We Keep Coding

getStringArrayExtra() returns null

I am trying to create an android app on android studio which scans WIFI signals, and passes all the WIFI signal SSIDs containing "WDT_" to another intent.
When I run the app, it crashes due to a NPE.
I debugged the app, and it says that intent.getStringArrayExtra() in MultipleWifi.java is null.
Am I doing something wrong with passing the string array?
MainActivity.java:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
WifiManager wifiManager = (WifiManager) this.getSystemService(Context.WIFI_SERVICE);
WifiConfiguration conf = new WifiConfiguration();
int WDTWifiCount = 0;
List<ScanResult> results = wifiManager.getScanResults();
for (ScanResult scanResult : results) {
if (scanResult.SSID.contains("WDT_")) {
SSIDString[0] = (scanResult.SSID);
WDTWifiCount++;
}
}
WDTWifiCount = 2;
SSIDString[0] = "WDT_12345";
SSIDString[1] = "WDT_14445";
if (WDTWifiCount < 1) {
startActivity(new Intent(this, NoWifi.class));
} else if (WDTWifiCount > 1) {
Intent intent = new Intent(this, MultipleWifi.class);
intent.putExtra("SSIDList", SSIDString);
startActivityForResult(intent, 1);
}
conf.SSID = "\"" + networkSSID + "\"";
conf.preSharedKey = "\"" + networkPass + "\"";
WDTWifiCount = 0;
wifiManager.addNetwork(conf);
List<WifiConfiguration> list = wifiManager.getConfiguredNetworks();
for (WifiConfiguration i : list) {
if (i.SSID != null && i.SSID.equals("\"" + networkSSID + "\"") && WDTWifiCount != 0) {
wifiManager.disconnect();
wifiManager.enableNetwork(i.networkId, true);
wifiManager.reconnect();
break;
}
}
myWebView = new WebView(this);
myWebView.setWebViewClient(new WebViewClient() {
#Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
view.loadUrl(url);
return true;
}
});
WebSettings webSettings = myWebView.getSettings();
webSettings.setJavaScriptEnabled(true);
webSettings.setLoadWithOverviewMode(true);
webSettings.setUseWideViewPort(true);
webSettings.setSupportZoom(true);
webSettings.setBuiltInZoomControls(true);
myWebView.setWebChromeClient(new WebChromeClient());
myWebView.loadUrl("http://192.168.1.1/index.html");
}
MultipleWifi.java:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.multiplewifi);
Intent intent = getIntent();
final String[] StringSSID = intent.getStringArrayExtra("SSIDstring");
List<String> SSIDList = new ArrayList<String>(Arrays.asList(StringSSID));
final Spinner spinner = (Spinner) findViewById(R.id.spinner);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, SSIDList);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);
Button button = (Button) findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
String SSID = spinner.getSelectedItem().toString();
Intent intent = new Intent();
intent.putExtra("SSID", SSID);
setResult(RESULT_OK, intent);
finish();
}
});
}
Debug:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.wdt, PID: 9031
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.wdt/com.example.wdt.MultipleWifi}: java.lang.NullPointerException: storage == null
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2200)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2250)
at android.app.ActivityThread.access$800(ActivityThread.java:139)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1200)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5105)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException: storage == null
at java.util.Arrays$ArrayList.<init>(Arrays.java:38)
at java.util.Arrays.asList(Arrays.java:155)
at com.example.wdt.MultipleWifi.onCreate(MultipleWifi.java:23)
at android.app.Activity.performCreate(Activity.java:5275)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2164)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2250) 
at android.app.ActivityThread.access$800(ActivityThread.java:139) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1200) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:136) 
at android.app.ActivityThread.main(ActivityThread.java:5105) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:515) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608) 
at dalvik.system.NativeStart.main(Native Method) 
EDIT: After editing the key in "intent.putExtra" to SSIDString it still returns null.
Debug:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.wdt, PID: 31443
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.wdt/com.example.wdt.MultipleWifi}: java.lang.NullPointerException: storage == null
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2200)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2250)
at android.app.ActivityThread.access$800(ActivityThread.java:139)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1200)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5105)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException: storage == null
at java.util.Arrays$ArrayList.<init>(Arrays.java:38)
at java.util.Arrays.asList(Arrays.java:155)
at com.example.wdt.MultipleWifi.onCreate(MultipleWifi.java:23)
at android.app.Activity.performCreate(Activity.java:5275)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2164)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2250) 
at android.app.ActivityThread.access$800(ActivityThread.java:139) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1200) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:136) 
at android.app.ActivityThread.main(ActivityThread.java:5105) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:515) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608) 
at dalvik.system.NativeStart.main(Native Method) 

You are using wrong key
Intent intent = new Intent(this, MultipleWifi.class);
intent.putExtra("SSIDList", SSIDString);
there is key that you are passing
startActivityForResult(intent, 1);
//change key you are using wrong key here
final String[] StringSSID = intent.getStringArrayExtra("SSIDList");

First take the user permisison!
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED){
requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION},
PERMISSIONS_REQUEST_CODE_ACCESS_COARSE_LOCATION);
//After this point you wait for callback in onRequestPermissionsResult(int, String[], int[]) overriden method
}else{
getScanningResults();
//do something, permission was previously granted; or legacy device
}

What exactly is causing this NullPointerException? [duplicate]

This question already has answers here:
Android: NullPointerException Working With SharedPreferences
(3 answers)
Closed 7 years ago.
I'm pretty new to Android development and am currently working on an app which is supposed to save the current time and date when a button is pressed, store it to SharedPreferences and then present the String when a different button is pressed. I got it working but did some tinkering today and now I'm getting a NullPointerException that I can't solve, even after having spent about 45 minutes on Google and Stackoverflow trying different code fragments. Can anyone who is better at this than me tell me what I'm missing?
Here is the relevant code:
public class GetTimeStamp extends AppCompatActivity {
private String date;
public void setDate (View view){
DateFormat df = new SimpleDateFormat("dd.MM.yyy 'om' HH:mm");
date = df.format(Calendar.getInstance().getTime());
}
public String getDate(){
return date;
}
SharedPreferences prefs = this.getSharedPreferences("SharedPrefs", Context.MODE_PRIVATE);
SharedPreferences.Editor editor = prefs.edit();
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_get_time_stamp);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fabSaveTimeStamp);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
setDate(view);
editor.putString("storedDate", date);
editor.commit();
Toast.makeText(getBaseContext(), "blablabla", Toast.LENGTH_SHORT).show();
}
})
FloatingActionButton fab3 = (FloatingActionButton) findViewById(R.id.fabShowTimeStamp);
fab3.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//retrieve the date from SharedPreferences and store it to a local String
String retrievedDate = prefs.getString("storedDate", null);
if (retrievedDate!=null){
AlertDialog alertDialog = new AlertDialog.Builder(GetTimeStamp.this).create(); //Read Update
alertDialog.setTitle("");
alertDialog.setMessage("somemessage" + retrievedDate);
alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
}
});
alertDialog.show();
}else {
//create an alert dialog explaining to the user that no date has been saved yet
AlertDialog alertDialog = new AlertDialog.Builder(GetTimeStamp.this).create(); //Read Update
alertDialog.setTitle("Error");
alertDialog.setMessage("errorexplanation");
alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
}
});
alertDialog.show();
}
}
});
And here are the errors:
02-08 22:49:36.142 19735-19735/? W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x41ed7ce0)
02-08 22:49:36.152 19735-19735/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.user.appname, PID: 19735
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.user.appname/com.example.user.appname.GetTimeStamp}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2131)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2264)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5139)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:796)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:612)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at android.content.ContextWrapper.getSharedPreferences(ContextWrapper.java:173)
at com.example.user.appname.GetTimeStamp.<init>(GetTimeStamp.java:36)
at java.lang.Class.newInstanceImpl(Native Method)
at java.lang.Class.newInstance(Class.java:1208)
at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2122)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2264) 
at android.app.ActivityThread.access$800(ActivityThread.java:144) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:136) 
at android.app.ActivityThread.main(ActivityThread.java:5139) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:515) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:796) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:612) 
at dalvik.system.NativeStart.main(Native Method) 

You are trying to initialize the following class field before you are allowed to:
SharedPreferences prefs = this.getSharedPreferences("SharedPrefs", Context.MODE_PRIVATE);
Only declare the field:
SharedPreferences prefs;
and then assign it in your onCreate() method:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
prefs = getSharedPreferences("SharedPrefs", Context.MODE_PRIVATE);
...
}

BigDecimal causes NumberFormatException

I am working on a financial app and i have to use BigDecimal to calculate currency.Now I am trying to make one entrance activity which is searching in the SharedPreferences for a previous registration and if their is one it starts another activity , if not it starts the registration activity.The problem is the registration activity causes NumberFormatException Error while I am trying to construct a new object of time Profit (the Profit class contains BigDecimal field).Also I am not quite sure that I am using SharedPreferences right.I am not quite sure that my idea and my coding are fine because I am new at android development and i am stuck with this problem so I am giving you all the classes.
the Registration activity:
public class Registration extends Activity {
private static String enteredPassword;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
final EditText password1 = (EditText) findViewById(R.id.password1);
final EditText password2 = (EditText) findViewById(R.id.password2);
final EditText availability = (EditText) findViewById(R.id.availability);
EditText profitEditText = (EditText) findViewById(R.id.profit);
Spinner spinner = (Spinner) findViewById(R.id.period_spinner);
Button registrationButton = (Button) findViewById(R.id.registrationButton);
DatePicker picker = (DatePicker) findViewById(R.id.thePicker);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,
R.array.periods_array, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);
final String balance = availability.getText().toString().replace(",",".");
String profitPeriod = ((Period) spinner.getSelectedItem()).name();
final Profit profit = new Profit("regular_profit", profitEditText.getText().toString(),
profitPeriod ,picker);
registrationButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (password1.getText().toString().equals(password2.getText().toString())) {
enteredPassword = password1.getText().toString();
Repository.setPassword(enteredPassword, mContext);
}
Repository.setBalance(balance, mContext);
Repository.setProfit(profit, mContext);
}
});
}
}
the profit activity
public class Profit {
private Date mProfitDate;
private Date mNextProfitDate;
private BigDecimal value;
public final static String TITLE = "title";
public final static String PERIOD = "period";
Profit(String title,String value, String period, DatePicker picker) {
this.mTitle = title;
if(value!=null){this.value = new BigDecimal(value);}else{ this.value = new BigDecimal("0.0");};
this.mPeriod = Period.class.cast(period);
this.mProfitDate = Repository.getDateFromPicker(picker);
}
public long getNextProfitDate(Date profitDate, Period period){
long unixProfitDate = profitDate.getTime() / 1000L;
long nextProfitDate=0;
switch (period){
case DAILY:
nextProfitDate = DateUtils.DAY_IN_MILLIS/1000 + unixProfitDate;
break;
case WEEKLY:
nextProfitDate = DateUtils.WEEK_IN_MILLIS/1000 + unixProfitDate;
break;
case MONTHLY:
Date dateNow = new Date();
dateNow.getTime();
nextProfitDate = Repository.monthsToSeconds(Calendar.getInstance()
.get(Calendar.MONTH)) + unixProfitDate;
break;
case YEARLY:
nextProfitDate = DateUtils.YEAR_IN_MILLIS/1000 + unixProfitDate;
break;
}
return nextProfitDate;
}
}
the entrance activity
public class EnterActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_enter);
CountDownTimer timer = new CountDownTimer(3000, 100) {
public void onTick(long millisUntilFinished) {
}
public void onFinish() {
if(Repository.getPassword(mContext.getApplicationContext()).equals("No Value")){
Intent registrationIntent = new Intent(mContext, Registration.class);
startActivity(registrationIntent);
}
else{
Intent configurationIntent = new Intent(mContext, Configuration.class);
startActivity(configurationIntent);
}
}
}.start();
}
}
the Repository
public class Repository {
public static SharedPreferences sharedPreferences;
private static SharedPreferences getPrefs(Context context) {
return context.getSharedPreferences(PREF_NAME, Context.MODE_PRIVATE);
}
public static String getPassword(Context context){
return getPrefs(context).getString(PASSWORD,"No Value");
}
public Repository() {
}
public static void setPassword(String password, Context context){
SharedPreferences.Editor editor = getPrefs(context).edit();
editor.putString(PASSWORD, password);
editor.commit();
}
public static void setBalance(String balance, Context context){
SharedPreferences.Editor editor = getPrefs(context).edit();
editor.putString(BALANCE, balance);
editor.commit();
}
public static void setProfit(Profit profit, Context context){
SharedPreferences.Editor editor = getPrefs(context).edit();
editor.putString(BALANCE, profit.getValue().toString());
editor.commit();
}
}
the output
E/AndroidRuntime: FATAL EXCEPTION: main
E/AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{/.Registration}: java.lang.NumberFormatException: Bad offset/length: offset=0 len=0 in.length=0
E/AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
E/AndroidRuntime: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
E/AndroidRuntime: at android.app.ActivityThread.access$600(ActivityThread.java:123)
E/AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
E/AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime: at android.os.Looper.loop(Looper.java:137)
E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:4424)
E/AndroidRuntime: at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime: at java.lang.reflect.Method.invoke(Method.java:511)
E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
E/AndroidRuntime: at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime: Caused by: java.lang.NumberFormatException: Bad offset/length: offset=0 len=0 in.length=0
E/AndroidRuntime: at java.math.BigDecimal.<init>(BigDecimal.java:282)
E/AndroidRuntime: at java.math.BigDecimal.<init>(BigDecimal.java:438)
E/AndroidRuntime: at .Profit.<init>(Profit.java:41)
E/AndroidRuntime: at .Registration.onCreate(Registration.java:57)
E/AndroidRuntime: at android.app.Activity.performCreate(Activity.java:4466)
E/AndroidRuntime: at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
E/AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
E/AndroidRuntime: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
E/AndroidRuntime: at android.app.ActivityThread.access$600(ActivityThread.java:123)
E/AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
E/AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime: at android.os.Looper.loop(Looper.java:137)
E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:4424)
E/AndroidRuntime: at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime: at java.lang.reflect.Method.invoke(Method.java:511)
E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
E/AndroidRuntime: at dalvik.system.NativeStart.main(Native Method)

You instantiate a Profit in only one place in the code you presented:
Profit profit = new Profit("regular_profit", profitEditText.getText().toString(),
profitPeriod, picker);
If that causes a NumberFormatException then it must come from this code in the Profit constructor:
if(value!=null){this.value = new BigDecimal(value);}else{ this.value = new BigDecimal("0.0");};
Since the value String will have come from invoking toString() on an object, you can rely on it to not be null (and anyway, if it were null then you would end up at new BigDecimal("0.0"), and you can verify for yourself that that works fine). That leaves us with new BigDecimal(value) as the culprit. The docs for this constructor provide details of the expected format of the argument string. If the argument does not comply with that format then a NumberFormatException will be thrown.
Among the more likely malformed strings that one might imagine in a scenario such as you describe is an empty string, which is not the same as null in Java. Given that the text is coming from a UI field, you also have to watch out for fun and difficult-to-spot malformations such as leading and trailing whitespace.
Perhaps it would be better to write the affected part of the constructior like so:
if (value != null) {
value = value.trim();
this.value = value.length() == 0 ? BigDecimal.ZERO : new BigDecimal(value);
} else {
this.value = BigDecimal.ZERO;
}
Do note that even with that change, this constructor will still throw NumberFormatException in the event of other kinds of malformation. Wherever you are uncertain about the validity of the data, you should be prepared to handle such an exception.

You aren't parsing your string to a Big Decimal correctly.
The following in your Profit contructor:
if(value!=null)
{
this.value = new BigDecimal(value);
}
else
{
this.value = new BigDecimal("0.0");
}
Needs to parse the string to a BigDecimal. Like the following where this.value is of type BigDecimal:
this.value = (BigDecimal) decimalFormat.parse(value);
Also keep in mind that decimalFormat.parse can throw a ParseException. You will need to handle it with try/catch or throw it.

NPE accessing Application method from AlerDialog OnClick method

Building on a theme from yesterday...I'm getting an NPE accessing a method in a singleton Application class from within an AlertDialog.
Activity SavedMealsActivity sets OnLongClickListenerSavedMeals as the listener for a series of TextViews in a ScrollView. OnLongClickListenerSavedMeals is defined as a separate class.
OnLongClickListenerSavedMeals displays an AlertDialog which gives the option of going to a different Activity, but it first needs to fire the methods of an Application class which is defined as a singleton (MealTimerApplication). This is the first line of the onClick method (line 25 in the first code sample below), and it throws the NPE because the activity is null at the time.
I've tried passing in the activity from the calling Activity (SavedMealsActivity) but for some reason it's not working as I'd hoped. Any ideas?
OnLongClick listener class - OnLongClickListenerSavedMeals:
public class OnLongClickListenerSavedMeals implements OnLongClickListener {
Context context;
String id;
private Activity activity;
public OnLongClickListenerSavedMeals(Activity activity) {
this.activity = activity;
this.context = activity;
}
#Override
public boolean onLongClick(View view){
// TODO Auto-generated method stub
this.context = context;
id = view.getTag().toString();
final CharSequence[] items = { "Edit", "Delete" };
//Set activity to allow context to be used in the OnClickListener/onClick method below
this.activity = activity;
new AlertDialog.Builder(context).setTitle("Meal Item")
.setItems(items, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int item) {
if (item == 0) {
//Set the global meal_id variable and invoke the MealActivity
((MealTimerApplication) activity.getApplication()).setMealId(Long.getLong(id));
Intent myIntent = new Intent(activity.getBaseContext(),MealActivity.class);
activity.startActivityForResult(myIntent, 0);
}
else if (item == 1) {
boolean deleteSuccessful = new TableControllerMeal(context).delete(id);
if (deleteSuccessful){
Toast.makeText(context, "Record was deleted.", Toast.LENGTH_SHORT).show();
}else{
Toast.makeText(context, "Unable to delete record.", Toast.LENGTH_SHORT).show();
}
((SavedMealsActivity) context).readRecords();
}
dialog.dismiss();
}
}).show();
return false;
}
Calling Activity - SavedMealsActivity:
public class SavedMealsActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_saved_meals);
//Read saved meal records from the database and display them
readRecords();
}
public void readRecords() {
LinearLayout linearLayoutRecords = (LinearLayout) findViewById(R.id.linearLayoutRecords);
linearLayoutRecords.removeAllViews();
List<meal> meal = new TableControllerMeal(this).read();
if (meal.size() > 0) {
for (meal obj : meal) {
long id = obj.id;
String MealDesc = obj.meal_desc;
int MealMinutes = obj.meal_ready_time;
String textViewContents = MealDesc + " - ready at "
+ Utilities.formatTime(MealMinutes);
TextView textViewItem = new TextView(this);
textViewItem.setPadding(0, 10, 0, 10);
textViewItem.setText(textViewContents);
textViewItem.setTag(Long.toString(id));
textViewItem.setOnLongClickListener(new OnLongClickListenerSavedMeals(this));
linearLayoutRecords.addView(textViewItem);
}
}
else {
TextView Item = new TextView(this);
Item.setPadding(8, 8, 8, 8);
Item.setText("No records yet.");
linearLayoutRecords.addView(Item);
}
}
Application class:
public class MealTimerApplication extends Application {
private static MealTimerApplication singleton;
private long mealId = 0;
// Returns the application instance
public static MealTimerApplication getInstance() {
return singleton;
}
public final void onCreate() {
super.onCreate();
singleton = this;
}
public void setMealId(long mealId) {
this.mealId = mealId;
}
public long getMealId() {
return this.mealId;
}
}
Logcat:
05-28 16:48:03.637: E/AndroidRuntime(4241): java.lang.NullPointerException
05-28 16:48:03.637: E/AndroidRuntime(4241): at com.ian.mealtimer.OnLongClickListenerSavedMeals$1.onClick(OnLongClickListenerSavedMeals.java:39)
05-28 16:48:03.637: E/AndroidRuntime(4241): at com.android.internal.app.AlertController$AlertParams$3.onItemClick(AlertController.java:941)
05-28 16:48:03.637: E/AndroidRuntime(4241): at android.widget.AdapterView.performItemClick(AdapterView.java:299)
05-28 16:48:03.637: E/AndroidRuntime(4241): at android.widget.AbsListView.performItemClick(AbsListView.java:1113)
05-28 16:48:03.637: E/AndroidRuntime(4241): at android.widget.AbsListView$PerformClick.run(AbsListView.java:2904)
05-28 16:48:03.637: E/AndroidRuntime(4241): at android.widget.AbsListView$3.run(AbsListView.java:3638)
05-28 16:48:03.637: E/AndroidRuntime(4241): at android.os.Handler.handleCallback(Handler.java:733)
05-28 16:48:03.637: E/AndroidRuntime(4241): at android.os.Handler.dispatchMessage(Handler.java:95)
05-28 16:48:03.637: E/AndroidRuntime(4241): at android.os.Looper.loop(Looper.java:136)
05-28 16:48:03.637: E/AndroidRuntime(4241): at android.app.ActivityThread.main(ActivityThread.java:5017)
05-28 16:48:03.637: E/AndroidRuntime(4241): at java.lang.reflect.Method.invokeNative(Native Method)
05-28 16:48:03.637: E/AndroidRuntime(4241): at java.lang.reflect.Method.invoke(Method.java:515)
05-28 16:48:03.637: E/AndroidRuntime(4241): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
05-28 16:48:03.637: E/AndroidRuntime(4241): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
05-28 16:48:03.637: E/AndroidRuntime(4241): at dalvik.system.NativeStart.main(Native Method)

You get NPE because of autoboxing. Long.getLong(String) is not what you actually you need, check its description:
Returns the Long value of the system property identified by string.
It definitely returns null in your case. Moreover it returns null reference to Long object, but your MealTimerApplication.setMealId expects argument with primitive type long. Here is the point where auto-boxing implicitly trying to cast your Long object returned by getLong method to the long primitive. But as value was null auto-boxing fails and you get NPE.
You should just use Long.valueOf(String) instead of Long.getLong(String).

adding a counter in an android activity

I am very new to android. I have a counter on some SomeActivity, but when I get to the page corresponding to SomeActivity, my app crashes :
final TextView counter = (TextView) findViewById(R.id.laws_counter);
ImageView handDown = (ImageView) findViewById(R.id.handViewDown);
counter.setText("" + 0);
I want that on click of the handown, the counter is idented by -1. Here's
handDown.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(NewsActivity.this,
"The favorite list would appear on clicking this icon",
Toast.LENGTH_LONG).show();
setDown();
}
private void setDown() {
String count = counter.getText().toString();
int now_count = Integer.parseInt(count) +1;
counter.setText(String.valueOf(now_count));
}
});
Is this code correct ?
Update : here's the logcat
10-22 00:18:05.579: ERROR/AndroidRuntime(378): FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.donnfelker.android.bootstrap/com.donnfelker.android.bootstrap.ui.NewsActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
at android.app.ActivityThread.access$1500(ActivityThread.java:117)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:3683)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.donnfelker.android.bootstrap.ui.NewsActivity.onCreate(NewsActivity.java:41)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
... 11 more

There are many ways that you can implement that functionality but think this would be an easy solution.
Make a helper method:
public class PreferencesData {
public static void saveInt(Context context, String key, int value) {
SharedPreferences sharedPrefs = PreferenceManager
.getDefaultSharedPreferences(context);
sharedPrefs.edit().putInt(key, value).commit();
}
public static int getInt(Context context, String key, int defaultValue) {
SharedPreferences sharedPrefs = PreferenceManager
.getDefaultSharedPreferences(context);
return sharedPrefs.getInt(key, defaultValue);
}
}
Then simply call the putInt method to save the counter in any Activity and getInt to get it again in any other Activity. As long as you use the same key both places.