Question

我想在Fragment中使用Spinner，但它在监听器上给我一个错误。我知道这里有一些类似的问题，但我无法弄清楚我的问题是什么。问题是什么？这是我的onCreateView：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.maps, container, false);

    // Gets the MapView from the XML layout and creates it
    mapView = (MapView) v.findViewById(R.id.mapview);
    mapView.onCreate(savedInstanceState);
    mapView.onResume();

    // Gets to GoogleMap from the MapView and does initialization stuff
    mapView.getMapAsync(this)   

    // get Spinner reference
    Spinner spinner = (Spinner) v.findViewById(R.id.spinner);

    // Spinner click listener
    spinner.setOnItemSelectedListener(this);                  **<======ERROR======**

    // Spinner Drop down elements
    List<String> buses = new ArrayList<>();
    buses.add("Összes megálló - válassz egy járatot");
    buses.add("26");
    buses.add("35");
    buses.add("37");
    buses.add("42");

    // Creating array adapter for spinner
    ArrayAdapter<String> dataAdapter = new ArrayAdapter<>(getActivity(), android.R.layout.simple_spinner_item, buses);

    // Drop down style will be listview with radio button
    dataAdapter.setDropDownViewResource(android.R.layout.select_dialog_singlechoice);

    // attaching data adapter to spinner
    spinner.setAdapter(dataAdapter);

    return v;
}
@Override
public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
    caseno = parent.getSelectedItemPosition();
    switch(caseno) {
        case 0: {

            //some code

            break;
        }
        case 1: {
                //some code

            break;
        }

    }
}

public void onNothingSelected(AdapterView<?> arg0) {
    Toast.makeText(getActivity(), "Nincs kiválasztott járat", Toast.LENGTH_LONG).show();
}

我的布局：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">

<com.google.android.gms.maps.MapView android:id="@+id/mapview"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_below="@id/line"/>

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="50dp"
    android:layout_margin="10dp"
    android:background="@drawable/shadow">

    <Spinner
        android:id="@+id/spinner"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingStart="8dp"/>

</RelativeLayout>

错误：

E/AndroidRuntime: FATAL EXCEPTION: main
              Process: com.koostamas.justtry, PID: 32434
              java.lang.NullPointerException
                  at com.koostamas.justtry.Map.onCreateView(Map.java:151)
                  at android.support.v4.app.Fragment.performCreateView(Fragment.java:2189)
                  at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1299)
                  at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1528)
                  at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1595)
                  at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:757)
                  at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2355)
                  at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2146)
                  at android.support.v4.app.FragmentManagerImpl.optimizeAndExecuteOps(FragmentManager.java:2098)
                  at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2008)
                  at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:710)
                  at android.os.Handler.handleCallback(Handler.java:733)
                  at android.os.Handler.dispatchMessage(Handler.java:95)
                  at android.os.Looper.loop(Looper.java:136)
                  at android.app.ActivityThread.main(ActivityThread.java:5146)
                  at java.lang.reflect.Method.invokeNative(Native Method)
                  at java.lang.reflect.Method.invoke(Method.java:515)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
                  at dalvik.system.NativeStart.main(Native Method)

Answer 1

在Fragment中你需要实现这个接口 AdapterView.OnItemClickListener或者您可以试试这个

spinner.setOnItemSelectedListener(new OnItemSelectedListener() {

            @Override
            public void onItemSelected(AdapterView<?> adapterView, View view,
                    int position, long id) {
                Object item = adapterView.getItemAtPosition(position);
                if (item != null) {
                    Toast.makeText(getContext(), item.toString(),
                            Toast.LENGTH_SHORT).show();
                }
                Toast.makeText(getContext(), "Selected",
                        Toast.LENGTH_SHORT).show();

            }

            @Override
            public void onNothingSelected(AdapterView<?> adapterView) {
                // TODO Auto-generated method stub

            }
        });

Answer 2

您需要实现您的微调器OnItemSelectedListener：

spinner.setOnItemSelectedListener(new OnItemSelectedListener() {
    @Override   
    public void onItemSelected(AdapterView<?> parent, View view, int pos,long id) 
    {
        //Called when item is selected, use position of item to find it from list of items
    }

    @Override
    public void onNothingSelected(AdapterView<?> arg0)
    {
        //Called when no item is selected
    }
});

Answer 3

在片段中使用微调器时，

奖金：自定义微调器样式

 private Spinner SortBySpinner;
 private SpinnerAdapter SortBy_adapterz;
 public static final String[] SortAdapterz = {"",

        " newest "," top brains "," most seen ",""
};

XML

               <Spinner
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:id="@+id/TimeSpinner"/>

自定义您的适配器

        oSpinner = (Spinner) v.findViewById(R.id.TimeSpinner);
        oAdapter = new ArrayAdapter<String>(getActivity(),R.layout.cutomized_spinner, SortAdapterz);

cutomized_spinner.xml

<TextView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="15sp"
android:layout_weight="1"
android:gravity="center"
android:text=" egypt "
android:fontFamily="sans-serif-smallcaps"
android:textColor="#464646"
android:textColorHint="#ffcc00"
android:padding="5dip"
android:layout_centerInParent="true"
/>

最后

            oSpinner.setAdapter(oAdapter);

如何确定价值？

  oSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            cck =  parent.getItemAtPosition(position).toString();

             System.out.println("Value was --->" + cck );

        }
        @Override
        public void onNothingSelected(AdapterView<?> parent) {
        }
    });

结果

Fragment中的微调器setOnItemSelectedListener

3 个答案: