Question

我有三个片段FragA，FragB，FragC。我通过捆绑＆＃34;折扣＆＃34;从FragA到FragB。然后从FragB发送两个参数＆＃34;折扣＆＃34;和＆＃34;地址＆＃34;去FragC。直到这里一切正常。

然后我必须从FragC回到FragB。我用了一个按钮＆＃39; backButton＆＃39;以此目的。但是当按钮点击时，我的应用程序因NPE而崩溃。我已经从FragC向FragB发送了参数，但是在FragB中没有任何参数。

附上我在下面使用的代码..

Fragement A

    class FragA extends Fragment
{
    public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
    {
        context = getActivity();
        View v = inflater.inflate(R.layout.layout_fragfirst, container, false);

        nextButton = (Button) v.findViewById(R.id.buttonnext);

        nextButton.setOnClickListener(new View.OnClickListener() 
        {

            @Override
            public void onClick(View v) 
            {
                fr = new FragB();
                Bundle bundle=new Bundle();
                    bundle.putString("discount", discount);
                    fr.setArguments(bundle);
                FragmentManager fm = getFragmentManager();
                FragmentTransaction fragmentTransaction = fm.beginTransaction();
                fragmentTransaction.replace(R.id.fragment_place, fr);
                fragmentTransaction.addToBackStack(null);
                fragmentTransaction.commit();
            }
        });
    }
}

Fragement B

    class FragB extends Fragment
{
    Context context;
    String discount = "";
    public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
    {
        context = getActivity();
        View v = inflater.inflate(R.layout.layout_fragsec, container, false);
        String addressid = "something";
        nextButton = (Button) v.findViewById(R.id.buttonnext);

        Bundle b = getArguments();
        discount = b.getString("discount");

        nextButton.setOnClickListener(new View.OnClickListener() 
        {

            @Override
            public void onClick(View v) 
            {
                fr = new FragC();
                Bundle bundle=new Bundle();
                    bundle.putString("discount", discount);
                    bundle.putString("address", addressid);
                    fr.setArguments(bundle);
                FragmentManager fm = getFragmentManager();
                FragmentTransaction fragmentTransaction = fm.beginTransaction();
                fragmentTransaction.replace(R.id.fragment_place, fr);
                fragmentTransaction.addToBackStack(null);
                fragmentTransaction.commit();
            }
        });
    }
}

Fragement C

   class FragC extends Fragment
{
    Context context;
    String discount = "",addressid="";
    public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
    {
        context = getActivity();
        View v = inflater.inflate(R.layout.layout_fragthird, container, false);
        backButton = (Button) v.findViewById(R.id.buttonnext);

        Bundle b = getArguments();
        discount = b.getString("discount");

//backButton to go to Fragment B(FragB)
        backButton.setOnClickListener(new View.OnClickListener() 
        {

            @Override
            public void onClick(View v) 
            {
                fr = new FragB();
                Bundle bundle=new Bundle();
                    bundle.putString("discount", discount);
                    fr.setArguments(bundle);
                FragmentManager fm = getFragmentManager();
                FragmentTransaction fragmentTransaction = fm.beginTransaction();
                fragmentTransaction.replace(R.id.fragment_place, fr);
                fragmentTransaction.addToBackStack(null);
                fragmentTransaction.commit();
            }
        });
    }
}

LogCat

java.lang.NullPointerException
           at com.abc.fragments.FragA.onCreateView(FragA.java:114)
           at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:829)
           at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1035)
           at android.app.BackStackRecord.run(BackStackRecord.java:635)
           at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1397)
           at android.app.FragmentManagerImpl$1.run(FragmentManager.java:426)
           at android.os.Handler.handleCallback(Handler.java:615)
           at android.os.Handler.dispatchMessage(Handler.java:92)
           at android.os.Looper.loop(Looper.java:137)
           at android.app.ActivityThread.main(ActivityThread.java:4745)
           at java.lang.reflect.Method.invokeNative(Native Method)
           at java.lang.reflect.Method.invoke(Method.java:511)
           at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
           at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
           at dalvik.system.NativeStart.main(Native Method)

请建议我一个解决方案......

Answer 1

问题可能是NullPointerException .... 当您在onCreateView中提取参数时，但是当您返回时，getArguments必须为您提供null，并且没有参数从FragC传递到FragB ...更好的是您在bundle周围进行null检查

Bundle b = getArguments();
if( b != null )
        discount = b.getString("discount");

当您按下后退按钮时，您正在恢复您的过去片段......但在您的代码中，您将进入Frag A＆gt; Frag B＆gt; Frag C＆gt; Frag B ....您正在以错误的方式实现它...只是不要将Frag B添加到片段堆栈

将参数传递给前一个片段时崩溃片段

1 个答案: