Fragment与Activity之间的通信

　　我个人将Fragment与Activity间的通信比喻为JSP与Servlet间的通信，fragment中用接口的方式来进行与Activity的通信。通信的结果可以作为数据传入另一个Fragment中。当然两个Fragment之间也是可以进行通信的~

注意加载或者切换Fragment时，必须new一个FragmentTransaction对象，不能用同一个FragmentTransaction对象进行对容器进行替换、增加fragment。将fragment填充进容器的方式是（这里分别给两个容器填充了两个fragment对象）：

　　　　 FragmentManager fragmentManager = getSupportFragmentManager();

        FragmentTransaction ft = fragmentManager.beginTransaction();  

        ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);

        ft.add(R.id.container_fragment, new MyFragment())

        .commit();

        //不能用同个FragmentTransaction来加载两个fragment

        fragmentManager.beginTransaction()

        .add(R.id.container_fragment02, new MyFragment02())

        .commit();

更换fragment的方式是：

        getSupportFragmentManager().beginTransaction().

        replace(R.id.container_fragment02, fragment)

        .addToBackStack(null)

        .commit();

　　本实例完成的是点击一个Fragment中的按钮后，fragment给activity传值，activity接受到值后给另一个fragment（右边的）传值，以此改变textview中的内容。

activity_main.xml （定义了2个布局来作为fragment的容器）

<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:background="#000000"

    android:orientation="horizontal" >

    <FrameLayout

        android:id="@+id/container_fragment"

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:layout_weight="1"

        android:background="#ffffff"

        android:layout_marginRight="1dp" />

    <FrameLayout

        android:id="@+id/container_fragment02"

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:layout_weight="1"

        android:background="#ffffff"

        android:layout_marginLeft="1dp" >

    </FrameLayout>

</LinearLayout>

fragment.xml

<RelativeLayout 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="${relativePackage}.${activityClass}" >

    <Button

        android:id="@+id/fragment_button"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_centerHorizontal="true"

        android:layout_centerVertical="true"

        android:layout_marginBottom="41dp"

        android:text="kale" />

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_above="@+id/fragment_button"

        android:layout_centerHorizontal="true"

        android:layout_marginBottom="46dp"

        android:text="点击后传值"

        android:textAppearance="?android:attr/textAppearanceLarge" />

</RelativeLayout>

MyFragment

package com.kale.activity;

import android.app.Activity;

import android.os.Bundle;

import android.support.annotation.Nullable;

import android.support.v4.app.Fragment;

import android.util.Log;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.view.View.OnClickListener;

import android.widget.Button;

public class MyFragment extends Fragment{

    private MyCallback mCallback;

    //定义一个调用接口}

    public interface MyCallback {

        public void onBtnClick(View v);

    }

    String TAG = getClass().getName();

    @Override

    public void onAttach(Activity activity) {

        super.onAttach(activity);

        Log.e(TAG, "F------------onAttach->");

        if(!(activity instanceof MyCallback)) {

            throw new IllegalStateException("fragment所在的Activity必须实现Callbacks接口");

        }

        //把绑定的activity当成callback对象

        mCallback = (MyCallback)activity;

    }

    @Override

    public void onActivityCreated(@Nullable Bundle savedInstanceState) {

        super.onActivityCreated(savedInstanceState);

        Log.e(TAG, "F------------onActivityCreated->");

        //一定要在定义好视图后才来初始化控件，不能放在onCreat()里面

        Button btn = (Button)getActivity().findViewById(R.id.fragment_button);

        btn.setOnClickListener(new OnClickListener() {

            @Override

            public void onClick(View v) {

                mCallback.onBtnClick(v);

            }

        });

    }

    @Override

    public void onDetach() {

        super.onDetach();

        Log.e(TAG, "F------------onDetach->");

        mCallback = null;//移除前幅值为空

    }

}

fragment02.xml

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="match_parent"

    android:layout_height="match_parent">

    <TextView

        android:id="@+id/fragment_textView"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_centerHorizontal="true"

        android:layout_centerVertical="true"

        android:text="null"

        android:textAppearance="?android:attr/textAppearanceLarge" />

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_above="@+id/fragment_textView"

        android:layout_centerHorizontal="true"

        android:layout_marginBottom="40dp"

        android:textAppearance="?android:attr/textAppearanceLarge"

        android:text="传来的信息" />

</RelativeLayout>

MyFragment02

package com.kale.activity;

import android.app.Activity;

import android.os.Bundle;

import android.support.annotation.Nullable;

import android.support.v4.app.Fragment;

import android.util.Log;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.TextView;

public class MyFragment02 extends Fragment{

    public static final String KEY = "key";

    String TAG = getClass().getName();

    @Override

    public View onCreateView(LayoutInflater inflater,

            @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        Log.e(TAG, "F------------onCreateView->");

        return inflater.inflate(R.layout.fragment02, container, false);

    }

    @Override

    public void onActivityCreated(@Nullable Bundle savedInstanceState) {

        super.onActivityCreated(savedInstanceState);

        Log.e(TAG, "F------------onActivityCreated->");

        //一定要在定义好视图后才来初始化控件，不能放在onCreat()里面

        TextView tv = (TextView)getActivity().findViewById(R.id.fragment_textView);

        tv.setText("haha");

          Bundle bundle = getArguments();

          if (bundle == null) {

            tv.setText("默认值01");

        }

          else {

              tv.setText(bundle.getString(KEY, "默认值02"));

        }

    }

}

MainActivity

package com.kale.activity;

import android.os.Bundle;

import android.support.v4.app.FragmentManager;

import android.support.v4.app.FragmentTransaction;

import android.support.v7.app.ActionBarActivity;

import android.util.Log;

import android.view.View;

import android.widget.Button;

import com.kale.activity.MyFragment.MyCallback;

public class MainActivity extends ActionBarActivity implements MyCallback{

    String TAG = getClass().getName();

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        Log.e(TAG, "------------onCreate------------");

        FragmentManager fragmentManager = getSupportFragmentManager();

        FragmentTransaction ft = fragmentManager.beginTransaction();  

        ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);

        ft.add(R.id.container_fragment, new MyFragment())

        .commit();

        //不能用同个FragmentTransaction来加载两个fragment

        fragmentManager.beginTransaction()

        .add(R.id.container_fragment02, new MyFragment02())

        .commit();

    }

    @Override

    protected void onStart() {

        super.onStart();

        Log.e(TAG, "------------onStart------------");

    }

    @Override

    protected void onRestart() {

        super.onRestart();

        Log.e(TAG, "------------onRestart------------");

    }

    @Override

    protected void onResume() {

        super.onResume();

        Log.e(TAG, "------------onResume------------");

    }

    @Override

    protected void onPause() {

        super.onPause();

        Log.e(TAG, "------------onPause------------");

    }

    @Override

    protected void onSaveInstanceState(Bundle outState) {

        super.onSaveInstanceState(outState);

        Log.e(TAG, "------------onSaveInstanceState------------");

    }

    @Override

    protected void onStop() {

        super.onStop();

        Log.e(TAG, "------------onStop------------");

    }

    @Override

    protected void onDestroy() {

        super.onDestroy();

        Log.e(TAG, "------------onDestroy------------");

    }

    @Override

    protected void onRestoreInstanceState(Bundle savedInstanceState) {

        super.onRestoreInstanceState(savedInstanceState);

        Log.e(TAG, "------------onRestoreInstanceState------------");

    }

    @Override

    public void onBtnClick(View v) {

        Button btn = (Button)v;

        Log.i(TAG, btn.getText()+"");

        Bundle bundle = new Bundle();

        bundle.putString(MyFragment02.KEY, btn.getText()+"");

        MyFragment02 fragment = new MyFragment02();

        fragment.setArguments(bundle);

        getSupportFragmentManager().beginTransaction().

        replace(R.id.container_fragment02, fragment)

        .addToBackStack(null)

        .commit();

    }

}

源码下载：http://download.csdn.net/detail/shark0017/7709315

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