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title
cv.put("weather","sun"); //添加weather
cv.put("context","xxxx"); //添加context
String publish = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
            .format(new Date());
cv.put("publish ",publish); //添加publish
db.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ContentValues
cv.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");
  }
}