Question

我正在使用导航抽屉布局中的片段。每当在frame_container中看到任何其他片段时，我想按下后退按钮返回HomeFragment。如果主片段已经可见，我想完成MainActivity（navigation_drawer_activity）。帮我修正主要活动中的OnBackPressed代码。

 @Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    }

    Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.fragment_home);
    if(fragment!=null && fragment.isVisible()){
        clearBackStack();
        finish();
    }else {
        clearBackStack();
        getSupportFragmentManager().beginTransaction().replace(R.id.frame_container,new HomeFragment()).commit();
    }

}

Answer 1

这是解决方案。我从frame_container找到了片段。然后签入if语句。 if(fragment!=null && fragment instanceof HomeFragment && fragment.isVisible())。这返回home_fragment。谢谢你的回答。

  @Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    }

    Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.frame_container);
    if(fragment!=null && fragment instanceof HomeFragment && fragment.isVisible()){
        clearBackStack();
        finish();
    }else {
        clearBackStack();
        getSupportFragmentManager().beginTransaction().replace(R.id.frame_container,new HomeFragment()).commit();
    }

}

Answer 2

试试这个

 @Override
    public void onBackPressed() {
        FragmentManager fm = getSupportFragmentManager();
        if (drawerLayout.isDrawerOpen(GravityCompat.START)) {
            drawerLayout.closeDrawer(GravityCompat.START);
        } else if (fm.getBackStackEntryCount() > 0) {
            Log.i("MainActivity", "popping backstack");
            getSupportFragmentManager().popBackStackImmediate();
        } else {
            Log.i("MainActivity", "nothing on backstack, calling super");
            super.onBackPressed();
        }
    }

如何在onBackPressed中实现findFragmentById来查找HomeFragment

2 个答案: