在Android开发中我们会接触到四种数据存储方式,每种存储方式都各有不同;以下eoe分别列举了Android开发中的不同存储方式的特点。 注意:Context.getSharedPreferences(Stringname,inttype)的参数更我们在创建数据的时候的数据权限属性是一样的,存储和取值的过程这有点像HashMap但是比HashMap更具人性化,getXXX(Objectkey,ObjectdefualtReturnValue),第二个参数是当你所要的key对应没有时候返回的值。这就省去了很多逻辑判断。 file = new File(FILE_PATH , FILE_NAME); file.createNewFile();
//打开文件file的OutputStream out = new FileOutputStream(file); String infoToWrite = "纸上得来终觉浅,绝知此事要躬行"; //将字符串转换成byte数组写入文件 out.write(infoToWrite.getBytes()); //关闭文件file的OutputStream out.close();
//打开文件file的InputStream in = new FileInputStream(file); //将文件内容全部读入到byte数组 int length = (int)file.length(); byte[] temp = new byte[length]; in.read(temp, 0, length); //将byte数组用UTF-8编码并存入display字符串中 display = EncodingUtils.getString(temp,TEXT_ENCODING); //关闭文件file的InputStream in.close(); } catch (IOException e) { //将出错信息打印到Logcat Log.e(TAG, e.toString()); this.finish(); }
//从资源读取
InputStream is=getResources().getRawResource(R.raw.文件名) 三.Databases DtabaseHelper mOpenHelper;
private static final int DATABASE_VERSION = 1; private static final String TABLE_NAME = "diary"; private static final String TITLE = "title"; private static final String BODY = "body";
DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); }
@Override public void onCreate(SQLiteDatabase db) {
String sql = "CREATE TABLE " + TABLE_NAME + " (" + TITLE + " text not null, " + BODY + " text not null " + ");"; Log.i("haiyang:createDB=", sql); db.execSQL(sql); }
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { } }
/* * 重新建立数据表 */ private void CreateTable() { SQLiteDatabase db = mOpenHelper.getWritableDatabase(); String sql = "CREATE TABLE " + TABLE_NAME + " (" + TITLE + " text not null, " + BODY + " text not null " + ");"; Log.i("haiyang:createDB=", sql);
try { db.execSQL("DROP TABLE IF EXISTS diary"); db.execSQL(sql); setTitle(" 数据表成功重建"); } catch (SQLException e) { setTitle("数据表重建错误"); } }
/* * 删除数据表 */ private void dropTable() { SQLiteDatabase db = mOpenHelper.getWritableDatabase(); String sql = "drop table " + TABLE_NAME; try { db.execSQL(sql); setTitle("数据表成功删除:" + sql); } catch (SQLException e) { setTitle("数据表删除错误"); } }
/* * 插入两条数据 */ private void insertItem() { SQLiteDatabase db = mOpenHelper.getWritableDatabase(); String sql1 = "insert into " + TABLE_NAME + " (" + TITLE + ", " + BODY + ") values('haiyang', 'android的发展真是迅速啊');"; String sql2 = "insert into " + TABLE_NAME + " (" + TITLE + ", " + BODY + ") values('icesky', 'android的发展真是迅速啊');"; try { Log.i("haiyang:sql1=", sql1); Log.i("haiyang:sql2=", sql2); db.execSQL(sql1); db.execSQL(sql2); setTitle(" 插入两条数据成功"); } catch (SQLException e) { setTitle("插入两条数据失败"); } }
/* * 删除其中的一条数据 */ private void deleteItem() { try { SQLiteDatabase db = mOpenHelper.getWritableDatabase(); db.delete(TABLE_NAME, " title = 'haiyang'", null); setTitle("删除title为haiyang的一条记录"); } catch (SQLException e) {
}
}
/* * 在屏幕的title区域显示当前数据表当中的数据的条数。 */ private void showItems() {
SQLiteDatabase db = mOpenHelper.getReadableDatabase(); String col[] = { TITLE, BODY }; Cursor cur = db.query(TABLE_NAME, col, null, null, null, null, null); Integer num = cur.getCount(); setTitle(Integer.toString(num) + " 条记录"); } 四,Network 例如: Cursor c = managedQuery(allCalls, null, null, null, null); |
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