如何从另一个活动中打开或启动片段？

Question

从Activity中包含的RecyclerView的适配器中，我试图在按下RecyclerView的元素时启动一个片段，这是我现在的代码：

@Override
public void onClick(View v) {
    Intent intent;

    int position = getAdapterPosition();

    SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
    String onoff = preferences.getString("it's", "");

    if (onoff.equalsIgnoreCase("on")) {
        if (position == 0) {

            CategoriesRecyclerView.fragSubreddit = "aww";

            intent = new Intent(context, MainFragment.class);
            context.startActivity(intent);
        }

        if (position == 1) {

            CategoriesRecyclerView.fragSubreddit = "food";

            intent = new Intent(context, MainFragment.class);
            context.startActivity(intent);
        }

        if (position == 2) {

            CategoriesRecyclerView.fragSubreddit = "funny";

            intent = new Intent(context, MainFragment.class);
            context.startActivity(intent);
        }

        if (position == 3) {

            CategoriesRecyclerView.fragSubreddit = "gaming";

            intent = new Intent(context, MainFragment.class);
            context.startActivity(intent);
        }

    } else if (onoff.equalsIgnoreCase("off")) {

        if (position == 0) {

            CategoriesRecyclerView.fragSubreddit = "gaming";
            intent = new Intent(context, MainFragment.class);
            context.startActivity(intent);
        }

        if (position == 1) {

            CategoriesRecyclerView.fragSubreddit = "funny";
            intent = new Intent(context, MainFragment.class);
            context.startActivity(intent);
        }

        if (position == 2) {

            CategoriesRecyclerView.fragSubreddit = "food";
            intent = new Intent(context, MainFragment.class);
            context.startActivity(intent);
        }

        if (position == 3) {

            CategoriesRecyclerView.fragSubreddit = "aww";
            intent = new Intent(context, MainFragment.class);
            context.startActivity(intent);
        }
    }
}

我测试了它是否启动了我创建的一些“测试活动”，所以我知道除了片段启动之外的所有功能都可以正常工作。

错误在这里：

intent = new Intent(context, MainFragment.class);
context.startActivity(intent);

我正在启动作为活动的Fragment，所以当我运行应用程序时，它崩溃了，并告诉我在清单中将MainFragment声明为活动。

如何从我的活动中启动该片段？

非常感谢。

Answer 1

您不能以开头Fragment，Intents因此我建议您使用的方法是：

Fragment mFragment = null;
mFragment = new MainFragment();
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().replace(R.id.frame_container, fragment).commit();

有关更多信息，请参见片段事务文档。