CHP3_Multiple Activities and Intents

• Multiple activities
• Most of the Apps have more than one activities.
• Intent
• Let Activities talk to each others
• Across the apps boundary , interact with other apps in the same device.

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Activity def what user can do (just one thing) ! 

Steps to build the App

1. app structure
2. build project
3. update layout
1. <Button>
2. android : onClick ="onSendMessage"
3. android : text = "@string/send"/>
4. update strings.xml
1. <string name = "send">Send Message</string>
5. New method for activity
1. public void onSendMessage (View view) {  }
6. The 2nd Activity and layout
1. File > New > Activity / Blank Activity / ReceiveMessageActivity ; activity_receive_message > finish
7. AndroidManifest.xml
8. Intent
1. import android.content.Intent
2. Intent intent = new Intent (this , ReceiveMessageActivity.class);
3. startActivity(intent);
9. Sending Text to the 2nd Intent
1. Layout
1. <TextView> ID
2. Delete hello world
2. Activity
1. putExtra()
1. intent.putExtra("message",value);
1. message => name of the string
2. overloaded
3. value => can be different types
2. getIntent();
1. String string = intent.getStringExtra("message");
2. int intNum = intent.getIntExtra("name,default_value");
10. Specific action's intent

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• New GUI components 
• Spinner
• EditText
• can edit text column
• can input text
• inherit from Android View (Class)
• TextView
• Button
• String Resources
• strings.xml
• Responsive Web Design
• em as unit

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• AndroidManifest.xml
• app/src/main
• include app significant info
• what activity include in the app (MAIN , LAUNCHER)
• which libraries and declaration(declare activity exist in application element)we've  used 
• package name
• default app icon
• app theme
• security permissions....
• if you're not using Android Studio IDE , you've to build it yourself.
• Intent
• Build Intent => Intent intent = new Intent (this , Target.class)
• mail address (sender , receiver)
• Launch Intent Activity => startActivity(intent)
• Not Found => ActivityNotFoundException

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• Why 2 activities rather than 1 activity handle all of the stuff
• coz the back button
• the order issue

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• Changing App , sending messages to others
• How does Android App works ?
• Android App , is combined by multiple Activities and other components
• activity1 > intent > Android (check) > intent >  activity2 (even though in other app) 
• How do we know which apps on the device?
• "action" can solve all the problem

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• Explicit intent
• directly tell Android what class
• Implicit intent.
• which activity let Android decide

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establish specific action's intent 

• Intent intent -= new Intent (action)
• action
• Intent.ACTION_DIAL
• Intent.ACTION_WEB_SEARCH
• Intent.ACTION_SEND
• extra message adding
• intent.setType("text/plain")
• intent.putExtra(Intent.EXTRA_TEXT , messageText) ;
• intent.putExtra(Intent.EXTRA_SUBJECT, subject);

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" intent filter " tell Android which activity can handle the action

• Intent resolution
• explicit intent
• it's easy 
• implicit intent
• Android
• app > AndroidManifest.xml > check intent filter to accomplish the work
• Intent filter
• indicate what  components can receive what types of intent 
• action
• what activity can do ?
• category
• provide activity extra informations
• main entry pt or not ?

for implicit intent

• android.intent.category.DEFAULT
• intent filter
• compare to app > AndroidManifest.xml
• action
• MIME

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run app on reality device

1. USB debugging
1. Developer options
2. Settings > About Phone > Click build number *7 times
3. Windows > install USB driver (http://developer.android.com/tools/extras/oem-usb.htmo)
4. USB cable to connect to your PC (allow to use USB debug) RSA key
2. createChooser()

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Quick Recap

• Task
• >=2 activities get together
• <EditText>
• Edit text ,input text 
• inherit from Android View
• Android Studio > File > New... > Activity (for new activity)
• AndroidManifest.xml
• intent
• a tool let Android elements can talk to each others
• explicit intent
• Intent intent = new Intent(this , Target.class);
• start activity
• startActivity(intent) 
• ActivityNotFoundException
• add more info to intent
• putExtra()
• get intent to launch activity
• getIntent()
• get relative info about intent
• get*Extra()
• getStringExtra()
• getIntExtra()
• activity action
• describe what act activity can do 
• eg  . sending message
• Intent.ACTION_SEND
• implicit intent
• Intent intent = new Intent (action);
• need to have DEFAULT category
• setType()
• to describe intent dataType
• Intent Resolution
• compare intent content to intent filter in app AnroidManifest.xml
• components name
• action
• data type
• category
• createChooser()
• overwrite default Android activity  select window
• add new topic
• no default 
• if no activity it will show mssage
• getString(R.string.stringname) to get string resource value