android 数据存储

android中的数据存储大致可以分为三种，第一种是通过文件流的方式；第二种是利用SharedPreferences，第三种是使用android提供的SQLite。总体看来，前两种适用于处理小型数据的读取和修改，第三种方法中，SQLite其实就是一个数据库，通过编写建表和查询语句等就可以处理较为大量的数据。

第一种方法

需要在AndroidManifest.xml文件中添加文件读写权限。

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

具体的代码为：

private void readFromSD() {FileInputStream input;try {// set the path to the file in the SD cardinput = new FileInputStream("/sdcard/lyricInSD");BufferedReader reader = new BufferedReader(new InputStreamReader(input));String string = "";String line = null;while ((line = reader.readLine()) != null) {string = string + line + "\n";}input.close();} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}

private void saveToSD() {String string = "the string save to SD card";FileOutputStream output;try {// set the file path to the SD cardoutput = new FileOutputStream("/sdcard/lyricInSD");output.write(string.getBytes());output.close();} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}

第二种方法SharedPreferences

private void savesharedPreferences() {    SharedPreferences preferences = getSharedPreferences("dataText", Context.MODE_WORLD_READABLE);    Editor tempEditor = preferences.edit();    tempEditor.putString("name", "the name to save");    tempEditor.putString("age", "the age to save");    tempEditor.putString("height", "the height to save");    tempEditor.commit();}private void loadsharedPreferences() {    SharedPreferences preferences = getSharedPreferences("dataText", Context.MODE_PRIVATE);    String nameString = preferences.getString("name", "Default value");    String ageString = preferences.getString("age", "Default value");    String heightString = preferences.getString("height", "Default value");}

第三种方法SQLite，先封装一个dataAadatper类。

public class dataAdatper {public static final String KEY_NAME = "name";public static final String KEY_INTRO = "intro";public static final String KEY_ID = "id";//建表语句，设置id为自动增加，还有注意一旦修改了建表语句，需要同时把手机中对应的数据表手动删除private static final String DATABASE_CREATE = "create table member (id integer primary key autoincrement, "+ "name text, intro text);";private static final String DATABASE_NAME = "memberDB";private static final String DATABASE_TABLE = "member";private static final int DATABASE_VERSION = 2;private final Context mCtx;private DatabaseHelper mDbHelper;private SQLiteDatabase mDb;private static class DatabaseHelper extends SQLiteOpenHelper {/* 构造函数 */DatabaseHelper(Context context) {super(context, DATABASE_NAME, null, DATABASE_VERSION);}/* 创建一个表 */@Overridepublic void onCreate(SQLiteDatabase db) {db.execSQL(DATABASE_CREATE);}/* 升级数据库 */@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {db.execSQL("DROP TABLE IF EXISTS notes");onCreate(db);}}/** * 构造函数-取得context * */public dataAdatper(Context ctx) {this.mCtx = ctx;}/** * 打开数据库，返回数据库对象 * */public dataAdatper open() throws SQLException {mDbHelper = new DatabaseHelper(mCtx);mDb = mDbHelper.getWritableDatabase();return this;}/** * 关闭数据库 * */public void close() {mDbHelper.close();}/** * 插入一条数据，并返回该数据对应的id * */public int createRecord(String name, String intro) {ContentValues cv = new ContentValues();cv.put(KEY_NAME, name);cv.put(KEY_INTRO, intro);return mDb.insert(DATABASE_TABLE, null, cv);}/** * 删除一条数据 * */public boolean deleteRecord(int ID) {return mDb.delete(DATABASE_TABLE, KEY_ID + "=" + ID, null) > 0;}/** * 通过Cursor查询所有数据 * */public Cursor fetchAllRecords() {Cursor cursor = mDb.query(DATABASE_TABLE, new String[] { KEY_ID,KEY_NAME, KEY_INTRO }, null, null, null, null, null);if (cursor.getCount() > 0)cursor.moveToFirst();return cursor;}/** * 通过ID查询指定的数据 * */public Cursor fetchRecord(long ID) throws SQLException {Cursor cursor = mDb.query(true, DATABASE_TABLE, new String[] { KEY_ID,KEY_NAME, KEY_INTRO }, KEY_ID + "=" + ID, null, null, null,null, null);if (cursor.getCount() > 0)cursor.moveToFirst();return cursor;}/** * 更新一条数据 * */public boolean updateRecord(long ID, String name, String intro) {ContentValues cv = new ContentValues();cv.put(KEY_NAME, name);cv.put(KEY_INTRO, intro);return mDb.update(DATABASE_TABLE, cv, KEY_ID + "=" + ID, null) > 0;}}

在主程序中调用相关的操作函数以及获取数据并解析。

private void test() {dataAdatper sqlData = new dataAdatper(this);sqlData.open();// 插入一条数据，s1和s2为字符串参数sqlData.createRecord(s1, s2);// 删除一条数据，id为数据对应的idsqlData.deleteRecord(id);// 更新数据库中的数据sqlData.updateRecord(id, s1, s2);// 获取所有数据并解析Cursor cursor = sqlData.fetchAllRecords();if (cursor.getCount() > 0) {// name为数据表中的一个属性值，通过getColumnIndex获取属性值对应的下标int index = cursor.getColumnIndex("name");do {// 获取name属性值存储的数据cursor.getString(index);} while (cursor.moveToNext()); // 移动cursor}}

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