android sudoku game, button press crashes the game

I'm creating a sudoku game, but when i press the button it crashes the game. Here's my code:

FPSudoku.java:

package org.example.fpsudoku;

import android.app.Activity; import
android.os.Bundle; import
android.content.Intent; import
android.view.View; import
android.view.View.OnClickListener;

public class FPSudoku extends Activity
implements OnClickListener{
     @Override    public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.main);

      View newButton = findViewById(R.id.new_game_button);
      newButton.setOnClickListener(this);
      View aboutButton = findViewById(R.id.how_to_play_button);
      aboutButton.setOnClickListener(this);
      View exitButton = findViewById(R.id.exit_game_button);
      exitButton.setOnClickListener(this);
          }

      public void onClick(View v) {
          switch (v.getId()) {
          case R.id.how_to_play_button:
          Intent i = new Intent(this, Howtoplay.class);
          startActivity(i);
          break;

      } 
  }
}

Howtoplay.java

package org.example.fpsudoku;

import android.app.Activity; import
android.os.Bundle;

public class Howtoplay extends
Activity {  @Override   protected void
onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.howtoplay);
    }

}

UPDATED

android manifest.xml

<application android:icon="@drawable/icon" android:label="@string/app_name">
    <activity android:name=".FPSudoku"
              android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
        <activity android:name=".Howtoplay"
                  android:label="@string/how_to_play_title" >
                </activity>
                </activity>

</application>

updated logcat

02-25 00:36:08.623: DEBUG/AndroidRuntime(818): >>>>>>>>>>>>>> AndroidRuntime START <<<<<<<<<<<<<<

02-25 00:36:08.623: DEBUG/AndroidRuntime(818): CheckJNI is ON

02-25 00:36:08.763: DEBUG/AndroidRuntime(818): --- registering native functions ---

02-25 00:36:09.504: DEBUG/dalvikvm(237): GC_EXPLICIT freed 130 objects / 6944 bytes in 127ms

02-25 00:36:09.544: DEBUG/PackageParser(43): Scanning package: /data/app/vmdl10845.tmp

02-25 00:36:09.544: WARN/PackageParser(43): Problem in package /data/app/vmdl10845.tmp:

02-25 00:36:09.544: WARN/PackageParser(43): Unknown element under : activity at /data/app/vmdl10845.tmp Binary XML file line #15

02-25 00:36:09.634: INFO/PackageManager(43): Removing non-system package:org.example.fpsudoku

02-25 00:36:09.634: INFO/ActivityManager(43): Force stopping package org.example.fpsudoku uid=10036

02-25 00:36:09.734: DEBUG/PackageManager(43): Scanning package org.example.fpsudoku

02-25 00:36:09.734: INFO/PackageManager(43): Package org.example.fpsudoku codePath changed from /data/app/org.example.fpsudoku-1.apk to /data/app/org.example.fpsudoku-2.apk; Retaining data and using new

02-25 00:36:09.744: INFO/PackageManager(43): /data/app/org.example.fpsudoku-2.apk changed; unpacking

02-25 00:36:09.754: DEBUG/installd(35): DexInv: --- BEGIN '/data/app/org.example.fpsudoku-2.apk' ---

02-25 00:36:09.904: DEBUG/dalvikvm(825): DexOpt: load 28ms, verify 17ms, opt 2ms

02-25 00:36:09.904: DEBUG/installd(35): DexInv: --- END '/data/app/org.example.fpsudoku-2.apk' (success) ---

02-25 00:36:09.914: WARN/PackageManager(43): Code path for pkg : org.example.fpsudoku changing from /data/app/org.example.fpsudoku-1.apk to /data/app/org.example.fpsudoku-2.apk

02-25 00:36:09.914: WARN/PackageManager(43): Resource path for pkg : org.example.fpsudoku changing from /data/app/org.example.fpsudoku-1.apk to /data/app/org.example.fpsudoku-2.apk

02-25 00:36:09.914: DEBUG/PackageManager(43): Activities: org.example.fpsudoku.FPSudoku

02-25 00:36:09.924: INFO/ActivityManager(43): Force stopping package org.example.fpsudoku uid=10036

02-25 00:36:10.004: INFO/installd(35): move /data/dalvik-cache/data@app@org.example.fpsudoku-2.apk@classes.dex -> /data/dalvik-cache/data@app@org.example.fpsudoku-2.apk@classes.dex

02-25 00:36:10.014: DEBUG/PackageManager(43): New package installed in /data/app/org.example.fpsudoku-2.apk

02-25 00:36:10.174: DEBUG/dalvikvm(43): GC_FOR_MALLOC freed 7382 objects / 491576 bytes in 97ms

02-25 00:36:10.274: INFO/ActivityManager(43): Force stopping package org.example.fpsudoku uid=10036

02-25 00:36:10.334: DEBUG/dalvikvm(117): GC_EXPLICIT freed 814 objects / 43456 bytes in 53ms

02-25 00:36:10.554: DEBUG/dalvikvm(43): GC_EXPLICIT freed 3804 objects / 210760 bytes in 102ms

02-25 00:36:10.574: WARN/RecognitionManagerService(43): no available voice recognition services found

02-25 00:36:10.614: INFO/installd(35): unlink /data/dalvik-cache/data@app@org.example.fpsudoku-1.apk@classes.dex

02-25 00:36:10.654: DEBUG/AndroidRuntime(818): Shutting down VM

02-25 00:36:10.664: DEBUG/dalvikvm(818): Debugger has detached; object registry had 1 entries

02-25 00:36:10.694: INFO/AndroidRuntime(818): NOTE: attach of thread 'Binder Thread #3' failed

02-25 00:36:11.254: DEBUG/AndroidRuntime(831): >>>>>>>>>>>>>> AndroidRuntime START <<<<<<<<<<<<<<

02-25 00:36:11.254: DEBUG/AndroidRuntime(831): CheckJNI is ON

02-25 00:36:11.414: DEBUG/AndroidRuntime(831): --- registering native functions ---

02-25 00:36:12.034: INFO/ActivityManager(43): Starting activity: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=org.example.fpsudoku/.FPSudoku }

02-25 00:36:12.064: INFO/ActivityManager(43): Start proc org.example.fpsudoku for activity org.example.fpsudoku/.FPSudoku: pid=837 uid=10036 gids={}

02-25 00:36:12.094: DEBUG/AndroidRuntime(831): Shutting down VM

02-25 00:36:12.104: DEBUG/dalvikvm(831): Debugger has detached; object registry had 1 entries

02-25 00:36:12.954: INFO/ActivityManager(43): Displayed activity org.example.fpsudoku/.FPSudoku: 901 ms (total 901 ms)

02-25 00:36:14.024: INFO/ActivityManager(43): Starting activity: Intent { cmp=org.example.fpsudoku/.Howtoplay }

02-25 00:36:14.034: DEBUG/AndroidRuntime(837): Shutting down VM

02-25 00:36:14.034: WARN/dalvikvm(837): threadid=1: thread exiting with uncaught exception (group=0x4001d800)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): FATAL EXCEPTION: main

02-25 00:36:14.044: ERROR/AndroidRuntime(837): android.content.ActivityNotFoundException: Unable to find explicit activity class {org.example.fpsudoku/org.example.fpsudoku.Howtoplay}; have you declared this activity in your AndroidManifest.xml?

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1404)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at android.app.Instrumentation.execStartActivity(Instrumentation.java:1378)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at android.app.Activity.startActivityForResult(Activity.java:2817)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at android.app.Activity.startActivity(Activity.java:2923)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at org.example.fpsudoku.FPSudoku.onClick(FPSudoku.java:31)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at android.view.View.performClick(View.java:2408)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at android.view.View$PerformClick.run(View.java:8816)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at android.os.Handler.handleCallback(Handler.java:587)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at android.os.Handler.dispatchMessage(Handler.java:92)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at android.os.Looper.loop(Looper.java:123)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at android.app.ActivityThread.main(ActivityThread.java:4627)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at java.lang.reflect.Method.invokeNative(Native Method)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at java.lang.reflect.Method.invoke(Method.java:521)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)

02-25 00:36:14.044: ERROR/AndroidRuntime(837): at dalvik.system.NativeStart.main(Native Method)

02-25 00:36:14.054: WARN/ActivityManager(43): Force finishing activity org.example.fpsudoku/.FPSudoku

02-25 00:36:14.564: WARN/ActivityManager(43): Activity pause timeout for HistoryRecord{43f8d620 org.example.fpsudoku/.FPSudoku}

02-25 00:36:15.764: INFO/Process(837): Sending signal. PID: 837 SIG: 9

02-25 00:36:15.774: INFO/ActivityManager(43): Process org.example.fpsudoku (pid 837) has died.

02-25 00:36:15.774: INFO/WindowManager(43): WIN DEATH: Window{440296f8 org.example.fpsudoku/org.example.fpsudoku.FPSudoku paused=false}

02-25 00:36:15.824: WARN/InputMa开发者_StackOverflow社区nagerService(43): Got RemoteException sending setActive(false) notification to pid 837 uid 10036

02-25 00:36:18.894: DEBUG/SntpClient(43): request time failed: java.net.SocketException: Address family not supported by protocol

02-25 00:36:20.194: DEBUG/dalvikvm(237): GC_EXPLICIT freed 156 objects / 11312 bytes in 133ms

02-25 00:36:24.782: WARN/ActivityManager(43): Activity destroy timeout for HistoryRecord{43f8d620 org.example.fpsudoku/.FPSudoku}

02-25 00:36:25.254: DEBUG/dalvikvm(262): GC_EXPLICIT freed 26 objects / 1144 bytes in 131ms

Hidden in your LogCat is the answer to your question:

ActivityNotFoundException: Unable to find explicit activity class {org.example.fpsudoku/org.example.fpsudoku.Howtoplay}; have you declared this activity in your AndroidManifest.xml?