How to read and write files to SDCARD and application SandBox in Android – A complete example?

By | September 6, 2012

Here is a complete example of How to read and write files to SDCARD and application SandBox in Android.

Files Example

First create a new project and inside the mainActivity paste this code.


package com.coderzheaven.filesexample;

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;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {

	EditText edittext;
	Button b1, b2, b3, b4;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        edittext = (EditText)findViewById(R.id.ed);
        edittext.setLines(10);
        b1 = (Button)findViewById(R.id.button1);
        b2 = (Button)findViewById(R.id.button2);
        b3 = (Button)findViewById(R.id.button3);
        b4 = (Button)findViewById(R.id.button4);
        
        b1.setOnClickListener(this);
        b2.setOnClickListener(this);
        b3.setOnClickListener(this);
        b4.setOnClickListener(this);        
        
    }
	@Override
	public void onClick(View v) {
		int id = v.getId();
		MyFile file = new MyFile(v.getContext());
		
		switch(id){
			case R.id.button1:
				if(!edittext.getText().toString().trim().equals("")){
					file.writeToSD(edittext.getText().toString());
				}else{
					Toast.makeText(v.getContext(), "Please enter some contents for the file", Toast.LENGTH_LONG).show();
				}
				break;
				
			case R.id.button2:
				edittext.setText(file.readFromSD());
				break;
			
			case R.id.button3:
				if(!edittext.getText().toString().trim().equals("")){
					file.writeToSandBox(edittext.getText().toString());
				}else{
					Toast.makeText(v.getContext(), "Please enter some contents for the file", Toast.LENGTH_LONG).show();
				}
				break;
				
			case R.id.button4:
				edittext.setText(file.readFromSandBox());
				break;
		}
		
		
		
	}

}

Now create another class named MyFile.java and copy this code into it.

package com.coderzheaven.filesexample;

import java.io. BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

import android.annotation.SuppressLint;
import android.content.Context;
import android.os.Environment;
import android.util.Log;

public class MyFile {

	String TAG = "MyFile";
	Context context;
	public MyFile(Context context){
		this.context = context;
	}
	
	public Boolean writeToSD(String text){
		Boolean write_successful = false;
		 File root=null;  
	        try {  
	            // check for SDcard   
	            root = Environment.getExternalStorageDirectory();  
	            Log.i(TAG,"path.." +root.getAbsolutePath());  
	  
	            //check sdcard permission  
	            if (root.canWrite()){  
	                File fileDir = new File(root.getAbsolutePath());  
	                fileDir.mkdirs();  
	  
	                File file= new File(fileDir, "samplefile.txt");  
	                FileWriter filewriter = new FileWriter(file);  
	                BufferedWriter out = new BufferedWriter(filewriter);  
	                out.write(text);  
	                out.close();  
	                write_successful = true;
	            }  
	        } catch (IOException e) {  
	            Log.e("ERROR:---", "Could not write file to SDCard" + e.getMessage());  
	            write_successful = false;
	        }  
		return write_successful;
	}
	
	public String readFromSD(){
		File sdcard = Environment.getExternalStorageDirectory();
		File file = new File(sdcard,"samplefile.txt");
		StringBuilder text = new StringBuilder();
		try {
		    BufferedReader br = new BufferedReader(new FileReader(file));
		    String line;
		    while ((line = br.readLine()) != null) {
		        text.append(line);
		        text.append('\n');
		    }
		}
		catch (IOException e) {
		}
		return text.toString();
	}

	@SuppressLint("WorldReadableFiles")
	@SuppressWarnings("static-access")
	public Boolean writeToSandBox(String text){
		Boolean write_successful = false;
		try{
			FileOutputStream fOut = context.openFileOutput("samplefile.txt",
					context.MODE_WORLD_READABLE);
			OutputStreamWriter osw = new OutputStreamWriter(fOut); 
			osw.write(text);
			osw.flush();
			osw.close();
		}catch(Exception e){
			write_successful = false;
		}
		return write_successful;
	}
	public String readFromSandBox(){
		String str ="";
		String new_str = "";
		try{
			FileInputStream fIn = context.openFileInput("samplefile.txt");
            InputStreamReader isr = new InputStreamReader(fIn);
            BufferedReader br=new BufferedReader(isr);
           
			while((str=br.readLine())!=null)
            {
				new_str +=str;
				System.out.println(new_str);
            }            
		}catch(Exception e)
		{			
		}
		return new_str;
	}
}

Now the layout for the xml file.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/LinearLayout1"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <EditText
        android:id="@+id/ed"
        android:layout_width="fill_parent" 
        android:layout_height="fill_parent"
        android:lines="5" android:gravity="top|left" 
        android:inputType="textMultiLine"
	android:scrollHorizontally="false" 
	android:minWidth="10.0dip"
	android:maxWidth="5.0dip"
        android:layout_weight="1"/>

    <Button
        android:id="@+id/button1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Write File to SDCARD" />
    
    <Button
        android:id="@+id/button2"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Read File from SDCARD" />
    
    <Button
        android:id="@+id/button3"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Write File to Application SandBox" />
    
    <Button
        android:id="@+id/button4"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Read File from Application SandBox" />

</LinearLayout>

Note you should give this permission in the AndroidManifest file.

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

OK Done. Now run the project.

To view the files

1. To see the SDCARD
Open File explorer -> expand sdcard (or mnt/sdcard).
2. To see the Application SANDBOX
Open File explorer -> expand data/data/your_package_name/files.

Download
.

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