Android在使用后退按钮时更改标题

我的活动：

TextView title;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    Overview overview = new Overview();

    setContentView(R.layout.activity_second);
    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.mycontainer, overview)
                .commit();
    }
    Toolbar toolbar = (Toolbar) findViewById(R.id.my_toolbar);
    //Some more code

    title = (TextView) toolbar.findViewById(R.id.screentitle);
    title.setText("Overzicht");


}



@Override
public boolean onNavigationItemSelected(MenuItem item) {

    switch(item.getItemId()){
        case R.id.nav_menu_overview:
            title.setText("Overzicht");
            getSupportFragmentManager().beginTransaction().replace(R.id.mycontainer, new Overview()).addToBackStack(null)
                    .commit();

            break;
        case R.id.nav_menu_favourites:
            title.setText("Favorieten");
            getSupportFragmentManager().beginTransaction().replace(R.id.mycontainer, new Favourites()).addToBackStack(null)
                    .commit();

            break;

        case R.id.nav_menu_profile:
            title.setText("Profiel");
            getSupportFragmentManager().beginTransaction().replace(R.id.mycontainer, new Profile()).addToBackStack(null)
                    .commit();
            break;
    }

@Override
protected void onResume() {
    Toolbar toolbar = (Toolbar) findViewById(R.id.my_toolbar);
    //Some more code 

    title = (TextView) toolbar.findViewById(R.id.screentitle);
    title.setText("Overzicht");

}

---

所以，现在，如果我使用菜单来更改片段，标题就会更改。但是，如果我使用安卓backbutton，标题不会被更改回来。每当使用“后退”按钮时，如何将标题更改回原来的位置？

将活动标题更改代码放入活动的

onResume（）

：

TextView title;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    Overview overview = new Overview();

    setContentView(R.layout.activity_second);
    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.mycontainer, overview)
                .commit();
    }
    Toolbar toolbar = (Toolbar) findViewById(R.id.my_toolbar);
    //Some more code

    title = (TextView) toolbar.findViewById(R.id.screentitle);
    title.setText("Overzicht");


}



@Override
public boolean onNavigationItemSelected(MenuItem item) {

    switch(item.getItemId()){
        case R.id.nav_menu_overview:
            title.setText("Overzicht");
            getSupportFragmentManager().beginTransaction().replace(R.id.mycontainer, new Overview()).addToBackStack(null)
                    .commit();

            break;
        case R.id.nav_menu_favourites:
            title.setText("Favorieten");
            getSupportFragmentManager().beginTransaction().replace(R.id.mycontainer, new Favourites()).addToBackStack(null)
                    .commit();

            break;

        case R.id.nav_menu_profile:
            title.setText("Profiel");
            getSupportFragmentManager().beginTransaction().replace(R.id.mycontainer, new Profile()).addToBackStack(null)
                    .commit();
            break;
    }

@Override
protected void onResume() {
    Toolbar toolbar = (Toolbar) findViewById(R.id.my_toolbar);
    //Some more code 

    title = (TextView) toolbar.findViewById(R.id.screentitle);
    title.setText("Overzicht");

}

---

您可以简单地覆盖活动的

onBackPressed

方法并处理场景

更好的方法是，您可以在片段

onViewCreated

中设置标题，这样无论哪个片段位于顶部，都会自动设置要设置的平铺

在片段内设置标题

Toolbar toolbar= (Toolbar) getActivity().findViewById(R.id.toolbar);
toolbar.setTitle("What ever you want to set");

---

另外，不要在

onNavigationItemSelected

its中设置标题，而不要设置标题。

您是否只有一个活动和3个片段？请参阅此链接