IllegalStateException when trying to schedule a timer

From the documentation of the cancel method:

(Loosely speaking, this method returns true if it prevents one or more scheduled executions from taking place.)

And when I execute this code:

private Timer timer = null;private TimerTask runnable = new TimerTask() {    @Override    public void run() {        Log.e("DEBUG", "Scheduled task tick");        if(!looper){            Looper.prepare();            looper = true;        }        VolleyConnect vc = new VolleyConnect();        vc.connect(ErrorListActivity.this);    }};@Overridepublic void onWindowFocusChanged(boolean focus){    if(!focus){        kill();    }else{        start();    }    Log.e("DEBUG", "FOCUS "+ focus);}public void start(){    if(timer == null){        timer = new Timer();        //180000 ms = 3 minutes        timer.scheduleAtFixedRate(runnable, 0L, 180000L);<--- This line is the one that triggers the error.    }}public void kill(){    if(timer != null) {        boolean rep = runnable.cancel();        Log.e("DEBUG", "REP = "+ rep);        timer.cancel();        timer = null;        looper = false;    }}

Unexpectedly, the debug statement prints:

E/DEBUG: REP = true

which shows that the cancel should be completed. However, when I regain window focus (and try to reschedule the timer), the app crashes with this error:

java.lang.IllegalStateException: Task already scheduled or cancelled    at java.util.Timer.sched(Timer.java:401)    at java.util.Timer.scheduleAtFixedRate(Timer.java:328)    at com.package.ErrorListActivity.start(ErrorListActivity.java:198)    at com.package.ErrorListActivity.onWindowFocusChanged(ErrorListActivity.java:189)    at android.support.v7.view.WindowCallbackWrapper.onWindowFocusChanged(WindowCallbackWrapper.java:128)    at android.support.v7.view.WindowCallbackWrapper.onWindowFocusChanged(WindowCallbackWrapper.java:128)    at com.android.internal.policy.DecorView.onWindowFocusChanged(DecorView.java:1414)    at android.view.View.dispatchWindowFocusChanged(View.java:10173)    at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:1192)    at android.view.ViewRootImpl$ViewRootHandler.handleMessage(ViewRootImpl.java:3757)    at android.os.Handler.dispatchMessage(Handler.java:102)    at android.os.Looper.loop(Looper.java:154)    at android.app.ActivityThread.main(ActivityThread.java:6120)    at java.lang.reflect.Method.invoke(Native Method)    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)

I have no clue how to fix this, and I have looked through the other similar questions but nothing has worked yet. Any ideas?

_{Incidentally, this is not a duplicate of this question. It is the same issue, but I call cancel and it returns true (meaning it should work, but it doesn't).}