如何使用另一个类中定义的参数？

Question

我在定义为

的主要活动中使用导航抽屉

private DrawerLayout drawerlayout;

我在主要活动中使用它来打开和关闭我的导航片段，但是导航片段类中有 3 个特定按钮，我想在其中使用导航片段功能drawerlayout.closedrawer(r.id.drawer) 但是每次我在导航片段类中再次定义它并尝试将其添加到这些按钮的 onclick 中时，单击按钮时，应用程序会因空指针异常而崩溃。我该怎么做？

谢谢！ 这是我的应用程序中的示例代码： 公共类 navfragment 扩展片段 {

public interface OnCloseDrawerListener
      {
         void onCloseDrawer();
      }
    @Override
    public void onClick(final View v) {
        switch (v.getId()) {
            case R.id.button_logout:

                final DialogFragment dialog = new LogoutCancelSignoutDialogFragment(mLogoutListener);
                dialog.show(getActivity().getSupportFragmentManager(), AbsBaseaActivity.TAG_LOGOUT_DIALOG);
                BangoHelper.eventLogout();
                ((OnCloseDrawerListener)getActivity()).onCloseDrawer();
                break;
}
}

在我的课堂 MainActivity：

public class MainActivity extends AbsBaseaActivity implements OnBackStackChangedListener {
    private DrawerLayout drawerLayout;
protected void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_activity);
        //----------Code for Navigation Drawer setup
        // 2. App Icon 
        drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        // 2.1 create ActionBarDrawerToggle
                 actionBarDrawerToggle = new ActionBarDrawerToggle(this, drawerLayout,
                            R.drawable.arrow_up, R.string.drawer_open, R.string.drawer_close){

                        /** Called when a drawer has settled in a completely closed state. */
                        public void onDrawerClosed(View view) {
                           // getActionBar().setTitle(NavigationPanelFragment.activeFragmentTitle);
                           // invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
                        }

                        /** Called when a drawer has settled in a completely open state. */
                        public void onDrawerOpened(View drawerView) {
                         //   getActionBar().setTitle(NavigationPanelFragment.activeFragmentTitle);
                          //  invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
                        }
                    };


                // 2.2 Set actionBarDrawerToggle as the DrawerListener
                drawerLayout.setDrawerListener(actionBarDrawerToggle);

}
public  void onCloseDrawer()
       {
         drawerLayout.closeDrawer(R.id.drawer);
       }
    Even after modifying the code as per the given suggestion it crashes when I click on the button defined onclick for the fragment class, any clue?

Answer 1

您可以将片段中的回调添加到您的活动以关闭抽屉..

例如

public class YourFragment extends Fragment
{

  public void onClick(View v)
  {
    ((OnCloseDrawerListener)getActivity()).onCloseDrawer();
  }

  public interface OnCloseDrawerListener
  {
     void onCloseDrawer();
  }
}

然后在你的活动中你需要实现这个接口

public class MyActivity extends Activity implements OnCloseDrawerListener
{
   @Override
   public  void onCloseDrawer()
   {
        // add whatever code you need to close the drawer
   }

}

显然，您可以将此接口命名为更准确地代表您的需求的名称，并将您需要的任何参数传递给它