Linking Activities using Intents - PowerPoint Presentation

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Linking Activities using Intents

How to navigate between Android Activities

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Navigation from an Activity to another Activity

Create an Intent object

Intents can be created in different ways

Intents can carry data from the calling Activity to the called Activity

Start the other Activity, using the Intent object

When the called Activity ends (finish() method) the control is returned to the calling ActivityThe return of controls can carry data back to the calling activityComparable to calling a method in Java.You use the keyword return to get back to the calling method.Example: IntentsNoData

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Different ways of creating an Intent object

Creating an Intent object linking to an Activity in

the same projectIntent intent = new Intent(this, Activity2.class)

Creating an Intent object linking to an Activity in

another

projectIntent intent = new Intent(”dk.easj.Activity2”);The other project must register the Intent name in the AndroidManifest.xml<activity android:name=".Activity2" <!-- .class name --> android:label="Activity 2"> <intent-filter > <action android:name

="dk.easj.Activity2" />

<category

android:name

="android.intent.category.DEFAULT" /> </intent-filter> </activity>

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The ”starter pattern”

Leave more responsibility

to the called Activity, and less

responsibility

to the

calling Activity.Code is easier to readExample: IntentsNoDataLinking Activities using Intents4Slide5

Passing data using an Intent object:

Sending dataYou can pass data from one Activity to another using the Intent object

Example: Sending dataIntent intent = new Intent(this, AnotherActivity.class

);

intent.putExtra

(“name”, “Anders”); // Generally putExtra(key, value)startActivity(intent);5Linking Activities using IntentsSlide6

Passing data using an Intent object:

Reading dataThe receiving Activity can read the data.

Example: Reading data from an IntentIntent intent = getIntent();

String name =

intent.getStringExtra

(“name”);Example: IntentsWithData6Linking Activities using IntentsSlide7

Returning results from an Intent

When the called Activity returns to the calling Activity, it can send data (results)

startActivity(…) No resultsstartActivityForResult(…) Results expectedstartActivityForResult(intent, request_Code);

Callback method in calling Activity:

protected void

onActivityResult(int requestCode, int resultCode, Intent data) { if (requestCode == request_Code) { // which request? Same request_Code as in the startActivityForResult(…) if (resultCode == RESULT_OK) { // or RESULT_CANCELLED final String fullData = data.getData().toString(); … } }}

Example: IntentsWithDataBack

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Making activities look like dialogs

With an Intent you go to another Activity.

Dialogs on the other hand usually show up on top of another Activity.Activities can look like DialogsShown on top of another ActivityExample: AndroidManifest.xml

<activity

android:name=".NameDialogActivity" android:theme="@android:style/Theme.Dialog"> </activity>Linking Activities using Intents8Slide9

Navigation to a another application using Intents

Android has several built-in applicationsBrowser, phone, etc.

You can navigate from you Activity to the built-in applications using Intent pairsCommon intentshttps://developer.android.com/guide/components/intents-common.html

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Implicit intents

Action

Describes what to be doneExamples: View an item, Edit an item, etc.Action examples: ACTION_VIEW, ACTION_DIAL, ACTION_PICKData

Describes which ”object” the intent affects

http://www.google.com

Tel:+4560609528Geo:38.999,-44.44Content://contactsCode exampleIntent intent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.amazon.com"));Example: IntentsImplicit

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Using Intent Filters

If you want other activities to invoke you activity, you must specify some Intent Filters in the AndroidManifest.xml file.Example: Messenger

Head First, chapter 3

Linking Activities using Intents

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