一、接口方式
在fragment類中定義一個接口並在Activity中實現它。Fragment在onAttach()回調函數中獲取接口的具體實現的對象。後面，fragment就可以調用接口中的方法實現與Activity的通信。

在Android5.0之後廢除了onAttach(Activity activity)的方法，轉而使用onAttach(Context context),也就是傳遞的參數發生變化

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中需要實現該接口

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

二、廣播

在Activity中註冊廣播接收器,在Fragment中發送廣播

    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 從Activity獲取數據

在Fragment 的getInstance()方法中setArguments()設置參數

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

再通過getArguments()方法獲取

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

Fragment與Activity之間的相互通信