Android SQlite返回0
首先,让我解释一下如何从SQLite插入和返回数据 首先,我创建如下表:Android SQlite返回0,android,sqlite,Android,Sqlite,首先,让我解释一下如何从SQLite插入和返回数据 首先,我创建如下表: private static final String CREATE_TABLE_STUDENT_LESSON = " create table STUDENTSPECIFICLESSON ( _id TEXT , _viewID INTEGER PRIMARY KEY AUTOINCREMENT , _LESSON_TITLE TEXT , _LESSON_DATE TEXT , _LESSON_PROBLEM TEXT
private static final String CREATE_TABLE_STUDENT_LESSON = " create table STUDENTSPECIFICLESSON ( _id TEXT , _viewID INTEGER PRIMARY KEY AUTOINCREMENT , _LESSON_TITLE TEXT , _LESSON_DATE TEXT , _LESSON_PROBLEM TEXT );";
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_TABLE_STUDENT_LESSON);
}
sqLiteHelper.insertLesson(id,etLessonTitle.getText().toString(),currentDateandTime,etLessonProbStu.getText().toString());
然后我在SQLite中插入如下表:
public void insertLesson(String _id, String lessonTitle, String lessonDate, String lessonProblem) {
ContentValues contentValue = new ContentValues();
contentValue.put(SQLiteHelper._ID, _id);
contentValue.put(SQLiteHelper.LESSON_TITLE, lessonTitle);
contentValue.put(SQLiteHelper.LESSON_DATE, lessonDate);
contentValue.put(SQLiteHelper.LESSON_PROBLEM, lessonProblem);
this.getWritableDatabase().insert(SQLiteHelper.TABLE_NAME_STUDENTSPECIFICLESSON, null, contentValue);
}
我从活动中插入如下内容:
private static final String CREATE_TABLE_STUDENT_LESSON = " create table STUDENTSPECIFICLESSON ( _id TEXT , _viewID INTEGER PRIMARY KEY AUTOINCREMENT , _LESSON_TITLE TEXT , _LESSON_DATE TEXT , _LESSON_PROBLEM TEXT );";
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_TABLE_STUDENT_LESSON);
}
sqLiteHelper.insertLesson(id,etLessonTitle.getText().toString(),currentDateandTime,etLessonProbStu.getText().toString());
您会注意到,我已经创建了\u viewID INTEGER主键AUTOINCREMENT
,我正在使用它获取适配器中的特定ViewHolder
我通过执行以下操作获得此\u viewID
:
public String getLessonViewHolderID(String _path){
String id = null;
Cursor cursor = getReadableDatabase().rawQuery("Select "+SQLiteHelper._viewID+" from "+SQLiteHelper.TABLE_NAME_STUDENTSPECIFICLESSON+" Where "
+SQLiteHelper.LESSON_TITLE +"='"+_path+"'",null);
if (cursor != null) {
cursor.moveToFirst();
}
if (cursor == null) {
} else if (cursor.moveToFirst()) {
do {
id = String.valueOf(cursor.getInt(cursor.getColumnIndex(SQLiteHelper._viewID)));
} while (cursor.moveToNext());
cursor.close();
} else {
}
return id;
}
public String getLessonProblem(String _id){
String id = null;
Cursor cursor = getReadableDatabase().rawQuery("Select _LESSON_PROBLEM from "+SQLiteHelper.TABLE_NAME_STUDENTSPECIFICLESSON+" Where "
+SQLiteHelper._viewID +"='"+_id+"'",null);
if (cursor != null) {
cursor.moveToFirst();
}
if (cursor == null) {
} else if (cursor.moveToFirst()) {
do {
id = String.valueOf(cursor.getInt(cursor.getColumnIndex("_LESSON_PROBLEM")));
} while (cursor.moveToNext());
cursor.close();
} else {
}
return id;
}
这项功能工作正常,并按预期正确返回\u viewId
然后,我尝试通过执行以下操作从SQLite获取
\u LESSON\u PROBLEM
:
public String getLessonViewHolderID(String _path){
String id = null;
Cursor cursor = getReadableDatabase().rawQuery("Select "+SQLiteHelper._viewID+" from "+SQLiteHelper.TABLE_NAME_STUDENTSPECIFICLESSON+" Where "
+SQLiteHelper.LESSON_TITLE +"='"+_path+"'",null);
if (cursor != null) {
cursor.moveToFirst();
}
if (cursor == null) {
} else if (cursor.moveToFirst()) {
do {
id = String.valueOf(cursor.getInt(cursor.getColumnIndex(SQLiteHelper._viewID)));
} while (cursor.moveToNext());
cursor.close();
} else {
}
return id;
}
public String getLessonProblem(String _id){
String id = null;
Cursor cursor = getReadableDatabase().rawQuery("Select _LESSON_PROBLEM from "+SQLiteHelper.TABLE_NAME_STUDENTSPECIFICLESSON+" Where "
+SQLiteHelper._viewID +"='"+_id+"'",null);
if (cursor != null) {
cursor.moveToFirst();
}
if (cursor == null) {
} else if (cursor.moveToFirst()) {
do {
id = String.valueOf(cursor.getInt(cursor.getColumnIndex("_LESSON_PROBLEM")));
} while (cursor.moveToNext());
cursor.close();
} else {
}
return id;
}
然后从我的适配器调用:
String lessonProblem = helper.getLessonProblem(viewId);
上面的字符串lessonProblem
将返回0
我已检查我的数据库,所有数据都已正确插入,以下是我的数据库的图像:
我不明白为什么它返回0,但显然不是,有人能帮我指出可能是什么问题吗
您将获取一个字符串值作为int,然后将其转换为字符串。把它改成
id = cursor.getString(cursor.getColumnIndex("_LESSON_PROBLEM"));
草率的错误。你应该使用而不是
以字符串形式返回请求列的值。结果及
当列值为null时,此方法是否引发异常
或者列类型不是实现定义的字符串类型
最后
cursor.getString(cursor.getColumnIndex("_LESSON_PROBLEM"));
非常感谢您的回答,我将接受@laalto的回答,因为他先回答了。再次感谢您。值得一提的是,您链接到了错误的getString(),还有一个额外的)
关闭paren。感谢您的回答。