如何在 MainActivity 的框架布局中加载默认片段？

Question

我在 mainActivity 中有 2 个片段 和 frameLayout。 每当我运行我的应用程序时，我希望将我的 Fragment1 加载到我的 frameLayout default 中，它位于 mainActivity 中。

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.prank.fragmentbackstack.MainActivity">

<FrameLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/frame"
    >

</FrameLayout>
</RelativeLayout>

Frag.class

import android.widget.Button;
    import android.widget.TextView;
    public class Frag extends Fragment {
        String Tag1="frag1";

        Button b;

        public View onCreateView(LayoutInflater inflater, ViewGroup viewGroup, Bundle saveInstanceState)
        {View view = inflater.inflate(R.layout.fragment, viewGroup, false);
            b=(Button)view.findViewById(R.id.button);

            return view;
        }
    }

Answer 1

使用此代码动态添加您的片段

// Create new fragment and transaction
Fragment newFragment = new ExampleFragment();
FragmentTransaction transaction = getFragmentManager().beginTransaction();

// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack if needed
transaction.replace(R.id.fragment_container, newFragment);
transaction.addToBackStack(null);

// Commit the transaction
transaction.commit();

Answer 2

试试这个：

public class MainActivity extends AppCompatActivity {

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

        setContentView(R.layout.activity_main);

        if (savedInstanceState == null) {
            getFragmentManager()
                    .beginTransaction()
                    .replace(R.id.frame, new Frag())
                    .commit();
        }
    }
}

Answer 3

使用此代码只需将 frameLayout 容器替换为 onCreate 内的 Fragment1 ：

getFragmentManager().beginTransaction()
                .replace(R.id. frameLayout, new Fragment1())
                .commit();

Answer 4

在你的主要活动中使用它：

frag_name frag_name = new frag_name();
                    FragmentManager manager = this.getSupportFragmentManager();
                    manager.beginTransaction().replace(R.id.youtframelayout, frag_name, frag_name.getTag()).commit();

它初始化 fragment 并将其替换为您的 FrameLayout

希望它有效！ :)

Answer 5

使用 sigleton 设计模式解决。

在你的fragment：

public static HomeFragment newInstance() {

    Bundle args = new Bundle();

    HomeFragment fragment = new HomeFragment();
    fragment.setArguments(args);
    return fragment;
}

在activity 中的onCreate 方法中添加fragment：

HomeFragment homeFragment = HomeFragment.newInstance();
    getSupportFragmentManager()
            .beginTransaction()
            .replace(R.id.yourFrameLayoutId, homeFragment)
            .commit();

Answer 6

制作 pushfragment 类并在您想添加或更新时使用。

pushFragments(R.id.frame, this, YourFragment, false, false, YourFragment.class.getSimpleName());

public static void pushFragments(int container, AppCompatActivity activity, Fragment fragment, boolean animate, boolean shouldAdd, String tag) {
        FragmentManager manager = activity.getSupportFragmentManager();
        FragmentTransaction ft = manager.beginTransaction();
        if (animate) { //For animation
            ft.setCustomAnimations(R.anim.enter, R.anim.exit, R.anim.pop_enter, R.anim.pop_exit);
        }

        if (shouldAdd) { //for add in stack
            ft.replace(container, fragment, tag);
            ft.addToBackStack(tag);
            ft.commitAllowingStateLoss();
        } else {
            manager.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
            ft.replace(container, fragment, tag);
            ft.commit();
        }
    }

将 Frag 传递给 pushFragments 并在 Mainactivity 的 onCreate 中添加调用。

Answer 7

设置这个：

 viewPager.setCurrentItem(index);

index = index of fragment 你要显示