我搜索了很多我发现与我的问题有关的问题，但我已经修好了，它仍然是错误我不知道为什么请帮我解决。
我想从getNotname方法中检索数据以在textview中显示，但是它出错我不知道为什么，我只是在DatabaseHandler类中复制getAllContacts方法，并在getNotename中调整了一点查询。
在getAllContacts中字符串selectQuery =“SELECT * FROM”+ TABLE_SONG_DETAIL;
在getNotename中字符串selectQuery =“SELECT”+ KEY_N_NAME +“FROM”+ TABLE_SONG_DETAIL +“WHERE KEY_ID ='2';”;
但是当我调用getNotename时，在mainactivity中，它出错，它没有显示任何内容。另一方面，当我调用getAllContacts而不是getNotename时，可以在textview上显示数据。我只是想知道为什么当我在getNotename中调整一点点查询时它会出错。
**List<Contact> contacts = db.getNotename();** // When I call getNotename method, It errors but when I change to call to getAllContacts, It can show data on textview.
这是我的代码
DatabaseHandler类
public class DatabaseHandler extends SQLiteOpenHelper {
// All Static variables
// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "PianoNote";
// Contacts table name
private static final String TABLE_SONG_DETAIL = "songDetail";
// Contacts Table Columns names
private static final String KEY_ID = "id";
private static final String KEY_S_NAME = "songname";
private static final String KEY_N_NAME = "notename";
private static final String KEY_TIME = "time";
public DatabaseHandler(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
// Creating Tables
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_CONTACTS_TABLE = "CREATE TABLE " + TABLE_SONG_DETAIL + "("
+ KEY_ID + " INTEGER PRIMARY KEY," + KEY_S_NAME + " TEXT," + KEY_N_NAME + " TEXT,"
+ KEY_TIME + " TEXT" + ")";
db.execSQL(CREATE_CONTACTS_TABLE);
}
// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Drop older table if existed
db.execSQL("DROP TABLE IF EXISTS " + TABLE_SONG_DETAIL);
// Create tables again
onCreate(db);
}
// Adding new data
void addContact(Contact contact) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues(); //import android.content.ContentValues
values.put(KEY_S_NAME, contact.getsongName()); // Song Name
values.put(KEY_N_NAME, contact.getNotename()); // Note name
values.put(KEY_TIME, contact.getTime()); // Time
// Inserting Row
db.insert(TABLE_SONG_DETAIL, null, values);
db.close(); // Closing database connection
}
// Getting All Data in Table
**public List<Contact> getAllContacts() {**
List<Contact> contactList = new ArrayList<Contact>();
// Select All Query
String selectQuery = "SELECT * FROM " + TABLE_SONG_DETAIL;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
Contact contact = new Contact();
contact.setID(Integer.parseInt(cursor.getString(0)));
contact.setsongName(cursor.getString(1));
contact.setNotename(cursor.getString(2));
contact.setTime(cursor.getString(3));
// Adding contact to list
contactList.add(contact);
} while (cursor.moveToNext());
}
// return contact list
return contactList;
}
// Getting Notename
**public List<Contact> getNotename() {**
List<Contact> contactList = new ArrayList<Contact>();
// Select Query
String selectQuery = "SELECT "+ KEY_N_NAME +" FROM " + TABLE_SONG_DETAIL+ " WHERE KEY_ID = '2';";
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
Contact contact = new Contact();
contact.setID(Integer.parseInt(cursor.getString(0)));
contact.setsongName(cursor.getString(1));
contact.setNotename(cursor.getString(2));
contact.setTime(cursor.getString(3));
// Adding contact to list
contactList.add(contact);
} while (cursor.moveToNext());
}
// return contact list
return contactList;
}
}
MainActivity类
public class MainActivity extends Activity {
SQLiteDatabase mDb;
Cursor mCursor;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TextView note = (TextView)findViewById(R.id.textView1);
DatabaseHandler db = new DatabaseHandler(this);
// Inserting Data
Log.d("Insert: ", "Inserting ..");
db.addContact(new Contact("Twinkle", "Do", "0.1"));
db.addContact(new Contact("Twinkle", "Do", "0.2"));
db.addContact(new Contact("Twinkle", "Sol", "0.3"));
db.addContact(new Contact("Twinkle", "Sol", "0.4"));
db.addContact(new Contact("Twinkle", "La", "0.5"));
// Reading all contacts
Log.d("Reading: ", "Reading all contacts..");
**List<Contact> contacts = db.getNotename();**
StringBuilder builder = new StringBuilder();
for (Contact cn : contacts) {
builder.append(cn.getNotename());
// Writing Contacts to log
String log = "Id: "+cn.getID()+" ,SongName: " + cn.getsongName() + " ,NoteName: " + cn.getNotename()+ " ,Time: " + cn.getTime();
Log.d("Name: ", log);
}
// print show on textview
note.setText(builder.toString());
}
}
联系班级
package com.example.databasehandler.java;
public class Contact {
//private variables
int _id;
String _songname;
String _note_name;
String _time;
// Empty constructor
public Contact(){
}
// constructor
public Contact(int id, String songname, String notename, String time){
this._id = id;
this._songname = songname;
this._note_name = notename;
this._time = time;
}
// constructor
public Contact(String songname, String notename, String time){
this._songname = songname;
this._note_name = notename;
this._time = time;
}
// getting ID
public int getID(){
return this._id;
}
// setting id
public void setID(int id){
this._id = id;
}
// getting name
public String getsongName(){
return this._songname;
}
// setting name
public void setsongName(String songname){
this._songname = songname;
}
// getting phone number
public String getNotename(){
return this._note_name;
}
// setting phone number
public void setNotename(String notename){
this._note_name = notename;
}
// getting phone number
public String getTime(){
return this._time;
}
// setting phone number
public void setTime(String time){
this._time = time;
}
}
答案 0 :(得分：0)
我认为您的问题是您在SQL select语句的末尾添加了一个半冒号。
如上所述： http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html#rawQuery(java.lang.String，java.lang.String []，android.os.CancellationSignal）
SQL字符串不能是“;”终止。