You need to specify that in the XML of your list item row file.
These are the attributes you need to play with on your TextView;
android:singleLine="true"
android:maxLength="someLengthofCharacters(int)"
android:ellipsize="end" //if you want an ellipse to be appended to the end of your String
EDIT: Try this approach to set the max character length of your TextView programmatically
TextView tv = new TextView(this);
int maxLength = 10;
InputFilter[] fArray = new InputFilter[1];
fArray[0] = new InputFilter.LengthFilter(maxLength);
tv.setFilters(fArray)
and set single line to true by using
TextView.setSingleLine or TextView.setLines(1)