Android External Storage Example

Like internal storage, we are able to save or read data from the device external memory such as sdcard. FileInputStream and FileOutputStream classes are used to read and write data into the file.

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Example of reading and writing data in the android external storage

activity_main.xml

Drag the 2 edittexts, 2 textviews and 2 buttons from the pallete, now the activity_main.xml file will like this:

File: activity_main.xml

1. <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  
2.     xmlns:tools="http://schemas.android.com/tools"  
3.     android:layout_width="match_parent"  
4.     android:layout_height="match_parent"  
5.     tools:context=".MainActivity" >  
6.   
7.     <EditText  
8.         android:id="@+id/editText1"  
9.         android:layout_width="wrap_content"  
10.         android:layout_height="wrap_content"  
11.         android:layout_alignParentRight="true"  
12.         android:layout_alignParentTop="true"  
13.         android:layout_marginRight="20dp"  
14.         android:layout_marginTop="24dp"  
15.         android:ems="10" >  
16.   
17.         <requestFocus />  
18.     </EditText>  
19.   
20.     <EditText  
21.         android:id="@+id/editText2"  
22.         android:layout_width="wrap_content"  
23.         android:layout_height="wrap_content"  
24.         android:layout_alignRight="@+id/editText1"  
25.         android:layout_below="@+id/editText1"  
26.         android:layout_marginTop="24dp"  
27.         android:ems="10" />  
28.   
29.     <TextView  
30.         android:id="@+id/textView1"  
31.         android:layout_width="wrap_content"  
32.         android:layout_height="wrap_content"  
33.         android:layout_alignBaseline="@+id/editText1"  
34.         android:layout_alignBottom="@+id/editText1"  
35.         android:layout_alignParentLeft="true"  
36.         android:text="File Name:" />  
37.   
38.     <TextView  
39.         android:id="@+id/textView2"  
40.         android:layout_width="wrap_content"  
41.         android:layout_height="wrap_content"  
42.         android:layout_alignBaseline="@+id/editText2"  
43.         android:layout_alignBottom="@+id/editText2"  
44.         android:layout_alignParentLeft="true"  
45.         android:text="Data:" />  
46.   
47.     <Button  
48.         android:id="@+id/button1"  
49.         android:layout_width="wrap_content"  
50.         android:layout_height="wrap_content"  
51.         android:layout_alignLeft="@+id/editText2"  
52.         android:layout_below="@+id/editText2"  
53.         android:layout_marginLeft="70dp"  
54.         android:layout_marginTop="16dp"  
55.         android:text="save" />  
56.   
57.     <Button  
58.         android:id="@+id/button2"  
59.         android:layout_width="wrap_content"  
60.         android:layout_height="wrap_content"  
61.         android:layout_alignBaseline="@+id/button1"  
62.         android:layout_alignBottom="@+id/button1"  
63.         android:layout_toRightOf="@+id/button1"  
64.         android:text="read" />  
65.   
66. </RelativeLayout>  

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Provide permission for the external storage

You need to provide the WRITE_EXTERNAL_STORAGE permission.

1. <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>  

File: Activity_Manifest.xml

1. <?xml version="1.0" encoding="utf-8"?>  
2. <manifest   
3.   
4. xmlns:android="http://schemas.android.com/apk/res/android"  
5.     package="com.example.externalstorage"  
6.     android:versionCode="1"  
7.     android:versionName="1.0" >  
8.   
9.     <uses-sdk  
10.         android:minSdkVersion="8"  
11.         android:targetSdkVersion="16" />  
12. <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>  
13.   
14.     <application  
15.         android:allowBackup="true"  
16.         android:icon="@drawable/ic_launcher"  
17.         android:label="@string/app_name"  
18.         android:theme="@style/AppTheme" >  
19.         <activity  
20.             android:name="com.example.externalstorage.MainActivity"  
21.             android:label="@string/app_name" >  
22.             <intent-filter>  
23.                 <action android:name="android.intent.action.MAIN" />  
24.   
25.                 <category android:name="android.intent.category.LAUNCHER" />  
26.             </intent-filter>  
27.         </activity>  
28.     </application>  
29.   
30. </manifest>  

Activity class

Let's write the code to write and read data from the android external storage.

File: MainActivity.java

1. package com.example.externalstorage;  
2.   
3. import java.io.BufferedReader;  
4. import java.io.File;  
5. import java.io.FileInputStream;  
6. import java.io.FileNotFoundException;  
7. import java.io.FileOutputStream;  
8. import java.io.IOException;  
9. import java.io.InputStreamReader;  
10. import java.io.OutputStreamWriter;  
11.   
12. import android.os.Bundle;  
13. import android.app.Activity;  
14. import android.content.Context;  
15. import android.view.Menu;  
16. import android.view.View;  
17. import android.view.View.OnClickListener;  
18. import android.widget.Button;  
19. import android.widget.EditText;  
20. import android.widget.Toast;  
21.   
22. public class MainActivity extends Activity {  
23.     EditText editTextFileName,editTextData;  
24.     Button saveButton,readButton;  
25.     @Override  
26.     protected void onCreate(Bundle savedInstanceState) {  
27.         super.onCreate(savedInstanceState);  
28.         setContentView(R.layout.activity_main);  
29.           
30.         editTextFileName=(EditText)findViewById(R.id.editText1);  
31.         editTextData=(EditText)findViewById(R.id.editText2);  
32.         saveButton=(Button)findViewById(R.id.button1);  
33.         readButton=(Button)findViewById(R.id.button2);  
34.           
35.         //Performing action on save button  
36.         saveButton.setOnClickListener(new OnClickListener(){  
37.   
38.             @Override  
39.             public void onClick(View arg0) {  
40.                 String filename=editTextFileName.getText().toString();  
41.                 String data=editTextData.getText().toString();  
42.                   
43.                 FileOutputStream fos;  
44.                    try {  
45.                        File myFile = new File("/sdcard/"+filename);  
46.                         myFile.createNewFile();  
47.                         FileOutputStream fOut = new   
48.   
49. FileOutputStream(myFile);  
50.                         OutputStreamWriter myOutWriter = new   
51.   
52. OutputStreamWriter(fOut);  
53.                         myOutWriter.append(data);  
54.                         myOutWriter.close();  
55.                         fOut.close();  
56.                      
57.             Toast.makeText(getApplicationContext(),filename + "   
58.   
59. saved",Toast.LENGTH_LONG).show();  
60.                       
61.                      
62.                    } catch (FileNotFoundException e) {e.printStackTrace();}  
63.                    catch (IOException e) {e.printStackTrace();}  
64.                   
65.             }  
66.               
67.         });  
68.   
69.         //Performing action on Read Button  
70.         readButton.setOnClickListener(new OnClickListener(){  
71.   
72.             @Override  
73.             public void onClick(View arg0) {  
74.                 String filename=editTextFileName.getText().toString();  
75.                 StringBuffer stringBuffer = new StringBuffer();    
76.                 String aDataRow = "";  
77.                 String aBuffer = "";  
78.                 try {  
79.                     File myFile = new File("/sdcard/"+filename);  
80.                     FileInputStream fIn = new FileInputStream(myFile);  
81.                     BufferedReader myReader = new BufferedReader(  
82.                             new InputStreamReader(fIn));  
83.                       
84.                     while ((aDataRow = myReader.readLine()) != null) {  
85.                         aBuffer += aDataRow + "\n";  
86.                     }  
87.                     myReader.close();  
88.                       
89.                 } catch (IOException e) {  
90.                     e.printStackTrace();  
91.                 }  
92.                 Toast.makeText(getApplicationContext  
93.   
94. (),aBuffer,Toast.LENGTH_LONG).show();  
95.                   
96.             }  
97.               
98.         });  
99.     }  
100.   
101.     @Override  
102.     public boolean onCreateOptionsMenu(Menu menu) {  
103.         // Inflate the menu; this adds items to the action bar if it is present.  
104.         getMenuInflater().inflate(R.menu.activity_main, menu);  
105.         return true;  
106.     }  
107.   
108. }