java 如何从另一个 Activity 打开或启动 Fragment？

How to open or launch a Fragment from another Activity?

提问by Sebastian Delgado

from the adapter of a RecyclerView which is contained in an Activity, i'm trying to launch a fragment when an element of the RecyclerView is pressed, this is my code right now :

从包含在 Activity 中的 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);
        }
    }
}

I Tested it launching some "testing activities" that i created, so i know that everything but the fragment launching works fine.

我测试了它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内容都可以正常工作。

The error is here :

错误在这里：

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

I'm launching the Fragment as it was an Activity, so when i run the app it crashes and tells me to declare the MainFragment as an activity in my manifest.

我正在启动 Fragment，因为它是一个 Activity，所以当我运行该应用程序时，它会崩溃并告诉我将 MainFragment 声明为我的清单中的一个 Activity。

How can i launch that Fragment from my Activity?

如何从我的 Activity 启动该 Fragment？

Thanks very much.

非常感谢。

采纳答案by Skizo-oz??S

You cannot start a Fragmentwith Intentsso the method that I recommend to you is :

你不能开始Fragment，Intents所以我推荐给你的方法是：

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

For more information see Fragments Transactions documents

有关更多信息，请参阅Fragments Transactions 文档

回答by Olkunmustafa

You can not start a Fragmentusing Intents. Intents provide a communication between activities.

你不能开始Fragment使用Intents。意图提供活动之间的通信。

If you want to launch a Fragmentfrom other Fragmentyou have two options.

如果您想Fragment从其他启动一个，Fragment您有两个选择。

1- You can replace or add a new fragment.

1- 您可以替换或添加新片段。

FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction
                .replace( R.id.content_frame, fragment )
                .addToBackStack( null )
                .commit();

In this case The activity has two fragments.

在这种情况下，活动有两个片段。

2- You can launch a new Activity that contains a Fragment.

2- 您可以启动一个包含片段的新活动。

回答by DragonFire

If you are using a Sections Pager Adapter, the simple thing to do would be using an onclick on image view or button like below:

如果您使用的是 Sections Pager Adapter，那么简单的事情就是使用 onclick 图像视图或按钮，如下所示：

In your starting activity (from where you want to go) use put extra to send some information to another activity

在您的开始活动中（从您想去的地方）使用 put extra 将一些信息发送到另一个活动

ivPhotoAlbums.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {

        // Send The Message Receiver ID & Name
        Intent intent = new Intent(v.getContext(), PhotosActivity.class);
        intent.putExtra("viewpager_position", 1);
        v.getContext().startActivity(intent);

    }
});

In your activity in which you want to land (at the end of your setupViewPager() function) catch that extra and use it as position

在您想要登陆的活动中（在 setupViewPager() 函数的末尾）捕获额外的内容并将其用作位置

int position = 0;
Bundle extras = getIntent().getExtras();
if (extras != null) {
    position = extras.getInt("viewpager_position");
}
viewPager.setCurrentItem(position);

Given the Assumption that your setupViewPager() function looks like below in your destination activity

假设您的 setupViewPager() 函数在目标活动中如下所示

SectionsPagerAdapter adapter = new SectionsPagerAdapter(getSupportFragmentManager());

adapter.addFragment(new FriendsAlbumsFragment()); //index 0
adapter.addFragment(new MyAlbumsFragment()); //index 1
adapter.addFragment(new AddPhotosFragment()); //index 2

final ViewPager viewPager = findViewById(R.id.l_center_view_pager_view_pager);
viewPager.setAdapter(adapter);

TabLayout tabLayout = findViewById(R.id.l_top_tabs_tabs);

tabLayout.setupWithViewPager(viewPager);
tabLayout.getTabAt(0).setIcon(R.drawable.ic_friends_photos);
tabLayout.getTabAt(1).setIcon(R.drawable.ic_my_photos);
tabLayout.getTabAt(2).setIcon(R.drawable.ic_add_photos);

And Your SectionsPagerAdapter class looks like below (separate public class)

您的 SectionsPagerAdapter 类如下所示（单独的公共类）

public class SectionsPagerAdapter extends FragmentPagerAdapter {

    private List<Fragment> mFragmentList = new ArrayList<>();

    public SectionsPagerAdapter(FragmentManager fm) {

        super(fm);

    }

    @Override
    public Fragment getItem(int i) {

        return mFragmentList.get(i);
    }

    @Override
    public int getCount() {

        return mFragmentList.size();
    }

    public void addFragment(Fragment fragment) {

        mFragmentList.add(fragment);
    }
}

And your center view pager layout is

你的中心视图寻呼机布局是

<merge xmlns:android="http://schemas.android.com/apk/res/android">

    <android.support.v4.view.ViewPager
        android:id="@+id/l_center_view_pager_view_pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingBottom="56dp">

    </android.support.v4.view.ViewPager>

</merge>

Included in another file like this (or not included - in my case it was included)

包含在这样的另一个文件中（或不包含 - 在我的情况下已包含）

<include layout="@layout/layout_center_viewpager" />

This will take you right from an activity to a fragment (in another activity) or from a fragment in one activity to a fragment in another activity...

这将带你从一个活动到一个片段（在另一个活动中）或从一个活动中的一个片段到另一个活动中的一个片段......