Android Listview SimpleCursorAdapter Error

Question

"QuoteTable" is a java class file that defines a database. The code below works perfectly fine.

// mCategory = (Spinner) findViewById(R.id.category); - created during OnCreate method 

private void fillData() {

// Fields from the database (projection)
// Must include the _id column for the adapter to work
String category = (String) mCategory.getSelectedItem();
String[] from = new String[] { QuoteTable.COLUMN_QUOTE };
// Fields on the UI to which we map
int[] to = new int[] { R.id.label };

getLoaderManager().initLoader(0, null, this);
adapter = new SimpleCursorAdapter(this, R.layout.motivate_row, null, from,
    to, 0);

setListAdapter(adapter); }

What I want to do is, select particular quotes from "QuoteTable" depending on the category selected in the Spinner. This category should match the COLUMN_CATEGORY field in "QuoteTable." So I tried this -

 private void fillData() {
String[] from = null;
// Fields from the database (projection)
// Must include the _id column for the adapter to work
if(category.equals("All")){
       from = new String[] { QuoteTable.COLUMN_QUOTE };
}
else{
        if(category.equals(QuoteTable.COLUMN_CATEGORY))
              from = new String[] { QuoteTable.COLUMN_QUOTE };
}
// Fields on the UI to which we map
int[] to = new int[] { R.id.label };

getLoaderManager().initLoader(0, null, this);
adapter = new SimpleCursorAdapter(this, R.layout.motivate_row, null, from,
    to, 0);

setListAdapter(adapter);  }

/* this error is resolved */ This gives me a "SimpleCursorAdapter" error at if(category == "All") Why is this the case? I've already used Cursor in another class to run a query in saving the database. This is merely my "View" and I want don't want to re-use that code.

Okay, now the previous (above mentioned) error is resolved. I had to fix the spinner in the layout file. However, although now there are no errors (runtime or compile time), the code logically does not do what I intend it to do. The spinner is present, but on selecting different options, nothing changes.

score 0 · Answer 1 · answered Mar 08 '14 at 20:29

0

String comparison should be done using .equals() method: "All".equals(category)

answered Mar 08 '14 at 20:29

nikis

11,166
2
35
45

alright I've corrected that. now I get a Null Pointer Exception – user2201545 Mar 08 '14 at 20:44

score 0 · Answer 2 · edited May 23 '17 at 10:26

0

You should use .equals() to compare strings

if(category.equals("All")){

Check

What is the difference between == vs equals() in Java?

You have

adapter = new SimpleCursorAdapter(this, R.layout.motivate_row, null, from,
to, 0);

The third param is null should be a cursor

edited May 23 '17 at 10:26

Community

1
1

answered Mar 08 '14 at 20:30

Raghunandan

132,755
26
225
256

alright I've corrected that. now I get a Null Pointer Exception – user2201545 Mar 08 '14 at 20:44
@user2201545 post the stacktrace – Raghunandan Mar 08 '14 at 20:44
@user2201545 third param to the constructor of cursor adapter is null – Raghunandan Mar 08 '14 at 20:48
@user2201545 post the stacktrace by extracting the exception part or forget further help. links won't help – Raghunandan Mar 08 '14 at 20:53
FATAL EXCEPTION: main java.lang.RuntimeException: Unable to start activity ComponentInfo{b.example.m/b.example.m.mOverviewActivity}:java.lang.NullPointerException – user2201545 Mar 08 '14 at 21:08
So I have to create a cursor object again? In the previous section also i passed null as third param, that time no error? – user2201545 Mar 08 '14 at 21:26

Android Listview SimpleCursorAdapter Error

2 Answers2