我正在尝试创建一个程序,它将采用我已经创建的SQLite数据库(称为os.sqlite)并能够读取/写入该数据库。我跟着来自here的代码并且Eclipse在复制数据库的过程中没有给我任何错误,但是当我尝试运行我的应用程序并显示表“OregonState”时,LogCat(我正在使用Eclipse Juno ADT插件并在SDK模拟器上运行我的应用程序)一直告诉我没有名为“OregonState”的表,这是我知道我创建的数据库中的一个表并放入项目中的assets文件夹中(I甚至可以看到坐在那里的文件)。尝试失败后,我注意到LogCat也说它无法打开数据库,因为数据库已被锁定。有人指出我可能正确地打开和关闭,但添加了这些,我的应用程序崩溃了。有人能帮忙吗?
我创建了一个Adapter(它还包含一个复制数据库的SQLiteHelper嵌套类)来访问数据库并允许我插入/删除/ etc。到桌子。我的主要活动然后使用此适配器。这是我的代码(为了彻底和完整,我已经包含了所有代码,不包括导入和包名):
public class SQLAdapter
{
private static final String TABLE_OSU = "OregonState";
private static final String COLUMN_ID = "_id";
private static final String COLUMN_NAME = "Name";
private static final String COLUMN_FIELD = "Field";
private static final String DATABASE_PATH = "/data/data/com.example.sql2/databases/";
private static final String DATABASE_NAME = "os.sqlite";
private static final int DATABASE_VERSION = 1;
MySQLiteHelper helper;
private final Context context;
public SQLAdapter(Context context)
{
this.context = context;
helper = new MySQLiteHelper(context);
}
private class MySQLiteHelper extends SQLiteOpenHelper
{
private final Context context;
public MySQLiteHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
this.context = context;
}
@Override
public void onCreate(SQLiteDatabase database)
{
try {
createDatabase();
} catch (IOException e) {
e.printStackTrace();
}
}
public void createDatabase() throws IOException
{
boolean dbExist = checkDatabase();
if (dbExist)
{
// Nothing
}
else
{
copyDatabase();
}
}
public boolean checkDatabase()
{
SQLiteDatabase checkDB = null;
try
{
String path = DATABASE_PATH + DATABASE_NAME;
checkDB = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READWRITE);
} catch (SQLiteException e) {}
if (checkDB != null)
checkDB.close();
return checkDB != null ? true : false;
}
public void copyDatabase() throws IOException
{
InputStream input = context.getAssets().open(DATABASE_NAME);
String outFileName = DATABASE_PATH + DATABASE_NAME;
OutputStream output = new FileOutputStream(outFileName);
byte[] buffer = new byte[1024];
int length;
while ((length = input.read(buffer))>0)
output.write(buffer, 0, length);
output.flush();
output.close();
input.close();
}
public void openDatabase()
{
String path = DATABASE_PATH + DATABASE_NAME;
SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READWRITE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
SQLiteDatabase database = this.getWritableDatabase();
Log.w(DATABASE_NAME, "Upgrading database from " + oldVersion + " to " + newVersion + ", which will erase all data.");
database.execSQL("DROP TABLE IF EXISTS " + TABLE_OSU);
onCreate(database);
database.close();
}
}
public SQLiteDatabase open() throws SQLException
{
SQLiteDatabase database = helper.getWritableDatabase();
return database;
}
public void close()
{
helper.close();
}
public long insert(SQLiteDatabase database, String name, String field)
{
ContentValues values = new ContentValues();
values.put(COLUMN_NAME, name);
values.put(COLUMN_FIELD, field);
long x = database.insert(TABLE_OSU, null, values);
database.close();
return x;
}
public int delete(SQLiteDatabase database, int id)
{
int x = database.delete(TABLE_OSU, COLUMN_ID + "=" + id, null);
return x;
}
public Cursor getAll(SQLiteDatabase database)
{
return database.query(TABLE_OSU, new String[] {COLUMN_ID, COLUMN_NAME, COLUMN_FIELD}, null, null, null, null, null);
}
public Cursor get(SQLiteDatabase database, int id) throws SQLException
{
return database.query(TABLE_OSU, new String[] {COLUMN_ID, COLUMN_NAME, COLUMN_FIELD}, COLUMN_ID + "=" + id, null, null, null, null);
}
public int update(SQLiteDatabase database, int id, String name, String field)
{
ContentValues values = new ContentValues();
values.put(COLUMN_NAME, name);
values.put(COLUMN_FIELD, field);
return database.update(TABLE_OSU, values, COLUMN_ID + "=" + id, null);
}
}
public class SQLTest extends Activity
{
SQLAdapter adapter;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
adapter = new SQLAdapter(this);
getAll();
}
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
getMenuInflater().inflate(R.menu.activity_sqltest, menu);
return true;
}
public long insert(String name, String field)
{
SQLiteDatabase database = adapter.open();
long id = adapter.insert(database, name, field);
adapter.close();
return id;
}
public int delete(int id)
{
SQLiteDatabase database = adapter.open();
int rowsDeleted = adapter.delete(database, id);
adapter.close();
return rowsDeleted;
}
public void getAll()
{
SQLiteDatabase database = adapter.open();
TextView tv = new TextView(this);
String table = "";
try
{
Cursor cursor = adapter.getAll(database);
if (cursor.moveToFirst())
{
do
{
table += "\n" + cursor.getString(0) + " " + cursor.getString(1) + " " + cursor.getString(2);
} while (cursor.moveToNext());
}
cursor.close();
} catch (Exception e) {}
tv.setText(table);
setContentView(tv);
adapter.close();
}
public void get(int id)
{
SQLiteDatabase database = adapter.open();
Cursor cursor = adapter.get(database, id);
TextView tv = new TextView(this);
String table = "";
if (cursor.moveToFirst())
table += "\n" + cursor.getString(0) + " " + cursor.getString(1) + " " + cursor.getString(2);
else
table += "No hall found with ID: " + id;
tv.setText(table);
setContentView(tv);
cursor.close();
adapter.close();
}
public int update(int id, String name, String field)
{
SQLiteDatabase database = adapter.open();
int rowsUpdated = adapter.update(database, id, name, field);
adapter.close();
return rowsUpdated;
}
}
我注意到this guy有一个类似的问题,虽然我从未真正工作,而他的确如此。我跟着他的代码了一点,这只会让我的应用程序开始崩溃。我只是评论,但我是新来的,所以没有足够的声誉。
答案 0 :(得分:0)
我按照Yaqub Ahmad和中提琴给我的指示!有效!之前我有一个Adapter类和一个SQLiteOpenHelper的迭代,但我认为将Helper作为嵌套类可能会让事情变得更加困难。我实际上不确定我做错了什么,但我在艾哈迈德的link得到的代码似乎工作得非常好,因为我的表能够在应用程序中打印。谢谢Yaqub Ahmad。我已经提供了代码的链接,这些代码对于我遇到问题的任何人都有用。