数据的本地存储

一，最简单实用的SharePreference

首先获取保存数据和提交数据的实例对象，参考如下:

shareDB = mContext.getSharedPreferences(ConstData.Share._SHARE_TBALE,
				Context.MODE_PRIVATE);
		sharEdit = shareDB.edit();

然后就可以开始保存和读取数据了：

// 保存数据
			sharEdit.putString(ConstData.Share._SHARE_COLUMN1, str);
			sharEdit.commit();
			// 读取数据
			String str1 = shareDB.getString(ConstData.Share._SHARE_COLUMN1,
					null);

二，然后就是保存在文件中。这个文件在当前软件的目录下。所以软件卸载了，数据也随之被清除

查询（读取）数据如下：即使这个文件根本就不存在也没关系

public String readFileData(String readFileName) {
		String res = "";
		try {
			FileInputStream fin = mContext.openFileInput(readFileName);
			// 一口气读完
			int length = fin.available();
			byte[] buffer = new byte[length];
			fin.read(buffer);
			res = EncodingUtils.getString(buffer, "utf-8");
			fin.close();
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
		return res;
	}

保存数据如下：

public boolean saveFile(String saveContent, String saveFileName) {
		try {
			byte[] buf = saveContent.getBytes();
			FileOutputStream fos = mContext.openFileOutput(saveFileName,
					Context.MODE_PRIVATE);
			fos.write(buf);
			fos.flush();
			fos.close();
		} catch (Exception e) {
			e.printStackTrace();
			return false;
		}
		return true;
	}

三，保存在SD卡中，比如图片，配置文件等。

首先判断有无SD卡，有的话，定义好文件在SD中的路径和文件名称

private final String FILEPATH = "/configfile/userinfo/";
	private final String FILENAME = "myfile.txt";
//---------------------------------
public String createSDCardDir() {
		String path = null;
		if (Environment.MEDIA_MOUNTED.equals(Environment
				.getExternalStorageState())) {
			File sdcardDir = Environment.getExternalStorageDirectory();
			path = sdcardDir.getPath() + FILEPATH;
			File path1 = new File(path);
			if (!path1.exists()) {
				path1.mkdirs();
			}
		}
		return path;
	}

保存文件参考如下代码

try {
					File file = new File(pathStr + FILENAME);
					file.createNewFile();// 不存在该文件的时候才创建。
					FileOutputStream fos = new FileOutputStream(file);
					fos.write(str.getBytes());
					fos.flush();
					fos.close();
				} catch (Exception e) {
					e.printStackTrace();
					Toast.makeText(mContext, "保存失败", Toast.LENGTH_SHORT).show();
				}

查询数据参考如下

try {
				File file = new File(pathStr + FILENAME);
				file.createNewFile();
				InputStream fis = new FileInputStream(file);
				byte[] buffer = new byte[fis.available()];
				fis.read(buffer);
				String str1 = new String(buffer);
				if (TextUtils.isEmpty(str1)) {
					Toast.makeText(mContext, "无数据", Toast.LENGTH_SHORT).show();
				} else {
					et1.setText(str1);
				}
			} catch (Exception e) {
				e.printStackTrace();
			}

最后别忘了在配置文件中添加操作外接存储设备的权限

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

四、SQLite关系型数据库

首先建立数据库DB和表Table，参考如下类：

public class DBHelper extends SQLiteOpenHelper {
	// 得到可写的SqliteDatabase
	public SQLiteDatabase sqliteDB = this.getWritableDatabase();

	public DBHelper(Context context) {
		super(context, ConstData.SQL._SQL_DBNAME, null, 1);
	}

	public void onCreate(SQLiteDatabase db) {
		// 创建表，两列
		String sql = "create table " + ConstData.SQL._SQL_TABLE1
				+ "(_id integer primary key autoincrement,"
				+ ConstData.SQL._SQL_COLUMN1 + " text,"
				+ ConstData.SQL._SQL_COLUMN2 + " text)";
		db.execSQL(sql);
	}

	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		
	}
}

然后定义一个数据访问对象接口类DAO,参考如下

public class DAO {
	public static Cursor queryAll(Context context) {
		Cursor cursor = null;
		try {
			String sql = "select _id," + ConstData.SQL._SQL_COLUMN1 + ","
					+ ConstData.SQL._SQL_COLUMN2 + " from "
					+ ConstData.SQL._SQL_TABLE1 + " order by _id desc";
			DBHelper dbHelper = new DBHelper(context);
			cursor = dbHelper.sqliteDB.rawQuery(sql, null);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return cursor;
	}

	public static boolean insert(Context context, String column1, String column2) {
		boolean flag = true;
		try {
			String sql = "insert into " + ConstData.SQL._SQL_TABLE1 + "("
					+ ConstData.SQL._SQL_COLUMN1 + ","
					+ ConstData.SQL._SQL_COLUMN2 + ") values('" + column1
					+ "','" + column2 + "')";
			DBHelper dbHelper = new DBHelper(context);
			dbHelper.sqliteDB.execSQL(sql);
			dbHelper.sqliteDB.close();
		} catch (SQLException e) {
			flag = false;
			e.printStackTrace();
		}
		return flag;
	}

	public static boolean update(Context context, int _id, String userName,
			String userMobile) {
		boolean flag = true;
		try {
			String sql = "update users set username='" + userName
					+ "',userMobile='" + userMobile + "' where _id=" + _id;
			DBHelper dbHelper = new DBHelper(context);
			dbHelper.sqliteDB.execSQL(sql);
			dbHelper.sqliteDB.close();
		} catch (SQLException e) {
			flag = false;
			e.printStackTrace();
		}
		return flag;
	}

	public static boolean delete(Context context, int _id) {
		boolean flag = true;
		try {
			String sql = "delete from users  where _id=" + _id;
			DBHelper dbHelper = new DBHelper(context);
			dbHelper.sqliteDB.execSQL(sql);
			dbHelper.sqliteDB.close();
		} catch (SQLException e) {
			flag = false;
			e.printStackTrace();
		}
		return flag;
	}
}

最后用DAO去操作数据的增删改查

boolean saveSuc = DAO.insert(mContext, str1, str2);
//-------------------------------
Cursor cursor = DAO.queryAll(mContext);
			StringBuilder sb1 = new StringBuilder();
			StringBuilder sb2 = new StringBuilder();
			if (cursor.moveToFirst()) {
				do {
					String str3 = cursor.getString(cursor
							.getColumnIndexOrThrow(ConstData.SQL._SQL_COLUMN1));
					String str4 = cursor.getString(cursor
							.getColumnIndexOrThrow(ConstData.SQL._SQL_COLUMN2));
					sb1.append(str3).append("--");
					sb2.append(str4).append("--");
				} while (cursor.moveToNext());
			}