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。