在方向改变时保留价值

Question

I am developing a very basic Android App that adds a number in TextView whenever I hit the Button . The digit showing in TextView is also preserved when the orientation of the Mobile changes using the onSaveInstanceState() and onRestoreInstanceState() functions.

The problem is when orientation changes the value is preserved but when the Button is pressed once again after the changing of the orientation it again starts the counting from 0 rather then starting it from the preserved value.

My code:

public class MainActivity extends AppCompatActivity {

    TextView showValue;
    int counter=0;

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

        showValue = (TextView) findViewById(R.id.CounterValue);
    }


    public void countIN(View view)
    {
        counter++;
        showValue.setText(Integer.toString(counter));
    }


    @Override
    protected void onSaveInstanceState(Bundle outState) {
        outState.putString("my_text", showValue.getText().toString());
        super.onSaveInstanceState(outState);
    }

    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);
        showValue.setText(savedInstanceState.getString("my_text"));
    }
 }

Thank You for your response.

Answer 1

You can save and get data using several methods

First If your data is small, then you can use onSavedInstanceState and onRestoreInstanceState .. for details follow this answer or this one

Second if you have too much data to store, then use ViewModel instead; this is a tutorial that you can start from.

Answer 2

add

counter=Integer.parseInt(savedInstanceState.getString("my_text"));

inside onRestoreInstanceState method

@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    showValue.setText(savedInstanceState.getString("my_text"));
    counter=Integer.parseInt(savedInstanceState.getString("my_text"));
}

Answer 3

The problem is when orientation changes the value is preserved but when the Button is pressed once again after the changing of the orientation it again starts the counting from 0 rather then starting it from the preserved value

That's because when you restore the value of counter after configuration change, you set it as a text on a TextView but you don't set it to counter variable. So when button is clicked, it takes the previous value of counter which is zero after each configuration change , it increments it and sets it as text on TextView .

Solution

Inside onRestoreInstanceState method, add the following statement

counter = Integer.parseInt(savedInstanceState.getString("my_text"));