fragment初级使用

第一步

创建fragment

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

    public void showTopFragmentMethod() {
        Toast.makeText(getActivity(), "TopFragemnt的方法", Toast.LENGTH_SHORT).show();
    }

    /**
     * 在fragment中调用activity中的方法
     */
    private void getActivityMethod() {
        FragmentActivity activity = (FragmentActivity) getActivity();
        activity.showActivityMethod();
    }

}

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

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

第二步

创建activity加载fragment，可以通过在布局文件中添加，也可以通过代码动态添加，详细见代码

public class FragmentActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fragment);
        replaceFragment(new BottomFragment());
        findViewById(R.id.change).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                replaceFragment(new AnotherBottomFragment());
                getFragmentMethod();
            }
        });
    }


    private void replaceFragment(Fragment fragment) {
        FragmentManager manager = getSupportFragmentManager();
        FragmentTransaction transaction = manager.beginTransaction();
        transaction.replace(R.id.frameLayout, fragment);
        transaction.addToBackStack(null);//在碎片中模拟返回栈。点击回退键时，回到上一个fragment不直接退出activity
        transaction.commit();

    }

    /**
     * 在activity中调用fragment的方法
     */
    private void getFragmentMethod() {
        TopFragemnt topFragemnt = (TopFragemnt) getSupportFragmentManager().findFragmentById(R.id.top_fragment);
        topFragemnt.showTopFragmentMethod();
    }

    public void showActivityMethod() {
        Toast.makeText(this, "FragmentActivity 方法", Toast.LENGTH_SHORT).show();
    }

    /**
     * 不同fragment间的交互，
     * 通过在一个fragment中先拿到activity的实例，然后在这个activity的实例中
     * 提供另一个fragment的实例。
     * @return
     */
    public BottomFragment returnBottomFragment() {
        BottomFragment bottomFragment = new BottomFragment();
        return bottomFragment;
    }

}

activity布局文件

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

    <fragment
        android:id="@+id/top_fragment"
        android:name="com.cecurs.helloandroid.Three_chapter.TopFragemnt"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

    <FrameLayout
        android:id="@+id/frameLayout"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

</LinearLayout>