当代码在MainActivity中工作，但您希望它在片段中时，将代码放在哪里

Question

我能够编写一个简单的计时器，通过按钮启动和重置时间。我可以在MainActivity中编写它，但现在我只希望它出现在一个特定的片段上。我有3个导航片段。主页、历史和学习。

目前，我的计时器显示在每个选项卡上。

以下是MainActivity 中的内容

public class MainActivity extends AppCompatActivity {
private Chronometer chronometer;
private boolean running;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
BottomNavigationView navView = findViewById(R.id.nav_view);
AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(
R.id.navigation_home, R.id.navigation_dashboard, R.id.navigation_notifications)
.build();
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);
NavigationUI.setupWithNavController(navView, navController);

chronometer = findViewById(R.id.chronometer);
}
public void startChronometer(View v) {
if(!running) {
chronometer.setBase(SystemClock.elapsedRealtime());
chronometer.start();
running = true;
((TextView)findViewById(R.id.startbutton)).setText("End");
} else {
if(running) {
chronometer.setBase(SystemClock.elapsedRealtime());
chronometer.stop();
running = false;
((TextView) findViewById(R.id.startbutton)).setText("Start");
}
}
} 
}

这是空的片段代码

public class HomeFragment extends Fragment {
Chronometer chronometer;
public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
HomeViewModel homeViewModel = ViewModelProviders.of(this).get(HomeViewModel.class);
View root = inflater.inflate(R.layout.fragment_home, container, false);
final TextView textView = root.findViewById(R.id.text_home);
homeViewModel.getText().observe(getViewLifecycleOwner(), new Observer<String>() {
@Override
public void onChanged(@Nullable String s) {
textView.setText(s);
}
});
return root;
}
}

感谢您的帮助和花时间阅读本文。

Answer 1

您可以将代码放入OnViewCreated函数中。或者简单地使用名为"root"的视图。为了更好地理解，我将名称更改为viewRoot。

当然，您需要将布局放在片段中，而不是放在活动中。

public class HomeFragment extends Fragment {
Chronometer chronometer;
public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
HomeViewModel homeViewModel = ViewModelProviders.of(this).get(HomeViewModel.class);
View viewRoot = inflater.inflate(R.layout.fragment_home, container, false);

final TextView textView = viewRoot.findViewById(R.id.text_home);
homeViewModel.getText().observe(getViewLifecycleOwner(), new Observer<String>() {
@Override
public void onChanged(@Nullable String s) {
textView.setText(s);
}
});

chronometer = viewRoot.findViewById(R.id.chronometer);
//If you want to start the timer    
startChronometer(viewRoot);
return root;
}
}

---

小心startChronometer，因为您调用findViewById。你知道这些按钮放在哪里吗？我添加了getView()，所以您可以从片段本身调用它们。

public void startChronometer(View v) {
if(!running) {
chronometer.setBase(SystemClock.elapsedRealtime());
chronometer.start();
running = true;
((TextView)getView().findViewById(R.id.startbutton)).setText("End");
} else {
if(running) {
chronometer.setBase(SystemClock.elapsedRealtime());
chronometer.stop();
running = false;
((TextView) getView().findViewById(R.id.startbutton)).setText("Start");
}
}
} 
}

希望我能帮忙。