Android File Writing to External Storage

CHANGE from Internal Storage=

• grab "directory handle" to SD card =Environment.getExtranalStorageDirectory();
• when opening file ---> specify the directory of where the file is on the SD card!!  

Step 0: Create unique directory on SD Card to store your file in using Environment.getExternalSgtorageDirectory() ----see below

 

//Inside your Activity class

File sdCard = Environment.getExternalStorageDirectory();

FIle directory = new File(sdCard.getAbsolutePath() + "/MyFiles" ); //here MyFiles is sub-directory unique to you
directory.mkdirs(); //create the directory.

 

 

Step 1: Use java.io.FileOutputStream class to open file, use Activities openFileOutput(file ) method from Activity class, where file = new File(directory, "filename") where directory created in step 1

 

//Inside your Activity class
//**CODE STEP 0

File file = new File(directory, "textfile.txt"); //creates file in specified directory which is on SD card


FileOutputStream fOut = new FileOutputStream(file);

Step 2: OPTIONAL convert your FileOutputStream instance of step 1 to a easier to use java.io class //NOTE Same as Internal Storage

OutputStreamWriter osw = new OutputSteramWriter (fOut);

 

Step 3: Write , Flush and Close when done //NOTE Same as Internal Storage

osw.write("string");

osw.flush();

osw.close();

 

 

 

Android File Reading from External Storage

Step 0: Build the directory name of where file is located on SD Card using Environment.getExternalSgtorageDirectory() ----see below

 

//Inside your Activity class

File sdCard = Environment.getExternalStorageDirectory();

File directory = new File(sdCard.getAbsolutePath() + "/MyFiles" ); //here MyFiles is sub-directory unique to you

 

Step 1: Use java.io.FileInputStream class to open file using openFileInput(*) method from Activity class

//inside Activity class
//****code from Step 0 ****

File file = new File(directory, "textfile.txt");
FileInputStream fIn = openFileInput(file);

 

Other Modes:           MODE_APPEND, MODE_WORLD_WRITEABLE

Step 2: OPTIONAL convert your FileOutputStream instance of step 1 to a easier to use java.io class //NOTE Same as Internal Storage

InputStreamReader isw = new InputStreamReader (fIn);

 

Step 3: Read and Close when done //NOTE Same as Internal Storage

int charRead = isw.read();

iws.close();

 

 

 

EXAMPLE: writing and reading to file in External Storage

main.xml App's Activity layout   

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 android:orientation="vertical" >
  <TextView
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:text="Please enter some text" />
  <EditText
     android:id="@+id/txtText1" 
     android:layout_width="fill_parent"
     android:layout_height="wrap_content" />
  <Button 
     android:id="@+id/btnSave"
     android:text="Save"
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:onClick="onClickSave" />
  <Button 
     android:id="@+id/btnLoad"
     android:text="Load"
     android:layout_width="fill_parent"
     android:layout_height="wrap_content" 
     android:onClick="onClickLoad" />
</LinearLayout>

 

App's Activity    

public class FilesActivity extends Activity {
 EditText textBox;
 static final int READ_BLOCK_SIZE = 100;
 /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.main);

      textBox = (EditText) findViewById(R.id.txtText1);
   
   
   }

  public void onClickSave(View view) {
      String str = textBox.getText().toString();
      try {
         //---SD Card Storage---   STEP 1: Open up OutputStream to File in /MyFiles/textfile.txt
         File sdCard = Environment.getExternalStorageDirectory();
         File directory = new File (sdCard.getAbsolutePath() + "/MyFiles");
         directory.mkdirs();
         File file = new File(directory, "textfile.txt");
         FileOutputStream fOut = new FileOutputStream(file);


        
   
          //STEP 2: Create OutputStreamWriter from FileOutputStream
         OutputStreamWriter osw = new OutputStreamWriter(fOut);

          //---write the string to the file---  STEP 3 write, flush, close
         osw.write(str);
         osw.flush(); 
         osw.close();

          //---display file saved message---
         Toast.makeText(getBaseContext(), "File saved successfully!",Toast.LENGTH_SHORT).show();

         //---clears the EditText---
         textBox.setText("");
      }
      catch (IOException ioe)
      {
         ioe.printStackTrace();
      }
   }


 public void onClickLoad(View view) {
   try {
      //---SD Storage---   //STEP 1 Opening to Read from /MyFiles/textfile.txt
      File sdCard = Environment.getExternalStorageDirectory();
      File directory = new File (sdCard.getAbsolutePath() + "/MyFiles");
      File file = new File(directory, "textfile.txt");
      FileInputStream fIn = new FileInputStream(file);
      InputStreamReader isr = new InputStreamReader(fIn);

       
   
      char[] inputBuffer = new char[READ_BLOCK_SIZE];
      String s = "";
      int charRead;
      while ((charRead = isr.read(inputBuffer))>0)     //STEP 3: read from file until eof, -1 returned
         {
            //---convert the chars to a String---
            String readString =  String.copyValueOf(inputBuffer, 0,charRead);
            s += readString;
            inputBuffer = new char[READ_BLOCK_SIZE];
         }
   
      //---set the EditText to the text that has been 
      // read---
      textBox.setText(s);
      Toast.makeText(getBaseContext(), "File loaded successfully!", Toast.LENGTH_SHORT).show();
   }
   catch (IOException ioe) {
      ioe.printStackTrace();
   }
 }

}