what case the managedQuery method return null if uri is provided?

I am doing some android applica开发者_运维技巧tion. I just wonder what will case the managedQuery method return a null value?

  if (getIntent().getData() == null) {
        getIntent().setData(Notepad.Notes.CONTENT_URI);
    }
    uri = getIntent().getData();
    c = managedQuery(uri, PROJECTION, null, null, null);// return null value. 

managedQuery() will return null if any of the following are true:

• The Uri supplied in the first parameter is null
• The content provider implementation returned null as a result of the query
• If an exception occurred when the content provider attempted to process the query

I really do not like your call to setData(). Please try something like:

Uri uri=getIntent().getData();

if (uri==null) {
  uri=Notepad.Notes.CONTENT_URI;
}

c=managedQuery(uri, PROJECTION, null, null, null);

This way, you know your Uri will not be null, so if you get null back from the managedQuery() call, your problem lies in the content provider.