安卓基础学习_ Android数据存储与IO

数据储存方式：1.文件2.SharesPreferences(偏好参数保存)3.SQLite数据库4.内容提供者（数据共享）5.网络一、SharePreferences偏好参数SharesPreferences保存用户偏好参数（XML文件形式保存在shared_prefs下）public void save(String username,Integer password)//保存参数{SharedPreferences preferences=context.getSharedPreferences("userinfo", Context.MODE_PRIVATE);Editor editor=preferences.edit();editor.putString("username", username);editor.putInt("password", password);editor.commit();}public Map<String,String> getPreferences()//读取参数{Map<String,String> userinfo=new HashMap<String, String>();SharedPreferences preferences=context.getSharedPreferences("userinfo", Context.MODE_PRIVATE);userinfo.put("username", preferences.getString("username", ""));userinfo.put("password", String.valueOf(preferences.getInt("password", 0)));return userinfo;}读写其他应用的SharePreferences要读写其他程序的SharePreferences指定相应的访问权限，MODE_WORLD_READABLE:可被其他程序读取，MODE_WORLD_WRITEABLE:可被其他程序写入实现步骤：1.需要创建其他程序对应的Context2.调用其他程序Context的getSharePreferences(String name,int mode)即可获取相应的SharePreferences对象3.调用SharePreferences的edit()方法获取相应的Editor即可UserCount应用：//MODE_WORLD_READABLE:This constant was deprecated in API level 17.SharedPreferences preferences = getSharedPreferences("count", MODE_WORLD_READABLE);// 读取SharedPreferences里的count数据int count = preferences.getInt("count", 0);Editor editor = preferences.edit();// 存入数据editor.putInt("count", ++count);// 提交修改editor.commit();public class ReadOtherPreferences extends Activity{@Overridepublic void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.main);Context useCount = null;try{// 获取其他程序所对应的ContextuseCount = createPackageContext("org.crazyit.io",Context.CONTEXT_IGNORE_SECURITY);}catch (NameNotFoundException e){e.printStackTrace();}// 使用其他程序的Context获取对应的SharedPreferencesSharedPreferences prefs = useCount.getSharedPreferences("count",Context.MODE_WORLD_READABLE);// 读取数据int count = prefs.getInt("count", 0);TextView show = (TextView) findViewById(R.id.show);// 显示读取的数据内容show.setText("UseCount应用程序以前被使用了" + count + "次。");}}二、File存储读写SD卡上的文件步骤：1.调用Environment的getExternalStorageState()判断手机上是否插入了SD卡，并且应用程序具有读写SD卡的权限;2.调用Environment的getExternalStorageDirectory()方法来获取外部存储器，也就是SD卡的目录;3.使用FileInputStream、FileOutputStream、FileReader或FileWriter读写SD卡里的文件.保存文件到SD卡public void onClick(View v) {String name=filename.getText().toString();String content=filecontent.getText().toString();FileService service=new FileService(getApplicationContext());try {if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){service.saveToSDCard(name, content);Toast.makeText(getApplicationContext(), "Save Success", 1000).show();}elseToast.makeText(getApplicationContext(), "SD is not avi...", 1000).show();} catch (Exception e) {Toast.makeText(getApplicationContext(), "Save ERROR", 1000).show();e.getStackTrace();}}publicvoid saveToSDCard(String filename,String filecontent) throws Exception{File file=new File(Environment.getExternalStorageDirectory(),filename);FileOutputStream fos=new FileOutputStream(file);fos.write(filecontent.getBytes());fos.close();}<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>保存文件public void save(String filename,String filecontent) throws Exception{FileOutputStream fos=context.openFileOutput(filename, Context.MODE_PRIVATE);---文件操作模式---// Context.MODE_PRIVATE:私有操作模式，不能被其他应用使用(覆盖)// Context.MODE_APPEND:追加操作模式，不能被其他应用使用(追加)// Context.MODE_WORLD_READABLE:可读操作模式，可被其他应用读取// Context.MODE_WORLD_WRITEABLE:可写操作模式，可被其他应用写入// Context.MODE_WORLD_READABLE+Context.MODE_WORLD_WRITEABLE:可读写模式fos.write(filecontent.getBytes());fos.close();}读取文件内容private static void read(String filepath) throws Exception{File path=new File(filepath);FileInputStream fis=new FileInputStream(path);ByteArrayOutputStream bos=new ByteArrayOutputStream();byte[] buffer=new byte[1024];int len=0;while((len=fis.read(buffer))!=-1){bos.write(buffer,0,len);}byte[] data=bos.toByteArray();String filecontent=new String(data);Log.i(TAG, filecontent);bos.close();fis.close();}往文件中写入内容private static void write(String filepath,String filecontent) throws Exception{File path=new File(filepath);FileOutputStream fos=new FileOutputStream(path);fos.write(filecontent.getBytes());fos.close();}Activity提供了getCacheDir(),getFilesDir方法getCacheDir():访问/data/data/<package name>/cache目录getFilesDir():访问文件/data/data/<package name>/files目录-------------------SD卡文件浏览器-----------------------public class SDFileExplorer extends Activity{ListView listView;TextView textView;// 记录当前的父文件夹File currentParent;// 记录当前路径下的所有文件的文件数组File[] currentFiles;@Overridepublic void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.main);// 获取列出全部文件的ListViewlistView = (ListView) findViewById(R.id.list);textView = (TextView) findViewById(R.id.path);// 获取系统的SD卡的目录File root = new File("/mnt/sdcard/");// 如果 SD卡存在if (root.exists()){currentParent = root;currentFiles = root.listFiles();// 使用当前目录下的全部文件、文件夹来填充ListViewinflateListView(currentFiles);}// 为ListView的列表项的单击事件绑定监听器listView.setOnItemClickListener(new OnItemClickListener(){@Overridepublic void onItemClick(AdapterView<?> parent, View view,int position, long id){// 用户单击了文件，直接返回，不做任何处理if (currentFiles[position].isFile()) return;// 获取用户点击的文件夹下的所有文件File[] tmp = currentFiles[position].listFiles();if (tmp == null || tmp.length == 0){Toast.makeText(SDFileExplorer.this, "当前路径不可访问或该路径下没有文件",Toast.LENGTH_SHORT).show();}else{// 获取用户单击的列表项对应的文件夹，设为当前的父文件夹currentParent = currentFiles[position]; //②// 保存当前的父文件夹内的全部文件和文件夹currentFiles = tmp;// 再次更新ListViewinflateListView(currentFiles);}}});// 获取上一级目录的按钮Button parent = (Button) findViewById(R.id.parent);parent.setOnClickListener(new OnClickListener(){@Overridepublic void onClick(View source){try{if (!currentParent.getCanonicalPath().equals("/mnt/sdcard")){// 获取上一级目录currentParent = currentParent.getParentFile();// 列出当前目录下所有文件currentFiles = currentParent.listFiles();// 再次更新ListViewinflateListView(currentFiles);}}catch (IOException e){e.printStackTrace();}}});}private void inflateListView(File[] files) //①{// 创建一个List集合，List集合的元素是MapList<Map<String, Object>> listItems = new ArrayList<Map<String, Object>>();for (int i = 0; i < files.length; i++){Map<String, Object> listItem = new HashMap<String, Object>();// 如果当前File是文件夹，使用folder图标；否则使用file图标if (files[i].isDirectory()){listItem.put("icon", R.drawable.folder);}else{listItem.put("icon", R.drawable.file);}listItem.put("fileName", files[i].getName());// 添加List项listItems.add(listItem);}// 创建一个SimpleAdapterSimpleAdapter simpleAdapter = new SimpleAdapter(this, listItems, R.layout.line, new String[]{ "icon", "fileName" }, new int[]{R.id.icon, R.id.file_name });// 为ListView设置AdapterlistView.setAdapter(simpleAdapter);try{textView.setText("当前路径为：" + currentParent.getCanonicalPath());}catch (IOException e){e.printStackTrace();}}}三、SQLite数据库SQLite数据库操作（增删改）public class DBOpenHelper extends SQLiteOpenHelper {public DBOpenHelper(Context context) {super(context, "userinfo.db", null, 1);}public void onCreate(SQLiteDatabase db) {//在数据库每一次被创建的时候调用的String sql="CREATE TABLE userinfo(_id integer primary key autoincrement,name varchar(10),phone varchar(11) NULL,amount integer NULL)";db.execSQL(sql);}public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {//数据库版本变更时调用String sql="ALTER TABLE userinfo ADD age ingeter";db.execSQL(sql);}}public class UserService {private DBOpenHelper dbhelper;public UserService(Context context) {this.dbhelper = new DBOpenHelper(context);}public void add(User user)//增加{SQLiteDatabase db=dbhelper.getWritableDatabase();String sql="INSERT INTO userinfo(name,phone,amount) values(?,?,?)";db.execSQL(sql, new Object[]{user.getName(),user.getPhone(),user.getAmount()});}public void add(User user){SQLiteDatabase db=dbhelper.getWritableDatabase();ContentValues values=new ContentValues();values.put("name", user.getName());values.put("phone", user.getPhone());values.put("amount", user.getAmount());db.insert("userinfo", null, values);//API方法}public void delete(Integer _id)//删除{SQLiteDatabase db=dbhelper.getWritableDatabase();String sql="DELETE FROM userinfo where _id=?";db.execSQL(sql, new Object[]{_id});}public void delete(Integer userid){SQLiteDatabase db=dbhelper.getWritableDatabase();db.delete("userinfo", "_id=?", new String[]{userid.toString()});//API方法}public void update(User user)//修改{SQLiteDatabase db=dbhelper.getWritableDatabase();String sql="UPDATE userinfo SET name=?,phone=?,amount=? where _id=?";db.execSQL(sql, new Object[]{user.getName(),user.getPhone(),user.getAmount(),user.get_id()});}public void update(User user){SQLiteDatabase db=dbhelper.getWritableDatabase();ContentValues values=new ContentValues();values.put("name", user.getName());values.put("phone", user.getPhone());values.put("amount", user.getAmount());db.update("userinfo", values, "_id=?", new String[]{user.get_id().toString()});//API方法}public User find(Integer _id)//查找{SQLiteDatabase db=dbhelper.getReadableDatabase();String sql="Select * from userinfo where _id=?";Cursor cursor=db.rawQuery(sql, new String[]{_id.toString()});if(cursor.moveToFirst()){int id=cursor.getInt(cursor.getColumnIndex("_id"));String name=cursor.getString(cursor.getColumnIndex("name"));String phone=cursor.getString(cursor.getColumnIndex("phone"));int amount=cursor.getInt(cursor.getColumnIndex("amount"));return new User(id,name,phone,amount);}cursor.close();return null;}public User find(Integer userid){SQLiteDatabase db=dbhelper.getReadableDatabase();Cursor cursor=db.query("userinfo", null, "_id=?", new String[]{userid.toString()}, null, null, null);//API方法if(cursor.moveToFirst()){int id=cursor.getInt(cursor.getColumnIndex("_id"));String name=cursor.getString(cursor.getColumnIndex("name"));String phone=cursor.getString(cursor.getColumnIndex("phone"));int amount=cursor.getInt(cursor.getColumnIndex("amount"));return new User(id,name,phone,amount);}cursor.close();return null;}public List<User> getScrollData(int offset,int maxResult)//分页获取记录，返回List{SQLiteDatabase db=dbhelper.getReadableDatabase();List<User> users=new ArrayList<User>();String sql="SELECT * FROM userinfo order by _id asc limit ?,?";Cursor cursor=db.rawQuery(sql, new String[]{String.valueOf(offset),String.valueOf(maxResult)});while(cursor.moveToNext()){int id=cursor.getInt(cursor.getColumnIndex("_id"));String name=cursor.getString(cursor.getColumnIndex("name"));String phone=cursor.getString(cursor.getColumnIndex("phone"));int amount=cursor.getInt(cursor.getColumnIndex("amount"));users.add(new User(id,name,phone,amount));}cursor.close();return users;}public List<User> getScrollData(int offset,int maxResult){SQLiteDatabase db=dbhelper.getReadableDatabase();Cursor cursor=db.query("userinfo", null, null, null, null, null, "_id asc", offset+","+maxResult);//API方法List<User> users=new ArrayList<User>();while(cursor.moveToNext()){int id=cursor.getInt(cursor.getColumnIndex("_id"));String name=cursor.getString(cursor.getColumnIndex("name"));String phone=cursor.getString(cursor.getColumnIndex("phone"));int amount=cursor.getInt(cursor.getColumnIndex("amount"));users.add(new User(id,name,phone,amount));}cursor.close();return users;}public Cursor getCursorScrollData(int offset,int maxResult)//分页获取记录，返回Cursor{SQLiteDatabase db=dbhelper.getReadableDatabase();String sql="SELECT * FROM userinfo order by _id asc limit ?,?";Cursor cursor=db.rawQuery(sql, new String[]{String.valueOf(offset),String.valueOf(maxResult)});return cursor;}public long getCount() //获取记录总数{SQLiteDatabase db=dbhelper.getReadableDatabase();String sql="SELECT count(*) FROM userinfo";Cursor cursor=db.rawQuery(sql, null);cursor.moveToFirst();long result=cursor.getLong(0);cursor.close();return result;}public long getCount(){SQLiteDatabase db=dbhelper.getReadableDatabase();Cursor cursor=db.query("userinfo", new String[]{"count(*)"}, null, null, null, null, null);cursor.moveToFirst();long count=cursor.getLong(0);return count;}public void payment()//数据库事务{SQLiteDatabase db=dbhelper.getWritableDatabase();db.beginTransaction();try{db.execSQL("UPDATE userinfo set amount=amount-10 where _id=88");db.execSQL("UPDATE userinfo set amount=amount+10 where _id=89");db.setTransactionSuccessful();}finally{db.endTransaction();}}}