Updating Database - retaining data issue

[Lylio]

Hi everyone,

I have a very simple app built in Android Studio. I'm trying to update information in a database, but some of the fields are being overwritten as blank. I've created a short video which shows the issue better than I can explain it here (best to watch it on YouTube rather than the preview here):

Basically, I'm using text fields to update parts of the information already stored in the database. The problems is, if I click on my 'update' button, and any of those fields are blank, the data is being erased. Hopefully the video above is a lot more clear.

If it helps, the code for the activity you see in the video is here: https://github.com/Lylio/GradeRunne...lechristine/graderunner/MainMenuActivity.java

and the database helper for the example in the video is here: https://github.com/Lylio/GradeRunne...lylechristine/graderunner/DatabaseHelper.java

I'd be really grateful if anyone could help. I presume the solution would involve saving the data that's already in the database into temporary variables, and then re-writing them when the 'update' button is pressed. But I'm a little unsure of where/how to code that.

Many thanks everyone,

Lylio

 

[Deleted User]

Well a simple solution would be to do some validation on your Text fields. If they are blank, then tell the user to enter a value, and don't call the database update statements.

 

[Lylio]

Thanks for the reply LV426. That was a great suggestion about validating text fields. I tried to implement your idea by checking if the field was not empty, and if it wasn't, then that data should be updated into the database; if the field was empty, then it should be ignored:

But the problem is, the database helper expects 4 String variables to be passed into the update method, so the whole thing didn't work:

I think the only option is to save what's already in the database row into temporary variables, then rewrite them as part of the update process. Do you know how I can save a database field with a specific row ID. Like, say I want to save the String that's in the 3rd row, 2nd column.... I'm struggling to understand how to use a Cursor to implement that.

 

[Deleted User]

You could write the updateData() method like this:

public boolean updateData(String id, String course, String assignment, String dueDate) {
  ContentValues contentValues = new ContentValues();
  if (course != null && course.length() > 0) {
    contentValues.put(COL2, course);
  }
  if (assignment != null && assignment.length() > 0) {
    contentValues.put(COL3, assignment);
  }
  if (dueDate != null && dueDate.length() > 0) {
    contentValues.put(COL4, dueDate);
  }
  ...
}

This way you're guaranteed not to overwrite existing fields with an empty string.

 

[Lylio]

Oh my God, it works, it works! Thank you so much LV426, I'm so grateful for your help - if you have a Patreon or PayPal I'd be happy to make a donation, I'm so relieved you've solved this for me! Thank you!

 

[Deleted User]

Hehe! Thanks, it's nice to be appreciated. All advice here provided for free. Your thanks is payment enough.