public abstract class BaseActivity extends AppCompatActivity { static final String TAG = "tag"; public final String ACTION = "NIGHT_SWITCH"; protected BroadcastReceiver receiver; protected IntentFilter filter; @Override protected void onCreate(Bundle savedInstanceState){ super.onCreate(savedInstanceState); setNightMode(); filter = new IntentFilter(); filter.addAction(ACTION); receiver = new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { Log.d(TAG, "onReceive: needRefresh"); needRefresh(); } }; registerReceiver(receiver, filter); } public boolean isNightMode(){ SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getBaseContext()); return sharedPreferences.getBoolean("nightMode", false); } public void setNightMode(){ if(isNightMode()) { SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getBaseContext()); Log.d(TAG, "setNightMode: " + sharedPreferences.getBoolean("nightMode", false)); this.setTheme(R.style.NightTheme); } else setTheme(R.style.DayTheme); } @Override protected void onDestroy() { super.onDestroy(); unregisterReceiver(receiver); } protected abstract void needRefresh(); }把activity改成fragment

好的，将这段代码转换成 Fragment 代码大致的步骤如下：

1. 创建一个新的 BaseFragment 类，继承自 Fragment。

2. 将原来在 BaseActivity 类中的代码复制到新的 BaseFragment 类中。

3. 在 BaseFragment 类中，将 onCreate() 方法改为 onActivityCreated() 方法，并将方法参数改为 savedInstanceState 和 View 类型的布局视图对象。

4. 在 onActivityCreated() 方法中，调用 setNightMode() 方法，用于设置当前主题。

5. 在 BaseFragment 类中，将 isNightMode() 方法中的 getBaseContext() 方法替换为 getContext() 方法。

6. 将原来在 BaseActivity 类中的 needRefresh() 抽象方法添加到 BaseFragment 类中，并实现该方法。

7. 在原本的 Activity 中找到容器布局，改为使用 FragmentTransaction 将新的 BaseFragment 实例添加到容器布局中。

下面是将 BaseActivity 转换为 BaseFragment 的代码示例：

public abstract class BaseFragment extends Fragment {
    static final String TAG = "tag";
    public final String ACTION = "NIGHT_SWITCH";
    protected BroadcastReceiver receiver;
    protected IntentFilter filter;

    @Override
    public void onActivityCreated(Bundle savedInstanceState, View view) {
        super.onActivityCreated(savedInstanceState, view);
        setNightMode();

        filter = new IntentFilter();
        filter.addAction(ACTION);

        receiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                Log.d(TAG, "onReceive: needRefresh");
                needRefresh();
            }
        };

        getContext().registerReceiver(receiver, filter);
    }

    public boolean isNightMode(){
        SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getContext());
        return sharedPreferences.getBoolean("nightMode", false);
    }

    public void setNightMode(){
        if(isNightMode()) {
            SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getContext());
            Log.d(TAG, "setNightMode: " + sharedPreferences.getBoolean("nightMode", false));
            getActivity().setTheme(R.style.NightTheme);
        }
        else getActivity().setTheme(R.style.DayTheme);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        getContext().unregisterReceiver(receiver);
    }

    protected abstract void needRefresh();
}

希望这个例子对您有所帮助。