CODEWITHSUNDEEP
javaandroidstringglobal-variables
marchemike
marchemike

Reputation: 3277

Saving data to a global variable in java android

I'm trying to save data to my global variables by doing this:

public static String UnitCode;
public static String RDate;
public static String AArea;

    final EditText unitCode = (EditText) findViewById(R.id.editText1);
    final EditText reservationDate = (EditText) findViewById(R.id.editText2);
    final EditText Area = (EditText) findViewById(R.id.editText3);

            UnitCode = unitCode.getText().toString();
            RDate = reservationDate.getText().toString();
            AArea = Area.getText().toString();

this is inside my ReservationActivity.class.

However whenever I access it on my ReservationProcessActivity class:

    UnitCode = ReservationActivity.UnitCode.toString();
    RDate = ReservationActivity.RDate.toString();
    Area = ReservationActivity.AArea.toString();

My android application suddenly crashes only when I uncomment the part in the ReservationProcessActivity, if I comment it, it works fine. Is what I'm doing wrong?

This is the logcat error:

02-06 11:50:10.956: E/AndroidRuntime(16482): FATAL EXCEPTION: main
02-06 11:50:10.956: E/AndroidRuntime(16482): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.appletest/com.example.appletest.ReservationProcessActivity}: java.lang.NullPointerException
02-06 11:50:10.956: E/AndroidRuntime(16482):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2308)
02-06 11:50:10.956: E/AndroidRuntime(16482):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2362)
02-06 11:50:10.956: E/AndroidRuntime(16482):    at android.app.ActivityThread.access$700(ActivityThread.java:168)
02-06 11:50:10.956: E/AndroidRuntime(16482):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1329)
02-06 11:50:10.956: E/AndroidRuntime(16482):    at android.os.Handler.dispatchMessage(Handler.java:99)
02-06 11:50:10.956: E/AndroidRuntime(16482):    at android.os.Looper.loop(Looper.java:137)
02-06 11:50:10.956: E/AndroidRuntime(16482):    at android.app.ActivityThread.main(ActivityThread.java:5493)
02-06 11:50:10.956: E/AndroidRuntime(16482):    at java.lang.reflect.Method.invokeNative(Native Method)
02-06 11:50:10.956: E/AndroidRuntime(16482):    at java.lang.reflect.Method.invoke(Method.java:525)
02-06 11:50:10.956: E/AndroidRuntime(16482):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1209)
02-06 11:50:10.956: E/AndroidRuntime(16482):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1025)
02-06 11:50:10.956: E/AndroidRuntime(16482):    at dalvik.system.NativeStart.main(Native Method)
02-06 11:50:10.956: E/AndroidRuntime(16482): Caused by: java.lang.NullPointerException
02-06 11:50:10.956: E/AndroidRuntime(16482):    at com.example.appletest.ReservationProcessActivity.onCreate(ReservationProcessActivity.java:102)
02-06 11:50:10.956: E/AndroidRuntime(16482):    at android.app.Activity.performCreate(Activity.java:5372)
02-06 11:50:10.956: E/AndroidRuntime(16482):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
02-06 11:50:10.956: E/AndroidRuntime(16482):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2270)
02-06 11:50:10.956: E/AndroidRuntime(16482):    ... 11 more

This is my ReservationProcessActivity class:

public class ReservationProcessActivity extends Activity {

    WebView webView;

    HttpResponse response;
    HttpClient httpclient;
    List<NameValuePair> nameValuePairs;
    StringBuffer buffer;
    HttpPost httppost;  

    String UnitCode;     
    String RDate;        
    String Area;         

    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.webpayment);

        webView = (WebView)findViewById(R.id.webView1);
        webView.getSettings().setLoadWithOverviewMode(true);
        webView.getSettings().setUseWideViewPort(true);
        webView.setWebChromeClient(new WebChromeClient());
        webView.setWebViewClient(new MyBrowser());
        webView.getSettings().setBuiltInZoomControls(false);
        webView.getSettings().setJavaScriptEnabled(true);
        webView.setHorizontalScrollBarEnabled(false);

        UnitCode = ReservationActivity.UnitCode.toString();
        RDate = ReservationActivity.RDate.toString();
        Area = ReservationActivity.AArea.toString();


        webView.loadUrl("http://google.com/");

    }

}

the ReservationActivity class:

package com.example.appletest;

import android.app.ActionBar;
import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.support.v4.app.NavUtils;
import android.text.Html;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RadioButton;

public class ReservationActivity extends Activity {


    public static String UnitCode;
    public static String RDate;
    public static String AArea;

    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.reservation_activity);

        //button
        final Button nextButton = (Button) findViewById(R.id.NextButton1);

        //textbox
        final EditText unitCode = (EditText) findViewById(R.id.editText1);
        final EditText reservationDate = (EditText) findViewById(R.id.editText2);
        final EditText Area = (EditText) findViewById(R.id.editText3);

        nextButton.setOnClickListener(new View.OnClickListener(){

            public void onClick(View v) {
                // TODO Auto-generated method stub

                UnitCode = unitCode.getText().toString();
                RDate = reservationDate.getText().toString();
                AArea = Area.getText().toString();                              

                Intent i = new Intent(ReservationActivity.this, ReservationProcessActivity.class);
                startActivity(i);
                finish();
            }

        });

}

Upvotes: 1

Views: 425

Answers (4)

Vasanth
Vasanth

Reputation: 60

I would recommend you by using getter and setter in case if you are playing with global variables. If I were you, I would have a seperate class for the global variables.

For example, have a seperate class called ReservationData. 

public class ReservationData {

 public static String UnitCode;
 public static String RDate;
 public static String AArea;

 public static String getUnitCode() {
     return UnitCode;
}

public static void setUnitCode(String unitCode) {
    UnitCode = unitCode;
}

public static String getRDate() {
    return RDate;
}

public static void setRDate(String RDate) {
    ReservationData.RDate = RDate;
}

public static String getAArea() {
    return AArea;
}

public static void setAArea(String AArea) {
    ReservationData.AArea = AArea;
}

}

From the Activity, call the setter methods.

public class ReservationActivity extends Activity {

public static String UnitCode;
public static String RDate;
public static String AArea;

@Override
protected void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.reservation_activity);

    //button
    final Button nextButton = (Button) findViewById(R.id.NextButton1);

    //textbox
    final EditText unitCode = (EditText) findViewById(R.id.editText1);
    final EditText reservationDate = (EditText) findViewById(R.id.editText2);
    final EditText Area = (EditText) findViewById(R.id.editText3);

    nextButton.setOnClickListener(new View.OnClickListener(){

        public void onClick(View v) {
            // TODO Auto-generated method stub

            UnitCode = unitCode.getText().toString();
            RDate = reservationDate.getText().toString();
            AArea = Area.getText().toString();

//// Call Setter Methods

            ReservationData.setAArea(AArea);
            ReservationData.setRDate(RDate);
            ReservationData.setUnitCode(UnitCode);

//// Call Setter Methods

            Intent i = new Intent(ReservationActivity.this, ReservationProcessActivity.class);
            startActivity(i);
            finish();
        }

    });

}

In the ReservationProcessActivity class call the getter methods from ReservationData.

Instead of the following code, 

    UnitCode = ReservationActivity.UnitCode.toString();
    RDate = ReservationActivity.RDate.toString();
    Area = ReservationActivity.AArea.toString();

use these,

           Area = ReservationData.setAArea(AArea);
           RDate =  ReservationData.setRDate(RDate);
           UnitCode = ReservationData.setUnitCode(UnitCode);

Upvotes: 1

ReZa
ReZa

Reputation: 1283

change this code in ReservationProcessActivity :

UnitCode = ReservationActivity.UnitCode.toString();
    RDate = ReservationActivity.RDate.toString();
    Area = ReservationActivity.AArea.toString();

to :

UnitCode = ReservationActivity.UnitCode;
    RDate = ReservationActivity.RDate;
    Area = ReservationActivity.AArea;

Upvotes: 2

1203_dube
1203_dube

Reputation: 214

If ReservationProcessActivity has its onCreate() called before the onCreate of a ReservationActivity in the same jvm, then the static variable UnitCode in ReservationActivity will still be null. When you use this from ReservationProcessActivity like this:

UnitCode = ReservationActivity.UnitCode.toString();

That will cause your crash. I am not certain what the sequence of events in your activities is, but I think something like that is happening.

Upvotes: 1

Mozzan
Mozzan

Reputation: 283

I think the crash is because of NullPointerException. It's because you call findViewById too early. Usually, we use findViewById after Activity.setContentView has been called. see : enter link description here

Upvotes: 1

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