Fragment与Activity之间的相互通信

一、接口方式
在fragment类中定义一个接口并在Activity中实现它。Fragment在onAttach()回调函数中获取接口的具体实现的对象。后面，fragment就可以调用接口中的方法实现与Activity的通信。

在Android5.0之后废除了onAttach(Activity activity)的方法，转而使用onAttach(Context context),也就是传递的参数发生变化

public interface showMsgListener{
        void showMsg(String str);
    }
    
    private showMsgListener msgListener;
    
    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            if(activity!=null){
                msgListener=(MainActivity)activity;
            }
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement showMsgListener");
        }
    }

        mButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                msgListener.showMsg("Hello Android!(接口)");
            }
        });

在Activity中需要实现该接口

 @Override
    public void showMsg(String str) {
        Toast.makeText(MainActivity.this, str, Toast.LENGTH_SHORT).show();
    }

二、广播

在Activity中注册广播接收器,在Fragment中发送广播

    private BroadcastReceiver mBroadcastReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (action.equals(ACTION_NAME)) {
                String msg = intent.getStringExtra("msg");
                Toast.makeText(MainActivity.this, msg, Toast.LENGTH_SHORT).show();
            }

        }
    };

    public void registerBoradcastReceiver() {
        IntentFilter myIntentFilter = new IntentFilter();
        myIntentFilter.addAction(ACTION_NAME);
        registerReceiver(mBroadcastReceiver, myIntentFilter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(mBroadcastReceiver);
    }

三、Fragment 从Activity获取数据

在Fragment 的getInstance()方法中setArguments()设置参数

public static Fragment getInstance(String msg){
        Bundle bundle = new Bundle();
        bundle.putString("msg",msg);
        MainFragment fragment=new MainFragment();
        fragment.setArguments(bundle);
        return fragment;
    }

再通过getArguments()方法获取

 public void initDatas() {
        Bundle bundle=getArguments();
        if(bundle!=null){
            String msg=bundle.getString("msg");
            Toast.makeText(getActivity(), msg, Toast.LENGTH_SHORT).show();
        }
    }