Question

Hai, in my calculator app when i click on calculate button result is appearing normally, but when i change the orientation calculated result is disappearing.

Answer 1

Please see this example on how to save the state of your Activity using a Bundle. First you have to override the onSaveInstanceState method.

public void onSaveInstanceState(Bundle savedInstanceState) {
    TextView  txtName = (TextView)findViewById(R.id.raj44);
    String  aString = txtName.getText().toString();
    savedInstanceState.putString("Name", aString);
    super.onSaveInstanceState(savedInstanceState);
} 

In the onCreate method you can then restore the state of your instance from the saved Bundle.

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.concretetool);
    if (savedInstanceState != null) {
        String  aString = savedInstanceState.getString("Name");
        if (aString != null) {
            txtName = (TextView)findViewById(R.id.raj44);
            txtName.setText(aString);
        }
    }
}