Android Application Activity Management

1. Managing State Activities:
In Android, managing the state of activities is crucial for providing a
smooth user experience. The state of an activity can be affected by
various factors such as configuration changes (like screen rotation) or
background processes.
Example:
Consider an Android application that has a simple counter. The counter
value needs to be retained even if the device is rotated. To manage the
state, you can use the onSaveInstanceState and onRestoreInstanceState
methods.

2. public class CounterActivity extends AppCompatActivity {
private int counter = 0;
private static final String KEY_COUNTER = "counter";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_counter);
if (savedInstanceState != null) {
counter = savedInstanceState.getInt(KEY_COUNTER);
updateCounter();
}

3. }
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt(KEY_COUNTER, counter);
}
private void updateCounter() {
// Update UI to display the current counter value
}
// Rest of the code for the counter increment/decrement
}
In this example, the onSaveInstanceState method is used to save the current state of
the activity, and the onRestoreInstanceState method is used to restore the state.

4. Implicit Intents:
Implicit intents are used to request functionality from other components in
your app or even from other apps. They don't specify the component (e.g.,
activity) to start explicitly but instead declare the action to perform.
Example:
Consider an app that needs to open a web page. Instead of specifying a
particular browser app, you can use an implicit intent to open the URL
and let the system choose an appropriate app.

5. public class WebActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_web);
// Example of an implicit intent to open a web page
String url = "https://www.example.com";
Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));

6. // Verify that the intent will resolve to an activity
if (intent.resolveActivity(getPackageManager()) != null) {
startActivity(intent);
} else {
// Handle the case where no activity can handle the intent
Toast.makeText(this, "No app to handle the request",
Toast.LENGTH_SHORT).show();
}
}
}

7. In this example, the Intent.ACTION_VIEW action is used to indicate that
we want to view something. The system then looks for the appropriate
activity to handle this request.
Combining the two concepts, you could use an implicit intent to navigate
to another activity while preserving its state by passing relevant data
through the intent or using other methods like a ViewModel.