Android 通过侦听器将数据从活动发送到片段

我有一个活动，其中有一个ViewPager，在这个ViewPager中有一些片段。当碎片显示在屏幕上时，我需要向碎片发送数据。所以我想在活动中实现一个接口，将数据发送到片段

public interface SetDataToFragment {
        void getData(List<FinanceOperationModel> aModels);
    }

public class FinanceMonitoringActivity extends ApiActivity2 implements FinanceMonitoringView
        , FinanceMonitoringFragment.SaveDataInterface {

    private SetDataToFragment mInterface;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_finance_monitoring);
        ButterKnife.bind(this);
        mInterface= (SetDataToFragment) this;
...

公共接口SetDataToFragment{
void getData（列出amodel）；
}
公共类FinanceMonitoringActivity扩展了ApiActivity2实现了FinanceMonitoringView
，FinanceMonitoringFragment.SaveDataInterface{
私有setdatatofragmentminterface；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity\u finance\u monitoring）；
把（这个）绑起来；
mInterface=（SetDataToFragment）this；
...

然后是一个错误：

原因：java.lang.ClassCastException:com.akbars.bankok.screens.financeMonitoring.FinanceMonitoringActivity无法强制转换为com.akbars.bankok.screens.financeMonitoring.SetDataToFragment

---

如何正确启动活动中的接口以使用片段中的数据？

在活动中创建一个接口，并通过该接口将数据传递给片段。在片段中实现该接口以获取数据

比如说

MainActivity.class

public class MainActivity extends AppCompatActivity {

    DataFromActivityToFragment dataFromActivityToFragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        FragmentA fr = new FragmentA();
        FragmentManager fm = getFragmentManager();
        dataFromActivityToFragment = (DataFromActivityToFragment) fr;
        FragmentTransaction fragmentTransaction = fm.beginTransaction();
        fragmentTransaction.replace(R.id.fragment_place, fr);
        fragmentTransaction.commit();


        final Handler handler = new Handler();

        final Runnable r = new Runnable() {
            public void run() {
                dataFromActivityToFragment.sendData("Hi");
            }
        };

        handler.postDelayed(r, 5000);


    }

    public interface DataFromActivityToFragment {
        void sendData(String data);
    }
}

public class FragmentA extends Fragment implements MainActivity.DataFromActivityToFragment {

    TextView text;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.content_main, null);
        text = (TextView) rootView.findViewById(R.id.fragment_text);

        return rootView;
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
    }

    @Override
    public void sendData(String data) {
        if(data != null)
        text.setText(data);
    }
}

FragmentA.class

public class MainActivity extends AppCompatActivity {

    DataFromActivityToFragment dataFromActivityToFragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        FragmentA fr = new FragmentA();
        FragmentManager fm = getFragmentManager();
        dataFromActivityToFragment = (DataFromActivityToFragment) fr;
        FragmentTransaction fragmentTransaction = fm.beginTransaction();
        fragmentTransaction.replace(R.id.fragment_place, fr);
        fragmentTransaction.commit();


        final Handler handler = new Handler();

        final Runnable r = new Runnable() {
            public void run() {
                dataFromActivityToFragment.sendData("Hi");
            }
        };

        handler.postDelayed(r, 5000);


    }

    public interface DataFromActivityToFragment {
        void sendData(String data);
    }
}

public class FragmentA extends Fragment implements MainActivity.DataFromActivityToFragment {

    TextView text;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.content_main, null);
        text = (TextView) rootView.findViewById(R.id.fragment_text);

        return rootView;
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
    }

    @Override
    public void sendData(String data) {
        if(data != null)
        text.setText(data);
    }
}

---

活动

FinanceMonitoringActivity

未实现

SetDataToFragment

，因此您无法将其强制转换为

SetDataToFragment

---

在

FinanceMonitoringActivity

中实现

SetDataToFragment

，如果要将数据发送到查看页面片段，可以从viewPager适配器类中执行，或者如果要从活动中执行，请在活动中实现接口，并从片段中调用该接口以返回所需数据。

FinanceMonitoringActivity未实现SetDataToFragment