错误说:column _id does not exists
但是该列在数据库中(设置为主键),并且该列位于外部 SD 文件夹中。我试图在活动的初始加载时返回数据库中包含的值,但似乎游标没有返回任何内容。
public class ComponentsDbAdapter {
public static final String COLUMN_ID = "_id";
public static final String COLUMN_SUBSTRUCTURE = "substructure";
public static final String COLUMN_TYPE = "type";
public static final String COLUMN_ORDERNUM = "ordernum";
public static final String COLUMN_INSTALLATION = "installation";
private static final String TAG = "ComponentsDbAdapter";
private DatabaseHelper mDbHelper;
private SQLiteDatabase mDb;
private static final String DATABASE_PATH = Environment.getExternalStorageDirectory().getAbsoluteFile()+ "/DATABASE_BACKUP/IMPORTED/";
private static final String DATABASE_NAME = "android.db";
private static final String TABLE_NAME = "TAB_WORKSCPE";
private static final int DATABASE_VERSION = 1;
private final Context mCtx;
public ComponentsDbAdapter open() throws SQLException {
mDbHelper = new DatabaseHelper(mCtx);
mDb = mDbHelper.getWritableDatabase();
return this;
}
private static class DatabaseHelper extends SQLiteOpenHelper {
DatabaseHelper(Context context) {
super(context, DATABASE_PATH+DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.query(TABLE_NAME, new String[] {COLUMN_ID, COLUMN_SUBSTRUCTURE, COLUMN_TYPE, COLUMN_ORDERNUM, COLUMN_INSTALLATION}, null, null, null, null, null);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
}
public ComponentsDbAdapter(Context ctx) {
this.mCtx = ctx;
}
public void close() {
if (mDbHelper != null) {
mDbHelper.close();
}
}
public Cursor fetchComponentsByName(String inputText) throws SQLException {
Log.w(TAG, inputText);
Cursor mCursor = null;
if (inputText == null || inputText.length () == 0) {
mCursor = mDb.query(TABLE_NAME, new String[] {COLUMN_ID, COLUMN_SUBSTRUCTURE, COLUMN_TYPE, COLUMN_ORDERNUM, COLUMN_INSTALLATION}, null, null, null, null, null);
} else {
mCursor = mDb.query(true, TABLE_NAME, new String[] {COLUMN_ID, COLUMN_SUBSTRUCTURE, COLUMN_TYPE, COLUMN_ORDERNUM, COLUMN_INSTALLATION}, COLUMN_TYPE + " like '%" + inputText + "%'", null, null, null, null, null);
}
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
public Cursor fetchAllComponents() {
Cursor mCursor = mDb.query(TABLE_NAME, new String[] {COLUMN_ID, COLUMN_SUBSTRUCTURE, COLUMN_TYPE, COLUMN_ORDERNUM, COLUMN_INSTALLATION}, null, null, null, null, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
}
public class AndroidListViewCursorAdaptorActivity extends Activity {
private ComponentsDbAdapter dbHelper;
private SimpleCursorAdapter dataAdapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
dbHelper = new ComponentsDbAdapter(this);
dbHelper.open();
//Generate ListView from SQLite Database
displayListView();
}
private void displayListView() {
Cursor cursor = dbHelper.fetchAllComponents();
// The desired columns to be bound
String[] columns = new String[] {
ComponentsDbAdapter.COLUMN_SUBSTRUCTURE,
ComponentsDbAdapter.COLUMN_TYPE,
ComponentsDbAdapter.COLUMN_ORDERNUM,
ComponentsDbAdapter.COLUMN_INSTALLATION
};
// the XML defined views which the data will be bound to
int[] to = new int[] {
R.id.inst,
R.id.subdt,
R.id.type,
R.id.ordernum,
};
// create the adapter using the cursor pointing to the desired data
//as well as the layout information
dataAdapter = new SimpleCursorAdapter(
this,
R.layout.country_info,
cursor,
columns,
to,
0);
ListView listView = (ListView) findViewById(R.id.listView1);
// Assign adapter to ListView
listView.setAdapter(dataAdapter);
listView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> listView, View view,
int position, long id) {
// Get the cursor, positioned to the corresponding row in the result set
Cursor cursor = (Cursor) listView.getItemAtPosition(position);
// Get the state's capital from this row in the database.
String compSubdt = cursor.getString(cursor.getColumnIndexOrThrow("subdt"));
Toast.makeText(getApplicationContext(), compSubdt, Toast.LENGTH_SHORT).show();
}
});
EditText myFilter = (EditText) findViewById(R.id.myFilter);
myFilter.addTextChangedListener(new TextWatcher() {
public void afterTextChanged(Editable s) {
}
public void beforeTextChanged(CharSequence s, int start,int count, int after) {
}
public void onTextChanged(CharSequence s, int start,int before, int count) {
dataAdapter.getFilter().filter(s.toString());
}
});
dataAdapter.setFilterQueryProvider(new FilterQueryProvider() {
public Cursor runQuery(CharSequence constraint) {
return dbHelper.fetchComponentsByName(constraint.toString());
}
});
}
}