Why is findFragmentById() returning null? - android

In the method below, NasaDailyFragment is always null in the debugger. The method call NasaDailyFragment.onRefresh(); fails using because of this. I can't figure out why its null.
public class NasaAppActivity extends FragmentActivity {
//other methods
public void onRefreshClicked(View view){
Log.d("debug", "in run");
FragmentManager fragmentManager=getSupportFragmentManager();
NasaDailyImage NasaDailyFragment=(NasaDailyImage)fragmentManager.findFragmentById(R.id.fragment_iotd);
if(NasaDailyFragment!=null){
Log.d("debug", "fragment has been casted and is NOT null!!!");
}
NasaDailyFragment.onRefresh();//always crashes here because NasaDailyFragment is null, this is "line 40" of the code
}
}
Here's the xml for the fragment defined by R.id.fragment_iotd
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<fragment android:name="com.wajumbie.nasadailyimage.NasaDailyImage"
android:id="#+id/fragment_iotd"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</LinearLayout>
The logcat output
07-19 11:21:25.916: D/debug(534): in run
07-19 11:21:25.916: D/AndroidRuntime(534): Shutting down VM
07-19 11:21:25.916: W/dalvikvm(534): threadid=1: thread exiting with uncaught exception (group=0x409c01f8)
07-19 11:21:25.936: E/AndroidRuntime(534): FATAL EXCEPTION: main
07-19 11:21:25.936: E/AndroidRuntime(534): java.lang.IllegalStateException: Could not execute method of the activity
07-19 11:21:25.936: E/AndroidRuntime(534): at android.view.View$1.onClick(View.java:3044)
07-19 11:21:25.936: E/AndroidRuntime(534): at android.view.View.performClick(View.java:3511)
07-19 11:21:25.936: E/AndroidRuntime(534): at android.view.View$PerformClick.run(View.java:14105)
07-19 11:21:25.936: E/AndroidRuntime(534): at android.os.Handler.handleCallback(Handler.java:605)
07-19 11:21:25.936: E/AndroidRuntime(534): at android.os.Handler.dispatchMessage(Handler.java:92)
07-19 11:21:25.936: E/AndroidRuntime(534): at android.os.Looper.loop(Looper.java:137)
07-19 11:21:25.936: E/AndroidRuntime(534): at android.app.ActivityThread.main(ActivityThread.java:4424)
07-19 11:21:25.936: E/AndroidRuntime(534): at java.lang.reflect.Method.invokeNative(Native Method)
07-19 11:21:25.936: E/AndroidRuntime(534): at java.lang.reflect.Method.invoke(Method.java:511)
07-19 11:21:25.936: E/AndroidRuntime(534): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
07-19 11:21:25.936: E/AndroidRuntime(534): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
07-19 11:21:25.936: E/AndroidRuntime(534): at dalvik.system.NativeStart.main(Native Method)
07-19 11:21:25.936: E/AndroidRuntime(534): Caused by: java.lang.reflect.InvocationTargetException
07-19 11:21:25.936: E/AndroidRuntime(534): at java.lang.reflect.Method.invokeNative(Native Method)
07-19 11:21:25.936: E/AndroidRuntime(534): at java.lang.reflect.Method.invoke(Method.java:511)
07-19 11:21:25.936: E/AndroidRuntime(534): at android.view.View$1.onClick(View.java:3039)
07-19 11:21:25.936: E/AndroidRuntime(534): ... 11 more
07-19 11:21:25.936: E/AndroidRuntime(534): Caused by: java.lang.NullPointerException
07-19 11:21:25.936: E/AndroidRuntime(534): at com.wajumbie.nasadailyimage.NasaAppActivity.onRefreshClicked(NasaAppActivity.java:40)
07-19 11:21:25.936: E/AndroidRuntime(534): ... 14 more
07-19 11:21:26.556: I/dalvikvm(534): threadid=3: reacting to signal 3
07-19 11:21:26.586: I/dalvikvm(534): Wrote stack traces to '/data/anr/traces.txt'

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We tried integrating HelpStack by following steps given on GitHub, but we kept getting the following errors:
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at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1967)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1992)
at android.app.ActivityThread.access$600(ActivityThread.java:127)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1158)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4448)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.tenmiles.helpstack.activities.HSActivityParent.onCreate(HSActivityParent.java:48)
at com.tenmiles.helpstack.activities.HomeActivity.onCreate(HomeActivity.java:46)
at android.app.Activity.performCreate(Activity.java:4465)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1931)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1992)
at android.app.ActivityThread.access$600(ActivityThread.java:127)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1158)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4448)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
at dalvik.system.NativeStart.main(Native Method)
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We have problem related with Imsdroid Integration with my android application.During the application startup it gives error as follow..
ExceptionInInitializerError
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07-19 19:55:58.047: E/AndroidRuntime(6858): FATAL EXCEPTION: main
07-19 19:55:58.047: E/AndroidRuntime(6858): java.lang.ExceptionInInitializerError
07-19 19:55:58.047: E/AndroidRuntime(6858): at org.doubango.imsdroid.MyMainClass.<init>(MyMainClass.java:43)
07-19 19:55:58.047: E/AndroidRuntime(6858): at java.lang.Class.newInstanceImpl(Native Method)
07-19 19:55:58.047: E/AndroidRuntime(6858): at java.lang.Class.newInstance(Class.java:1319)
07-19 19:55:58.047: E/AndroidRuntime(6858): at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
07-19 19:55:58.047: E/AndroidRuntime(6858): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2099)
07-19 19:55:58.047: E/AndroidRuntime(6858): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2211)
07-19 19:55:58.047: E/AndroidRuntime(6858): at android.app.ActivityThread.access$600(ActivityThread.java:149)
07-19 19:55:58.047: E/AndroidRuntime(6858): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1300)
07-19 19:55:58.047: E/AndroidRuntime(6858): at android.os.Handler.dispatchMessage(Handler.java:99)
07-19 19:55:58.047: E/AndroidRuntime(6858): at android.os.Looper.loop(Looper.java:153)
07-19 19:55:58.047: E/AndroidRuntime(6858): at android.app.ActivityThread.main(ActivityThread.java:4987)
07-19 19:55:58.047: E/AndroidRuntime(6858): at java.lang.reflect.Method.invokeNative(Native Method)
07-19 19:55:58.047: E/AndroidRuntime(6858): at java.lang.reflect.Method.invoke(Method.java:511)
07-19 19:55:58.047: E/AndroidRuntime(6858): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:821)
07-19 19:55:58.047: E/AndroidRuntime(6858): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:584)
07-19 19:55:58.047: E/AndroidRuntime(6858): at dalvik.system.NativeStart.main(Native Method)
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07-19 19:55:58.047: E/AndroidRuntime(6858): at org.doubango.ngn.NgnEngine.<clinit>(NgnEngine.java:75)
07-19 19:55:58.047: E/AndroidRuntime(6858): ... 16 more
I think its with your AndroidManifest. Try putting this on your Application tag
android:name="org.doubango.ngn.NgnApplication"
or
if you have a custom Application object extend NgnApplication object instead of Application object.
If you want to use imsdroid in your application then you need to use ChromeView instead of WebView in android xml file.
I found more information and at here
<us.costan.chrome.ChromeView
android:id="#+id/customWebView"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
/>

show text after pressing button in android

I'm new to android, now i want to press a button then display text on the screen. here's my code:
xml
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="sendMessages"
android:text="Button" />
<TextView
android:id="#+id/buttonText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:ems="10"
android:inputType="textMultiLine"
android:text="hello" />
main activity
public class MainActivity extends ActionBarActivity {
protected void onCreate(Bundle savedInstanceState){
.......
}
public void sendMessages(View view) {
TextView welcome = (TextView) findViewById(R.id.buttonText);
welcome.setText("button clicked");
}
}
but when i run this on a simulator, after pressing the button, the application will report
fortunately, First Android App has stopped
does anyone know what's wrong with my program?
04-18 00:56:20.147: D/AndroidRuntime(1280): Shutting down VM
04-18 00:56:20.147: W/dalvikvm(1280): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
04-18 00:56:20.177: E/AndroidRuntime(1280): FATAL EXCEPTION: main
04-18 00:56:20.177: E/AndroidRuntime(1280): java.lang.IllegalStateException: Could not execute method of the activity
04-18 00:56:20.177: E/AndroidRuntime(1280): at android.view.View$1.onClick(View.java:3591)
04-18 00:56:20.177: E/AndroidRuntime(1280): at android.view.View.performClick(View.java:4084)
04-18 00:56:20.177: E/AndroidRuntime(1280): at android.view.View$PerformClick.run(View.java:16966)
04-18 00:56:20.177: E/AndroidRuntime(1280): at android.os.Handler.handleCallback(Handler.java:615)
04-18 00:56:20.177: E/AndroidRuntime(1280): at android.os.Handler.dispatchMessage(Handler.java:92)
04-18 00:56:20.177: E/AndroidRuntime(1280): at android.os.Looper.loop(Looper.java:137)
04-18 00:56:20.177: E/AndroidRuntime(1280): at android.app.ActivityThread.main(ActivityThread.java:4745)
04-18 00:56:20.177: E/AndroidRuntime(1280): at java.lang.reflect.Method.invokeNative(Native Method)
04-18 00:56:20.177: E/AndroidRuntime(1280): at java.lang.reflect.Method.invoke(Method.java:511)
04-18 00:56:20.177: E/AndroidRuntime(1280): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
04-18 00:56:20.177: E/AndroidRuntime(1280): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
04-18 00:56:20.177: E/AndroidRuntime(1280): at dalvik.system.NativeStart.main(Native Method)
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04-18 00:56:20.177: E/AndroidRuntime(1280): at java.lang.reflect.Method.invokeNative(Native Method)
04-18 00:56:20.177: E/AndroidRuntime(1280): at java.lang.reflect.Method.invoke(Method.java:511)
04-18 00:56:20.177: E/AndroidRuntime(1280): at android.view.View$1.onClick(View.java:3586)
04-18 00:56:20.177: E/AndroidRuntime(1280): ... 11 more
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04-18 00:56:20.177: E/AndroidRuntime(1280): at com.example.firstandroidapp.MainActivity.sendMessages(MainActivity.java:110)
04-18 00:56:20.177: E/AndroidRuntime(1280): ... 14 more
Do button and TextView exist in the activity layout?
Do you call setContentView(Layout) in onCreate?
Are you working with ADT?
If you are working with ADT you can create a new activity and
a new xml layout, so call setContentView(R.layout.YourLayout)
in onCreate
YourLayout.xml has to contains button and TextView

android arduino usb communication

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LogCat:
E/AndroidRuntime(535): FATAL EXCEPTION: main
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E/AndroidRuntime(535): at com.example.mypro.MainActivity.onCreate(MainActivity.java:123)
E/AndroidRuntime(535): at android.app.Activity.performCreate(Activity.java:4465)
E/AndroidRuntime(535): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
E/AndroidRuntime(535): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)
E/AndroidRuntime(535): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
E/AndroidRuntime(535):at android.app.ActivityThread.access$600(ActivityThread.java:122)
E/AndroidRuntime(535):at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
E/AndroidRuntime(535):at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime(535):at android.os.Looper.loop(Looper.java:137)
E/AndroidRuntime(535):at android.app.ActivityThread.main(ActivityThread.java:4340)
E/AndroidRuntime(535):at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(535):at java.lang.reflect.Method.invoke(Method.java:511)
E/AndroidRuntime(535):at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
E/AndroidRuntime(535):at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
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Hello i am using the tabhost in my application it works fine in 4.0 and up but when i try to run it in 2.3.3 it returns me a null pointer exception and force closes the application
here is the code i am getting error in :
TextView t = new TextView(this) ;
t= (TextView) getTabWidget().getChildAt(i).findViewById(android.R.id.title);
t.setTextColor(Color. parseColor("#ffffff"));
if (i == 0) tabHost.getTabWidget().getChildAt(i).setBackgroundColor(Color.parseColor("#00aedb"));
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this is my logcat output :
05-16 12:29:27.009: E/AndroidRuntime(534): FATAL EXCEPTION: main
05-16 12:29:27.009: E/AndroidRuntime(534): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.moneyminder/com.example.moneyminder.MainActivity}: java.lang.NullPointerException
05-16 12:29:27.009: E/AndroidRuntime(534): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
05-16 12:29:27.009: E/AndroidRuntime(534): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
05-16 12:29:27.009: E/AndroidRuntime(534): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
05-16 12:29:27.009: E/AndroidRuntime(534): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
05-16 12:29:27.009: E/AndroidRuntime(534): at android.os.Handler.dispatchMessage(Handler.java:99)
05-16 12:29:27.009: E/AndroidRuntime(534): at android.os.Looper.loop(Looper.java:123)
05-16 12:29:27.009: E/AndroidRuntime(534): at android.app.ActivityThread.main(ActivityThread.java:3683)
05-16 12:29:27.009: E/AndroidRuntime(534): at java.lang.reflect.Method.invokeNative(Native Method)
05-16 12:29:27.009: E/AndroidRuntime(534): at java.lang.reflect.Method.invoke(Method.java:507)
05-16 12:29:27.009: E/AndroidRuntime(534): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
05-16 12:29:27.009: E/AndroidRuntime(534): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
05-16 12:29:27.009: E/AndroidRuntime(534): at dalvik.system.NativeStart.main(Native Method)
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05-16 12:29:27.009: E/AndroidRuntime(534): at com.example.moneyminder.MainActivity.onCreate(MainActivity.java:78)
05-16 12:29:27.009: E/AndroidRuntime(534): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
05-16 12:29:27.009: E/AndroidRuntime(534): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
05-16 12:29:27.009: E/AndroidRuntime(534): ... 11 more

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