我正在尝试制作一个从数据库中填充的列表视图。在数据库中，我使用与列表相同的活动中的警报对话框输入数据。我在警报对话框中有 3 个按钮：保存、删除、关闭。我的问题是，当我单击保存按钮时，它给了我一个错误。
这是我的 Liste.class （列表在哪里的活动）：
private View.OnClickListener onAdd = new View.OnClickListener() {
public void onClick(View v) {
edit_box();
}
};
private AdapterView.OnItemClickListener onListClick = new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
noteId = String.valueOf(id);
edit_box();
}
};
private void edit_box(){
final View addView = getLayoutInflater().inflate(R.layout.add, null);
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setView(addView);
EditText editNote=(EditText) addView.findViewById(R.id.title);
if(noteId != null)
{
Cursor c = helper.getById(noteId);
c.moveToFirst();
editNote.setText(helper.getNote(c));
}
builder.setPositiveButton("Save", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton){
EditText editNote = (EditText) addView.findViewById(R.id.title);
if(noteId==null){
helper.insert(editNote.getText().toString());
noteId = null;
}
dataset_cursor.requery();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialog, int whichButton){
}
});
builder.setNeutralButton("Delete", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
if(noteId == null)
{
return;
}
else{
helper.delete(noteId);
noteId=null;
}
dataset_cursor.requery();
}
});
builder.show();
}
class NoteAdapter extends CursorAdapter{
NoteAdapter(Cursor c){
super(Liste.this, c);
}
@Override
public void bindView(View row, Context ctxt, Cursor c) {
NoteHolder holder = (NoteHolder) row.getTag();
holder.populateFrom(c, helper);
}
@Override
public View newView(Context ctxt, Cursor c, ViewGroup parent) {
LayoutInflater inflater=getLayoutInflater();
View row =inflater.inflate(R.layout.row, parent, false);
NoteHolder holder = new NoteHolder(row);
row.setTag(holder);
return(row);
}}
static class NoteHolder {
private TextView note = null;
NoteHolder(View row) {
note=(TextView)row.findViewById(R.id.note);
}
void populateFrom(Cursor c, DBhelp helper){
note.setText(helper.getNote(c));
}
}
这是我的 DBHelper 课程的一部分：
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE Notes(_id INTEGER PRIMARY KEY AUTOINCREMENT, note TEXT);");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
public void insert(String note){
ContentValues cv = new ContentValues();
cv.put("note", note);
getWritableDatabase().insert("Notes", "note", cv);
}
public void update(String id, String note) {
ContentValues cv = new ContentValues();
String[] args={id};
cv.put("note", note);
getWritableDatabase().update("Notes", cv, "_id=?", args);
}
public void delete(String id){
getWritableDatabase().delete("Notes", "_id=?", new String[] {id});
}
public Cursor getAll(){
return(getReadableDatabase()
.rawQuery("SELECT _id, note FROM Notes", null));
}
public Cursor getById(String id){
String[] args={id};
return(getReadableDatabase()
.rawQuery("SELECT _id, note FROM Notes WHERE _id=?",
args));
}
public String getNote(Cursor c){
return(c.getString(1));
}
}
我在问你们大家是否能说出可能是什么问题。我真诚地验证了所有代码，但我无法弄清楚我写错的地方。如果您能给我一个建议，我将不胜感激，或者更好的是，您可以告诉我问题出在哪里。谢谢 ！
PS：这是logcat：
12-30 12:57:59.079: W/KeyCharacterMap(340): Using default keymap: /system/usr/keychars/qwerty.kcm.bin
12-30 12:58:00.359: D/AndroidRuntime(340): Shutting down VM
12-30 12:58:00.359: W/dalvikvm(340): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
12-30 12:58:00.390: E/AndroidRuntime(340): FATAL EXCEPTION: main
12-30 12:58:00.390: E/AndroidRuntime(340): java.lang.NullPointerException
12-30 12:58:00.390: E/AndroidRuntime(340): at com.project.mapshop.Liste$3.onClick(Liste.java:96)
12-30 12:58:00.390: E/AndroidRuntime(340): at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:158)
12-30 12:58:00.390: E/AndroidRuntime(340): at android.os.Handler.dispatchMessage(Handler.java:99)
12-30 12:58:00.390: E/AndroidRuntime(340): at android.os.Looper.loop(Looper.java:123)
12-30 12:58:00.390: E/AndroidRuntime(340): at android.app.ActivityThread.main(ActivityThread.java:4627)
12-30 12:58:00.390: E/AndroidRuntime(340): at java.lang.reflect.Method.invokeNative(Native Method)
12-30 12:58:00.390: E/AndroidRuntime(340): at java.lang.reflect.Method.invoke(Method.java:521)
12-30 12:58:00.390: E/AndroidRuntime(340): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
12-30 12:58:00.390: E/AndroidRuntime(340): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
12-30 12:58:00.390: E/AndroidRuntime(340): at dalvik.system.NativeStart.main(Native Method)