java - 点击底部菜单时如何打开侧面抽屉导航？

Question

这就是我想要实现的目标

我想要设置菜单点击将出现侧面抽屉导航

HomeActivity.java

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

    mMainFrame  =   (FrameLayout) findViewById(R.id.main_frame);
    mMainNav    =   (BottomNavigationView) findViewById(R.id.main_nav);

    homeFragment         =   new HomeFragment();
    analyticsFragment    =   new AnalyticsFragment();
    paymentFragment      =   new PaymentFragment();
    settingsFragment     =   new SettingsFragment();

    drawerLayout = findViewById(R.id.drawerlayout);

    FragmentManager fragmentManager = getSupportFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    fragmentTransaction.replace(R.id.main_frame,new HomeFragment()).commit();

    mMainNav.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {

            switch (menuItem.getItemId()) {
                case R.id.navigation_home:
                    setFragment(homeFragment);
                    return true;

                case R.id.navigation_analytics:
                    setFragment(analyticsFragment);
                    return true;

                case R.id.navigation_payment:
                    setFragment(paymentFragment);
                    return true;

                case R.id.navigation_settings:
                    drawerLayout.openDrawer(GravityCompat.END);
                    return true;

                default:
                    return false;
            }
        }
    });

    BottomNavigationView navView = findViewById(R.id.main_nav);
    navView.setItemIconTintList(null);

这是我得到的错误

Unable to start activity ComponentInfo{com.example.ewallet/com.example.ewallet.HomeActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.app.Activity.findViewById(int)' on a null object reference

编辑:我尝试在此处粘贴一些代码，但 StackOverflow 错误代码太多，无法发布

Answer 1

您没有正确绑定(bind)对象并导致 NullPointerException。

请粘贴您的代码，我们可以为您提供帮助。

我看到了一个奇怪的部分，但也许这个错误仍然会出现，你可能需要粘贴你的layout.xml

mMainNav    =   (BottomNavigationView) findViewById(R.id.main_nav);


BottomNavigationView navView = findViewById(R.id.main_nav);
navView.setItemIconTintList(null);

应修改为

mMainNav.setItemIconTintList(null);

您可以使用

检查它是否为空

getActivity().findViewById(R.id.XXX)

更新

    drawerLayout = (DrawerLayout)getView().findViewById(R.id.drawerlayout);

    case R.id.navigation_settings:
                drawerLayout.openDrawer(drawerLayout);
                return true;