Android CustomView zu Fragment hinzufügen

Hey, ich bin gerade dabei eine Zeichenapp zu entwickeln und verharre schon etwas länger an einem Problem. Ich möchte die CustomView, die ich zum zeichnen erstellt habe, in einem Fragment hinzufügen. Allerdings bekomme ich immer eine InflateException und die App startet nicht.

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E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: de.sentoon.touchtesterv4, PID: 11743
                  java.lang.RuntimeException: Unable to start activity ComponentInfo{de.sentoon.touchtesterv4/de.sentoon.touchtesterv4.MainActivity}: android.view.InflateException: Binary XML file line #20: Binary XML file line #20: Error inflating class de.sentoon.touchtesterv4.DrawingView
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2702)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2788)
                      at android.app.ActivityThread.-wrap12(ActivityThread.java)
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1503)
                      at android.os.Handler.dispatchMessage(Handler.java:102)
                      at android.os.Looper.loop(Looper.java:154)
                      at android.app.ActivityThread.main(ActivityThread.java:6209)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
                   Caused by: android.view.InflateException: Binary XML file line #20: Binary XML file line #20: Error inflating class de.sentoon.touchtesterv4.DrawingView
                   Caused by: android.view.InflateException: Binary XML file line #20: Error inflating class de.sentoon.touchtesterv4.DrawingView
                   Caused by: java.lang.NoSuchMethodException: <init> [class android.content.Context, interface android.util.AttributeSet]
                      at java.lang.Class.getConstructor0(Class.java:2204)
                      at java.lang.Class.getConstructor(Class.java:1683)
                      at android.view.LayoutInflater.createView(LayoutInflater.java:618)
                      at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:787)
                      at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:727)
                      at android.view.LayoutInflater.rInflate(LayoutInflater.java:858)
                      at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:821)
                      at android.view.LayoutInflater.inflate(LayoutInflater.java:518)
                      at android.view.LayoutInflater.inflate(LayoutInflater.java:426)
                      at android.view.LayoutInflater.inflate(LayoutInflater.java:377)
                      at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:288)
                      at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:140)
                      at de.sentoon.touchtesterv4.MainActivity.onCreate(MainActivity.java:27)
                      at android.app.Activity.performCreate(Activity.java:6745)
                      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1134)
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2655)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2788)
                      at android.app.ActivityThread.-wrap12(ActivityThread.java)
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1503)
                      at android.os.Handler.dispatchMessage(Handler.java:102)
                      at android.os.Looper.loop(Looper.java:154)
                      at android.app.ActivityThread.main(ActivityThread.java:6209)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)

— geändert am 28.02.2017, 13:27:24