我有一个简单的代码，它从另一个活动中存在的SQLite代码创建一个数组列表。我想使用其他活动的参数，但保持得到错误： “android.database.sqlite.SQliteOpenHelper中没有可用的默认构造函数。”
你能告诉我我错过了什么吗？
这是第一个将SQLite数据库转换为arraylist的活动：
GpsPage.java：
class myLocationListener implements LocationListener {
@Override
public void onLocationChanged(Location location) {
if (location != null) {
double pLong = location.getLongitude();
double pLat = location.getLatitude();
float pAcc = location.getAccuracy();
long pTime = location.getTime();
textLat.setText(Double.toString(pLat));
textLong.setText(Double.toString(pLong));
db.addRecord(new Record(pLong, pLat, pAcc, pTime));
class PersonsDatabaseHandler extends SQLiteOpenHelper {
//Database Name
private static final String DATABASE_NAME = "RecordsDB";
private static final String TABLE_RECORD = "record";
//Table names
// private static final TABLE_RECORD = "records";
//Get all Persons
ArrayList<Record> getAllPersons() {
ArrayList<Record> localList = new ArrayList<Record>();
String selectQuery = "SELECT * FROM " + TABLE_RECORD;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
//Loops through all rows and adds them to the local list
if(cursor.moveToFirst())
{
do {
//Get person information
Record record = new Record();
record.setpLong(cursor.getDouble(0));
record.setpLat(cursor.getDouble(1));
record.setpAcc(cursor.getFloat(2));
record.setpTime(cursor.getLong(3));
//Add person to list
localList.add(record);
} while (cursor.moveToNext());
}
return localList;
这是数据库所在的第二个活动：
MySQLiteHelper.java：
public class MySQLiteHelper extends SQLiteOpenHelper {
// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "RecordsDB";
public MySQLiteHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
// SQL statement to create record table
String CREATE_RECORD_TABLE = "CREATE TABLE RECORD ( " +
"id INTEGER PRIMARY KEY AUTOINCREMENT, " +
"latitude TEXT NOT NULL, " +
"longtitude TEXT NOT NULL, " +
"accuracy TEXT NOT NULL, " +
"time TEXT NOT NULL )";
// create books table
db.execSQL(CREATE_RECORD_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Drop older books table if existed
db.execSQL("DROP TABLE IF EXISTS RECORD");
// create fresh record table
this.onCreate(db);
}
// Books table name
private static final String TABLE_RECORD = "record";
// Books Table Columns names
private static final String KEY_ID = "id";
private static final String KEY_LONG = "longtitude";
private static final String KEY_LAT = "latitude";
private static final String KEY_ACC = "accuracy";
private static final String KEY_TIME = "time";
private static final String[] COLUMNS = {KEY_ID, KEY_LONG, KEY_LAT, KEY_ACC, KEY_TIME};
public void addRecord(Record record) {
//for logging
Log.d("addRecord", record.toString());
// 1. get reference to writable DB
SQLiteDatabase db = this.getWritableDatabase();
// 2. create ContentValues to add key "column"/value
ContentValues values = new ContentValues();
values.put(KEY_LONG, record.getpLong());
values.put(KEY_LAT, record.getpLat());
values.put(KEY_ACC, record.getpAcc());
values.put(KEY_TIME, record.getpTime());
// 3. insert
db.insert(TABLE_RECORD, // table
null, //nullColumnHack
values); // key/value -> keys = column names/ values = column values
// 4. close
db.close();
}
public Record getRecord(int id) {
// 1. get reference to readable DB
SQLiteDatabase db = this.getReadableDatabase();
// 2. build query
Cursor cursor =
db.query(TABLE_RECORD, // a. table
COLUMNS, // b. column names
" id = ?", // c. selections
new String[]{String.valueOf(id)}, // d. selections args
null, // e. group by
null, // f. having
null, // g. order by
null); // h. limit
// 3. if we got results get the first one
if (cursor != null)
cursor.moveToFirst();
// 4. build book object
Record record = new Record();
record.setID(Integer.parseInt(cursor.getString(0)));
record.setpLat(cursor.getDouble(1));
record.setpLong(cursor.getDouble(2));
record.setpAcc(cursor.getFloat(2));
record.setpTime(cursor.getLong(2));
//log
Log.d("getBook(" + id + ")", record.toString());
// 5. return book
return record;
}
public List<Record> getAllRecords() {
List<Record> records = new LinkedList<Record>();
// 1. build the query
String query = "SELECT * FROM " + TABLE_RECORD;
// 2. get reference to writable DB
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(query, null);
// 3. go over each row, build book and add it to list
Record record = null;
if (cursor.moveToFirst()) {
do {
record = new Record();
record.setID(Integer.parseInt(cursor.getString(0)));
record.setpLat(cursor.getDouble(1));
record.setpLong(cursor.getDouble(2));
record.setpAcc(cursor.getFloat(2));
record.setpTime(cursor.getLong(2));
// Add book to books
records.add(record);
} while (cursor.moveToNext());
}
Log.d("getAllRecords()", record.toString());
// return books
return records;
}
public int UpdateRecords(Record record) {
// 1. get reference to writable DB
SQLiteDatabase db = this.getWritableDatabase();
// 2. create ContentValues to add key "column"/value
ContentValues values = new ContentValues();
values.put("Latitude", record.getpLat()); //
values.put("Longtitude", record.getpLong());
values.put("Accuracy", record.getpAcc());
values.put("Time", record.getpTime());
// 3. updating row
int i = db.update(TABLE_RECORD, //table
values, // column/value
KEY_ID + " = ?", // selections
new String[]{String.valueOf(record.getID())}); //selection args
// 4. close
db.close();
return i;
}
public void deleteRecords(Record record) {
// 1. get reference to writable DB
SQLiteDatabase db = this.getWritableDatabase();
// 2. delete
db.delete(TABLE_RECORD, //table name
KEY_ID + " = ?", // selections
new String[]{String.valueOf(record.getID())}); //selections args
// 3. close
db.close();
//log
Log.d("deleteBook", record.toString());
}
答案 0 :(得分：3)
SQLiteHelper需要一个Context变量作为参数的构造函数。
你应该致电：
MySQLiteHelper database = new MySQLiteHelper(context);
Context context变量......或直接从Application类继承（你应该记得在清单文件中声明这个类）。
例如：
MySQLiteHelper database = new MySQLitehelper(activity.getApplicationContext());
另请注意，您应使用Application Context而不是Activity context。要查看差异，您会看到以下链接：Application Context vs Activity Context
希望这有帮助：）