我是android的新手。我尝试使用片段来实现待办事项列表应用程序。使用listadpater显示列表视图。但是，在我构建数据库并使用另一个数据源文件来实现操作之后，其中一个是getAllTodos（），然后我遇到了错误：no column _id： 然后我将代码复制到一个新项目，使用Activity创建数据源的列表视图，看起来很好，没有＆＃34;不幸停止＆＃34;。这是我的代码：首先是片段类中的onCreate，第二个是数据源函数，第三个是我的databaseHelper，最后是错误。
这些onCreate函数似乎有很大问题。
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_todo, container, false);
listTask=(ListView) rootView.findViewById(android.R.id.list);
return rootView;
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Activity activity = getActivity();
if (activity != null) {
// Create an instance of the custom adapter for the GridView. A static array of location data
// is stored in the Application sub-class for this app. This data would normally come
// from a database or a web service.
datasource = new TodoDataSource(getActivity());
datasource.open();
todoList = datasource.getAllTodos();
adapt= new MyCustomAdapter(getActivity(), R.layout.todo_list, todoList);
//ListView listTask =(ListView) rootView.findViewById(android.R.id.list);
listTask.setAdapter(adapt);
}
}
这是数据源getAllTodos（）和allColumns值
private String[] allColumns = {
DatabaseHelper.COLUMN_ID,
DatabaseHelper.COLUMN_CATEGORY,
DatabaseHelper.COLUMN_SUMMARY,
DatabaseHelper.COLUMN_DESCRIPTION,
DatabaseHelper.COLUMN_STATUS };
public List<Todo> getAllTodos() {
List<Todo> todos = new ArrayList<Todo>();
Cursor cursor = database.query(DatabaseHelper.TABLE_TODO, allColumns, null, null, null, null, null); // here came with the error
cursor.moveToFirst();
while (!cursor.isAfterLast()) {
Todo todo = cursorToTodo(cursor);
todos.add(todo);
cursor.moveToNext();
}
// Make sure to close the cursor
cursor.close();
return todos;
}
public class DatabaseHelper extends SQLiteOpenHelper {
// Database table
public static final String TABLE_TODO = "todo";
public static final String COLUMN_ID = "_id";
public static final String COLUMN_CATEGORY = "category";
public static final String COLUMN_SUMMARY = "summary";
public static final String COLUMN_DESCRIPTION = "description";
public static final String COLUMN_STATUS = "status";
private static final String DATABASE_NAME = "todolist.db";
private static final int DATABASE_VERSION = 1;
// Database creation SQL statement
private static final String DATABASE_CREATE = "CREATE TABLE IF NOT EXISTS "
+ TABLE_TODO
+ " ("
+ COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ COLUMN_CATEGORY + " TEXT NOT NULL, "
+ COLUMN_SUMMARY + " TEXT NOT NULL, "
+ COLUMN_DESCRIPTION + " TEXT, "
+ COLUMN_STATUS + " INTEGER NOT NULL);";
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
// Method is called during creation of the database
@Override
public void onCreate(SQLiteDatabase database) {
database.execSQL(DATABASE_CREATE);
}
// Method is called during an upgrade of the database,
// e.g. if you increase the database version
@Override
public void onUpgrade(SQLiteDatabase database, int oldVersion,
int newVersion) {
//TodoTable.onUpgrade(database, oldVersion, newVersion);
Log.w(DatabaseHelper.class.getName(),
"Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
database.execSQL("DROP TABLE IF EXISTS " + TABLE_TODO);
onCreate(database);
}
}
错误：
03-06 01:02:41.318: E/AndroidRuntime(9091): FATAL EXCEPTION: main
03-06 01:02:41.318: E/AndroidRuntime(9091): android.database.sqlite.SQLiteException: no such column: _id: , while compiling: SELECT _id, category, summary, description, status FROM todo
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.database.sqlite.SQLiteCompiledSql.native_compile(Native Method)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.database.sqlite.SQLiteCompiledSql.<init>(SQLiteCompiledSql.java:68)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.database.sqlite.SQLiteProgram.compileSql(SQLiteProgram.java:143)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.database.sqlite.SQLiteProgram.compileAndbindAllArgs(SQLiteProgram.java:361)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:127)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:94)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:53)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:47)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1564)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1449)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1405)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1485)
03-06 01:02:41.318: E/AndroidRuntime(9091): at kidslist.sqlite.helper.TodoDataSource.getAllTodos(TodoDataSource.java:93)
03-06 01:02:41.318: E/AndroidRuntime(9091): at com.example.kidslist.TodoFragment.onActivityCreated(TodoFragment.java:68)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:847)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1032)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.app.BackStackRecord.run(BackStackRecord.java:622)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1382)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.app.FragmentManagerImpl$1.run(FragmentManager.java:426)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.os.Handler.handleCallback(Handler.java:605)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.os.Handler.dispatchMessage(Handler.java:92)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.os.Looper.loop(Looper.java:137)
03-06 01:02:41.318: E/AndroidRuntime(9091): at android.app.ActivityThread.main(ActivityThread.java:4424)
03-06 01:02:41.318: E/AndroidRuntime(9091): at java.lang.reflect.Method.invokeNative(Native Method)
03-06 01:02:41.318: E/AndroidRuntime(9091): at java.lang.reflect.Method.invoke(Method.java:511)
03-06 01:02:41.318: E/AndroidRuntime(9091): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:787)
03-06 01:02:41.318: E/AndroidRuntime(9091): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:554)
03-06 01:02:41.318: E/AndroidRuntime(9091): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：2)
您是否添加了列＆＃39; _id＆＃39;运行应用程序后（即数据库已经创建没有列_id）？
最简单的方法是清除设置中的应用程序数据（如果您的应用尚未启动）以删除数据库。
如果您的应用已经推出，可以尝试按照
private static final int DATABASE_VERSION = 2; // indicate database update
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
if (oldVersion < 2)
db.execSQL("ALTER TABLE "+ TABLE_TODO +" ADD "+ COLUMN_ID +" INTEGER PRIMARY KEY AUTOINCREMENT");
}
答案 1 :(得分：0)
在android的sqlite中，有一个_id列，当你将这个数据库用于adpters 时，不能省略。由于您尚未发布APP，因此可以考虑将此列添加到数据库中。
您可以参考此问题进行进一步研究。
About "_id" field in Android SQLite