如何从 Mainactivity 编辑 Fragment 中的 TextView

Posted 2023-04-18

【中文标题】如何从 Mainactivity 编辑 Fragment 中的 TextView

【英文标题】：How to edit TextView in Fragment from Mainactivity

【发布时间】：2021-12-24 14:13:35

【问题描述】：

我搜索了很多文档，并在下面编写了完整的代码， 但是每次我运行它时，它都说 view is null ？

请帮帮我

片段文件

public class LoginFrag extends Fragment 
View view;
public LoginFrag()


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) 
   
 view =  inflater.inflate(R.layout.fragment_login, container, false);
return view;


public void setTextView(int layout, String content)
    if(view == null)
     //Always return view=null ???
        Log.e("view_null","yes");
        return;
    
    TextView textView = view.findViewById(layout);
    textView.setText(content);

MainActivity 文件

LoginFrag loginFrag = new LoginFrag();
goToFrag(loginFrag);

String text= "test set Text";

loginFrag.setTextView(R.id.fg,text);

函数 goToFrag

private void goToFrag(Fragment fragment)
    fragment.setArguments(getIntent().getExtras());
    FragmentManager fragManager = getSupportFragmentManager();
    FragmentTransaction transaction = fragManager.beginTransaction();
    transaction.add(R.id.fragment_container_start, fragment);
    transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
    transaction.commit();

片段布局中的TextView

<TextView
    android:id="@+id/fg"
    android:layout_
    android:layout_
    android:text="" />

【参考方案1】：

请尝试以下方法

(1)单向

public class LoginFrag extends Fragment 
View view;
String text;
public LoginFrag(String text
  this.text = text;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) 
   
 view =  inflater.inflate(R.layout.fragment_login, container, false);
 setTextView(R.id.fg,text); 
 return view;


public void setTextView(int layout, String content)    
    TextView textView = view.findViewById(layout);
    textView.setText(content);




MainActivity
  String text= "test set Text";
  LoginFrag loginFrag = new LoginFrag(text.toString() 
  goToFrag(loginFrag);

(2)第二种方式

public class LoginFrag extends Fragment 
View view;
MainActivity mainActivty;
public LoginFrag(MainActivity mainActivty
  this.mainActivty = mainActivty

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) 
   
 view =  inflater.inflate(R.layout.fragment_login, container, false); 
 return view;


@Override
void onStart()
  super.onStart();
  mainActivty.refresh(this) 


public void setTextView(int layout, String content)
    if(view == null)
     //Always return view=null ???
        Log.e("view_null","yes");
        return;
    
    TextView textView = view.findViewById(layout);
    textView.setText(content);
 


MainActivity
  String text= "test set Text"; 
  LoginFrag loginFrag = new       LoginFrag(text.toString() 
  goToFrag(loginFrag);

 public void onRefresh(Fragment fragment)
   if(fragment instanceOf LoginFrag)
     ((LoginFrag)fragment).setTextView(R.id.fg,text);
   elseif(fragment instanceOf Signup)
     ((Signup)fragment).setTextView(R.id.fg,text);   
  
     
 

(3)第三条路

 LoginFragment
       public boolean setTextView(int layout, String content)
        if(view == null)
         //Always return view=null ???
            Log.e("view_null","yes");
            return false;
        
        TextView textView = view.findViewById(layout);
        textView.setText(content);
        return true;
      
    

MainActivity

 LoginFrag loginFrag = new LoginFrag();
goToFrag(loginFrag);

  String text= "test set Text";
  new Handler().postDelayed(new Runnable()

    boolean isSuccess = loginFrag.setTextView(R.id.fg,text); 
     if(isSuccess)
       handler.removeCallbacks(this)
       handler.postDelayed(1000);
           
  ,1000)
  

【讨论】：

在片段构造函数中传递参数不是一个好方法 - best practice for instantiating a fragment

在上面的答案中刚刚分享了3种方法来解决@bao ol根据这里的问题所面临的实际问题......希望它可以帮助