Question

This is goign to be very simple i expect to sort out and just me being a newbie going about in circles.

I have multiple tabs across my screen. The following code should read a text input and assign its value to Shared Preferences when another tab is selected. However, whenever i change to another tab my code fails with a NullPointerException – I believe i have tracked it down to the onPause() of the below code, and I believe it is because i am failing to pass the data within the variable correctly.

Any pointers appreciated!

package com.androidbook.epcsn;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;

import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

@SuppressWarnings("unused")
public class jobActivity extends Activity {   

public static final String SN_PREFERENCES  = "SiteNotePrefs";

SharedPreferences mPrefSettings;
String jobID;
String jobAddress ;
String jobPostcode ;

public void onCreate(Bundle savedInstanceState) {        
    super.onCreate(savedInstanceState);          
    setContentView(R.layout.joblayout); 

    final SharedPreferences mPrefSettings = getSharedPreferences (SN_PREFERENCES, Context.MODE_WORLD_WRITEABLE);

    initjobID();
    initjobaddress();
    initjobpostcode();
}

private void initjobpostcode() {
    EditText jobPostcode = (EditText)findViewById(R.id.jobPostcodeText);
}

private void initjobaddress() {
    EditText jobAddress = (EditText)findViewById(R.id.jobAddressText);
}

private void initjobID() {
    EditText jobID = (EditText)findViewById(R.id.jobIDText);
}

@Override
protected void onPause(){
    super.onPause();

    String strjobID = jobID;
    String strjobAddress = jobAddress;
    String strjobPostcode = jobPostcode;

    Editor editor = mPrefSettings.edit();
    editor.putString("jobID", strjobID);
    editor.putString("jobAddress", strjobAddress);
    editor.putString("jobPostcode", strjobPostcode);
    editor.commit();
}
}

Answer 1

You set values to local variables in the init methods, not the class properties as intended, e.g.:

EditText jobID;

// Then later... it's clobberin' time.
private void initjobID() {
    EditText jobID = (EditText)findViewById(R.id.jobIDText);
}

The property jobID is shadowed by the local jobID declared in the method.

(Java conventions would name the method initJobId, and the property jobId).

To set instance properties in the init methods, remove the local declarations and use this pattern:

EditText jobID;
private void initjobID() {
    jobID = (EditText)findViewById(R.id.jobIDText);
}