将背压上的底部导航项状态从活动更改为主页片段

Question

你好伟大的社区我有一个应用程序，我在其中使用带有 4 个片段的底部导航。要移动到最后一个片段，用户必须登录，因此当新用户打开应用程序并点击第 4 项时，会打开登录活动。 问题是当我从登录活动中退出时，它会将我移动到主页片段 1，这没问题，但底部导航项的状态不会改变片段 4 仍然突出显示。那么如何管理它，当我从登录活动返回时，应该突出显示主片段项目。

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这是我的底部导航主要活动

public class Bottom_Nav extends AppCompatActivity implements BottomNavigationView.OnNavigationItemSelectedListener {

SparseArray<Fragment> myFragments;
String user_type;

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

    SharedPreferences sharedPreferences = getSharedPreferences("DataStore", Context.MODE_PRIVATE);
    user_type = sharedPreferences.getString("user_type", "");


    BottomNavigationView bottomNavigationView = (BottomNavigationView) findViewById(R.id.navigation);
    Nav_Helper.disableShiftMode(bottomNavigationView);

    //make array to avoid re creating of fragments
    myFragments = new SparseArray<Fragment>();

    //loading the default fragment
    loadFragment(new HomeFragment());

    //getting bottom navigation view and attaching the listener
    bottomNavigationView.setOnNavigationItemSelectedListener(this);


}

private void loadFragment(Fragment fragment) {

    //switching fragment
    FragmentTransaction fragmentTransaction =
            getSupportFragmentManager().beginTransaction();
    fragmentTransaction.replace(R.id.content, fragment);
    fragmentTransaction.commit();

}


@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
    Fragment fragment = null;

    int id = item.getItemId();

    if (id == R.id.navigation_home) {

            fragment = new HomeFragment();
            myFragments.put(1, fragment);


        loadFragment(fragment);

    } else if (id == R.id.navigation_use) {

        getFragmentManager().popBackStack();



                switch (user_type) {
                    case "detailer":

                        fragment = new Detailer_Zone();
                        myFragments.put(4, fragment);
                        loadFragment(fragment);
                        break;
                    case "customer":

                        fragment = new Customer_Zone();
                        myFragments.put(4, fragment);
                        loadFragment(fragment);
                        break;
                    case "empty":

                        Intent intent = new Intent(this, Login_Activity.class);
                        startActivity(intent);
                        break;
                }

            }


    else if (id == R.id.navigation_search) {
        // get cached instance of the fragment
        fragment = myFragments.get(2);

        // if fragment doesn't exist in myFragments, create one and add to it
        if (fragment == null) {
            fragment = new SearchFragment();
            myFragments.put(2, fragment);
        }

        loadFragment(fragment);

    } else if (id == R.id.navigation_map) {
        // get cached instance of the fragment
        fragment = myFragments.get(3);

        // if fragment doesn't exist in myFragments, create one and add to it
        if (fragment == null) {
            fragment = new MapsActivity();
            myFragments.put(3, fragment);
        }

        loadFragment(fragment);

    }
    return true;
}

Answer 1

登录案例：

 case "empty": 
        Intent intent = new Intent(this, Login_Activity.class);
        startActivityForResult(intent , 101);
        break; 

登录活动：

当用户点击后退按钮时，执行下面的代码。

setResult(RESULT_CANCELED);
finish(); 

在Bottom_Nav活动中处理案例：

  // This method is called when the second activity finishes 
@Override 
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    // check that it is the SecondActivity with an OK result 
    if (requestCode == 101) {
        if (resultCode == RESULT_CANCELED) {

           onNavigationItemSelected(menuItem)
        } 
    } 
} 

Answer 2

试试这个解决方法。用这个替换你的case "empty":：

case "empty":
    bottomNavigationView.setSelectedItemId(R.id.navigation_home);
    Intent intent = new Intent(this, Login_Activity.class);
    startActivity(intent);
    break;

告诉我这是否有效。