[移动开发]Android Fragment碎片

Fragment是依赖于Activity的，不能独立存在的。

一、案例演示

点击左侧button按钮，新的fragment会覆盖原来的fragment

二、实现步骤

1、新建fragment

在新建的BlankFragment中暂时只保留onCreatView方法

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_blank, container, false);
    }

2、左侧fragment

2.1、left_fragment.xml
相当与一个自定义布局嵌套在activity上

<?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"
    android:layout_gravity="center_horizontal"
    android:background="@color/teal_200">

    <TextView
        android:id="@+id/textview1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="25dp"
        android:text="左侧fragment"></TextView>

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="button"></Button>

</LinearLayout>

2.2、LeftFragment.java
onCreateView回调函数在每次创建绘制该Fragment的View组件时回调，Fragment将会显示该方法返回的View组件
对一个没有被载入或者想要动态载入的界面，需要使用LayoutInflater对象的inflate ( )方法存放当前fragment的布局的ViewGroup对象

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

3、右侧fragment

3.1、right_fragment.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"
    android:layout_gravity="center_horizontal"
    android:background="@color/white">

    <TextView
        android:id="@+id/textview2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="25dp"
        android:text="右侧fragment"></TextView>
</LinearLayout>

3.1、RightFragment.java

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

3、另一个fragment

3.1、another_fragment.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"
    android:layout_gravity="center_horizontal"
    android:background="@color/teal_700">

    <TextView
        android:id="@+id/textview3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="25dp"
        android:text="另一个fragment"></TextView>
    
</LinearLayout>

3.1、AnotherFragment.java

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

三、activity页面

1、activity_main.xml

<?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="horizontal"
    tools:context=".MainActivity4">

    <fragment
        android:id="@+id/left_fragment"
        android:name="com.example.listview.LeftFragment"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"></fragment>
    <FrameLayout
        android:id="@+id/right_layout"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1">
        <fragment
            android:id="@+id/right_fragment"
            android:name="com.example.listview.RightFragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent"></fragment>
    </FrameLayout>


</LinearLayout>

2、MainActivity.java

按钮点击事件也可以写在fragment中

public class MainActivity4 extends AppCompatActivity {
    private Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main4);

        button=findViewById(R.id.button1);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //创建新的fragment实列
                AnotherFragment fragment=new AnotherFragment();
                //获取fragmentmanager对象
                FragmentManager manager= getFragmentManager();
                //开启一个事务
                FragmentTransaction transaction=manager.beginTransaction();
                //像容器中添加新的fragment，一般我们用replace方法
                transaction.replace(R.id.right_layout,fragment);
                //回退后显示原来页面
                transaction.addToBackStack(null);
                //提交事务
                transaction.commit();
            }
        });
    }
}