android - item.getActionView() 返回 null

Question

<item
    android:id="@+id/menu_spinner"
    android:actionViewClass="android.widget.Spinner"
    android:showAsAction="always"
    android:visible="true"  />

  public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
      MenuItem mSpinnerItem = menu.findItem(R.id.menu_spinner);mSpinnerItem.setVisible(true);
      aSpinner = (Spinner) MenuItemCompat.getActionView(mSpinnerItem);
  }

通过使用这个...我将菜单项微调器项放入普通视图微调器中...设置适配器我确实喜欢这个...但是在这样做时微调器项正在获得空引用...请帮助我如何摆脱这个...

Answer 1

这就是你应该如何填充微调器。

http://developer.android.com/guide/topics/ui/controls/spinner.html

但这就是您应该通过代码执行此操作的方式。

Spinner spinner = (Spinner) findViewById(R.id.spinner);
// Create an ArrayAdapter using the string array and a   default spinner layout
ArrayAdapter<CharSequence> adapter =      ArrayAdapter.createFromResource(this,
    R.array.planets_array,       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);

编辑：这是 ActionBar 微调器的代码。

    import android.app.ActionBar;
    import android.app.Fragment;
    import android.os.Bundle;
    import android.support.v4.app.FragmentActivity;
    import android.view.Gravity;
    import android.view.LayoutInflater;
    import android.view.Menu;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.ArrayAdapter;
    import android.widget.TextView;

    public class MainActivity extends FragmentActivity implements
    ActionBar.OnNavigationListener {


    /**
   * The serialization (saved instance state) Bundle key representing the
   * current dropdown position.
   */

  private static final String STATE_SELECTED_NAVIGATION_ITEM = "selected_navigation_item";

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

    // Set up the action bar to show a dropdown list.
    final ActionBar actionBar = getActionBar();
    actionBar.setDisplayShowTitleEnabled(false);
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_LIST);

    final String[] dropdownValues = getResources().getStringArray(R.array.dropdown);

    // Specify a SpinnerAdapter to populate the dropdown list.
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(actionBar.getThemedContext(),
        android.R.layout.simple_spinner_item, android.R.id.text1,
        dropdownValues);

    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

    // Set up the dropdown list navigation in the action bar.
    actionBar.setListNavigationCallbacks(adapter, this);

    // use getActionBar().getThemedContext() to ensure
    // that the text color is always appropriate for the action bar
    // background rather than the activity background.
  }

  @Override
  public void onRestoreInstanceState(Bundle savedInstanceState) {
    // Restore the previously serialized current dropdown position.
    if (savedInstanceState.containsKey(STATE_SELECTED_NAVIGATION_ITEM)) {
      getActionBar().setSelectedNavigationItem(savedInstanceState.getInt(STATE_SELECTED_NAVIGATION_ITEM));
    }
  }

  @Override
  public void onSaveInstanceState(Bundle outState) {
    // Serialize the current dropdown position.
    outState.putInt(STATE_SELECTED_NAVIGATION_ITEM, getActionBar()
        .getSelectedNavigationIndex());
  }

  @Override
  public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
  }

  @Override
  public boolean onNavigationItemSelected(int position, long id) {
    // When the given dropdown item is selected, show its contents in the
    // container view.
    Fragment fragment = new DummySectionFragment();
    Bundle args = new Bundle();
    args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, position + 1);
    fragment.setArguments(args);
    getFragmentManager().beginTransaction()
        .replace(R.id.container, fragment).commit();
    return true;
  }


/**
   * A dummy fragment
   */

  public static class DummySectionFragment extends Fragment {

    public static final String ARG_SECTION_NUMBER = "placeholder_text";

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
      TextView textView = new TextView(getActivity());
      textView.setGravity(Gravity.CENTER);
      textView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
      return textView;
    }
  }

}