (Spinner) findviewbyid(r.id.my_spinner); removing it to see what happens. ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.countries, android.r.layout.simple_spinner_item); myspinner.setadapter(adapter);

24 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Spinner myspinner = (Spinner) If you have resource already, then create an ArrayAdapter from that resource. findviewbyid(r.id.my_spinner); ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.countries, android.r.layout.simple_spinner_item); myspinner.setadapter(adapter);

25 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Spinner myspinner = (Spinner) findviewbyid(r.id.my_spinner); ArrayAdapter<CharSequence> adapter = First argument is of type Context, you can just pass the "this" keyword here (because of the state of app) ArrayAdapter.createFromResource(this, R.array.countries, android.r.layout.simple_spinner_item); myspinner.setadapter(adapter);

26 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Spinner myspinner = (Spinner) findviewbyid(r.id.my_spinner); This is the resource that you're creating the ArrayAdapter<CharSequence> from. adapter = ArrayAdapter.createFromResource(this, R.array.countries, android.r.layout.simple_spinner_item); myspinner.setadapter(adapter);

27 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Spinner myspinner = (Spinner) findviewbyid(r.id.my_spinner); ArrayAdapter<CharSequence> 3rd argument expects adapter = of a TextView. ArrayAdapter.createFromResource(this, R.array.countries, android.r.layout.simple_spinner_item); myspinner.setadapter(adapter);

28 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Spinner myspinner = (Spinner) findviewbyid(r.id.my_spinner); android.r gives you ArrayAdapter<CharSequence> resources that exist for adapter = use even before you ArrayAdapter.createFromResource(this, your app R.array.countries, android.r.layout.simple_spinner_item); myspinner.setadapter(adapter);

29 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Spinner myspinner = (Spinner) findviewbyid(r.id.my_spinner); So instead of creating and using your own TextView for this ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, purpose, use this one R.array.countries, android.r.layout.simple_spinner_item); myspinner.setadapter(adapter);

30 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Spinner myspinner = (Spinner) findviewbyid(r.id.my_spinner); ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.countries, android.r.layout.simple_spinner_item); Attach the Adapter to the Spinner in order to populate the Spinner! myspinner.setadapter(adapter);

31 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Spinner myspinner = (Spinner) findviewbyid(r.id.my_spinner); ArrayAdapter<CharSequence> adapter = Finally, this line of code is not required, but it makes your drop down look pretty. ArrayAdapter.createFromResource(this, R.array.countries, android.r.layout.simple_spinner_item); adapter.setdropdownviewresource (android.r.layout.simple_spinner_dropdown_item); myspinner.setadapter(adapter);

32 Selection Widgets - Spinner Both ways give you a Spinner which uses predetermined entries How do you populate the Spinner at runtime, when the entries are also determined at runtime?

33 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Spinner myspinner = (Spinner) findviewbyid(r.id.my_spinner); String[] countries = new String[]{ "Brazil", "China", "Denmark" ; ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.r.layout.simple_spinner_item, countries); myspinner.setadapter(adapter);

34 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Create and initialize a String array Spinner spinner = (Spinner) findviewbyid(r.id.my_spinner); String[] countries = new String[] { "Brazil", "China", "Denmark" ; ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.r.layout.simple_spinner_item, countries); myspinner.setadapter(adapter);

35 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Spinner myspinner = (Spinner) findviewbyid(r.id.my_spinner); String[] countries = new String[] { "Brazil", "China", Create an ArrayAdapter to populate "Denmark"; the Spinner with ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.r.layout.simple_spinner_item, countries); myspinner.setadapter(adapter);

36 Selection Widgets - Spinner public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Spinner myspinner = (Spinner) findviewbyid(r.id.my_spinner); String[] countries = new String[] { "Brazil", "China", "Denmark" ; 3rd argument accepts a List of Strings ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.r.layout.simple_spinner_item, countries); myspinner.setadapter(adapter);

37 Selection Widgets - ListView A ListView is similar to a Spinner They both show the user a list of items They both have the android:entries attribute, so they can both be set using the resource or the same ArrayAdapter

38 Selection Widgets - ListView A ListView is similar to a Spinner with some exceptions, to name a few: A Spinner is normally used for forms, a ListView not so much A Spinner only shows one item at a time A Spinner item can be "selected", a ListView item can be "clicked" or "selected"

39 Selection Widgets - ListView A ListView is similar to a Spinner with some exceptions, to name a few: A Spinner is normally used for forms, a ListView not This was added in so much hindsight. On A Spinner only non-touch-screen shows one devices item at a time can be selected A Spinner item can be "selected", a ListView item can be "clicked" or "selected"

40 Events - Spinner OnItemSelected You can set an EventListener for when the user selects an item from the Spinner

41 Events - Spinner OnItemSelected myspinner.setonitemselectedlistener(new OnItemSelectedListener() public void onitemselected(adapterview<?> parent, View view, int position, long id) { Toast.makeText(getApplicationContext(), ((TextView) view).gettext(), Toast.LENGTH_SHORT).show(); public void onnothingselected(adapterview<?> parent) { Toast.makeText(getApplicationContext(), "You didn't select anything", Toast.LENGTH_SHORT).show();

42 Events Setter - method Spinner for OnItemSelected setting the EventListener myspinner.setonitemselectedlistener(new OnItemSelectedListener() public void onitemselected(adapterview<?> parent, View view, int position, long id) { Toast.makeText(getApplicationContext(), ((TextView) view).gettext(), Toast.LENGTH_SHORT).show(); public void onnothingselected(adapterview<?> parent) { Toast.makeText(getApplicationContext(), "You didn't select anything", Toast.LENGTH_SHORT).show();

43 Events - Spinner OnItemSelected Anonymous class myspinner.setonitemselectedlistener(new OnItemSelectedListener() public void onitemselected(adapterview<?> parent, View view, int position, long id) { Toast.makeText(getApplicationContext(), ((TextView) view).gettext(), Toast.LENGTH_SHORT).show(); public void onnothingselected(adapterview<?> parent) { Toast.makeText(getApplicationContext(), "You didn't select anything", Toast.LENGTH_SHORT).show();

44 Events - Spinner OnItemSelected When an item is myspinner.setonitemselectedlistener(new selected..., OnItemSelectedListener() public void onitemselected(adapterview<?> parent, View view, int position, long id) { Toast.makeText(getApplicationContext(), ((TextView) view).gettext(), Toast.LENGTH_SHORT).show(); public void onnothingselected(adapterview<?> parent) { Toast.makeText(getApplicationContext(), "You didn't select anything", Toast.LENGTH_SHORT).show();

45 Events - Spinner OnItemSelected You can now reference the actual View (i.e., myspinner.setonitemselectedlistener(new OnItemSelectedListener() each entry in Spinner { is a public void onitemselected(adapterview<?> parent, View view, int position, long id) { Toast.makeText(getApplicationContext(), ((TextView) view).gettext(), Toast.LENGTH_SHORT).show(); public void onnothingselected(adapterview<?> parent) { Toast.makeText(getApplicationContext(), "You didn't select anything", Toast.LENGTH_SHORT).show();

46 Events - Spinner OnItemSelected myspinner.setonitemselectedlistener(new OnItemSelectedListener() { The position of the in the Adapter public void onitemselected(adapterview<?> parent, View view, int position, long id) { Toast.makeText(getApplicationContext(), ((TextView) view).gettext(), Toast.LENGTH_SHORT).show(); public void onnothingselected(adapterview<?> parent) { Toast.makeText(getApplicationContext(), "You didn't select anything", Toast.LENGTH_SHORT).show();

47 Events - Spinner OnItemSelected myspinner.setonitemselectedlistener(new The android:id attribute OnItemSelectedListener() of the view public void onitemselected(adapterview<?> parent, View view, int position, long id) { Toast.makeText(getApplicationContext(), ((TextView) view).gettext(), Toast.LENGTH_SHORT).show(); public void onnothingselected(adapterview<?> parent) { Toast.makeText(getApplicationContext(), "You didn't select anything", Toast.LENGTH_SHORT).show();

48 Events - Spinner OnItemSelected myspinner.setonitemselectedlistener(new OnItemSelectedListener() public void onitemselected(adapterview<?> parent, View view, Cast the generic View int position, to long a TextView id) { Toast.makeText(getApplicationContext(), ((TextView) view).gettext(), Toast.LENGTH_SHORT).show(); public void onnothingselected(adapterview<?> parent) { Toast.makeText(getApplicationContext(), "You didn't select anything", Toast.LENGTH_SHORT).show();

49 Events - Spinner OnItemSelected myspinner.setonitemselectedlistener(new OnItemSelectedListener() public void onitemselected(adapterview<?> Get the android:text parent, View view, int position, long id) { value Toast.makeText(getApplicationContext(), ((TextView) view).gettext(), Toast.LENGTH_SHORT).show(); public void onnothingselected(adapterview<?> parent) { Toast.makeText(getApplicationContext(), "You didn't select anything", Toast.LENGTH_SHORT).show();

50 Events - Spinner OnItemSelected Note that we're using OnItemSelectedListener instead of OnItemClickListener for Spinner! If you try to use OnItemClickListener you may get errors Also, note the difference between these two listeners and OnClickListener OnItemClickListener an entry in the Spinner has been clicked, don't use this OnClickListener the Spinner has been clicked OnItemSelectedListener an entry in the Spinner has been selected

51 Events - ListView OnItemClick As mentioned before, a ListView item can be clicked, or selected In that case, you use OnItemClickListener or OnItemSelectedListener

52 Events - ListView OnItemClick mylistview.setonitemclicklistener(new OnItemClickListener() public void onitemclick(adapterview<?> parent, View view, int position, long id) { Toast.makeText(getApplicationContext(), ((TextView) view).gettext(), Toast.LENGTH_SHORT).show(); );

53 Android Application Components So far we've only been working with 1 of the 4 Android components, namely Activity

54 Android Application Components The 4 Android application components are 1. Activity 2. Broadcast Receiver 3. Content Provider 4. Service

55 Android Application Components 1. Activity 2. Broadcast Receiver 3. Content Provider 4. Service

56 Activity So far we've only been working with a single Activity Remember, an Activity is a single screen with a user interface Each Activity in an application is independent

57 Activity An Activity is the only Android application component with a UI!

58 Activity In Homework 2, you're creating a form that doesn't do anything after the form is submitted If you want to take the user to a different screen after the form is submitted, you should add a new Activity to your app

59 Activity To add a new Activity Right-click your project and choose New > Activity Select an Activity template, provide a name for the Layout Resource file and provide any other necessary information Click Finish Or Create a new Java class that extends the Activity base class Open the AndroidManifest.xml file Add a new <activity> tag and configure the appropriate attributes Save the AndroidManifest.xml file

60 Activity You can design the UI for your second Activity as well e.g. add another res/layout/xml_file.xml Now we need to figure out how to launch the second Activity B from the first Activity A

61 Intent An Intent is an abstract description of an operation to be performed You can use an Intent to launch another Activity B from within Activity A

62 Activity and Intent... public void onclick(view view) { Intent myintent = new Intent(A.this, B.class); startactivity(intent);...

63 Activity and Intent... public void onclick(view view) { Intent myintent = new Intent(A.this, B.class); startactivity(myintent); The name of the Activity the app is currently running...

64 Activity and Intent... public void onclick(view view) The name of the Activity { that should be launched Intent myintent = new Intent(A.this, B.class); startactivity(myintent);...

65 Activity and Intent... public void onclick(view view) { Intent Launch Activity B myintent now = new Intent(A.this, B.class); startactivity(myintent);...

66 Activity - Android Manifest File If you added the second Activity B using the wizard/template, then B will be automatically added to the Android Manifest file If you added it manually, then Activity B may not be in the Manifest File. This is an easy to get a Force Close when you try to launch Activity B! Android needs to know what Activities your app may launch

67 Activity - ListActivity Sometimes the entire UI for your Activity may be a ListView In this case, you can extend ListActivity instead of extending Activity You don't need a layout.xml file for a ListActivity!

68 Activity - ListActivity public class MyListActivity extends ListActivity public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); String[] list = new String[] { "one", "two", "three" ; ArrayAdapter<CharSequence> adapter = new ArrayAdapter<CharSequence>(this, android.r.layout.simple_list_item_1, list); setlistadapter(adapter);

69 Activity - ListActivity extend ListActivity instead of Activity public class MyListActivity extends ListActivity public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); String[] list = new String[]{"one","two","three"; ArrayAdapter<CharSequence> adapter = new ArrayAdapter<CharSequence>(this, android.r.layout.simple_list_item_1, list); setlistadapter(adapter);

70 Activity - ListActivity public class MyListActivity extends ListActivity public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); We don't need to setcontentview because we're String[] list = new String[]{"one","two","three"; extending ListActivity ArrayAdapter<CharSequence> adapter = new ArrayAdapter<CharSequence>(this, android.r.layout.simple_list_item_1, list); setlistadapter(adapter);

71 Activity - ListActivity public class MyListActivity extends ListActivity public void oncreate(bundle savedinstancestate) { We've seen this before in this lecture super.oncreate(savedinstancestate); String[] list = new String[] { "Brazil", "China", "Denmark"; ArrayAdapter<CharSequence> adapter = new ArrayAdapter<CharSequence>(this, android.r.layout.simple_list_item_1, list); setlistadapter(adapter);

72 Activity - ListActivity public class MyListActivity extends ListActivity public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); We've also seen this before in this lecture String[] list = new String[]{ "Brazil", "China", "Denmark"; ArrayAdapter<CharSequence> adapter = new ArrayAdapter<CharSequence>(this, android.r.layout.simple_list_item_1, list); setlistadapter(adapter);

73 Activity - ListActivity public class MyListActivity extends ListActivity public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); String[] list = new String[] { "Brazil", "China", "Denmark"; ArrayAdapter<CharSequence> adapter = We call setlistadapter on this ListActivity instead of calling it on a ListView (we don't have a ListView specified in an XML file this time!) new ArrayAdapter<CharSequence>(this, android.r.layout.simple_list_item_1, list); setlistadapter(adapter);

74 Activity - ListActivity public class MyListActivity extends ListActivity public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); String[] list = new String[] { "Brazil", "China", "Denmark"; ArrayAdapter<CharSequence> adapter = This is equivalent to calling this.setlistadapter(adapter); i.e., using the this keyword to refer to this instance of MyListActivity new ArrayAdapter<CharSequence>(this, android.r.layout.simple_list_item_1, list); setlistadapter(adapter);

75 References The Busy Coder's Guide to Android Development - Mark Murphy Android Developers The Mobile Lab at Florida State University