The app won't open

Here is my code: package com.example.overmind.funfacts2;

import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.TextView;

public class FunFactsactivity extends AppCompatActivity { //Declare our View variables private TextView mFactTextView; private Button mShowFactButton;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_fun_factsactivity);

    // Assign the Views from the layput file to the corresponding variables
    mFactTextView = (TextView) findViewById(R.id.FacttextView);
    mShowFactButton = (Button) findViewById(R.id.ShowFactButton);
    View.OnClickListener listen = new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String fact = "Ostriches can run faster than horses.";
            mFactTextView.setText(fact);
        }
    };
    mShowFactButton.setOnClickListener(listen);
}

}

And here is the error:10/13 21:23:02: Launching app $ adb push C:\Users\Overmind\AndroidStudioProjects\FunFacts2\app\build\outputs\apk\app-debug.apk /data/local/tmp/com.example.overmind.funfacts2 $ adb shell pm install -r "/data/local/tmp/com.example.overmind.funfacts2" Success

$ adb shell am start -n "com.example.overmind.funfacts2/com.example.overmind.funfacts2.FunFactsactivity" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER Client not ready yet..Connected to process 2185 on device emulator-5554 W/System: ClassLoader referenced unknown path: /data/app/com.example.overmind.funfacts2-2/lib/x86 I/InstantRun: Instant Run Runtime started. Android package is com.example.overmind.funfacts2, real application class is null. W/System: ClassLoader referenced unknown path: /data/app/com.example.overmind.funfacts2-2/lib/x86 W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable D/AndroidRuntime: Shutting down VM

              --------- beginning of crash

E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.overmind.funfacts2, PID: 2185 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.overmind.funfacts2/com.example.overmind.funfacts2.FunFactsactivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707) at android.app.ActivityThread.-wrap12(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6077) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference at com.example.overmind.funfacts2.FunFactsactivity.onCreate(FunFactsactivity.java:29) at android.app.Activity.performCreate(Activity.java:6664) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2599) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)  at android.app.ActivityThread.-wrap12(ActivityThread.java)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)  at android.os.Handler.dispatchMessage(Handler.java:102)  at android.os.Looper.loop(Looper.java:154)  at android.app.ActivityThread.main(ActivityThread.java:6077)  at java.lang.reflect.Method.invoke(Native Method)  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755) 

The app will not open. If you have completed this already, can you tell me what you did and what I did wrong. Also can you post your code?