Question

我在this tutorial之后为我的ListView制作了一个自定义适配器但是当我在我的设备上运行我的应用程序时，它会在启动时出错当MainActivity的onCreate()方法尝试调用NotesDbHelper类的getData()方法时，会出现错误。

你能帮助我吗？

MainActivity.java

public class MainActivity extends Activity
{

private EditText mEditText;
private Button mButton;

NotesCustomAdapter notesCustomAdapter = null;
ListView listView = null;
NotesDbHelper database = null;
ArrayList<Notes> notes = null;

/** Called when the activity is first created.
 * @param savedInstanceState */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mButton = (Button) findViewById(R.id.button);
    mEditText = (EditText) findViewById(R.id.editText);

    database = new NotesDbHelper(this);
    notes = database.getData();
    notesCustomAdapter= new NotesCustomAdapter(this,R.layout.notes_details,notes);

    listView = (ListView) findViewById(R.id.simpleListView);
    listView.setAdapter(notesCustomAdapter);

    mButton.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            String input = mEditText.getText().toString();

            if (input.length() > 0) {
            database.insertNote(input);
            }
        }
    });

    listView.setOnItemClickListener(new OnItemClickListener() {
    public void onItemClick(AdapterView<?> a, View v, final int position, long id) {
    AlertDialog.Builder adb=new AlertDialog.Builder(MainActivity.this);
    adb.setTitle("Delete?");
    adb.setMessage("Are you sure you want to delete this note?");
    final int positionToRemove = position;
    adb.setNegativeButton("Cancel", null);
    adb.setPositiveButton("Ok", new AlertDialog.OnClickListener() {
        public void onClick(DialogInterface dialog, int which) {
            database.deleteNote(which);
            notes.remove(positionToRemove);
            notesCustomAdapter.remove(String.valueOf(positionToRemove));
            notesCustomAdapter.notifyDataSetChanged();
        }});
    adb.show();
    }
});
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
  }
}

NotesDbHelper.java

public class NotesDbHelper extends SQLiteOpenHelper {

    public static final String DATABASE_NAME = "Notes.db";
    public static final String NOTES_TABLE_NAME = "Notes.user";
    public static final String NOTES_COLUMN_ID = "id";
    public static final String NOTES_COLUMN_NAME = "n_text";

    public NotesDbHelper(Context context) {
        super(context, DATABASE_NAME, null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table  " + NOTES_TABLE_NAME +
                   "(_id integer primary key AUTOINCREMENT NOT NULL," + NOTES_COLUMN_NAME +
                   ")"
        );
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int i, int i1) {
        db.execSQL("DROP TABLE IF EXISTS "+ DATABASE_NAME);
        onCreate(db);
    }

    public boolean insertNote(String text) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put("n_text", text);

        db.insert(NOTES_TABLE_NAME, null, contentValues);
        return true;
    }

    public ArrayList<Notes> getData() {
        SQLiteDatabase db = this.getReadableDatabase();
        ArrayList<Notes> notes = new ArrayList<Notes>();
        Cursor result = db.rawQuery("select * from "+ NOTES_TABLE_NAME , null);
        while(result.moveToNext()){
           notes.add( new Notes(result.getString(result.getColumnIndex(NOTES_COLUMN_NAME))));

        }
        return notes;
    }

    public boolean updateNotes(int id, int text) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues contentValues = new ContentValues();
        contentValues.put("n_text", text);

        db.update(NOTES_TABLE_NAME, contentValues, "id = ? ", new String[]{Integer.toString(id)});
        return true;
    }

    public Integer deleteNote(Integer id) {
        SQLiteDatabase db = this.getWritableDatabase();
        return db.delete(NOTES_TABLE_NAME,
                "id = ? ",
                new String[]{Integer.toString(id)});
    }

}

Notes.java

    public class Notes {
    String text;

    public Notes(String text) {
        this.text = text;
    }

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }
}

NotesCustomAdapter.java

public class NotesCustomAdapter extends ArrayAdapter{
    private Context context;
    private ArrayList<Notes> notes;

    public NotesCustomAdapter(Context context, int textViewResourceId, ArrayList objects) {
        super(context,textViewResourceId, objects);

        this.context= context;
        notes=objects;

    }

    private class ViewHolder
    {
        TextView text;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent)
    {
        ViewHolder holder=null;
        if (convertView == null)
        {
            LayoutInflater vi = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = vi.inflate(R.layout.notes_details, null);

            holder = new ViewHolder();
            holder.text = (TextView) convertView.findViewById(R.id.text);
            convertView.setTag(holder);

        }
        else {
            holder = (ViewHolder) convertView.getTag();
        }

        Notes textNotes = notes.get(position);
        holder.text.setText(textNotes.getText());
        return convertView;
    }
}

logcat的

第一行说：

java.lang.RuntimeException: Unable to start activity ComponentInfo{agenda.com/agenda.com.MainActivity}: android.database.sqlite.SQLiteException: unknown database Notes (code 1): while compiling: create table Notes.user(_id integer primary key AUTOINCREMENT NOT NULL,n_text)

Answer 1

为什么Notes.user？你正在放一个不必要的点。与您引用的链接进行比较。

只需使用Notes或UserNotes

即可

SQLiteException：未知数据库

1 个答案: