NullPointerException

when build sample on my phone (api17) , return null for dispatcher in prepare and crashed sample,

01-05 16:32:57.105 32068-32068/org.firezenk.audiowaves.sample E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{org.firezenk.audiowaves.sample/org.firezenk.audiowaves.sample.MainActivity}: android.view.InflateException: Binary XML file line #9: Error inflating class org.firezenk.audiowaves.Visualizer
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2351)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2403)
at android.app.ActivityThread.access$600(ActivityThread.java:165)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1373)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5391)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
at dalvik.system.NativeStart.main(Native Method)
Caused by: android.view.InflateException: Binary XML file line #9: Error inflating class org.firezenk.audiowaves.Visualizer
at android.view.LayoutInflater.createView(LayoutInflater.java:613)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:687)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:746)
at android.view.LayoutInflater.inflate(LayoutInflater.java:489)
at android.view.LayoutInflater.inflate(LayoutInflater.java:396)
at android.view.LayoutInflater.inflate(LayoutInflater.java:352)
at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:249)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:106)
at org.firezenk.audiowaves.sample.MainActivity.onCreate(MainActivity.java:15)
at android.app.Activity.performCreate(Activity.java:5122)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1150)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2315)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2403) 
at android.app.ActivityThread.access$600(ActivityThread.java:165) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1373) 
at android.os.Handler.dispatchMessage(Handler.java:107) 
at android.os.Looper.loop(Looper.java:194) 
at android.app.ActivityThread.main(ActivityThread.java:5391) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:525) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600) 
at dalvik.system.NativeStart.main(Native Method) 
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Constructor.constructNative(Native Method)
at java.lang.reflect.Constructor.newInstance(Constructor.java:417)
at android.view.LayoutInflater.createView(LayoutInflater.java:587)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:687) 
at android.view.LayoutInflater.rInflate(LayoutInflater.java:746) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:489) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:396) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:352) 
at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:249) 
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:106) 
at org.firezenk.audiowaves.sample.MainActivity.onCreate(MainActivity.java:15) 
at android.app.Activity.performCreate(Activity.java:5122) 
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1150) 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2315) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2403) 
at android.app.ActivityThread.access$600(ActivityThread.java:165) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1373) 
at android.os.Handler.dispatchMessage(Handler.java:107) 
at android.os.Looper.loop(Looper.java:194) 
at android.app.ActivityThread.main(ActivityThread.java:5391) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:525) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600) 
at dalvik.system.NativeStart.main(Native Method) 
Caused by: java.lang.NullPointerException
at org.firezenk.audiowaves.Visualizer.prepare(Visualizer.java:290)
at org.firezenk.audiowaves.Visualizer.init(Visualizer.java:152)
at org.firezenk.audiowaves.Visualizer.(Visualizer.java:71)
at java.lang.reflect.Constructor.constructNative(Native Method) 
at java.lang.reflect.Constructor.newInstance(Constructor.java:417) 
at android.view.LayoutInflater.createView(LayoutInflater.java:587) 
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:687) 
at android.view.LayoutInflater.rInflate(LayoutInflater.java:746) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:489) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:396) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:352) 
at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:249) 
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:106) 
at org.firezenk.audiowaves.sample.MainActivity.onCreate(MainActivity.java:15) 
at android.app.Activity.performCreate(Activity.java:5122) 
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1150) 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2315) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2403) 
at android.app.ActivityThread.access$600(ActivityThread.java:165) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1373) 
at android.os.Handler.dispatchMessage(Handler.java:107) 
at android.os.Looper.loop(Looper.java:194) 
at android.app.ActivityThread.main(ActivityThread.java:5391) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:525) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600) 
at dalvik.system.NativeStart.main(Native Method) 

Inspect org.firezenk.audiowaves.Visualizer.prepare at line 290, following the calls from init and the constructor; compare this with the sample layout at XML line 9 and MainActivity.onCreate at line 15. Reproduce the sample on an API 17 phone or emulator and trace why dispatcher is null. Done means the sample inflates Visualizer and starts without the reported NullPointerException.

Written by the indexing model from the issue text.