How can I save an activity state using the save instance state?

 

In Android, you can save an Activity's state using the onSaveInstanceState() method and then restore that state in the onCreate() or onRestoreInstanceState() method. This allows you to preserve data when an Activity is temporarily destroyed and recreated, such as during screen rotations or when the system reclaims resources. Here's an example of how to do it:

java

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.EditText;

public class MainActivity extends AppCompatActivity {
    private EditText editText;
    private String savedText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        editText = findViewById(R.id.editText);

        // Check if there's a saved state
        if (savedInstanceState != null) {
            savedText = savedInstanceState.getString("textKey");
            editText.setText(savedText);
        }
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);

        // Save the state of your activity here
        savedText = editText.getText().toString();
        outState.putString("textKey", savedText);
    }
}

In this example:

1. We have an EditText field where the user can input text.

2. In the onCreate() method, we check if there's a saved state in the savedInstanceState bundle. If there is, we retrieve the saved text and set it to the EditText.

3. In the onSaveInstanceState() method, we save the state of the EditText (in this case, the text entered by the user) into the outState bundle using a key-value pair. The key "textKey" is used to identify this piece of data.

By saving the state in onSaveInstanceState() and restoring it in onCreate(), you ensure that your Activity retains its state even when the system destroys and recreates it. This is particularly useful for preserving user input or other important data across configuration changes or interruptions.