1. Linking Activities using Intents
How to navigate between
Android Activities
Linking Activities using Intents

2. 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 Activity
The return of controls can carry data back to the calling activity
Comparable to calling a method in Java.
You use the keyword return to get back to the calling method.
Example: IntentsSimple
Linking Activities using Intents

3. Different ways of creating an Intent object
Creating an Intent object linking to an Activity in the same project
Intent intent = new Intent(this, Activity2.class)
Creating an Intent object linking to an Activity in another project
Intent 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>
Linking Activities using Intents

4. Passing data using an Intent object: Sending data
You can pass data from one Activity to another using the Intent object
Example: Sending data
Intent intent = new Intent(this, AnotherActivity.class);
intent.putExtra(“name”, “Anders”);
// Generally putExtra(key, value)
startActivityForResult(intent, request_Code);
Linking Activities using Intents

5. Passing data using an Intent object: Reading data
The receiving Activity can read the data.
Example: Reading data from an Intent
Intent intent = getIntent();
CharSequence name = intent.getCharSequenceExtra(“name”);
// CharSequence is s super-class of String
Example: IntentsWithData
Linking Activities using Intents

6. Returning results from an Intent
When the called Activity returns to the calling Activity, it can send data (results)
startActivity(…) No results
startActivityForResult(…) Results expected
startActivityForResult(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: IndentDataExample
Linking Activities using Intents

7. 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 Dialogs
Shown on top of another Activity
Example: AndroidManifest.xml
<activity
android:name=".NameDialogActivity"
</activity>
Linking Activities using Intents

8. Navigation to a another application using Intents
Android has several built-in applications
Browser, phone, etc.
You can navigate from you Activity to the built-in applications using Intent pairs
Common intents
Linking Activities using Intents

9. Intent pairs (action, data)
Describes what to be done
Examples: View an item, Edit an item, etc.
Action examples: ACTION_VIEW, ACTION_DIAL, ACTION_PICK
Data
Describes which ”object” the intent affects
Tel:
Geo:38.999,-44.44
Content://contacts
Code example
Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse("
Example: IntentsForBuiltinApps
Linking Activities using Intents

10. Linking Activities using Intents
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, page 103
Linking Activities using Intents