java.lang.NullPointerException: Attempt to invoke virtual method 'void java.util.Calendar.setTimeInMillis(long)' on a null object reference
14,468
You're not initializing the calendar variable c. Try:
private Calendar c = Calendar.getInstance();
One word of advice: don't use one-character variable names, unless it's an iteration variable.
Author by
Tandy
Updated on June 05, 2022Comments
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Tandy almost 2 years
I am new to Android and I'm currently working on a alarm clock app. But when i run it, i get a
NullPointerException
. Can anyone help me with that? Here is my code:public class MainActivity extends ActionBarActivity { private Calendar c; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); final TextView textView=(TextView)findViewById(R.id.textview1); final Button setbtn=(Button)findViewById(R.id.setclock); final Button unsetbtn=(Button)findViewById(R.id.unsetclock); setbtn.setOnClickListener(new OnClickListener(){ @Override public void onClick(View v){ long current=System.currentTimeMillis(); c.setTimeInMillis(current); int mHour=c.get(Calendar.HOUR_OF_DAY); int mMinute=c.get(Calendar.MINUTE); new TimePickerDialog(MainActivity.this, new TimePickerDialog.OnTimeSetListener() { @Override public void onTimeSet(TimePicker view, int hourOfDay, int minute) { c.setTimeInMillis(System.currentTimeMillis()); c.set(Calendar.HOUR_OF_DAY,hourOfDay); c.set(Calendar.MINUTE, minute); c.set(Calendar.SECOND,0); c.set(Calendar.MILLISECOND,0); Intent intent=new Intent(MainActivity.this, CallAlarm.class); PendingIntent sender= PendingIntent.getBroadcast(MainActivity.this, 1, intent, PendingIntent.FLAG_UPDATE_CURRENT); AlarmManager am=(AlarmManager)getSystemService(ALARM_SERVICE); am.set(AlarmManager.RTC_WAKEUP,c.getTimeInMillis(),sender); String tmpS= format(hourOfDay)+""+format(minute); textView.setText(tmpS); Toast.makeText(MainActivity.this, "The alarm seted: "+tmpS, Toast.LENGTH_LONG).show(); } },mHour,mMinute,true).show(); } }); unsetbtn.setOnClickListener(new OnClickListener(){ public void onClick(View v){ Intent intent= new Intent(MainActivity.this, CallAlarm.class); PendingIntent sender=PendingIntent.getBroadcast(MainActivity.this,0, intent, 0); AlarmManager am=(AlarmManager)getSystemService(ALARM_SERVICE); am.cancel(sender); textView.setText("Current No Alarm!"); Toast.makeText(MainActivity.this, "Alarm Canceled", Toast.LENGTH_LONG).show(); } }); } private String format(int x) { String s=""+x; if(s.length()==1) s="0"+s; return s; } }
And i get these in my logcat:
01-12 14:18:16.620: D/AndroidRuntime(2092): Shutting down VM 01-12 14:18:16.628: E/AndroidRuntime(2092): FATAL EXCEPTION: main 01-12 14:18:16.628: E/AndroidRuntime(2092): Process: com.example.alarm1, PID: 2092 **01-12 14:18:16.628: E/AndroidRuntime(2092): java.lang.NullPointerException: Attempt to invoke virtual method 'void java.util.Calendar.setTimeInMillis(long)' on a null object reference** 01-12 14:18:16.628: E/AndroidRuntime(2092): at com.example.alarm1.MainActivity$1.onClick(MainActivity.java:32) 01-12 14:18:16.628: E/AndroidRuntime(2092): at android.view.View.performClick(View.java:4756) 01-12 14:18:16.628: E/AndroidRuntime(2092): at android.view.View$PerformClick.run(View.java:19749) 01-12 14:18:16.628: E/AndroidRuntime(2092): at android.os.Handler.handleCallback(Handler.java:739) 01-12 14:18:16.628: E/AndroidRuntime(2092): at android.os.Handler.dispatchMessage(Handler.java:95) 01-12 14:18:16.628: E/AndroidRuntime(2092): at android.os.Looper.loop(Looper.java:135) 01-12 14:18:16.628: E/AndroidRuntime(2092): at android.app.ActivityThread.main(ActivityThread.java:5221) 01-12 14:18:16.628: E/AndroidRuntime(2092): at java.lang.reflect.Method.invoke(Native Method) 01-12 14:18:16.628: E/AndroidRuntime(2092): at java.lang.reflect.Method.invoke(Method.java:372) 01-12 14:18:16.628: E/AndroidRuntime(2092): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) 01-12 14:18:16.628: E/AndroidRuntime(2092): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
I have no idea why I get a null pointer exception. Can anyone help me with that?? Thank you so much !!!