How to find out programatically that file is already exist or not?

[Pramod P Deore]

Hello everybody,

Actually I am developing one application in that when application run
first time it will create one txt file and save IMSI number in that
file. when mobile boot it will matches it's current IMSI number with
IMSI number present in the txt file.But I don't know how to check programatically that
file is exist or not.
Please help me
Thanks

[Monu Tripathi]

You need to read up on Java File IO; creating and writing to files on Android is similar to what we do in Java (save for some extra settings like permissions).

java.io.File class is an abstraction for a file or directory on a System. And you can use its interface to do lots of stuff including questioning existence of a File. For details of what interface the class provides, you need to read the documentation.

For instance, if you want to check if a file named "temp.txt" exists on my sdcard, create a File object representing this file and call exists() method.

File file = new File("/sdcard/tempt.txt");
Log.i(TAG,"temp exists : " + file.exists());

[Pramod P Deore]

Hello everybody again,

I am developing one application that will create one txt file when it runs first time and saves IMSI number in that file , After that when phone boots every time it checks that IMSI number with IMSI number which is stored at txt file. But when I run this program it gives me Null pointer Exception. I have following code.


//FinalSMS.java

  

package com.micro;

import android.app.Activity;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.telephony.TelephonyManager;
import android.telephony.gsm.SmsManager;
import android.widget.Toast;

import java.io.*;

public class FinalSMS extends Activity
{
    /** Called when the activity is first created. */
	
	File myFile;
	String imsi;
	String data;
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        createFile();  
        checkIMSI();
    }
    
    public void createFile()
    {
    	try
    	{
    		myFile = new File ("tempt.txt");
    		if (myFile.exists())
    		{
    			FileReader fr = new FileReader(myFile);
    			BufferedReader br = new BufferedReader(fr);
    			data = br.readLine();
    			
    		}
    		else
    		{
    			displayIMSI();
    			myFile.createNewFile();
    			PrintWriter pw = new PrintWriter(myFile);
    			TelephonyManager mTelephonyMgr = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE); 
    	    	String imsi = mTelephonyMgr.getSubscriberId(); 
    			pw.println(imsi);
    			pw.flush();
    			pw.close();
    		}
    	
    	}
    	
    	catch (IOException ioe)
    	{
    		ioe.printStackTrace();
    	}
    }
    
    public void checkIMSI()
    {
    	TelephonyManager mTelephonyMgr = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE); 
    	String imsi = mTelephonyMgr.getSubscriberId(); 
    	if(data.equals(imsi))
    	{
    		sendSMS("9960510915","Sim has not changed.");
    	}
    	else
    	{
    		sendSMS("9960510915","Sim has been changed.");
    	}
    }
    
    public void displayIMSI()
    {
    	TelephonyManager mTelephonyMgr = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE); 
    	imsi = mTelephonyMgr.getSubscriberId(); 
    	    	
    } 
    
    public  void sendSMS(String phoneNumber, String message)
    {        
        String SENT = "SMS_SENT";
        String DELIVERED = "SMS_DELIVERED";
 
        PendingIntent sentPI = PendingIntent.getBroadcast(this, 0,new Intent(SENT), 0);
 
        PendingIntent deliveredPI = PendingIntent.getBroadcast(this, 0,new Intent(DELIVERED), 0);
 
        //---when the SMS has been sent---
        registerReceiver(new BroadcastReceiver(){
           
            public void onReceive(Context arg0, Intent arg1)
            {
                switch (getResultCode())
                {
                    case Activity.RESULT_OK:
                        Toast.makeText(getBaseContext(), "SMS sent", 
                                Toast.LENGTH_SHORT).show();
                        break;
                    case SmsManager.RESULT_ERROR_GENERIC_FAILURE:
                        Toast.makeText(getBaseContext(), "Generic failure", 
                                Toast.LENGTH_SHORT).show();
                        break;
                    case SmsManager.RESULT_ERROR_NO_SERVICE:
                        Toast.makeText(getBaseContext(), "No service", 
                                Toast.LENGTH_SHORT).show();
                        break;
                    case SmsManager.RESULT_ERROR_NULL_PDU:
                        Toast.makeText(getBaseContext(), "Null PDU", 
                                Toast.LENGTH_SHORT).show();
                        break;
                    case SmsManager.RESULT_ERROR_RADIO_OFF:
                        Toast.makeText(getBaseContext(), "Radio off", 
                                Toast.LENGTH_SHORT).show();
                        break;
                }
            }
        }, new IntentFilter(SENT));
 
        //---when the SMS has been delivered---
        registerReceiver(new BroadcastReceiver()
        {
                public void onReceive(Context arg0, Intent arg1)
                {
                	switch (getResultCode())
                	{
                    	case Activity.RESULT_OK:
                        Toast.makeText(getBaseContext(), "SMS delivered", 
                        Toast.LENGTH_SHORT).show();
                        break;
                    	case Activity.RESULT_CANCELED:
                        Toast.makeText(getBaseContext(), "SMS not delivered",Toast.LENGTH_SHORT).show();
                        break;                        
                	}
                }
        },new IntentFilter(DELIVERED));        
 
        SmsManager sms = SmsManager.getDefault();
        sms.sendTextMessage(phoneNumber, null, message, sentPI, deliveredPI);        
    }
    	
}


 

###############################################################

//MyStartupIntentReceiver .java

  

package com.micro;

import android.content.Context; 
import android.content.Intent; 
import android.content.BroadcastReceiver; 

public class MyStartupIntentReceiver extends BroadcastReceiver { 

     @Override 
     public void onReceive(Context context, Intent intent) { 
          /* Create intent which will finally start the Main-Activity. */ 
          Intent myStarterIntent = new Intent(context, FinalSMS.class); 
          /* Set the Launch-Flag to the Intent. */ 
          //myStarterIntent.setLaunchFlags(Intent.NEW_TASK_LAUNCH);
          myStarterIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); 

          /* Send the Intent to the OS. */ 
          context.startActivity(myStarterIntent); 
     } 
}



 

################################################################################


//AndroidManifest.java

 


<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.micro"
      android:versionCode="1"
      android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".FinalSMS"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
 <receiver android:name=".MyStartupIntentReceiver">
		<intent-filter>
			<action android:name="android.intent.action.BOOT_COMPLETED" />
		</intent-filter>
	</receiver>
    </application>
    <uses-sdk android:minSdkVersion="3" />

<uses-permission android:name="android.permission.SEND_SMS">
    </uses-permission>
    
    <uses-permission android:name="android.permission.RECEIVE_SMS">
    </uses-permission>
    
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
 <uses-permission android:name="android.permission.READ_PHONE_STATE" />
</manifest> 

 

#################################################################################

But when I run it it gives me following error messages

 


01-29 14:58:28.948: ERROR/AndroidRuntime(837): Uncaught handler: thread main exiting due to uncaught exception
01-29 14:58:28.978: ERROR/AndroidRuntime(837): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.micro/com.micro.FinalSMS}: java.lang.NullPointerException
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2268)
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2284)
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at android.app.ActivityThread.access$1800(ActivityThread.java:112)
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1692)
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at android.os.Looper.loop(Looper.java:123)
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at android.app.ActivityThread.main(ActivityThread.java:3948)
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at java.lang.reflect.Method.invokeNative(Native Method)
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at java.lang.reflect.Method.invoke(Method.java:521)
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:782)
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:540)
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at dalvik.system.NativeStart.main(Native Method)
01-29 14:58:28.978: ERROR/AndroidRuntime(837): Caused by: java.lang.NullPointerException
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at com.micro.FinalSMS.checkIMSI(FinalSMS.java:68)
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at com.micro.FinalSMS.onCreate(FinalSMS.java:29)
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123)
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2231)
01-29 14:58:28.978: ERROR/AndroidRuntime(837):     ... 11 more


  

######################################################

when I had checked whether the file is created or not in data/data/com/micro/files/ The file is not present.
Because file is not created therefore it throws run time exception (NullPointerException) , Please help me

Thanks