Bugs and How to Fix them ! for Android Beginners

Unknown Host Exception in Android
When you try to load something from web, and you have done almost everything right still you might get this exception.

06-10 11:08:50.217: WARN/System.err(868): java.net.UnknownHostException: nopsa.hiit.fi
06-10 11:08:50.217: WARN/System.err(868):     at java.net.InetAddress.lookupHostByName(InetAddress.java:497)
06-10 11:08:50.217: WARN/System.err(868):     at java.net.InetAddress.getAllByNameImpl(InetAddress.java:294)
06-10 11:08:50.217: WARN/System.err(868):     at java.net.InetAddress.getAllByName(InetAddress.java:256)
06-10 11:08:50.237: WARN/System.err(868):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpConnection.(HttpConnection.java:69)
06-10 11:08:50.237: WARN/System.err(868):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpConnection.(HttpConnection.java:48)
06-10 11:08:50.272: WARN/System.err(868):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpConnection$Address.connect(HttpConnection.java:322)
06-10 11:08:50.272: WARN/System.err(868):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpConnectionPool.get(HttpConnectionPool.java:89)
06-10 11:08:50.272: WARN/System.err(868):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpURLConnectionImpl.getHttpConnection(HttpURLConnectionImpl.java:285)
06-10 11:08:50.277: WARN/System.err(868):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpURLConnectionImpl.makeConnection(HttpURLConnectionImpl.java:267)
06-10 11:08:50.277: WARN/System.err(868):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpURLConnectionImpl.retrieveResponse(HttpURLConnectionImpl.java:1018)
06-10 11:08:50.297: WARN/System.err(868):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:512)

Solutions:
1.) Change the host name ( here it is nopsa.hiit.fi) to the ip address of the host. It can work.
2.) Restart your emulator ( few times.. may be )
3.) add folowing code to AndroidManifest.xml

<uses-permission android:name="android.permission.INTERNET" />

In some cases when you have'nt done the last change i suggested you might bet the following error as well.

06-10 22:47:29.866: WARN/System.err(380): java.net.SocketException: Permission denied
06-10 22:47:29.896: WARN/System.err(380):     at org.apache.harmony.luni.platform.OSNetworkSystem.socket(Native Method)
06-10 22:47:29.946: WARN/System.err(380):     at dalvik.system.BlockGuard$WrappedNetworkSystem.socket(BlockGuard.java:335)
06-10 22:47:29.946: WARN/System.err(380):     at org.apache.harmony.luni.net.PlainSocketImpl.create(PlainSocketImpl.java:216)
06-10 22:47:29.997: WARN/System.err(380):     at java.net.Socket.checkOpenAndCreate(Socket.java:802)
06-10 22:47:30.026: WARN/System.err(380):     at java.net.Socket.connect(Socket.java:948)
06-10 22:47:30.026: WARN/System.err(380):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpConnection.(HttpConnection.java:75)
06-10 22:47:30.058: WARN/System.err(380):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpConnection.(HttpConnection.java:48)
06-10 22:47:30.077: WARN/System.err(380):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpConnection$Address.connect(HttpConnection.java:322)
06-10 22:47:30.116: WARN/System.err(380):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpConnectionPool.get(HttpConnectionPool.java:89)
06-10 22:47:30.146: WARN/System.err(380):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpURLConnectionImpl.getHttpConnection(HttpURLConnectionImpl.java:285)
06-10 22:47:30.146: WARN/System.err(380):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpURLConnectionImpl.makeConnection(HttpURLConnectionImpl.java:267)
06-10 22:47:30.176: WARN/System.err(380):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpURLConnectionImpl.retrieveResponse(HttpURLConnectionImpl.java:1018)
06-10 22:47:30.186: WARN/System.err(380):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:512)

ActivityNotFoundException

06-10 22:50:18.256: ERROR/AndroidRuntime(572): FATAL EXCEPTION: main
06-10 22:50:18.256: ERROR/AndroidRuntime(572): android.content.ActivityNotFoundException: Unable to find explicit activity class {hiit.nopsa.pirate/hiit.nopsa.pirate.GameHome}; have you declared this activity in your AndroidManifest.xml?
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1405)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at android.app.Instrumentation.execStartActivity(Instrumentation.java:1379)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at android.app.Activity.startActivityForResult(Activity.java:2827)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at android.app.Activity.startActivity(Activity.java:2933)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at android.view.View.dispatchTouchEvent(View.java:3885)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:942)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:942)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1691)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1125)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at android.app.Activity.dispatchTouchEvent(Activity.java:2096)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1675)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at android.view.ViewRoot.deliverPointerEvent(ViewRoot.java:2194)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1878)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at android.os.Handler.dispatchMessage(Handler.java:99)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at android.os.Looper.loop(Looper.java:123)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at android.app.ActivityThread.main(ActivityThread.java:3683)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at java.lang.reflect.Method.invokeNative(Native Method)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at java.lang.reflect.Method.invoke(Method.java:507)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
06-10 22:50:18.256: ERROR/AndroidRuntime(572):     at dalvik.system.NativeStart.main(Native Method)

to fix this bug you should add the following code to the AndroidManifest.xml

<activity  android:name=".ClassName"/>

The ClassName should be replaced by your Class name which is a Activity.