Data access in Android-Method 2: File)

In Android, these files are stored in/Data/Package_name/FilesDirectory.

Data Reading

 
Public static string read (context, string file) {string data = ""; try {fileinputstream stream = context. openfileinput (File); stringbuffer sb = new stringbuffer (); int C; while (C = stream. read ())! =-1) {sb. append (char) C);} stream. close (); Data = sb. tostring ();} catch (filenotfoundexception e) {} catch (ioexception e) {} return data ;}
 

SlaveCodeThe only difference seems to be the file opening method: context. openfileinput (File); In Android, file read/write has permission control, so context (parent class of activity) is used to open the file, which is shared in the same package. The Package concept here is different from the package mentioned in preferences.

Data Writing

Public static void write (context, string file, string MSG) {try {fileoutputstream stream = context. openfileoutput (file, context. mode_world_writeable); stream. write (MSG. getbytes (); stream. flush (); stream. close ();} catch (filenotfoundexception e) {} catch (ioexception e ){}}
 

When opening the file here, the method of opening the file is declared.

In general, it may be difficult to directly use files. In particular, if we want to store some trivial data, we need to generate some trivial files or define the format in the same file. In fact, you can also package it into properties for use:

Public static properties load (context, string file) {properties Properties = new properties (); try {fileinputstream stream = context. openfileinput (File); properties. load (Stream);} catch (filenotfoundexception e) {} catch (ioexception e) {} return properties;} public static void store (context, string file, properties Properties) {try {fileoutputstream stream = context. openfileoutput (file, context. mode_world_writeable); properties. store (stream, "");} catch (filenotfoundexception e) {} catch (ioexception e ){}}
 

 
/Chapter09_data_02/src/COM/Amaker/test/mainactivity. Java
 

 Code 
   Package Com. Amaker. test;

  Import  Java. Io. fileinputstream;
  Import  Java. Io. fileoutputstream;

  Import  Android. App. activity;
  Import  Android. OS. Bundle;
  Import  Android. View. view;
  Import  Android. View. View. onclicklistener;
  Import Android. widget. Button;
  Import  Android. widget. edittext;

  Public     Class  Mainactivity  Extends  Activity {
  Private     Static     Final  String file_name  = "  Temp.txt  "  ;
  Private  Button B1, B2;
  Private  Edittext ET1, et2;
@ Override
  Public     Void  Oncreate (bundle savedinstancestate ){
  Super  . Oncreate (savedinstancestate );
Setcontentview (R. layout. Main );
B1  = (Button) findviewbyid (R. Id. button01 );
B2  =  (Button) findviewbyid (R. Id. button02 );

ET1  =  (Edittext) findviewbyid (R. Id. edittext01 );
Et2  =  (Edittext) findviewbyid (R. Id. edittext02 );

B1.setonclicklistener (  New  Onclicklistener (){
@ Override
  Public     Void Onclick (view v ){
Write (et1.gettext (). tostring ());
}
});

B2.setonclicklistener (  New  Onclicklistener (){
@ Override
  Public     Void  Onclick (view v ){
Et2.settext (read ());
}
});
}

  Private  String read (){
  Try  {
Fileinputstream  = Openfileinput (file_name );
  Byte  [] Buffer  =     New     Byte  [FCM. Available ()];
FS. Read (buffer );
  Return     New  String (buffer );
}  Catch  (Exception e ){
E. printstacktrace ();
}
 Return     Null  ;
}

  Private     Void  Write (string content ){
  Try  {
Fileoutputstream fos  =  Openfileoutput (file_name, mode_append );
FOS. Write (content. getbytes ());
FOS. Close ();
}  Catch (Exception e ){
E. printstacktrace ();
}
}
} 
 
 
 
 
/Chapter09_data_02/RES/layout/Main. xml
 
 Code 
    <?  XML version  =  "  1.0  "  Encoding  =  "  UTF-8 "  ?>  
  <  Linearlayout xmlns: Android  =  "  Http://schemas.android.com/apk/res/android  "  
Android: Orientation  =  "  Vertical  "  Android: layout_width  = "  Fill_parent  "  
Android: layout_height  =  "  Fill_parent  "  >  

  <  Textview Android: layout_width  =  "  Fill_parent  " 
Android: layout_height  =  "  Wrap_content  "  Android: Text  =  "  File Test  "     />  

  <  Edittext Android: Text  =  "" Android: ID  =  "  @ + ID/edittext01  "  
Android: layout_width  =  "  Fill_parent  "  Android: layout_height  =  "  Wrap_content  "  Android: Height  = "  100px  "  > </  Edittext  >  

  <  Button Android: ID  =  "  @ + ID/button01  "  Android: layout_width  =  "  Wrap_content "  
Android: layout_height  =  "  Wrap_content  "  Android: Text  =  "  Write  "  > </  Button  >  

  <  Edittext Android: Text =  ""  Android: ID  =  "  @ + ID/edittext02  "  
Android: layout_width  =  "  Fill_parent  "  Android: layout_height  =  "  Wrap_content  " Android: Height  =  "  100px  "  > </  Edittext  >  

  <  Button Android: ID  =  "  @ + ID/button02  "  Android: layout_width  = "  Wrap_content  "  
Android: layout_height  =  "  Wrap_content  "  Android: Text  =  "  Read  "  > </  Button  >  

 </  Linearlayout  >  
 
 
 
 
 
/Chapter09_data_02/androidmanifest. xml
 
 Code 
     <?  XML version = "1.0" encoding = "UTF-8"  ?>  
  <  Manifest  Xmlns: Android = "Http://schemas.android.com/apk/res/android"  
Package  = "Com. Amaker. test"  
Android: versioncode  = "1"  
Android: versionname  = "1.0"  >  
  <  Application  Android: icon  = "@ Drawable/icon"  Android: Label  = "@ String/app_name" >  
  <  Activity  Android: Name  = ". Mainactivity"  
Android: Label  = "@ String/app_name"  >  
  <  Intent-Filter  >  
  <  Action Android: Name  = "Android. Intent. Action. Main"     />  
  <  Category  Android: Name  = "Android. Intent. Category. launcher"     />  
  </  Intent-Filter  >  
 </  Activity  >  

  </  Application  >  
  <  Uses-SDK  Android: minsdkversion  = "3"     />  

  </  Manifest >