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Android Flow example crashes with ClassNotFoundException

I'm Naive in Android development. I tried to use flow/mortar for development and stuck with an exception.
Here's what I did. In Eclipse, I chose New (Crtl N) -> Android Project from existing code and imported the flow sample downloaded from the square flow website https://github.com/square/flow/.
Eclipse marked errors in all the files as the package name was not matching the file's location. So to fix the package mismatch issue, I moved the files from : \flow-master\flow-sample\src\main\java\com\example\flow to : \flow-master\flow-sample\src\com\example\flow.
After this, I got some more errors saying 'Unresolved to a Type' which I fixed by importing proper jar files. Now all the errors are cleared and I tried to install and launch the app.
The app crashes as soon as we launch with the Logcat error below:
E/AndroidRuntime(5438): FATAL EXCEPTION: main
E/AndroidRuntime(5438): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.flow/com.example.flow.MainActivity}: java.lang.ClassNotFoundException: com.example.flow.MainActivity
E/AndroidRuntime(5438): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1888)
E/AndroidRuntime(5438): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1989)
E/AndroidRuntime(5438): at android.app.ActivityThread.access$600(ActivityThread.java:126)
E/AndroidRuntime(5438): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1155)
E/AndroidRuntime(5438): at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime(5438): at android.os.Looper.loop(Looper.java:137)
E/AndroidRuntime(5438): at android.app.ActivityThread.main(ActivityThread.java:4482)
E/AndroidRuntime(5438): at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(5438): at java.lang.reflect.Method.invoke(Method.java:511)
E/AndroidRuntime(5438): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:787)
E/AndroidRuntime(5438): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:554)
E/AndroidRuntime(5438): at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime(5438): Caused by: java.lang.ClassNotFoundException: com.example.flow.MainActivity
E/AndroidRuntime(5438): at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:61)
E/AndroidRuntime(5438): at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
E/AndroidRuntime(5438): at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
E/AndroidRuntime(5438): at android.app.Instrumentation.newActivity(Instrumentation.java:1023)
E/AndroidRuntime(5438): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1879)
E/AndroidRuntime(5438): ... 11 more
The error says that the file MainActivity is not found even when the file is available in the path com.example.flow.. Can someone please help me understand what the issue is?
Android Manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.flow"
android:versionCode="1"
android:versionName="1.0">
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="18"/>
<application
android:icon="#drawable/flow_icon">
<activity
android:label="Flow"
android:name="com.example.flow.MainActivity"
android:theme="#android:style/Theme.Holo.Light.DarkActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
</application>
</manifest>

How to avoid class not found exception in android

I am getting class not found exception on some android devices, it's happening only on some devices.
This is the call-stack i have got,
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.picframes.android/com.picframes.android.first}: java.lang.ClassNotFoundException: com.picframes.android.first
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2240)
at android.app.ActivityThread.access$600(ActivityThread.java:139)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1262)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:156)
at android.app.ActivityThread.main(ActivityThread.java:4987)
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.ClassNotFoundException: com.picframes.android.first
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:61)
at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
at android.app.Instrumentation.newActivity(Instrumentation.java:1039)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112)
Any suggestions for resolving this problem, I could not reproduce this problem on my device.

On devices with which android version program works and where it doesn't work? I am not sure if this is the case but you probably get this error on older devices, is that right? You should make sure that all the functionality of your program is available on older systems. Use your manifest file:
<uses-sdk android:minSdkVersion="integer"
android:targetSdkVersion="integer"
android:maxSdkVersion="integer" />
to define minimum sdk version, and you will get errors in your code if you are trying to use features that are not available on the device that you target.

When people download my app from the google play i get this error: java.lang.RuntimeException: Unable to instantiate activity

my name is Walid.
im having this error when people download my app from google play i get this error
i think its when certain devices download the app it causes the app to crash .
this is the sdk in the manifest.
please if anyone knows how to fix this please let me know .
Thank you.
<uses-sdk
android:minSdkVersion="2"
android:targetSdkVersion="17" />
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{tigris.code.oneallah.walid/tigris.code.oneallah.walid.MenuPage}: java.lang.ClassNotFoundException: tigris.code.oneallah.walid.MenuPage in loader dalvik.system.PathClassLoader[/data/app/tigris.code.oneallah.walid-1.apk]
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1573)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
at android.app.ActivityThread.access$1500(ActivityThread.java:117)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:130)
at android.app.ActivityThread.main(ActivityThread.java:3693)
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:907)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:665)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.ClassNotFoundException: tigris.code.oneallah.walid.MenuPage in loader dalvik.system.PathClassLoader[/data/app/tigris.code.oneallah.walid-1.apk]
at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:240)
at java.lang.ClassLoader.loadClass(ClassLoader.java:551)
at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1565)
... 11 more

Your APK file does not contain a class named tigris.code.oneallah.walid.MenuPage. Either the APK is missing the class, or ProGuard renamed it.

Unable to start activity On Sony Experia S

I recently published my app to the android play store.
I see a whole lot of error logs from one device in particular. It's a Sony Experia S.
I contacted the owner of the device, and he says he has the latest version of android ( don't know the exact version ).
I heard from a colluege developer that there are more known issieus with sony devices and android.
This app in particular works with fragments... Don't know if this is the problem but... Maybe the sony's don't know how to cope with them.
Does anyone have an idea what this problem could be.
Error logs looks like:
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.crosscommunications.kvodeventer/com.crosscommunications.kvodeventer.KVODeventerActivity}: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.crosscommunications.kvodeventer/com.crosscommunications.kvodeventer.TabControllerHome}: java.lang.NullPointerException
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:4511)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:980)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.crosscommunications.kvodeventer/com.crosscommunications.kvodeventer.TabControllerHome}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1967)
at android.app.ActivityThread.startActivityNow(ActivityThread.java:1808)
at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:135)
at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:347)
at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:682)
at android.widget.TabHost.setCurrentTab(TabHost.java:346)
at android.widget.TabHost.addTab(TabHost.java:236)
at com.crosscommunications.kvodeventer.KVODeventerActivity.onCreate(KVODeventerActivity.java:27)
at android.app.Activity.performCreate(Activity.java:4470)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1052)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1931)
... 11 more
Caused by: java.lang.NullPointerException
at com.crosscommunications.kvodeventer.KVOHome.onCreateView(KVOHome.java:52)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:870)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1080)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:622)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1416)
at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:505)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1136)
at android.app.Activity.performStart(Activity.java:4480)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1940)
... 21 more
Thnx

Just put a null check to your code:
KVOHome Acvitivity, line 52.
at com.crosscommunications.kvodeventer.KVOHome.onCreateView(KVOHome.java:52)
Most probably, Sony sends a null value to your code.

Crashing on layout.main

I have released my app to Market yesterday and I get a strange crash report telling me that it doesnt find the layout.main. If the layout wouldnt exist, I would wouldnt be able to start the app on my own device. Which is not the case. Too bad the report doesnt tell which device or Android version it is running on.
Maybe someone can download my app (mytaxicontrol - it's free) and tell me under which conditions its crashing or has an idea what the problem could be?
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mytaxicontrol/com.mytaxicontrol.MyTaxiControlActivity}: android.content.res.Resources$NotFoundException: Resource ID #0x7f030004
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
at android.app.ActivityThread.access$1500(ActivityThread.java:117)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:130)
at android.app.ActivityThread.main(ActivityThread.java:3687)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
at dalvik.system.NativeStart.main(Native Method)
Caused by: android.content.res.Resources$NotFoundException: Resource ID #0x7f030004
at android.content.res.Resources.getValue(Resources.java:892)
at android.content.res.Resources.loadXmlResourceParser(Resources.java:1869)
at android.content.res.Resources.getLayout(Resources.java:731)
at android.view.LayoutInflater.inflate(LayoutInflater.java:318)
at android.view.LayoutInflater.inflate(LayoutInflater.java:276)
at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:209)
at android.app.Activity.setContentView(Activity.java:1657)
at com.mytaxicontrol.MyTaxiControlActivity.onCreate(Unknown Source)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)

In the manifest you should have added this because you do not need support for small screens devices as layout is not mentioned.
<supports-screens
android:smallScreens="false"
android:normalScreens="true"
android:largeScreens="true"
android:anyDensity="true" />
And your layout folder name should be
layout-normal
layout-large