java lang RuntimeException Unable to start activity ComponentInfo

Question

I know this error appeared on forum million of times  but please help me find what I missed  I m trying to do simple tab orientated application I don t have much  except errors   1  my main activity is based on tablayout tutorial what I found  public class MainTabPanel extends TabActivity        public void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           setContentView R layout mainlayout           Resources res   getResources            TabHost tabHost   getTabHost            TabHost TabSpec spec          Intent intent          intent   new Intent   setClass this  MyBookActivity class           spec   tabHost newTabSpec  main                    setIndicator  Main   res getDrawable R drawable ic mybook                    setContent intent           tabHost addTab spec           tabHost setCurrentTab 0              2  mainlayout xml   lt  xml version  1 0  encoding  utf-8   gt   lt TabHost xmlns android  http   schemas android com apk res android   android id   android id tabhost   android layout width  fill parent   android layout height  fill parent  gt    lt LinearLayout      android orientation  vertical       android layout width  fill parent          android layout height  fill parent             android padding  5dp  gt    lt TabWidget    android id   android id tabs     android layout width  fill parent    android layout height  wrap content    gt              lt FrameLayout         android id   android id tabcontent     android layout width  fill parent       android layout height  fill parent    android padding  5dp    gt       lt  LinearLayout gt  lt  TabHost gt    3  my second activity is basically almost empty  it s just display current date and time  worked before I tried to add tab panel  4  my manifest file   lt  xml version  1 0  encoding  utf-8   gt   lt manifest xmlns android  http   schemas android com apk res android      package  org th mybook      android versionCode  1      android versionName  1 0   gt       lt uses-sdk android minSdkVersion  8    gt       lt application         android icon   drawable ic launcher          android label   string app name   gt           lt activity             android name   MainTabPanel              android label   string app name   gt               lt intent-filter gt                   lt action android name  android intent action MAIN    gt                   lt category android name  android intent category LAUNCHER    gt               lt  intent-filter gt           lt  activity gt           lt activity             android name  MyBookActivity              android label   string app name   gt               lt intent-filter gt                   lt action android name  android intent action MAIN    gt                   lt category android name  android intent category ALTERNATIVE    gt               lt  intent-filter gt           lt  activity gt       lt  application gt   lt  manifest gt    5 log cat error  02-10 21 04 45 203  E AndroidRuntime 1107   FATAL EXCEPTION  main 02-10 21 04 45 203  E AndroidRuntime 1107   java lang RuntimeException  Unable to start activity ComponentInfo org th mybook org th mybook MainTabPanel   java lang RuntimeException  Unable to instantiate activity ComponentInfo org th mybook org th mybook MyBookActivity   java lang NullPointerException 02-10 21 04 45 203  E AndroidRuntime 1107       at android app ActivityThread performLaunchActivity ActivityThread java 2663  02-10 21 04 45 203  E AndroidRuntime 1107       at android app ActivityThread handleLaunchActivity ActivityThread java 2679  02-10 21 04 45 203  E AndroidRuntime 1107       at android app ActivityThread access 2300 ActivityThread java 125  02-10 21 04 45 203  E AndroidRuntime 1107       at android app ActivityThread H handleMessage ActivityThread java 2033  02-10 21 04 45 203  E AndroidRuntime 1107       at android os Handler dispatchMessage Handler java 99  02-10 21 04 45 203  E AndroidRuntime 1107       at android os Looper loop Looper java 123  02-10 21 04 45 203  E AndroidRuntime 1107       at android app ActivityThread main ActivityThread java 4627  02-10 21 04 45 203  E AndroidRuntime 1107       at java lang reflect Method invokeNative Native Method  02-10 21 04 45 203  E AndroidRuntime 1107       at java lang reflect Method invoke Method java 521  02-10 21 04 45 203  E AndroidRuntime 1107       at com android internal os ZygoteInit MethodAndArgsCaller run ZygoteInit java 868  02-10 21 04 45 203  E AndroidRuntime 1107       at com android internal os ZygoteInit main ZygoteInit java 626  02-10 21 04 45 203  E AndroidRuntime 1107       at dalvik system NativeStart main Native Method  02-10 21 04 45 203  E AndroidRuntime 1107   Caused by  java lang RuntimeException  Unable to instantiate activity ComponentInfo org th mybook org th mybook MyBookActivity   java lang NullPointerException 02-10 21 04 45 203  E AndroidRuntime 1107       at android app ActivityThread performLaunchActivity ActivityThread java 2585  02-10 21 04 45 203  E AndroidRuntime 1107       at android app ActivityThread startActivityNow ActivityThread java 2503  02-10 21 04 45 203  E AndroidRuntime 1107       at android app LocalActivityManager moveToState LocalActivityManager java 127  02-10 21 04 45 203  E AndroidRuntime 1107       at android app LocalActivityManager startActivity LocalActivityManager java 339  02-10 21 04 45 203  E AndroidRuntime 1107       at android widget TabHost IntentContentStrategy getContentView TabHost java 651  02-10 21 04 45 203  E AndroidRuntime 1107       at android widget TabHost setCurrentTab TabHost java 323  02-10 21 04 45 203  E AndroidRuntime 1107       at android widget TabHost addTab TabHost java 213  02-10 21 04 45 203  E AndroidRuntime 1107       at org th mybook MainTabPanel onCreate MainTabPanel java 30  02-10 21 04 45 203  E AndroidRuntime 1107       at android app Instrumentation callActivityOnCreate Instrumentation java 1047  02-10 21 04 45 203  E AndroidRuntime 1107       at android app ActivityThread performLaunchActivity ActivityThread java 2627  02-10 21 04 45 203  E AndroidRuntime 1107           11 more 02-10 21 04 45 203  E AndroidRuntime 1107   Caused by  java lang NullPointerException 02-10 21 04 45 203  E AndroidRuntime 1107       at android content ContextWrapper getApplicationContext ContextWrapper java 100  02-10 21 04 45 203  E AndroidRuntime 1107       at org th mybook MyBookActivity  lt init gt  MyBookActivity java 16  02-10 21 04 45 203  E AndroidRuntime 1107       at java lang Class newInstanceImpl Native Method  02-10 21 04 45 203  E AndroidRuntime 1107       at java lang Class newInstance Class java 1429  02-10 21 04 45 203  E AndroidRuntime 1107       at android app Instrumentation newActivity Instrumentation java 1021  02-10 21 04 45 203  E AndroidRuntime 1107       at android app ActivityThread performLaunchActivity ActivityThread java 2577  02-10 21 04 45 203  E AndroidRuntime 1107           20 more   please help me  and tell me what i missed  im comparing this code with my old one and i can t find anything regards  6  my book activity  public class MyBookActivity extends Activity       java text DateFormat dateFormat   android text format DateFormat getDateFormat getApplicationContext            Override     public void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           setContentView R layout main           DigitalClock clock    DigitalClock  findViewById R id digitalClock1           final TextView date    TextView  findViewById R id textView1           date setText dateFormat format new Date              TextWatcher watcher   new TextWatcher                   Override             public void afterTextChanged Editable s                                Override             public void beforeTextChanged CharSequence s  int start  int count                      int after                                Override             public void onTextChanged CharSequence s  int start  int before                      int count                     if  s toString   startsWith  00 00 00                              s toString   startsWith  12 00 00                          date setText dateFormat format new Date                                                         clock addTextChangedListener watcher              7  main xml layout -  for my book activity   lt  xml version  1 0  encoding  utf-8   gt   lt LinearLayout xmlns android  http   schemas android com apk res android      android layout width  fill parent      android layout height  fill parent      android gravity  right      android orientation  horizontal   gt         lt LinearLayout         android id    id DatePanel1          android layout width  wrap content          android layout height  wrap content   gt             lt TextView             android id    id textView1              android layout width  match parent              android layout height  wrap content              android layout marginRight   dimen space              android layout weight  1              android text  TextView    gt            lt DigitalClock             android id    id digitalClock1              android layout width  0dp              android layout height  wrap content              android layout weight  1              android text  DigitalClock    gt       lt  LinearLayout gt    lt  LinearLayout gt

User · Answer

Your Manifest Must Change like this Activity name must Specified like   YourActivityname     lt  xml version  1 0  encoding  utf-8   gt   lt manifest xmlns android  http   schemas android com apk res android  package  org th mybook  android versionCode  1  android versionName  1 0   gt    lt uses-sdk      android minSdkVersion  8  android targetSdkVersion  8    gt    lt application     android icon   drawable ic launcher      android label   string app name   gt       lt activity         android name   MainTabPanel          android label   string app name   gt           lt intent-filter gt               lt action android name  android intent action MAIN    gt               lt category android name  android intent category LAUNCHER    gt           lt  intent-filter gt       lt  activity gt       lt activity         android name   MyBookActivity    gt                   lt  activity gt   lt  application gt

User · Answer

Dear You have used two Intent launcher in your Manifest  Make only one Activity as launcher  Your manifest activity is      lt  xml version  1 0  encoding  utf-8   gt   lt manifest xmlns android  http   schemas android com apk res android      package  org th mybook      android versionCode  1      android versionName  1 0   gt       lt uses-sdk android minSdkVersion  8    gt       lt application         android icon   drawable ic launcher          android label   string app name   gt           lt activity             android name   MainTabPanel              android label   string app name   gt               lt intent-filter gt                   lt action android name  android intent action MAIN    gt                   lt category android name  android intent category LAUNCHER    gt               lt  intent-filter gt           lt  activity gt           lt activity             android name  MyBookActivity              android label   string app name   gt               lt intent-filter gt                   lt action android name  android intent action MAIN    gt                   lt category android name  android intent category ALTERNATIVE    gt               lt  intent-filter gt           lt  activity gt       lt  application gt   lt  manifest gt    now write code will be   i have made your  MyActivityBook  your default activity launcher  Copy and paste it on your manifest    lt  xml version  1 0  encoding  utf-8   gt       lt manifest xmlns android  http   schemas android com apk res android          package  org th mybook          android versionCode  1          android versionName  1 0   gt           lt uses-sdk android minSdkVersion  8    gt           lt application             android icon   drawable ic launcher              android label   string app name   gt               lt activity                 android name   MainTabPanel                  android label   string app name   gt                lt  activity gt               lt activity                 android name  MyBookActivity                  android label   string app name   gt                   lt intent-filter gt                       lt action android name  android intent action MAIN    gt                       lt category android name  android intent category LAUNCHER    gt                   lt  intent-filter gt               lt  activity gt           lt  application gt       lt  manifest gt    and Second error may be if you copy paste old code then please update com example packagename FILE NAME  hope this will work

User · Answer

lt activity         android name  MyBookActivity          android label   string app name   gt           lt intent-filter gt               lt action android name  android intent action MAIN    gt               lt category android name  android intent category ALTERNATIVE    gt           lt  intent-filter gt       lt  activity gt    where is your dot before MyBookActivity

User · Answer

I had the same issue  I cleaned and rebuilt the project and it worked

User · Answer

It was my own stupidity   java text DateFormat dateFormat   android text format DateFormat getDateFormat getApplicationContext       Putting this inside onCreate   method fixed my problem

User · Answer

After trying few answers they are either not related to my project or   I have tried cleaning and rebuilding  https   stackoverflow com a 48760966 8463813   But it didn t work for me directly  I have compared it with older version of code  in which i observed some library files jars and aars in External Libraries directory  are missing  Tried Invalidate Cache and Restart worked  which created all the libraries and working fine

[android] java.lang.RuntimeException: Unable to start activity ComponentInfo

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