Fragment-加载方式与数据通信

手机开发 2017-03-22

一、加载方式

1. 静态加载

1.1 加载步骤

(1) 创建fragment:创建自定义Fragment类继承自Fragment类,同时将自定义Fragment类与Fragment视图绑定(将layout转换成View)

View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)

  inflater用于绑定Fragment的布局文件,同时将该布局转换成View对象并返回;container为Fragment的UI所在的父容器。返回值为Fragment显示的UI,若不显示,则返回null。

inflate(int resource, ViewGroup root, boolean attachToRoot)

  resource为Fragment需要加载的布局文件;root为加载Fragment的父ViewGroup,也就是onCreateView传递进来的container;attachToRoot为是否返回父ViewGroup。

(2) 使用fragment:在父视图中引入fragment,静态加载必须指定name属性以及一个唯一标识符,标识符可以为id或者tag

<!--指定在layout中实例化的Fragment类,需要为“包名.类名”的完整形式-->
android:name
<!--唯一标识,id和tag可任选其一,不可两者都没有-->
android:id
android:tag

(3) 监听事件:若在父视图对应的类中设置监听事件,可以直接访问fragment中的子组件;若在Fragment的类中设置,则必须通过inflate()返回的View对象访问Fragment中的子组件(view.findViewById(id))。

1.2 简单范例

MyFragment视图:

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

    <TextView
        android:id="@+id/fragment_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

MyFragment类:

public class MyFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    
        //将layout布局转换成View对象
        View view = inflater.inflate(R.layout.myfragment, container, false);
        
        //必须通过view对象对其子组件进行访问
        TextView textView = (TextView) view.findViewById(R.id.fragment_text);
        textView.setText("这里是fragment");
        
        //返回Fragment显示UI
        return view;
    }
}

引用fragment的父视图:

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

    <fragment
        android:tag="fragment"
        android:name="com.joahyau.studying.MyFragment"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</LinearLayout>

父视图对应的类设置事件监听:

public class StaticFragmentActivity extends Activity {

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

        //可直接通过findViewById访问
        findViewById(R.id.fragment_text).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(StaticFragmentActivity.this, "点击了文本", Toast.LENGTH_SHORT).show();
            }
        });
    }
}

2. 动态加载

2.1 加载步骤

(1) 获取事务管理器:对Fragment进行的添加、移除、替换等操作,均为事务。需通过以下代码获取事务管理器,从而对fragment进行动态操作。

FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();

(2) 创建Fragment对象:创建需要加载的fragment,而后通过add或replace等方法实现动态加载。

2.2 简单范例

布局:

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

    <Button
        android:id="@+id/load"
        android:text="加载"
        android:layout_width="match_parent"
        android:layout_height="80dp" />

    <LinearLayout
        android:id="@+id/container"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal" />
</LinearLayout>

Java:

public class DynamicFragmentActivity extends Activity {

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

        findViewById(R.id.load).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //获取事务管理器
                FragmentManager fragmentManager = getFragmentManager();
                FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

                //创建fragment,并将其动态加载到id位container的布局中
                MyFragment myFragment = new MyFragment();
                fragmentTransaction.add(R.id.container, myFragment);
                //提交事务
                fragmentTransaction.commit();
            }
        });
    }
}

二、数据通信

3. Activity向Fragment传递数据

3.1 Activity向动态加载的Fragment传递数据

  (1)在Activity中获取Fragment对象;

  (2)创建Bundle对象并传入数据;

  (3)将Bundle对象传递给Fragment对象;

  (4)在Fragment中获取Bundle对象并拆包得到数据。

范例:Activity中只有一个id为send的Button,MyFragment中只有一个TextView,这里就不再放布局代码了。

Activity:

public class MainActivity extends Activity {

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

        findViewById(R.id.send).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //创建Fragment对象
                MyFragment myFragment = new MyFragment();

                //创建Bundle对象并传入数据
                Bundle bundle = new Bundle();
                bundle.putString("info", "这里是向Fragment传递的数据");
                myFragment.setArguments(bundle);

                //加载Fragment
                FragmentManager fragmentManager = getFragmentManager();
                FragmentTransaction beginTransaction = fragmentManager.beginTransaction();
                beginTransaction.add(R.id.layout, myFragment, "myfragment");
                beginTransaction.commit();
            }
        });
    }
}

Fragment:

public class MyFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.my_fragment, container, false);
        TextView tv = (TextView) view.findViewById(R.id.text);

        //获取数据
        String text = getArguments().get("info") + "";
        tv.setText(text);

        return view;
    }
}

3.2 Activity向静态加载的Fragment传递数据

  (1)在Fragment中创建作为容器的数据对象,并创建getter和setter;

  (2)在Activity中获取FragmentManager;

  (3)通过事务管理器的findFragmentById或findFragmentByTag方法,获得fragment对象;

  (4)通过获得的fragment对象调用容器的setter方法进行传值。

范例:这里的布局与动态加载的布局唯一不同的就是将send按钮放在了Fragment里面,其它相同。

Fragment:

public class MyFragment extends Fragment {

    private Button btn;
    private String received;//作为容器的对象

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.my_fragment, container, false);
        TextView tv = (TextView) view.findViewById(R.id.text);
        tv.setText("这里是Fragment");

        btn = (Button) view.findViewById(R.id.send);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(getActivity(), "成功接收\"" + getReceived() + "\"", Toast.LENGTH_SHORT).show();
            }
        });

        return view;
    }

    public String getReceived() {
        return received;
    }

    public void setReceived(String received) {
        this.received = received;
    }
}

Activity:

public class MainActivity extends Activity {


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

        FragmentManager fragmentManager = getFragmentManager();
        MyFragment myFragment = (MyFragment) fragmentManager.findFragmentById(R.id.my_fragment);
        myFragment.setReceived("this is a test.");
    }
}

4. Fragment向Activity传递数据

  (1)在Fragment中写一个回调接口;

  (2)在activity中实现这个回调接口,实现的函数用于传值;

  (3)重写Fragment中onAttach,在其中创建一个接口对象,得到传递过来的activity(我的理解是这个接口其实相当于传递过来的activity的一个父类,这一步是用到了多态的特性);

  (4)用得到的接口对象进行传值。

Fragment:

public class MyFragment extends Fragment {

    private SendData sendData;

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        //获取实现的接口对象
        sendData = (SendData) activity;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.my_fragment, container, false);
        TextView tv = (TextView) view.findViewById(R.id.text);
        tv.setText("这里是Fragment");

        //通过接口对象传递数据
        sendData.sendMsg("this is a test.");

        return view;
    }

    //定义一个回调接口
    public interface SendData{
        void sendMsg(String str);
    }
}

Activity:

public class MainActivity extends Activity implements MyFragment.SendData{

    private Button btn;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn = (Button) findViewById(R.id.send);

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                MyFragment myFragment = new MyFragment();

                FragmentManager fragmentManager = getFragmentManager();
                FragmentTransaction beginTransaction = fragmentManager.beginTransaction();
                beginTransaction.add(R.id.layout, myFragment);
                beginTransaction.commit();
            }
        });
    }

    //实现SendData接口,接收数据
    @Override
    public void sendMsg(String str) {
        Toast.makeText(this, "成功接收\"" + str + "\"", Toast.LENGTH_SHORT).show();
    }
}

相关推荐