加载fragment的两种方式

1.静态加载

1、首先，新建FragmentTest.java类继承fragment

public class FragmentTest extends Fragment {

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_test, container, false);
        return view;
    }
}

2、创建fragment中的布局fragment_test.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="我是fragment" />

</LinearLayout>

3、创建activity中的布局activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <fragment
        android:id="@+id/fragment_test"
        android:name="com.bignerdranch.android.litepalstudy.fragment.FragmentTest"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</LinearLayout>

注意，这里的fragment控件一定要加android:id="@+id/fragment_test"不然会报异常
android.view.InflateException: Binary XML file line #13: Binary XML file line #13: Error inflating class fragment

4、创建MainActivity.java

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}

2.动态加载

动态加载fragment的静态加载fragment的一、二步相同。从第三步开始。
3、创建activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

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

</LinearLayout>

Framelayout是一个用来存放Fragment的容器

3、创建MainActivity.java类

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //创建fragment管理类
        FragmentManager fm = getSupportFragmentManager();
        //查找当前容器中是否有fragment
        Fragment fragment = fm.findFragmentById(R.id.fragment_test);
        if (fragment == null){
            //如果没有，创建fragment
            fragment = new FragmentTest();
            //添加fragment到activity中
            fm.beginTransaction()
                    .add(R.id.fragment_test, fragment)
                    .commit();
        }
    }
}