如何从子片段获取到父片段的价值?

Question

我很沮丧。
我想从子片段到父片段获取值 我尝试了很多方法。
界面，视图模型，共享首选项，但没有人工作。

我遵循了这种方法

但它对我不起作用。
这是我的代码父片段：

public class Chart_Fragment extends Fragment
implements Product_Fragment.pf_interface {
String dt;
TextView tv;

public Chart_Fragment() {
// Required empty public constructor
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View v = inflater.inflate(R.layout.chart_fragment, container, false);
// create product_fragment as childfragment
FragmentManager fm = getChildFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
Product_Fragment product_fragment = new Product_Fragment();
ft.replace(R.id.fl_two, new Product_Fragment());
ft.commit();
return v;
}
public void onViewCreated(View v, Bundle savedInstanceState){
super.onViewCreated(v,savedInstanceState);
tv = (TextView)v.findViewById(R.id.rcv);
}
@Override
public void data(String d) {
FragmentManager fragmentManager = getChildFragmentManager();
Product_Fragment product_fragment = 
(Product_Fragment)fragmentManager.findFragmentByTag("data");
if(product_fragment != null){
String dt = d;
tv.setText(dt);
}
}
}

我的孩子片段是：

public class Product_Fragment extends Fragment {
private pf_interface pf;
public Product_Fragment() {
// Required empty public constructor
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View v = inflater.inflate(R.layout.product_fragment, container, false);
Button b = (Button)v.findViewById(R.id.btn_sender);
b.setOnClickListener(new btnClick());
return v;
}
public void onAttachToParentFragment(Fragment fragment){
try {
pf = (pf_interface)fragment;
}catch (ClassCastException e){
throw new ClassCastException(
fragment.toString()+ "must implement pf_interface"
);
}
}
public void onCreate(Bundle savedInstanceState){
Log.i(TAG, "onCreate");
super.onCreate(savedInstanceState);
onAttachToParentFragment(getParentFragment());
}

private class btnClick implements View.OnClickListener{
@Override
public void onClick(View v) {
switch (v.getId()){
case R.id.btn_sender:
if(pf != null){
pf.data("button click interface");
}break;
}
}
}
public interface pf_interface{
void data(String d);
}
}

父片段上的文本视图未显示子片段中的字符串 D("按钮单击界面"(

Answer 1

为什么要在父片段的回调中检查子片段？

@Override
public void data(String d) {
FragmentManager fragmentManager = getChildFragmentManager();
Product_Fragment product_fragment = 
(Product_Fragment)fragmentManager.findFragmentByTag("data");
if(product_fragment != null){ // Why to check for child fragment nullability?
String dt = d;
tv.setText(dt);
}
}

您可以像这样直接使用：

@Override
public void data(String d) {
tv.setText(d);
}

注意：在任何特定情况下，如果任何对象为空，则不会执行您的回调。您已经检查了空引用。