基础学习总结（三）--文本、SD卡数据读写

简单的文本数据写入文件不需要权限，读写SD卡在4.0版本前需要写权限、在4.0后需要读写权限

布局：

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:orientation="vertical"
     tools:context=".MainActivity" >

     <EditText android:id="@+id/et_number"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:phoneNumber="true"
         android:hint="请输入手机号" />

     <EditText
         android:id="@+id/et_pwd"
         android:layout_width="fill_parent"
         android:layout_height="match_parent"
         android:hint="请输入密码"
         android:inputType="textPassword" />

     <CheckBox android:id="@+id/cb_remerber_pwd"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:checked="true"
         android:text="记住密码" />

     <Button android:id="@+id/btn_Login"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="登陆"
          />

 </LinearLayout>

Manifest.xml添加权限

 <!-- 写入外部设备(sdka)的权限 -->
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
     <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

MainActivity：

 public class MainActivity extends Activity implements OnClickListener {
     private static final String TAG = "MainActivity";
     private EditText etNumber;
     private EditText etPwd;
     private CheckBox cbRemerber;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         //获取控件中数据
         etNumber = (EditText)findViewById(R.id.et_number);
         etPwd=(EditText)findViewById(R.id.et_pwd);
         cbRemerber=(CheckBox)findViewById(R.id.cb_remerber_pwd);
         Button btnLogin = (Button)findViewById(R.id.btn_Login);
         //添加点击事件
         btnLogin.setOnClickListener(this);
         //获取SD卡数据
         Map<String,String> userInfo=UtilsOfSDCard.getUserInfo(this);
         if(userInfo!=null){
             etNumber.setText(userInfo.get("number"));
             etPwd.setText(userInfo.get("pwd"));
         }
     }

     @Override
     public void onClick(View v) {
         // TODO Auto-generated method stub
         //1.取出账号，密码
         String Number=etNumber.getText().toString();
         String Pwd=etPwd.getText().toString();
         //判断是否有值，弹出吐司
         if(TextUtils.isEmpty(Number) || TextUtils.isEmpty(Pwd)){
             Toast.makeText(this, "请正确数据账号、密码", Toast.LENGTH_SHORT).show();
             return;
         }
         //2.判断cb是否被选中
         if(cbRemerber.isChecked()){
             Log.i(TAG, "记住密码"+Number+","+Pwd);
             boolean isSuccess=UtilsOfSDCard.saveUserInfo(this,Number, Pwd);
             if(isSuccess)
                 Toast.makeText(this, "保存成功", Toast.LENGTH_SHORT).show();
             else
                 Toast.makeText(this, "保存失败", Toast.LENGTH_SHORT).show();
         }

         //3.登陆成功
         Toast.makeText(this, "登陆成功", Toast.LENGTH_SHORT).show();
     }

 }

UtilsOfSDCard类：

 public class UtilsOfSDCard {
     //保存信息到sd卡
     public static boolean saveUserInfo(Context context, String number,String pwd){
         try {
             //获取SD卡状态
             String state=Environment.getExternalStorageState();
             //判断SD卡状态
             if(!Environment.MEDIA_MOUNTED.equals(state))
             {
                 return false;
             }
             //动态获取SD卡路径
             File sdCardFile = Environment.getExternalStorageDirectory();
             File f=new File(sdCardFile,"qqLogin1.txt");
             //写入流
             FileOutputStream fos=new FileOutputStream(f);

             String data=number+"##"+pwd;
             fos.write(data.getBytes());
             fos.flush();
             fos.close();
             return true;
         } catch (Exception e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }

         return false;
     }

     //返回信息
     public static Map<String,String> getUserInfo(Context context){
         try {
             String state=Environment.getExternalStorageState();
             if(!Environment.MEDIA_MOUNTED.equals(state))
             {
                 return null;
             }
             File sdCartFile=Environment.getExternalStorageDirectory();
             File f=new File(sdCartFile,"qqLogin1.txt");
             BufferedReader br=new BufferedReader(new InputStreamReader(new FileInputStream(f)));
             String text=br.readLine();
             br.close();
             if(!TextUtils.isEmpty(text)){
                 Map<String,String> userInfoMap=new HashMap<String,String>();
                 String[] split = text.split("##");
                 userInfoMap.put("number", split[0]);
                 userInfoMap.put("pwd", split[1]);
                 Log.w("UtilsOfSDCard", split[0]+","+split[1]);
                 return userInfoMap;
             }

         } catch (Exception e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }

         return null;
     }
 }

Utils类：

 public class Utils {
     /*
      * 保存用户信息
      * */
     public static boolean saveUserInfo(String number,String pwd){

         try {
             String path="/data/data/com.cui.qqlogin/QQLogin.txt";
             //写入流
             FileOutputStream fs=new FileOutputStream(path);
             String data=number+"##"+pwd;
             fs.write(data.getBytes());
             fs.flush();
             fs.close();
             return true;
         } catch (Exception e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }

         return false;
     }

 public static boolean saveUserInfo(Context context, String number,String pwd){

         try {
             //动态获取文件路径
             File filesDir = context.getFilesDir();
             File f=new File(filesDir,"QQLogin.txt");
             //写入流
             FileOutputStream fs=new FileOutputStream(f);
             String data=number+"##"+pwd;
             fs.write(data.getBytes());
             fs.flush();
             fs.close();
             return true;
         } catch (Exception e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }

         return false;
     }

     public static Map<String,String> getUserInfo(){
         try {
             String path="/data/data/com.cui.qqlogin/QQLogin.txt";
             //输出流
             FileInputStream fis=new FileInputStream(path);
             //字符流
             BufferedReader reader=new BufferedReader(new InputStreamReader(fis));
             String text = reader.readLine();
             if(!TextUtils.isEmpty(text)){
                 String[] split=text.split("##");
                 Map<String,String> userofMap=new HashMap<String,String>();
                 userofMap.put("number", split[0]);
                 userofMap.put("pwd", split[1]);
                 return userofMap;
             }

         } catch (Exception e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }

         return null;
     }

     public static Map<String,String> getUserInfo(Context context){
         try {
             //String path="/data/data/com.cui.qqlogin/QQLogin.txt";
             //动态获取文件路径
             File filesDir = context.getFilesDir();
             File f=new File(filesDir,"QQLogin.txt");
             //输出流
             FileInputStream fis=new FileInputStream(f);
             //字符流
             BufferedReader reader=new BufferedReader(new InputStreamReader(fis));
             String text = reader.readLine();
             reader.close();
             if(!TextUtils.isEmpty(text)){
                 String[] split=text.split("##");
                 Map<String,String> userofMap=new HashMap<String,String>();
                 userofMap.put("number", split[0]);
                 userofMap.put("pwd", split[1]);
                 return userofMap;
             }

         } catch (Exception e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }

         return null;
     }
 }

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====================

文件存储地址:

this.getFilesDir(); // /data/data/包名/files
this.getCacheDir(); // /data/data/包名/cache
openFileOutput("aa.txt", 0); /data/data/包名/files/aa.txt
context.getSharedPreferences("cuidemo", context.MODE_PRIVATE); /data/data/包名/shared_prefs/cuidemo.xml

 public class UtilsOfSharedPreferences {
     //保存信息到sd卡
     public static boolean saveUserInfo(Context context, String number,String pwd){
         try {
     sp=context.getSharedPreferences("cuidemo", context.MODE_PRIVATE);
             //获得一个编辑对象
             Editor edit = sp.edit();
             edit.putString("number", number);
             edit.putString("pwd", pwd);
             edit.commit();
             return true;
         } catch (Exception e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
         return false;
     }

     //返回信息
     public static Map<String,String> getUserInfo(Context context){
         SharedPreferences sp=context.getSharedPreferences("cuidemo", context.MODE_PRIVATE);
         String number=sp.getString("number", null);
         String pwd=sp.getString("pwd", null);

         if(!TextUtils.isEmpty(number)&& !TextUtils.isEmpty(pwd)){
             Map<String,String> userInfoMap=new HashMap<String,String>();
             userInfoMap.put("number", number);
             userInfoMap.put("pwd", pwd);
             return userInfoMap;
         }

         return null;
     }
 }

权限相关:
1. 私有文件
Context.MODE_PRIVATE
2. 可读文件
Context.MODE_WORLD_READABLE
3. 可写文件
Context.MODE_WORLD_WRITEABLE
4. 可读可写文件.
Context.MODE_WORLD_WRITEABLE+Context.MODE_WORLD_READABLE

权限二进制图解：