java - 如何从 fragment 中的另一个布局访问按钮

Question

我正在尝试从 fragment 中的另一个布局获取一个按钮。这个 fragment 有另一个膨胀另一个布局。我得到一个 java.lang.NullPointerException。如何解决这个问题？

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    final View view = inflater.inflate(R.layout.add_to_cart_display, container, false);


    myAdapter=new MyAdapter(getActivity());

    Button remove=(Button) view.findViewById(R.id.remove_cart_items);
    RecyclerView recyclerView=(RecyclerView)view.findViewById(R.id.recyclerView);
    recyclerView.setHasFixedSize(true);
    ch=new CartHelper(getActivity());
    recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
    rc=new RCadapter(getDataset());
    recyclerView.setAdapter(rc);



    return view;


}

从上面的 pgm 中，删除按钮不在 add_cart_display xml 文件中。它位于另一个布局文件中。我在这里访问这个按钮。它给出了以下错误。

10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: FATAL EXCEPTION: main 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: Process: com.infizoom.infishopping, PID: 13886 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: java.lang.NullPointerException 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at com.infizoom.infishopping.add_cart_class.onStart(add_cart_class.java:75) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at android.app.Fragment.performStart(Fragment.java:1724) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:918) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at android.app.BackStackRecord.run(BackStackRecord.java:698) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at android.app.FragmentManagerImpl$1.run(FragmentManager.java:443) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at android.os.Handler.handleCallback(Handler.java:808) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at android.os.Handler.dispatchMessage(Handler.java:103) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at android.os.Looper.loop(Looper.java:193) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:5341) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at java.lang.reflect.Method.invokeNative(Native Method) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at java.lang.reflect.Method.invoke(Method.java:515) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:825) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:641) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at dalvik.system.NativeStart.main(Native Method)

add_to_cart_display.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_marginTop="@dimen/abc_action_bar_default_height_material"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/recyclerView"
    android:layout_width="fill_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    />

删除 CardView 中的按钮

Answer 1

   final View view = inflater.inflate(R.layout.add_to_cart_display, container, false);
   Button remove=(Button) view.findViewById(R.id.remove_cart_items);

您正在 add_to_cart_display 中寻找 ID 为 remove_cart_items 的按钮。但在布局中可能没有 ID 为 remove_cart_items 的按钮。这就是你得到 null 的方式