Android 中 Spinner 上的“NullPointErexception”

Question

我在创建微调器时发现错误。似乎微调器为 Null，但我不确定问题出在哪里。我在strings.xml 中创建了一个字符串数组。有什么我错过的吗？

代码：

public class NewWorkOrder extends ActionBarActivity {

    private Spinner spinner;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_new_work_order);

        this.spinner = (Spinner) findViewById(R.id.workTypeSpinner);
        // Create an ArrayAdapter using the string array and a default spinner layout
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                R.array.work_type, android.R.layout.simple_spinner_item);
        // Specify the layout to use when the list of choices appears
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        // Apply the adapter to the spinner
        spinner.setAdapter(adapter);

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();

        }   

    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.new_work_order, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_new_work_order,
                    container, false);
            return rootView;
        }
    }

}

LogCat

06-11 03:02:30.174: E/AndroidRuntime(1389): FATAL EXCEPTION: main
06-11 03:02:30.174: E/AndroidRuntime(1389): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.cosmic.workorder/com.cosmic.workorder.NewWorkOrder}: java.lang.IllegalArgumentException: No view found for id 0x7f05003c (com.cosmic.workorder:id/container) for fragment PlaceholderFragment{41735b50 #0 id=0x7f05003c}
06-11 03:02:30.174: E/AndroidRuntime(1389):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at android.os.Handler.dispatchMessage(Handler.java:99)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at android.os.Looper.loop(Looper.java:137)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at android.app.ActivityThread.main(ActivityThread.java:5103)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at java.lang.reflect.Method.invokeNative(Native Method)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at java.lang.reflect.Method.invoke(Method.java:525)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at dalvik.system.NativeStart.main(Native Method)
06-11 03:02:30.174: E/AndroidRuntime(1389): Caused by: java.lang.IllegalArgumentException: No view found for id 0x7f05003c (com.cosmic.workorder:id/container) for fragment PlaceholderFragment{41735b50 #0 id=0x7f05003c}
06-11 03:02:30.174: E/AndroidRuntime(1389):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:930)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1115)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1478)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:570)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at android.app.Activity.performStart(Activity.java:5143)
06-11 03:02:30.174: E/AndroidRuntime(1389):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
06-11 03:02:30.174: E/AndroidRuntime(1389):     ... 11 more

Answer 1

使用这个：（我已经测试过了）

ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                    android.R.layout.simple_spinner_item,array);
            // Specify the layout to use when the list of choices appears
            adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            // Apply the adapter to the spinner
            spinner.setAdapter(adapter);

Answer 2

改变

ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                R.array.work_type, android.R.layout.simple_spinner_item);

到

ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                 android.R.layout.simple_spinner_item, R.array.work_type);

适配器将数组作为最后一个参数，但您将它作为第二个参数传递。将其作为第三个参数传递。它应该可以工作

Answer 3

您的微调器可能位于片段布局中，而不是活动...所以将您的工作放在 onCreateView 中，如下所示：

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

    Spinner spinner = (Spinner) rootView.findViewById(R.id.workTypeSpinner);
    // Create an ArrayAdapter using the string array and a default spinner layout
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(), 
        android.R.layout.simple_spinner_item, R.array.work_type);
    // Specify the layout to use when the list of choices appears
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    // Apply the adapter to the spinner
    spinner.setAdapter(adapter);

    return rootView;
}