Android编程中的5种数据存储方式

class ViewOcl implements View.OnClickListener{    @Override    public void onClick(View v) {      switch(v.getId()){      case R.id.btnSet:        //步骤1：获取输入值        String code = txtCode.getText().toString().trim();        //步骤2-1：创建一个SharedPreferences.Editor接口对象，lock表示要写入的XML文件名，MODE_WORLD_WRITEABLE写操作        SharedPreferences.Editor editor = getSharedPreferences("lock", MODE_WORLD_WRITEABLE).edit();        //步骤2-2：将获取过来的值放入文件        editor.putString("code", code);        //步骤3：提交        editor.commit();        Toast.makeText(getApplicationContext(), "口令设置成功", Toast.LENGTH_LONG).show();        break;      case R.id.btnGet:        //步骤1：创建一个SharedPreferences接口对象        SharedPreferences read = getSharedPreferences("lock", MODE_WORLD_READABLE);        //步骤2：获取文件中的值        String value = read.getString("code", "");        Toast.makeText(getApplicationContext(), "口令为："+value, Toast.LENGTH_LONG).show();        break;      }    }}

public String read() {    try {      FileInputStream inStream = this.openFileInput("message.txt");      byte[] buffer = new byte[1024];      int hasRead = 0;      StringBuilder sb = new StringBuilder();      while ((hasRead = inStream.read(buffer)) != -1) {        sb.append(new String(buffer, 0, hasRead));      }      inStream.close();      return sb.toString();    } catch (Exception e) {      e.printStackTrace();    }     return null;  }  public void write(String msg){    // 步骤1：获取输入值    if(msg == null) return;    try {      // 步骤2:创建一个FileOutputStream对象,MODE_APPEND追加模式      FileOutputStream fos = openFileOutput("message.txt",          MODE_APPEND);      // 步骤3：将获取过来的值放入文件      fos.write(msg.getBytes());      // 步骤4：关闭数据流      fos.close();    } catch (Exception e) {      e.printStackTrace();    }}

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

// 文件写操作函数  private void write(String content) {    if (Environment.getExternalStorageState().equals(        Environment.MEDIA_MOUNTED)) { // 如果sdcard存在      File file = new File(Environment.getExternalStorageDirectory()          .toString()          + File.separator          + DIR          + File.separator          + FILENAME); // 定义File类对象      if (!file.getParentFile().exists()) { // 父文件夹不存在        file.getParentFile().mkdirs(); // 创建文件夹      }      PrintStream out = null; // 打印流对象用于输出      try {        out = new PrintStream(new FileOutputStream(file, true)); // 追加文件        out.println(content);      } catch (Exception e) {        e.printStackTrace();      } finally {        if (out != null) {          out.close(); // 关闭打印流        }      }    } else { // SDCard不存在，使用Toast提示用户      Toast.makeText(this, "保存失败，SD卡不存在！", Toast.LENGTH_LONG).show();    }  }  // 文件读操作函数  private String read() {    if (Environment.getExternalStorageState().equals(        Environment.MEDIA_MOUNTED)) { // 如果sdcard存在      File file = new File(Environment.getExternalStorageDirectory()          .toString()          + File.separator          + DIR          + File.separator          + FILENAME); // 定义File类对象      if (!file.getParentFile().exists()) { // 父文件夹不存在        file.getParentFile().mkdirs(); // 创建文件夹      }      Scanner scan = null; // 扫描输入      StringBuilder sb = new StringBuilder();      try {        scan = new Scanner(new FileInputStream(file)); // 实例化Scanner        while (scan.hasNext()) { // 循环读取          sb.append(scan.next() + "/n"); // 设置文本        }        return sb.toString();      } catch (Exception e) {        e.printStackTrace();      } finally {        if (scan != null) {          scan.close(); // 关闭打印流        }      }    } else { // SDCard不存在，使用Toast提示用户      Toast.makeText(this, "读取失败，SD卡不存在！", Toast.LENGTH_LONG).show();    }    return null;}

db.executeSQL(String sql); db.executeSQL(String sql, Object[] bindArgs);//sql语句中使用占位符，然后第二个参数是实际的参数集

db.insert(String table, String nullColumnHack, ContentValues values); db.update(String table, Contentvalues values, String whereClause, String whereArgs); db.delete(String table, String whereClause, String whereArgs);

ContentValues cv = new ContentValues();//实例化一个ContentValues用来装载待插入的数据cv.put("title","you are beautiful");//添加titlecv.put("weather","sun"); //添加weathercv.put("context","xxxx"); //添加contextString publish = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")            .format(new Date());cv.put("publish ",publish); //添加publishdb.insert("diary",null,cv);//执行插入操作

String sql = "insert into user(username,password) values ('Jack Johnson','iLovePopMuisc');//插入操作的SQL语句db.execSQL(sql);//执行SQL语句

String whereClause = "username=?";//删除的条件String[] whereArgs = {"Jack Johnson"};//删除的条件参数db.delete("user",whereClause,whereArgs);//执行删除

String sql = "delete from user where username='Jack Johnson'";//删除操作的SQL语句db.execSQL(sql);//执行删除操作

ContentValues cv = new ContentValues();//实例化ContentValuescv.put("password","iHatePopMusic");//添加要更改的字段及内容String whereClause = "username=?";//修改条件String[] whereArgs = {"Jack Johnson"};//修改条件的参数db.update("user",cv,whereClause,whereArgs);//执行修改

String sql = "update user set password = 'iHatePopMusic' where username='Jack Johnson'";//修改的SQL语句db.execSQL(sql);//执行修改

db.rawQuery(String sql, String[] selectionArgs);db.query(String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy);db.query(String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy, String limit);db.query(String distinct, String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy, String limit);

c.move(int offset); //以当前位置为参考,移动到指定行 c.moveToFirst();  //移动到第一行 c.moveToLast();   //移动到最后一行 c.moveToPosition(int position); //移动到指定行 c.moveToPrevious(); //移动到前一行 c.moveToNext();   //移动到下一行 c.isFirst();    //是否指向第一条 c.isLast();   //是否指向最后一条 c.isBeforeFirst(); //是否指向第一条之前 c.isAfterLast();  //是否指向最后一条之后 c.isNull(int columnIndex); //指定列是否为空(列基数为0) c.isClosed();    //游标是否已关闭 c.getCount();    //总数据项数 c.getPosition();  //返回当前游标所指向的行数 c.getColumnIndex(String columnName);//返回某列名对应的列索引值 c.getString(int columnIndex);  //返回当前行指定列的值 

String[] params = {12345,123456};Cursor cursor = db.query("user",columns,"ID=?",params,null,null,null);//查询并获得游标if(cursor.moveToFirst()){//判断游标是否为空  for(int i=0;i<cursor.getCount();i++){    cursor.move(i);//移动到指定记录    String username = cursor.getString(cursor.getColumnIndex("username");    String password = cursor.getString(cursor.getColumnIndex("password"));  }}

Cursor result=db.rawQuery("SELECT ID, name, inventory FROM mytable");//Cursor c = db.rawQuery("s name, inventory FROM mytable where ID=?",new Stirng[]{"123456"});   result.moveToFirst(); while (!result.isAfterLast()) {   int id=result.getInt(0);   String name=result.getString(1);   int inventory=result.getInt(2);   // do something useful with these   result.moveToNext();  }  result.close();

import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteDatabase.CursorFactory;import android.database.sqlite.SQLiteOpenHelper;public class SqliteDBHelper extends SQLiteOpenHelper {  // 步骤1：设置常数参量  private static final String DATABASE_NAME = "diary_db";  private static final int VERSION = 1;  private static final String TABLE_NAME = "diary";  // 步骤2：重载构造方法  public SqliteDBHelper(Context context) {    super(context, DATABASE_NAME, null, VERSION);  }  /*   * 参数介绍：context 程序上下文环境 即：XXXActivity.this    * name 数据库名字    * factory 接收数据，一般情况为null   * version 数据库版本号   */  public SqliteDBHelper(Context context, String name, CursorFactory factory,      int version) {    super(context, name, factory, version);  }  //数据库第一次被创建时，onCreate()会被调用  @Override  public void onCreate(SQLiteDatabase db) {    // 步骤3：数据库表的创建    String strSQL = "create table "        + TABLE_NAME        + "(tid integer primary key autoincrement,title varchar(20),weather varchar(10),context text,publish date)";    //步骤4：使用参数db,创建对象    db.execSQL(strSQL);  }  //数据库版本变化时，会调用onUpgrade()  @Override  public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {  }}

import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import com.chinasoft.dbhelper.SqliteDBHelper;public class DiaryDao {  private SqliteDBHelper sqliteDBHelper;  private SQLiteDatabase db;  // 重写构造方法  public DiaryDao(Context context) {    this.sqliteDBHelper = new SqliteDBHelper(context);    db = sqliteDBHelper.getWritableDatabase();  }  // 读操作  public String execQuery(final String strSQL) {    try {      System.out.println("strSQL>" + strSQL);      // Cursor相当于JDBC中的ResultSet      Cursor cursor = db.rawQuery(strSQL, null);      // 始终让cursor指向数据库表的第1行记录      cursor.moveToFirst();      // 定义一个StringBuffer的对象，用于动态拼接字符串      StringBuffer sb = new StringBuffer();      // 循环游标，如果不是最后一项记录      while (!cursor.isAfterLast()) {        sb.append(cursor.getInt(0) + "/" + cursor.getString(1) + "/"            + cursor.getString(2) + "/" + cursor.getString(3) + "/"            + cursor.getString(4)+"#");        //cursor游标移动        cursor.moveToNext();      }      db.close();      return sb.deleteCharAt(sb.length()-1).toString();    } catch (RuntimeException e) {      e.printStackTrace();      return null;    }  }  // 写操作  public boolean execOther(final String strSQL) {    db.beginTransaction(); //开始事务    try {      System.out.println("strSQL" + strSQL);      db.execSQL(strSQL);      db.setTransactionSuccessful(); //设置事务成功完成       db.close();      return true;    } catch (RuntimeException e) {      e.printStackTrace();      return false;    }finally {       db.endTransaction();  //结束事务     }   }}

public synchronized SQLiteDatabase getReadableDatabase() {   if (mDatabase != null && mDatabase.isOpen()) {     // 如果发现mDatabase不为空并且已经打开则直接返回     return mDatabase;   }   if (mIsInitializing) {     // 如果正在初始化则抛出异常     throw new IllegalStateException("getReadableDatabase called recursively");   }   // 开始实例化数据库mDatabase   try {     // 注意这里是调用了getWritableDatabase()方法     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);   }   // 如果无法以可读写模式打开数据库 则以只读方式打开   SQLiteDatabase db = null;   try {     mIsInitializing = true;     String path = mContext.getDatabasePath(mName).getPath();// 获取数据库路径     // 以只读方式打开数据库     db = SQLiteDatabase.openDatabase(path, mFactory, SQLiteDatabase.OPEN_READONLY);     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;// 为mDatabase指定新打开的数据库     return mDatabase;// 返回打开的数据库   } finally {     mIsInitializing = false;     if (db != null && db != mDatabase)       db.close();   } }

public synchronized SQLiteDatabase getWritableDatabase() {   if (mDatabase != null && mDatabase.isOpen() && !mDatabase.isReadOnly()) {     // 如果mDatabase不为空已打开并且不是只读模式 则返回该实例     return mDatabase;   }   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;   // 如果mDatabase不为空则加锁 阻止其他的操作   if (mDatabase != null)     mDatabase.lock();   try {     mIsInitializing = true;     if (mName == null) {       db = SQLiteDatabase.create(null);     } else {       // 打开或创建数据库       db = mContext.openOrCreateDatabase(mName, 0, mFactory);     }     // 获取数据库版本(如果刚创建的数据库,版本为0)     int version = db.getVersion();     // 比较版本(我们代码中的版本mNewVersion为1)     if (version != mNewVersion) {       db.beginTransaction();// 开始事务       try {         if (version == 0) {           // 执行我们的onCreate方法           onCreate(db);         } else {           // 如果我们应用升级了mNewVersion为2,而原版本为1则执行onUpgrade方法           onUpgrade(db, version, mNewVersion);         }         db.setVersion(mNewVersion);// 设置最新版本         db.setTransactionSuccessful();// 设置事务成功       } finally {         db.endTransaction();// 结束事务       }     }     onOpen(db);     success = true;     return db;// 返回可读写模式的数据库实例   } finally {     mIsInitializing = false;     if (success) {       // 打开成功       if (mDatabase != null) {         // 如果mDatabase有值则先关闭         try {           mDatabase.close();         } catch (Exception e) {         }         mDatabase.unlock();// 解锁       }       mDatabase = db;// 赋值给mDatabase     } else {       // 打开失败的情况：解锁、关闭       if (mDatabase != null)         mDatabase.unlock();       if (db != null)         db.close();     }   } }

public class SQLiteActivity extends Activity {  public DiaryDao diaryDao;  //因为getWritableDatabase内部调用了mContext.openOrCreateDatabase(mName, 0, mFactory);   //所以要确保context已初始化,我们可以把实例化Dao的步骤放在Activity的onCreate里  @Override  protected void onCreate(Bundle savedInstanceState) {    diaryDao = new DiaryDao(SQLiteActivity.this);    initDatabase();  }  class ViewOcl implements View.OnClickListener {    @Override    public void onClick(View v) {      String strSQL;      boolean flag;      String message;      switch (v.getId()) {      case R.id.btnAdd:        String title = txtTitle.getText().toString().trim();        String weather = txtWeather.getText().toString().trim();;        String context = txtContext.getText().toString().trim();;        String publish = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")            .format(new Date());        // 动态组件SQL语句        strSQL = "insert into diary values(null,'" + title + "','"            + weather + "','" + context + "','" + publish + "')";        flag = diaryDao.execOther(strSQL);        //返回信息        message = flag?"添加成功":"添加失败";        Toast.makeText(getApplicationContext(), message, Toast.LENGTH_LONG).show();        break;      case R.id.btnDelete:        strSQL = "delete from diary where tid = 1";        flag = diaryDao.execOther(strSQL);        //返回信息        message = flag?"删除成功":"删除失败";        Toast.makeText(getApplicationContext(), message, Toast.LENGTH_LONG).show();        break;      case R.id.btnQuery:        strSQL = "select * from diary order by publish desc";        String data = diaryDao.execQuery(strSQL);        Toast.makeText(getApplicationContext(), data, Toast.LENGTH_LONG).show();        break;      case R.id.btnUpdate:        strSQL = "update diary set title = '测试标题1-1' where tid = 1";        flag = diaryDao.execOther(strSQL);        //返回信息        message = flag?"更新成功":"更新失败";        Toast.makeText(getApplicationContext(), message, Toast.LENGTH_LONG).show();        break;      }    }  }  private void initDatabase() {    // 创建数据库对象    SqliteDBHelper sqliteDBHelper = new SqliteDBHelper(SQLiteActivity.this);    sqliteDBHelper.getWritableDatabase();    System.out.println("数据库创建成功");  }}