问题
My frist post only had less than half my text hence the second (complete) post.
I'm working on a test app using sqlite to populate two AutoCompleteTextView's i'm using car make and model for the test
AutoComplete's:
makeAutocomplete
modelAutocomplete
makeAutocomplete's list is populated from a sql query and it works fine
the second is populated when the make is selected
makeAutoComplete.setOnItemSelectedListener(new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
final String[] makeSelected = {arg0.getItemAtPosition(arg2).toString()};
final String[] modelDeal = sqlDBModel.getAllModelFilter(makeSelected);
ArrayAdapter<String> modelAdapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_dropdown_item_1line, modelDeal);
initModelAutoComplete(modelAdapter);
}
@Override
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
});
initModelAutoComplete Declaration
public void initModelAutoComplete(ArrayAdapter<String> adapter){
//adapter = new ArrayAdapter<String>(this, android.R.layout.simple_dropdown_item_1line, list);
modelAutoComplete.setAdapter(adapter);
modelAutoComplete.setThreshold(1);
modelAutoComplete.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3){
arg0.getItemAtPosition(arg2);
}
});
}
SQLiteModelSearch.getAllModelFilter Declaration
public String[] getAllModelFilter(String[] vehiclemake){
if(vehiclemake != null){
Cursor cursor = this.sqliteDBInstance.query(DB_MAKEMODEL_TABLE,
new String[]{DB_COLUMN_MAKE, DB_COLUMN_MODEL},
DB_COLUMN_MAKE+"=?",
vehiclemake,
null,
null,
null,
null);
if( cursor != null){
String[] str = new String[cursor.getCount()];
int i = 0;
while(cursor.moveToNext()){
str[i] = cursor.getString(cursor.getColumnIndex(DB_COLUMN_MODEL));
i++;
}
return str;
} else {
Log.i("vehiclemake = ", "NULL");
return new String[]{};
}
}
return new String[]{};
}
LogCat
07-31 13:00:19.631: E/AndroidRuntime(1302): at android.app.ActivityThread.main(ActivityThread.java:3683)
07-31 13:00:19.631: E/AndroidRuntime(1302): at java.lang.reflect.Method.invokeNative(Native Method) 07-31 13:00:19.631: E/AndroidRuntime(1302): FATAL EXCEPTION: main
07-31 13:00:19.631: E/AndroidRuntime(1302): java.lang.NullPointerException
07-31 13:00:19.631: E/AndroidRuntime(1302): at com.myapp.sqltest.database.SQLiteModelSearch.getAllModelFilter(SQLiteModelSearch.java:100)
07-31 13:00:19.631: E/AndroidRuntime(1302): at com.myapp.sqltest.activity.addVehicleActivity$2.onItemSelected(addVehicleActivity.java:62)
07-31 13:00:19.631: E/AndroidRuntime(1302): at android.widget.AdapterView.fireOnSelected(AdapterView.java:871)
07-31 13:00:19.631: E/AndroidRuntime(1302): at android.widget.AdapterView.access$200(AdapterView.java:42)
07-31 13:00:19.631: E/AndroidRuntime(1302): at android.widget.AdapterView$SelectionNotifier.run(AdapterView.java:837)
07-31 13:00:19.631: E/AndroidRuntime(1302): at android.os.Handler.handleCallback(Handler.java:587)
07-31 13:00:19.631: E/AndroidRuntime(1302): at android.os.Handler.dispatchMessage(Handler.java:92)
07-31 13:00:19.631: E/AndroidRuntime(1302): at android.os.Looper.loop(Looper.java:130)
07-31 13:00:19.631: E/AndroidRuntime(1302): at java.lang.reflect.Method.invoke(Method.java:507)
07-31 13:00:19.631: E/AndroidRuntime(1302): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
07-31 13:00:19.631: E/AndroidRuntime(1302): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
07-31 13:00:19.631: E/AndroidRuntime(1302): at dalvik.system.NativeStart.main(Native Method)
I can see that the exception is being thrown at:
Cursor cursor = this.sqliteDBInstance.query(DB_MAKEMODEL_TABLE,
new String[]{DB_COLUMN_MAKE, DB_COLUMN_MODEL},
DB_COLUMN_MAKE+"=?",
vehiclemake,
null,
null,
null,
null);
but can't tell why, i've watched all the variables going into the functions and none of them are null?
回答1:
I doubt believe OnItemSelected will ever be called by an AutoCompleteTextView, when the user clicks an item in the dropdown list the AutoComplete will only trigger an OnItemClick event.
Try moving your OnItemSelectedListener code into the OnItemClickListener.
Addition
SQLiteDatabase.query() will always return a valid Cursor, you need to check the size of the Cursor to see if it is valid:
if(cursor != null){ // Not applicable
Try:
if(cursor.getCount() > 0)
Also you don't particularly need to convert your Cursor into a String array, a SimpleCursorAdapter will handle the details of this. But your approach will work as well (with a few changes).
Null Pointer Exception
If you are receiving a NPE here:
Cursor cursor = this.sqliteDBInstance.query(...);
Then simply sqliteDBInstance is null. Where do you initialize sqliteDBInstance? Do you have an open() method in SQLiteModelSearch, if so did you call it?
回答2:
I've figured it out. the issue was that I had defined
public AutoCompleteTextView modelAutoComplete;
public AutoCompleteTextView makeAutoComplete;
Then then in function onCreate
I had defined:
AutoCompleteTextView modelAutoComplete = (AutoCompleteTextView) findViewById(R.id.autoCompleteModel);
AutoCompleteTextView makeAutoComplete = (AutoCompleteTextView) findViewById(R.id.autoCompleteModel);
I overlooked variable scope since both makeAutoComplete and modelAutoComplete where defined twice, one as a global class variable, and the second as a local function variable.
since the global variable was only defined and not initialized. The function initModelAutoComplete() was referencing the global public variable modelAutoComplete causing the NPE exception.
来源：https://stackoverflow.com/questions/11764099/autocompletetextview-sqlite-poplulation-exception