Manifest File, Intents, and Multiple Activities

1. Manifest File, Intents, and Multiple Activities

2. Manifest File

3. Manifest file • AndroidManifest.xml • required • indicates application information • activities (within application tag) • Android SDK version • activities used within the app • services that will be used (Web, phone, etc.) • other aspects

4. Manifest file – Application tag <application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name="edu.csci153.MultActivities" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name="Screen2" android:label="Second Screen" > </activity> </application>

5. Manifest File • Exploring the <application> tag • android:allowBackup=“true” • allows app and data to be backed up with a system restore • android:icon=“@drawable/ic_launcher” • Icon to display in the drawer • android:label="@string/app_name“ • Name of the icon in the drawer • <activity> • child of <application>

6. Manifest File • Exploring the <activity> tag • android:name=“edu.csci153.MultActivities” • Associated .java file • android:label=“@string/app_name” • Text that appears in title bar when this activity is displayed • <intent-filter> • child of <activity>

7. Manifest File • Exploring the <intent-filter> tag • <action android:name="android.intent.action.MAIN" /> • Indicates this is the main entry point of the application • <category android:name="android.intent.category.LAUNCHER" /> • Indicates that the activity should be launched • Without these lines, the application is started but no activity is presented • intent-filters ‘filter’ what an object can do – if there is no action defined within the filter, they implicitly deny that the action can be performed

8. Intents

9. Intent • Class within Android • android.content.Intent • contains information regarding some action to be performed • starting the phone dialer • starting an activity • opening a web page • other

10. Intent Example • Starting the phone dialer (no special permission needed) Intentintent = new Intent(Intent.ACTION_DIAL, Uri.parse("tel:5551234")); startActivity(intent);

11. Intent Example • Opening a web page • Permission in manifest file • well over 100 different permissions • access internet, bluetooth, vibrate phone, change wall paper, etc. • http://developer.android.com/reference/android/Manifest.permission.html • uses-permission tag (child of manifest tag) <uses-permission android:name="android.permission.INTERNET" /> • Intent in corresponding java file Intentintent = new Intent(Intent.ACTION_VIEW, Uri.parse(”http://www.google.com”)); startActivity(intent);

12. Intent Example • Opening an Activity Intent intent = new Intent(this, Screen2.class); startActivity(intent); • ‘this’ refers to the current activity • Screen2.class refers to the class file associated with the new activity to be opened • implies a corresponding Sreen2.java file exists • activity MUST be referenced in the manifest file

13. Intents • Methods in the Intent class • The intent class has many methods to put or retrieve data • useful when one Activity launches another • put methods used by current Activity that will instantiate another Activity • get methods used by new instantiated Activity

14. Intents • put… methods • put… allows information to be passed from current Activity to newly instantiated Activity • putExtra – simple data types and arrays • passing an integer • i.putExtra(“Key1”, 17); • Key1 – name of the integer to be passed • 17 – contents of the integer to be passed • passing a String • i.putExtra(“Key2”, “Value”); • passing an array • i.putExtra(“Key3”, new int [] {1, 2, 3});

15. Intents • get… methods • get… allows information to be retrieved by the newly instantiated Activity • get…Extra – datatype must be known • getting an integer • getIntent().getIntExtra(“Key1”, 0); • 2nd argument is default value in case Key1 does not exist, or is not an integer • getIntent().getStringExtra(“Key2”); • retrieves value associated with Key2 • if no value, null is returned – no default option • getting an array • int [] z = getIntent().getIntArrayExtra(”Key3"); • if no value, null is returned – no default option

16. Activities • Helpful hints about Activities • Each Activity has: • a corresponding .java file • at least one corresponding .xml file (may have additional menu file) • Each Activity must be referenced in the manifest file • The Activity class has a getIntent() method to retrieve the intent that initiated it • Each activity has a lifecycle • http://developer.android.com/reference/android/app/Activity.html#ActivityLifecycle

17. Activity lifecycle methods • Most important (signatures) • protected void onCreate(Bundle savedInstanceState); • called when created or phone rotated • protected void onPause(); • called when still visible but focus is lost • protected void onResume(); • called when focus is set AFTER being completely obscured • When overriding methods, super class’ version MUST be called

18. Example method @Override protected void onResume() { super.onResume(); //Code goes here //Clear fields, set focus, restart sensor //listeners, etc. }

19. Additional information • Sending information back • When one Activity finishes, activity can be sent back to the Activity that started it as follows: • In the original Activity, 2 methods are needed • startActivityForResult(Intent data, intrequestCode); must be called to open Activity • any non-negative integer can be used for requestCode • onActivityResult(intrequestCode, intresultCode, Intent data) must be implemented • Called when other Activity exits – just before onResume() • requestCode is same code from above • resultCode is sent from closing Activity • data stores any data that was sent back

20. Additional information • Continued from previous slide • In the opened Activity, 1 method is needed • setResult(intresultCode, Intent data) must be called prior to finish() • any integer can be used for resultCode • Activity.RESULT_CANCELED • Activity.RESULT_OK • other • data stores any data to be sent back

21. Sample Code • In original Activity public void openActivityAndWaitForResults() { Intent i = new Intent(this, SecondActivity.class); i.putExtra("StringValue", "Coming to you"); startActivityForResult(i, 1); } protected void onActivityResult(intrequestCode, intresultCode, Intent data) { Toast.makeText(this, "From second activity: " + requestCode + " " + resultCode + " " +data.getStringExtra("InfoBack"), Toast.LENGTH_LONG).show(); } • In opened Activity public void closeActivityAndSendInfoBack () { Intent output = new Intent(); output.putExtra("InfoBack", "Back at you!"); setResult(7, output); finish(); }