Activity Life Cycle and database

问题

I have an application that reads values from a Database table (Database is named SoftCopyDatabase) and populates a List with the values read from Database. On clicking an item from the list a New Activity Starts.

The problem is when I press the back key I got an error

          IllegalStateException: database already closed

My code is as follows:

public class OpenClick extends ListActivity {

public static String subjectName;
private SoftCopyDatabase lectures;
private static int[] subTO = { R.id.subject };
private static String[] subFROM = { SUBJECT };

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    lectures = new SoftCopyDatabase(this);

}

public void onStart() {
    super.onStart();

    try {
        Cursor cursor = getSubjects();
        showSubjects(cursor);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

public void onRestart() {
    super.onRestart();
    lectures = new SoftCopyDatabase(this);

}

public void onStop() {
    super.onStop();
    lectures.close();
}

public void onDestroy() {
    super.onDestroy();
    lectures.close();
}
//remaining code....

}

One point I would like to mention is if I remove the onStop() Method the application is working properly. But I have to include onstop() because I want to control the opening and closing of Database.

回答1:

Here is a good article covering the topic:

http://awiden.wordpress.com/2010/03/26/database-mangement-and-the-activity-lifecycle/

回答2:

That's normal because both methods are executed... just do this on both methods (onDestroy and onStop):

if(lectures.isOpen()){
    lectures.close();
}

Although I think you can just put a .close invokation in one of them. Make sure to create the isOpen method in your SoftCopyDatabase class which must call the SqliteDatabase object's isOpen method.

来源：https://stackoverflow.com/questions/7125755/activity-life-cycle-and-database

标签

android

lifecycle