非法状态异常：任务已安排或取消

Question

我有一个片段，其中包含一个图像按钮，该按钮通过计时器和其他4个链接到其他片段的按钮定期更改图像。当我按下任何按钮时，它会跳转到该特定片段，但在按下后退按钮时，应用程序会崩溃。我试过了timer.cancel，但它没有用。这是片段的代码：

public class Main2Activity extends Fragment {
View v;
Timer timer;
ImageView iv;
int i=0;
Integer[] imagechange = {

        R.drawable.capture1,R.drawable.capture2,R.drawable.capture,R.drawable.capture

};
String[] linkstop = new String[]{"http://www.webmd.com/","http://www.drugs.com/","http://www.cancer.gov/","http://www.nlm.nih.gov/medlineplus/"};
ListView lv;
TimerTask updateTask = new TimerTask() {

    @Override
    public void run() {

        getActivity().runOnUiThread(new Runnable() {

            @Override
            public void run() { // TODO Auto-generated method stub
                iv.setImageResource(imagechange[i]);
                i++;
                if (i > 3) {
                    i = 0;
                }
            }

        });
    }
};



@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
v=inflater.inflate(R.layout.activity_main2,container,false);
    //lv=(ListView)v.findViewById(R.id.list);
    iv=(ImageView)v.findViewById(R.id.imge);
     timer = new Timer();
    timer.scheduleAtFixedRate(updateTask,0,2000);
    Button btn=(Button)v.findViewById(R.id.a);
    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

          // timer.cancel();
          // timer=null;

            HomeFragment q=new HomeFragment();
            FragmentManager fm=getFragmentManager();
            FragmentTransaction ft=fm.beginTransaction();
            ft.replace(R.id.container_body,q);
                 ft.addToBackStack(null);
            ft.commit();


        }
    });
    Button btn1=(Button)v.findViewById(R.id.b);
    btn1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

          //  timer.cancel();
           // timer=null;

            QueriesFragment q=new QueriesFragment();
            FragmentManager fm=getFragmentManager();
            FragmentTransaction ft=fm.beginTransaction();
            ft.replace(R.id.container_body,q);
            ft.addToBackStack(null);
            ft.commit();


        }
    });
    Button btn2=(Button)v.findViewById(R.id.c);
    btn2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
          //  timer.cancel();
           // timer=null;


            EquipmentsFragment q=new EquipmentsFragment();
            FragmentManager fm=getFragmentManager();
            FragmentTransaction ft=fm.beginTransaction();
            ft.replace(R.id.container_body,q);
            ft.addToBackStack(null);
            ft.commit();


        }
    });
    Button btn3=(Button)v.findViewById(R.id.d);
    btn3.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

           // timer.cancel();
            //timer=null;

            PostQueryFragment q=new PostQueryFragment();
            FragmentManager fm=getFragmentManager();
            FragmentTransaction ft=fm.beginTransaction();
            ft.replace(R.id.container_body,q);
            ft.addToBackStack(null);
            ft.commit();


        }
    });
    iv.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            try {
                Intent myIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(linkstop[i]));
                startActivity(myIntent);
            } catch (ActivityNotFoundException e) {
                Toast.makeText(getActivity(), "No application can handle this request."
                        + " Please install a webbrowser", Toast.LENGTH_LONG).show();
                e.printStackTrace();
            }
        }
    });


return v;

}


}

以下是日志文件详细信息：

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.example.aakar.agstart.Main2Activity.onCreateView(Main2Activity.java:82)
                                                   at android.support.v4.app.Fragment.performCreateView(Fragment.java:1789)
                                                   at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:955)
                                                   at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1138)
                                                   at android.support.v4.app.BackStackRecord.popFromBackStack(BackStackRecord.java:960)
                                                   at android.support.v4.app.FragmentManagerImpl.popBackStackState(FragmentManager.java:1553)
                                                   at android.support.v4.app.FragmentManagerImpl.popBackStackImmediate(FragmentManager.java:506)
                                                   at android.support.v4.app.FragmentActivity.onBackPressed(FragmentActivity.java:178)
                                                   at android.app.Activity.onKeyUp(Activity.java:2725)
                                                   at android.view.KeyEvent.dispatch(KeyEvent.java:2712)
                                                   at android.app.Activity.dispatchKeyEvent(Activity.java:3029)
                                                   at android.support.v7.internal.view.WindowCallbackWrapper.dispatchKeyEvent(WindowCallbackWrapper.java:49)
                                                   at android.support.v7.app.AppCompatDelegateImplBase$AppCompatWindowCallbackBase.dispatchKeyEvent(AppCompatDelegateImplBase.java:258)
                                                   at android.support.v7.internal.view.WindowCallbackWrapper.dispatchKeyEvent(WindowCallbackWrapper.java:49)
                                                   at com.android.internal.policy.DecorView.dispatchKeyEvent(DecorView.java:320)
                                                   at android.view.ViewRootImpl$ViewPostImeInputStage.processKeyEvent(ViewRootImpl.java:4331)
                                                   at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4302)
                                                   at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3853)
                                                   at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3906)
                                                   at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3872)
                                                   at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3999)
                                                   at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3880)
                                                   at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4056)
                                                   at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3853)
                                                   at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3906)
                                                   at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3872)
                                                   at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3880)
                                                   at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3853)
                                                   at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3906)
                                                   at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3872)
                                                   at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4032)
                                                   at android.view.ViewRootImpl$ImeInputStage.onFinishedInputEvent(ViewRootImpl.java:4193)
                                                   at android.view.inputmethod.InputMethodManager$PendingEvent.run(InputMethodManager.java:2400)
                                                   at android.view.inputmethod.InputMethodManager.invokeFinishedInputEventCallback(InputMethodManager.java:1964)
                                                   at android.view.inputmethod.InputMethodManager.finishedInputEvent(InputMethodManager.java:1955)
                                                   at android.view.inputmethod.InputMethodManager$ImeInputEventSender.onInputEventFinished(InputMethodManager.java:2377)
                                                   at android.view.InputEventSender.dispatchInputEventFinished(InputEventSender.java:141)
                                                   at android.os.MessageQueue.nativePollOnce(Native Method)
                                                   at android.os.MessageQueue.next(MessageQueue.java:323)
                                                   at android.os.Looper.loop(Looper.java:136)
                                                   at android.app.ActivityThread.main(ActivityThread.java:6121)
                                                   at java.lang.reflect.Method.invoke(Native Method)
                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:889)
                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:779)

Answer 1

您无法重复已为计时器安排的时间任务。像这样更改你的代码，

timer = new Timer();
timer.scheduleAtFixedRate(createTimerTask(), 0, 100);

并创建这样的函数，

private TimerTask createTimerTask() {
        return new TimerTask() {
            @Override
            public void run() {
                getActivity().runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        iv.setImageResource(imagechange[i]);
                        i++;
                        if (i > 3) {
                            i = 0;
                        }
                    }

                });
            }
        };
    }