Data Transfer between Activities & Databases
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The document explains the concept of intents in Android, which are used for communication between application components, such as activities, services, and broadcast receivers. It details the types of intents (explicit and implicit), their uses, the structure of intent filters, and how to implement broadcast receivers and content providers. Additionally, it covers the lifecycle of activities and methods for managing data through content providers.
Data Transfer between Activities & Databases
- 1. Data Transfer between Activities & Databases Lecturer Faiz Ur Rehman University of Mianwali
- 2. Intent • Android uses Intent for communicating between the components of an Application and also from one application to another application. • Intent are the objects which is used in android for passing the information among Activities in an Application and from one app to another also. Intent are used for communicating between the Application components and it also provides the connectivity between two apps
- 3. Example Intent intent = new Intent(getApplicationContext(), SecondActivity.class); startActivity(intent); getApplicationContext() returns the context for your foreground activity. Android intents are mainly used to: •Start the service •Launch an activity •Display a web page •Display a list of contacts •Broadcast a message •Dial a phone call etc.
- 7. Explicit Intent: • Explicit Intents are used to connect the application internally. • Explicit Intent work internally within an application to perform navigation and data transfer. • Example Intent intent = new Intent(getApplicationContext(), SecondActivity.class); startActivity(intent);
- 8. Implicit Intent: • In Implicit Intents we do need to specify the name of the component. • We just specify the Action which has to be performed and further this action is handled by the component of another application. • The basic example of implicit Intent is to open any web page • Example Intent intentObj = new Intent(Intent.ACTION_VIEW); intentObj.setData(Uri.parse("https://www.abhiandroid.com")); startActivity(intentObj);
- 9. Intent Uses in android: 1. Intent for an Activity: • Every screen in Android application represents an activity. To start a new activity you need to pass an Intent object to startActivity() method. This Intent object helps to start a new activity and passing data to the second activity.
- 10. 2. Intent for Services: • Services work in background of an Android application and it does not require any user Interface. Intents could be used to start a Service that performs one-time task • (for example: Downloading some file)
- 11. 3. Intent for Broadcast Receivers: • There are various message that an app receives, these messages are called as Broadcast Receivers. (For example, a broadcast message could be initiated to intimate that the file downloading is completed and ready to use). Android system initiates some broadcast message on several events, such as System Reboot, Low Battery warning message etc. 4. Display a list of contacts 5. Dial a phone call etc.
- 12. Intent Filter: • decide the behavior of an intent. • -Intent about the navigation of one activity to another, that can be achieve by declaring intent filter. • -We can declare an Intent Filter for an Activity in manifest file. • - Intent filters specify the type of intents that an Activity, service or Broadcast receiver can respond to.
- 13. Syntax of Intent Filters: • <activity android:name=".MainActivity"> • <intent-filter • android:icon="@drawable/icon" android:label="@string/label" > • <action android:name="android.intent.action.MAIN" /> • <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> • </activity>
- 14. What are icons and labels • icon: This is displayed as icon for activity. You can check or save png image of name icon in drawable folder. android:icon="@drawable/icon" • • label: The label / title that appears at top in Toolbar of that particular Activity. You can check or edit label name by opening String XML file present inside Values folder android:label = "@string/label“ or android:label = "New Activity“ Just like icon attribute, if you have not declared any label for your activity then it will be same as your parent activity
- 15. • Elements In Intent Filter: • There are following three elements in an intent filter: • 1.Action • 2.Data • 3.Category
- 18. Action
- 19. Examples
- 20. Data
- 22. Activity Lifecycle: • Activity is a screen that user interact with. Every Activity in android has lifecycle like created, started, resumed, paused, stopped or destroyed. These different states are known as Activity Lifecycle.
- 23. • onCreate() – Called when the activity is first created • onStart() – Called just after it’s creation or by restart method after onStop(). Here Activity start becoming visible to user • onResume() – Called when Activity is visible to user and user can interact with it . • onPause() – Called when Activity content is not visible because user resume previous activity. • onStop() – Called when activity is not visible to user because some other activity takes place of it • onRestart() – Called when user comes on screen or resume the activity which was stopped • onDestroy – Called when Activity is not in background
- 25. Broadcast Receiver • Broadcast Receiver is a component which will allow android system or other apps to deliver events to the app like sending a low battery message or screen turned off message to the app. The apps can also initiate broadcasts to let other apps know that required data available in a device to use it. • Generally, we use Intents to deliver broadcast events to other apps and Broadcast Receivers use status bar notifications to let user know that broadcast event occurs. • is implemented as a subclass of Broadcast Receiver and each broadcast is delivered as an Intent object.
- 26. Two important steps to make BroadcastReceiver: • Registering Broadcast Receiver • • Creating the Broadcast Receiver
- 27. • A broadcast receiver is implemented as a subclass of BroadcastReceiver class and overriding the onReceive() method where each message is received as a Intent object parameter. • Example- public class MyReceiver extends BroadcastReceiver { public void onReceive(Context context, Intent intent) { Toast.makeText(context, "Intent Detected.", Toast.LENGTH_LONG).show(); } }
- 28. System generated events are: • android.intent.action.BATTERY_CHANGED • • android.intent.action.BATTERY_LOW • • android.intent.action.BATTERY_OKAY • • android.intent.action.BOOT_COMPLETED • • android.intent.action.BUG_REPORT • • android.intent.action.CALL • • android.intent.action.CALL_BUTTON • • android.intent.action.DATE_CHANGED • • android.intent.action.REBOOT
- 32. Create Button click Event
- 33. Registered this button to event Go to your xml file
- 34. Create intent instance , set action , set flag, send intent
- 35. Create another app for Receiving
- 36. Receiver app is not registered yet
- 47. Content Provider: • Content Provider will act as a central repository to store the applications data in one place and make that data available for different applications to access whenever it’s required. • the Content Provider is a part of an android application and it will act as more like relational database to store the app data. We can perform a multiple operations like insert, update, delete and edit on the data stored in content provider using insert(), update(), delete() and query() methods. • content provider is having different ways to store app data. The app data can be stored in a SQLite database or in files or even over a network based on our requirements. By using content providers we can manage data such as audio, video, images and personal contact information.
- 49. • ContentResolverTo access a data from content provider, we need to use Content Resolver • Cursor Loader is used to run the query asynchronously in background • Content Provider receive a data requests from client, performs the requested actions (create, update, delete, retrieve) and return the result. • Content URIs: To query a content provider, you specify the query string in the form of a URI which has following format − content://authority/path content:// - The string content:// is always present in the URI authority - It represents the name of content provider path - It represents the table’s path. The Content Resolver object use the URI’s authority to find the appropriate provider and send the query objects to the correct provider. After that Content Provider uses the path of content URI to choose the right table to access.
- 50. Working
- 51. To create a content provider in android applications we should follow below steps. • 1. We need to create a content provider class that extends the ContentProvider base class. • 2. We need to define our content provider URI to access the content. • 3. The ContentProvider class defines a six abstract methods (insert(), update(), delete(), query(), getType()) which we need to implement all these methods as a part of our subclass. • 4. We need to register our content provider in AndroidManifest.xml using tag.
- 52. Methods • query() - It receives a request from the client. By using arguments it will get a data from requested table and return the data as a Cursor object. • insert() - This method will insert a new row into our content provider and it will return the content URI for newly inserted row. • update() - This method will update an existing rows in our content provider and it return the number of rows updated. • delete() - This method will delete the rows in our content provider and it return the number of rows deleted. • getType() - This method will return the MIME type of data to given content URI. • onCreate() - This method will initialize our content provider. The android system will call • this method immediately after it creates our provider.