您好我是Android的新手，请各位帮我们如何创建一个处理数据库的类。
答案 0 :(得分：2)
你必须在你的src包中创建一个jav文件并扩展SQLiteOpenHelper类。
然后使用示例教程来了解更多...
以下是示例代码和链接
public class DatabaseHandler extends SQLiteOpenHelper
{
private static final int DATBASE_VERSION = 1; // database version
private static final String DATABASE_NAME = "MyManager"; // database name
private static final String TABLE_NAME = "ImageTable"; // 1st table name
private static final String KEY_ID = "id"; // 1st column name
private static final String KEY_IMAGE = "image"; // 2nd Column name
// Constructor
public DatabaseHandler(Context context)
{
super(context, DATABASE_NAME, null, DATBASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
String CREATE_IMAGE_TABLE = "CREATE TABLE " + TABLE_NAME + "(" + KEY_ID
+ " INTEGER PRIMARY KEY , " + KEY_IMAGE + " BLOB "+ ")";
db.execSQL(CREATE_IMAGE_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
onCreate(db);
}
}
你可以在这里找到更多
在您想要调用此类方法的主要活动中，创建类的对象并访问或调用方法。
答案 1 :(得分：1)
您需要做的是创建一个普通类并将其扩展到SQLLiteOpenHelper类
并实现相应的方法，你可以参考我的例子
public class dbHandler extends SQLiteOpenHelper{
static String DB_NAME="mapsDb";
static int DB_VERSION=1;
String TAB_NAME="usertable";
String FILED_ID="id";
String FILED_DRIVERNAME="driver_name";
String FILED_CARNUMBER="cno";
String FILED_CARMODEL="cmodel";
String MARKER_TAB="markerTable";
String FILED_DRIVERID="id";
String FILED_LAT="latitude";
String FILED_LON="longtitude";
public static Context con;
public dbHandler(Context context) {
super(context, DB_NAME, null, DB_VERSION);
// TODO Auto-generated constructor stub
this.con=context;
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
String CREATE_TABLE="CREATE TABLE "+TAB_NAME+" ("+FILED_ID+" TEXT PRIMARY KEY,"+FILED_DRIVERNAME+" TEXT,"+FILED_CARNUMBER+" TEXT,"+FILED_CARMODEL+" TEXT);";
String CREATE_MARKE_TABLE="CREATE TABLE "+MARKER_TAB+" ("+FILED_DRIVERID+" TEXT,"+FILED_LAT+" TEXT,"+FILED_LON+" TEXT);";
db.execSQL(CREATE_TABLE);
db.execSQL(CREATE_MARKE_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS "+TAB_NAME);
db.execSQL("DROP TABLE IF EXISTS "+MARKER_TAB);
onCreate(db);
}
public void insertDriverDetails(String id, String name,
String cno, String mno) {
// TODO Auto-generated method stub
SQLiteDatabase db=this.getWritableDatabase();
ContentValues cv=new ContentValues();
cv.put(FILED_ID, id);
cv.put(FILED_DRIVERNAME, name);
cv.put(FILED_CARNUMBER, cno);
cv.put(FILED_CARMODEL, mno);
try{
db.insert(TAB_NAME, null, cv);
}
catch(Exception e)
{
e.printStackTrace();
}
db.close();
}
public void updateMarkerForId(String id, String longt, String lat) {
// TODO Auto-generated method stub
SQLiteDatabase db=this.getWritableDatabase();
String UPDATE_QUERY="UPADATE "+MARKER_TAB+" SET "+FILED_LON+"=\""+longt+"\","+FILED_LAT+"\""+lat+"\" WHERE "+FILED_DRIVERID+"=\""+id+"\";";
db.execSQL(UPDATE_QUERY);
}
}
答案 2 :(得分：1)
public class DatabaseHelper extends SQLiteOpenHelper
{
public final static String DB_NAME = "sample.sqlite";
private final static String DB_KEY = "db_key";
public static String DATABASE_PATH;
private static SQLiteDatabase sqliteDatabase;
private static int DB_VERSION = 1;
private static Context myContext;
private SharedPreferences sharedPreference;
private SharedPreferences.Editor editor;
public DatabaseHelper(Context context)
{
super(context, DB_NAME, null, DB_VERSION = getVersionCode(myContext = context));
DATABASE_PATH = myContext.getFilesDir().toString() + "/" + DB_NAME;
sharedPreference = PreferenceManager.getDefaultSharedPreferences(myContext);
initDB();
}
private void initDB()
{
if(isDbExists())
{
if(getVersion() != DB_VERSION)
{
myContext.deleteDatabase(DATABASE_PATH);
copyDataBase();
}
else
{
openDataBase();
}
}
else
{
copyDataBase();
}
}
/** Get the database version from a shared preference*/
private int getVersion()
{
return sharedPreference.getInt(DB_KEY, 1);
}
/** Save the database version in a shared preference*/
private void saveVersion()
{
editor= sharedPreference.edit();
editor.putInt(DB_KEY, DB_VERSION);
editor.commit();
}
private boolean isDbExists()
{
return new File(DATABASE_PATH).exists();
}
public static SQLiteDatabase openDataBase() throws SQLException
{
if(sqliteDatabase == null || !sqliteDatabase.isOpen())
{
if(DATABASE_PATH==null || DATABASE_PATH.equalsIgnoreCase(""))
DATABASE_PATH = LiveSdkSampleApplication.context.getFilesDir().toString() + "/" + DB_NAME;
sqliteDatabase = SQLiteDatabase.openDatabase(DATABASE_PATH, null, SQLiteDatabase.OPEN_READWRITE | SQLiteDatabase.CREATE_IF_NECESSARY);
}
return sqliteDatabase;
}
public synchronized static void closedatabase()
{
if(sqliteDatabase != null)
sqliteDatabase.close();
}
@Override
public void onCreate(SQLiteDatabase db)
{
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
}
public static int getVersionCode(Context context)
{
int version = -1;
try
{
PackageInfo pInfo = context.getPackageManager().getPackageInfo(context.getPackageName(), PackageManager.GET_META_DATA);
version = pInfo.versionCode;
}
catch (NameNotFoundException e1)
{
}
return version;
}
public synchronized static DictionaryEntry[][] get(String query_str)
{
DictionaryEntry dir = null;
String[] columns;
int index;
int rowIndex = 0;
DictionaryEntry[] row_obj = null; //An array of columns and their values
DictionaryEntry[][] data_arr = null;
Cursor c;
if(sqliteDatabase != null)
{
try
{
openDataBase();
c = sqliteDatabase.rawQuery(query_str, null);
if(c.moveToFirst())
{
rowIndex = 0;
data_arr = new DictionaryEntry[c.getCount()][];
do
{
columns = c.getColumnNames();
row_obj = new DictionaryEntry[columns.length];
for(int i=0; i<columns.length; i++)
{
dir = new DictionaryEntry();
dir.key = columns[i];
index = c.getColumnIndex(dir.key);
dir.value = c.getString(index);
row_obj[i] = dir;
}
data_arr[rowIndex] = row_obj;
rowIndex++;
}
while(c.moveToNext());
}
c.close();
}
catch(Exception e)
{
e.printStackTrace();
}
}
return data_arr;
}
public void copyDataBase()
{
//If database not copied from assets
try
{
boolean isFound = false;
int i=0;
String str = "";
ZipFile zip = null;
ZipEntry zipen = null;
while(!isFound)
{
try
{
if(i == 0)
{
str = "";
}
else
{
str = "-"+i;
}
zip = new ZipFile("/data/app/"+myContext.getPackageName()+str+".apk");
zipen = zip.getEntry("assets/" + DB_NAME);
isFound = true;
}
catch(Exception e)
{
isFound = false;
}
++i;
}
InputStream is = zip.getInputStream(zipen);
OutputStream os = null;
os = myContext.openFileOutput(DB_NAME, Context.MODE_WORLD_READABLE);
int len;
byte[] buffer = new byte[4096];
while ((len = is.read(buffer)) >= 0)
{
os.write(buffer, 0, len);
}
is.close();
os.close();
openDataBase();
}
catch (Exception e)
{
e.printStackTrace();
}
finally
{
saveVersion();
}
}
}
答案 3 :(得分：0)
答案 4 :(得分：0)
如果您可以按照Android文档本身进行操作，那将会非常棒，因为它会以标准的代码编写方式为您提供支持...
查看http://developer.android.com/training/basics/data-storage/databases.html