有的时候，做一些软件时因为数据库文件较大，如果采取内置的数据库是不可取的，这时我们可以引用别人写的SDSQliteHelper
SDSqliteHelper跟系统的SQliteHelper操作差不多，只有一个地方不同
不同点：
SDSQliteHelper的数据库名称要带格式如sqlite.db
而系统的SqliteHelper的数据库不用带格式，直接文件名如sqlite
SDSQliteHelper.java内容如下，使用的时候只需，复制SDSQliteHelper.java文件到相应包，其他的操作参考系统引用SQliteHelper的例子或参考http://7071976.blog.51cto.com/blog/7061976/1232364
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 | import java.io.File; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteException; import android.database.sqlite.SQLiteDatabase.CursorFactory; import android.os.Environment; import android.util.Log; /** * A helper class to manage database creation and version management. * You create a subclass implementing {@link #onCreate}, {@link #onUpgrade} and * optionally {@link #onOpen}, and this class takes care of opening the database * if it exists, creating it if it does not, and upgrading it as necessary. * Transactions are used to make sure the database is always in a sensible state. * <p>For an example, see the NotePadProvider class in the NotePad sample application, * in the <em>samples/</em> directory of the SDK.</p> */ public abstract class SDSQLiteOpenHelper { private static final String TAG = SDSQLiteOpenHelper. class .getSimpleName(); public static String sdcardpath; private final Context mContext; private final String mName; private final CursorFactory mFactory; private final int mNewVersion; private SQLiteDatabase mDatabase = null ; private boolean mIsInitializing = false ; /** * Create a helper object to create, open, and/or manage a database. * The database is not actually created or opened until one of * {@link #getWritableDatabase} or {@link #getReadableDatabase} is called. * * @param context to use to open or create the database * @param name of the database file, or null for an in-memory database * @param factory to use for creating cursor objects, or null for the default * @param version number of the database (starting at 1); if the database is older, * {@link #onUpgrade} will be used to upgrade the database */ public SDSQLiteOpenHelper(Context context, String name, CursorFactory factory, int version) { if (version < 1 ) throw new IllegalArgumentException( "Version must be >= 1, was " + version); mContext = context; mName = name; mFactory = factory; mNewVersion = version; } /** * Create and/or open a database that will be used for reading and writing. * Once opened successfully, the database is cached, so you can call this * method every time you need to write to the database. Make sure to call * {@link #close} when you no longer need it. * * <p>Errors such as bad permissions or a full disk may cause this operation * to fail, but future attempts may succeed if the problem is fixed.</p> * * @throws SQLiteException if the database cannot be opened for writing * @return a read/write database object valid until {@link #close} is called */ public synchronized SQLiteDatabase getWritableDatabase() { if (mDatabase != null && mDatabase.isOpen() && !mDatabase.isReadOnly()) { return mDatabase; // The database is already open for business } if (mIsInitializing) { throw new IllegalStateException( "getWritableDatabase called recursively" ); } // If we have a read-only database open, someone could be using it // (though they shouldn't), which would cause a lock to be held on // the file, and our attempts to open the database read-write would // fail waiting for the file lock. To prevent that, we acquire the // lock on the read-only database, which shuts out other users. boolean success = false ; SQLiteDatabase db = null ; try { mIsInitializing = true ; if (mName == null ) { db = SQLiteDatabase.create( null ); } else { String path = getDatabasePath(mName).getPath(); db = SQLiteDatabase.openOrCreateDatabase(path,mFactory); } int version = db.getVersion(); if (version != mNewVersion) { db.beginTransaction(); try { if (version == 0 ) { onCreate(db); } else { onUpgrade(db, version, mNewVersion); } db.setVersion(mNewVersion); db.setTransactionSuccessful(); } finally { db.endTransaction(); } } onOpen(db); success = true ; return db; } finally { mIsInitializing = false ; if (success) { if (mDatabase != null ) { try { mDatabase.close(); } catch (Exception e) { } } mDatabase = db; } else { if (db != null ) db.close(); } } } /** * Create and/or open a database. This will be the same object returned by * {@link #getWritableDatabase} unless some problem, such as a full disk, * requires the database to be opened read-only. In that case, a read-only * database object will be returned. If the problem is fixed, a future call * to {@link #getWritableDatabase} may succeed, in which case the read-only * database object will be closed and the read/write object will be returned * in the future. * * @throws SQLiteException if the database cannot be opened * @return a database object valid until {@link #getWritableDatabase} * or {@link #close} is called. */ public synchronized SQLiteDatabase getReadableDatabase() { if (mDatabase != null && mDatabase.isOpen()) { return mDatabase; // The database is already open for business } if (mIsInitializing) { throw new IllegalStateException( "getReadableDatabase called recursively" ); } try { return getWritableDatabase(); } catch (SQLiteException e) { if (mName == null ) throw e; // Can't open a temp database read-only! Log.e(TAG, "Couldn't open " + mName + " for writing (will try read-only):" , e); } SQLiteDatabase db = null ; try { mIsInitializing = true ; String path = getDatabasePath(mName).getPath(); db = SQLiteDatabase.openDatabase(path, mFactory, SQLiteDatabase.OPEN_READWRITE); if (db.getVersion() != mNewVersion) { throw new SQLiteException( "Can't upgrade read-only database from version " + db.getVersion() + " to " + mNewVersion + ": " + path); } onOpen(db); Log.w(TAG, "Opened " + mName + " in read-only mode" ); mDatabase = db; return mDatabase; } finally { mIsInitializing = false ; if (db != null && db != mDatabase) db.close(); } } /** * Close any open database object. */ public synchronized void close() { if (mIsInitializing) throw new IllegalStateException( "Closed during initialization" ); if (mDatabase != null && mDatabase.isOpen()) { mDatabase.close(); mDatabase = null ; } } public File getDatabasePath(String name) //得到数据库位置可以看需求相应更改 { if ( this .ExistSDCard()){ sdcardpath = Environment.getExternalStorageDirectory().getPath()+ "/" ; } return new File(sdcardpath+ name); } /** * Called when the database is created for the first time. This is where the * creation of tables and the initial population of the tables should happen. * * @param db The database. */ public abstract void onCreate(SQLiteDatabase db); /** * Called when the database needs to be upgraded. The implementation * should use this method to drop tables, add tables, or do anything else it * needs to upgrade to the new schema version. * * <p>The SQLite ALTER TABLE documentation can be found * <a href="http://sqlite.org/lang_altertable.html">here</a>. If you add new columns * you can use ALTER TABLE to insert them into a live table. If you rename or remove columns * you can use ALTER TABLE to rename the old table, then create the new table and then * populate the new table with the contents of the old table. * * @param db The database. * @param oldVersion The old database version. * @param newVersion The new database version. */ public abstract void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion); /** * Called when the database has been opened. * Override method should check {@link SQLiteDatabase#isReadOnly} before * updating the database. * * @param db The database. */ public void onOpen(SQLiteDatabase db) {} private boolean ExistSDCard() { //判断SD卡是否存在 Log.d( "Exitsdcard" ,String.valueOf(android.os.Environment.getExternalStorageState().equals( android.os.Environment.MEDIA_MOUNTED))); if (android.os.Environment.getExternalStorageState().equals( android.os.Environment.MEDIA_MOUNTED)) { return true ; } else return false ; } } |
本文转自lilin9105 51CTO博客，原文链接：http://blog.51cto.com/7071976/1232485，如需转载请自行联系原作者