Intents - Intents & Intent Filters   An...

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Unformatted text preview: Intents & Intent Filters   An Intent is a data structure that specifies   An operation to be performed   An event that has occurred   Broadcast by one component   Received by 0 or more components   This lectures focuses on using Intents to represent operations, rather than events   String representing the operation   Examples:   Setting the Intent Action new Intent(Intent.ACTION_VIEW); Intent newInt = new Intent(); newInt.setAction(Intent.ACTION_VIEW);   Data associated with the Intent   Formatted as a Uniform Resource Identifier (URI)   Examples:   Data to view on a map ▪  geo:0,0?q=1600+Pennsylvania+Ave +Washington+DC   Number to dial in the phone dialer ▪  tel:+15555555555   Setting the Intent data new Intent(Intent.ACTION_VIEW, Uri.parse("tel:+15555555555")); Intent newInt = new Intent(Intent.ACTION_VIEW); newInt.setData(Uri.parse("tel:+15555555555"));   Additional information about the components that handle the intent   Examples:   Sets the MIME type of the Intent data   E.g., “image/*”   If unspecified, Android will infer the type   Setting the mime type Intent.setType(String type) Intent.setDataAndType(Uri data, String type)   The component to receive this intent   Setting the component Intent(Context packageContext, Class<?> cls); Intent newInt = new Intent (); newInt.setComponent(ComponentName) ; newInt.setClass(Context, Class));   Additional information associated with Intent   Treated as a map (key ­value pairs)   Setting the Extra attribute   Several forms depending on data types, e.g., ▪  putExtra(String name, String value); ▪  putExtra(String name, float value);   EXTRA_EMAIL: List of email recipients Intent newInt= new Intent(Intent.ACTION_SEND); newInt.putExtra ( android.content.Intent.EXTRA_EMAIL, new String{ aporter@cs.umd.edu, billg@microsoft.com, ohhdl@dalailama.com, ladygaga@musician.org } );   Specify how Intent should be handled   Examples:   FLAG_ACTIVITY_NO_HISTORY ▪  Don’t put this Activity in the History stack   FLAG_DEBUG_LOG_RESOLUTION ▪  Causes extra logging information to be printed when this Intent is processed Intent newInt= new Intent(Intent.ACTION_SEND); newInt.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);   Intents can be used to activate Activities   startActivity(Intent intent)   startActivityForResult(Intent intent, …)   The target Activity can be   Named explicitly in the Intent, or   Determined implicitly via intent resolution   HelloWorldWithLogin   Users must authenticate before they can view the “Hello, Android” screen   LoginActivity   Accepts username & password   If password correct, starts HelloAndroid Activity public class LoginScreen extends Activity { public void onCreate(Bundle savedInstanceState) { … loginButton.setOnClickListener(new OnClickListener() { public void onClick(View v) { if (checkPassword(uname.getText(), passwd.getText())){ Intent helloAndroidIntent = new Intent(LoginScreen.this, HelloAndroid.class); startActivity(helloAndroidIntent); } } }); }   When the Activity to be activated is not named, the system attempts to find Activities that match the Intent   Called Intent Resolution   A process for matching Intents with Activities that want to receive them   Intent Filters describe which Intents an Activity can handle   Usually specified in an AndroidManifest.xml file   Intent Resolution only matches   Action   Data (both URI and mime data type)   Category <activity ….> <intent ­filter android:icon="drawable resource” android:label="string resource” android:priority="integer” . . . <action android:name=”actionName" /> … </intent ­filter> … </activity>   android:icon – Icon representing the activity   android:label  ­ User ­readable label for the parent component   android:priority – Priority given to the parent component when handling matching Intents   Causes Android to prefer one activity over another   Higher values represent higher priorities <intent ­filter …> … <data android:host="string" android:mimeType="string" android:path="string" android:pathPattern="string" android:pathPrefix="string" android:port="string" android:scheme="string" /> … </intent ­filter> <intent ­filter …> . . . <category android:name="string" /> … </intent ­filter> <intent ­filter …> <action android:name= "android.intent.action.VIEW" /> <category android:name= "android.intent.category.DEFAULT" /> <category android:name= "android.intent.category.BROWSABLE" /> <data android:scheme="geo”/> <intent ­filter>   Note: to receive implicit intents an Activity must specify an IntentFilter with the category   "android.intent.category.DEFAULT” category public class CheckIntents extends Activity { … public void onCreate(Bundle savedInstanceState) { … checkButton.setOnClickListener(new OnClickListener() { public void onClick(View v) { List<String> acts = CheckIntents.getActivitiesForAction( CheckIntents.this, intentText.getText().toString()) // output results } }); } public static List<String> getActivitiesForAction( Context context,String action) { final PackageManager packageManager = context.getPackageManager(); final Intent intent = new Intent(action); final List<ResolveInfo> list = packageManager.queryIntentActivities(intent, 0); final List<String> acts = new ArrayList<String>(); for (ResolveInfo ri : list) { acts.add(ri.activityInfo.name); } return acts; } …   Show application info   % adb shell dumpsys package   HelloAndroidWithLogin   CheckActivityIntents ...
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