一.Fragment向Activity传值的步骤 接口回调传递(5部曲)

• fragment中准备回调接口 接口中声明传值的回调方法

• 在fragment中定义属性private MyListener myListener

• 重写fragment中的onAttach()方法
  listener = (MyLisener)getActivity();

• fragment触发事件时回传值

• Activity中实现回调接口 重写回调方法获取回传的值并显示

代码：

import com.qianfeng.day16_fragmenttoactivity.MyFragment.MyListener;
import android.app.Activity;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity implements MyListener{
    private TextView textView;  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = (TextView) findViewById(R.id.textView);
        FragmentManager manager = getFragmentManager();
        FragmentTransaction transaction = manager.beginTransaction();
        transaction.add(R.id.layout_container_fragment, new MyFragment());
        transaction.commit();        
    }

    @Override
    public void sendContent(String info) {
        if (info!=null && !"".equals(info)) {
            textView.setText(info);
        }else {
            Toast.makeText(MainActivity.this, "请输入内容", Toast.LENGTH_SHORT).show();
        }
    }
}

import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;

public class MyFragment extends Fragment {
    private EditText editText;
    private Button button;  
    private MyListener myListener;//②作为属性定义 
    //①定义回调接口
    public interface MyListener{
        public void sendContent(String info);
    }
    
    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        myListener = (MyListener) getActivity();
    }
    
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.layout_fragment, container, false);
        editText = (EditText) view.findViewById(R.id.editText1);
        button = (Button) view.findViewById(R.id.button1);
        
        //点击按钮时需要将EditText中的值取出来传给宿主Activity
        button.setOnClickListener(new OnClickListener() {
            
            @Override
            public void onClick(View v) {
                String value = editText.getText().toString();
                myListener.sendContent(value);//将内容进行回传
            }
        });
        return view;
    }
}

layout_fragment布局

<?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"
    android:orientation="vertical" >
    
    <EditText 
        android:id="@+id/editText1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:hint="请输入传递的数据"
        android:ems="10"/>
    
    <Button
        android:id="@+id/button1" 
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@id/editText1"
        android:layout_marginTop="20dp"
        android:text="点击传值"/>

</RelativeLayout>

activity_main布局

<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" >
   <LinearLayout 
       android:layout_width="match_parent"
       android:layout_height="0dp"
       android:layout_weight="1"
       android:gravity="center"
       android:orientation="horizontal">      
       <TextView 
           android:id="@+id/textView"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:textSize="22sp"
           android:text="TextView"/>
       
   </LinearLayout>
   
   <LinearLayout
       android:id="@+id/layout_container_fragment"
       android:layout_width="match_parent"
       android:layout_height="0dp"
       android:layout_weight="1"
       android:background="#5f00"
       android:orientation="vertical">      
   </LinearLayout>   
</LinearLayout>