(Android review) File read/write (File Operations), androidreview

(Android review) File read/write (File Operations), androidreview

Files operated in Android can be divided into File, XML, and SharedPreference.

This blog mainly introduces File operations:

1. MainActivity

Package com. example. filetest; import android. OS. bundle; import android. OS. environment; import android. app. activity; import android. view. menu; import android. view. view; import android. widget. button; import android. widget. editText; import android. widget. toast; public class MainActivity extends Activity {private EditText et_name; private EditText et_content; private Button sdBtn; @ Overrideprotected void onCreate (Bundle savedInstanceState) {super. onCreate (savedInstanceState); setContentView (R. layout. main); et_name = (EditText) findViewById (R. id. nameET); et_content = (EditText) findViewById (R. id. contentET); sdBtn = (Button) findViewById (R. id. sdcBT) ;}@ Overrideprotected void onResume () {// This method is executed when the interface is switched to the foreground... super. onResume (); // set whether the button is available based on the SD card status. if (! Environment. getExternalStorageState (). equals (Environment. MEDIA_MOUNTED) {sdBtn. setEnabled (false);} else {sdBtn. setEnabled (true) ;}} public void onClick (View view) {String name = et_name.getText (). toString (); String content = et_content.getText (). toString (); FileService service = new FileService (this); try {switch (view. getId () {case R. id. romBT: System. out. println ("---------> Save to rom"); service. saveToRom (name, content); break; case R. id. sdcBT: System. out. println ("---------> Save to SD card"); service. saveToSD (name, content); break;} Toast. makeText (getApplicationContext (), "saved successfully", 1 ). show ();} catch (Exception e) {e. printStackTrace (); Toast. makeText (getApplicationContext (), "failed to save", 1 ). show () ;}@ Overridepublic boolean onCreateOptionsMenu (Menu menu) {// Inflate the menu; this adds items to the action bar if it is present. getMenuInflater (). inflate (R. menu. main, menu); return true ;}}

2. FileService

Package com. example. filetest; import java. io. fileOutputStream; import android. content. context; import android. OS. environment; public class FileService {private Context context; public FileService (Context context) {this. context = context;} public void saveToSD (String name, String content) throws Exception {/*** create an output stream and specify the location of the SD card * Environment. getExternalStorageDirectory (): Location of the SD card,/mnt/sdcard **/FileOutputStream fos = new FileOutputStream (Environment. getExternalStorageDirectory () + "/" + name); fos. write (content. getBytes (); fos. close ();} public void saveToRom (String name, String content) throws Exception {/*** if enabled successfully, you will create a file directory under/data/package name/and put the file in ** Context. MODE_PRIVATE: only the user can access the created file * Context. MODE_WORLD_READABLE: the world can read, that is, everyone can read * Context. MODE_WORLD_WRITEABLE: can be written all over the world, that is, anyone can write. * Context. MODE_WORLD_READABLE + Context. MODE_WORLD_WRITEABLE: reads and writes can be performed all over the world... * Context. MODE_APPEND: Private & append only. MODE_PRIVATE. At this time, other programs cannot read or write data, but they can only read and write data themselves... */FileOutputStream fos = context. openFileOutput (name, Context. MODE_WORLD_READABLE); // open the file fos for/data/Application Registration. write (content. getBytes (); // write content to ROM without permission fos. close ();}}

3. FileTest (used for testing)

Package com. example. filetest; import java. io. byteArrayOutputStream; import java. io. fileInputStream; import java. io. fileOutputStream; import android. content. context; import android. test. androidTestCase; public class FileTest extends AndroidTestCase {/*** read by yourself (normal result: Successful ). used to test Context. whether MODE_PRIVATE works correctly * @ throws Exception */public void testRead () throws Exception {FileInputStream FCM = getContext (). openFile Input ("wr.txt"); // FileInputStream in = new FileInputStream ("/data/com. exmaple. filetest/files/hjd.txt "); // This method is equivalent to the preceding method: ByteArrayOutputStream baos = new ByteArrayOutputStream (); byte [] buffer = new byte [1024]; int len; while (len = Fi. read (buffer ))! =-1) {baos. write (buffer, 0, len);} FD. close (); baos. close (); String content = new String (baos. toByteArray (); System. out. println ("----> content:" + content);} public void testWrite () throws Exception {FileOutputStream fos = new FileOutputStream ("/data/com. example. filetest/files/hjd.txt "); String content =" hahahahahah "; fos. write (content. getBytes (); fos. close ();}}

II,

Several Modes of Context can be viewed from/data/Application name/files/file in DDMS.

Source code download: http://download.csdn.net/detail/caihongshijie6/7613405

Android file: // Where is the path in the project file?

Click "Window"-"Show View"-"Other" in the Eclipse menu, expand the android folder in the dialog box, and select the File Explorer View below, expand the/data/<package name>/files directory in the File Explorer view to view the File.

Where is the file read/write stored in android real machine debugging? The Virtual Machine path is/data/<package name>/file/filename.

If the real machine does not have root, the folder DDMS cannot be viewed.
Of course, the application can write in it

It is better to apply for sdcard permissions to/mnt/sdcard/filename (more than 2.2)/sdcard/filename (less than 2.1) for debugging)