Android学习之路-Fragment之二

上篇学习了Fragment的静态和动态添加的简单使用，以及生命周期，为了更好的理解和使用fragment，本节结合实际应用，和大家分享fragment与activity之间以及与fragment之间的交互。

1、fragment与activity交互。

activity向fragment传递参数：

在提交事务实例化fragment时将参数传给fragment，在newInstance()方法里调用色图setArguments（）将参数保存起来。

在oncreate（）方法中getAraguments()将参数取出来使用。

fragment向activity传递参数：

这个采用了接口回调机制，在fragment里定义交互接口，让activity实现接口，fragment生命周期的

onAttach(Activity activity)里将activity强转为接口对象，得到接口实例，调用接口交互方法将参数传回给activity。

例子：

从效果图可以看出，左边是个fragment里面放了listView，点击Item可以将参数传递给Activity，Activiyt接收到参数后根据条件判断替换右边对应的framgent.并将参数传递给替换的fragment。

左边的fragemnt:xml文件：

<FrameLayout 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="fragment_demo.fragment.FragmentTwo"
    android:background="@android:color/holo_blue_bright">

    <ListView
        android:id="@+id/fragment_listview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</FrameLayout>

package fragment_demo.fragment;


import android.app.Activity;
import android.app.Fragment;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import com.example.call.R;

/**
 * A simple {@link Fragment} subclass.
 */
public class FragmentTwo extends Fragment implements AdapterView.OnItemClickListener {


    private ListView mListView;
    private String[] data = new String[]{"新闻", "电影", "旅游"};
    private OnCallBackInter mOnCallBackInter;
    /*注册与Activity交互的接口*/
    public interface OnCallBackInter{
        public void OngetMsg(String msg);
    }

    @Override
    /*交互接口*/
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        mOnCallBackInter = (OnCallBackInter)activity;   //得到了实现接口的实例了
    }

    /*返回Fragment实例*/
    public static FragmentTwo newInstance(){
        FragmentTwo fragmentTwo = new FragmentTwo();
        return fragmentTwo;
    }

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

        View v = inflater.inflate(R.layout.fragment_fragment_two_layout, container, false);
        mListView = (ListView) v.findViewById(R.id.fragment_listview);
        FragmentListAdapter adapter = new FragmentListAdapter(getActivity());
        adapter.setDataStr(data);
        mListView.setAdapter(adapter);
        mListView.setOnItemClickListener(this);
        return v;
    }

    @Override
    public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
        String str = (String) adapterView.getAdapter().getItem(i);
        Toast.makeText(getActivity(), str, Toast.LENGTH_SHORT).show();
        mOnCallBackInter.OngetMsg(str);   //将参数回传给Activity
    }


    public class FragmentListAdapter extends BaseAdapter {
        private String[] dataStr = new String[]{};
        private LayoutInflater inflater;
        public FragmentListAdapter(Context context) {
            this.inflater = LayoutInflater.from(context);
        }

        public void setDataStr(String[] data) {
            this.dataStr = data;
            notifyDataSetChanged();
        }

        @Override
        public int getCount() {
            return dataStr.length;
        }

        @Override
        public Object getItem(int i) {
            return dataStr[i];
        }

        @Override
        public long getItemId(int i) {
            return i;
        }

        @Override
        public View getView(int i, View view, ViewGroup viewGroup) {
            if (view == null) {
                view = inflater.inflate(android.R.layout.simple_list_item_1, null);
            }
            TextView txt = (TextView) view;
            txt.setText((CharSequence) getItem(i));
            return view;
        }

    }

}

fragment里传参数给activity，是通过接口回调的方式实现的。

右边的3个fragment几乎相同，这里指贴出一个。

xml布局：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/holo_red_light">

    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="电影Fragment"
        android:textSize="20sp"
        android:layout_centerInParent="true"/>

    <TextView
        android:id="@+id/movies_fragment_txt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="20sp"
        android:layout_alignParentBottom="true"/>

</RelativeLayout>

java代码：

package fragment_demo.fragment;


import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.example.call.R;

/**
 * A simple {@link Fragment} subclass.
 */
public class MoviesFragment extends Fragment {
    private static final String ARG_PARAM1 = "param1";
    private String mParam1;

    public MoviesFragment() {
        // Required empty public constructor
    }

    public static MoviesFragment newInstance(String str){
        MoviesFragment fragment = new MoviesFragment();
        Bundle bundle = new Bundle();
        bundle.putString(ARG_PARAM1,str);
        fragment.setArguments(bundle);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if(getArguments() != null){
            mParam1 = getArguments().getString(ARG_PARAM1);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View v = inflater.inflate(R.layout.fragment_movies_layout, container, false);
        TextView txt = (TextView) v.findViewById(R.id.movies_fragment_txt);
        txt.setText(mParam1);
        return v;
    }

}

可以看出，从Activity传参到Fragment相对简单，在生命周期对应方法写对应代码就可以了。

最后再来看看MainActivity里面做了写什么判断？

MainActivity  XML布局：

<?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="horizontal">

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

    <FrameLayout
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="2"
        android:id="@+id/fragment_content_framentlayout">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/fragment_showTxt"
            android:layout_gravity="center"
            android:background="@android:color/holo_purple"/>
    </FrameLayout>

</LinearLayout>

java代码：

package fragment_demo.fragment;

import android.app.Activity;
import android.app.FragmentManager;
import android.os.Bundle;
import android.widget.TextView;

import com.example.call.R;

public class FragmentMainActivity extends Activity implements FragmentTwo.OnCallBackInter {
    private TextView mShowTxt;
    private FragmentManager manager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fragment_main_layout);
        mShowTxt = (TextView) findViewById(R.id.fragment_showTxt);
        manager = getFragmentManager();

        manager.beginTransaction().add(R.id.fragment_title_frameLayout, FragmentTwo.newInstance()).commit();

        /*这里本应该注册接口的，但是Fragment里的OnAttach()方法已经实现了这一步*/
    }

    @Override
    /*实现交互接口方法*/
    public void OngetMsg(String msg) {
       if(msg.equals("新闻")) {
           manager.beginTransaction().replace(R.id.fragment_content_framentlayout, NewsFragment.newInstance(msg)).commit();
       }else if (msg.equals("电影")){
            manager.beginTransaction().replace(R.id.fragment_content_framentlayout,MoviesFragment.newInstance(msg)).commit();
       }else if (msg.equals("旅游")){
           manager.beginTransaction().replace(R.id.fragment_content_framentlayout,TravealFragment.newIntance(msg)).commit();
       }


    }
}

最后就实现了上面的效果。