Question

我正在尝试在片段中添加文本，但是每当我调用函数时：updateTextField尽管他是万能的，但仍然看到错误，但不知道经常尝试解决的问题，是否可能进行修改一些代码来纠正错误请帮我代码： // MainActivity

public class MainActivity extends AppCompatActivity {


    private android.view.View mEditText;

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

    }


    public void test_btn(View V){

        SecondFragment newGamefragment = new SecondFragment();
        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        transaction.replace(R.id.fragment2 , newGamefragment);
        transaction.addToBackStack(null);
        transaction.commit();
        newGamefragment.updateTextField("asdas");


    }



}

//SecondFragment



public class SecondFragment extends Fragment {

    private TextView updateText;

    public SecondFragment(){

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_second, container, false);
        updateText = (TextView)view.findViewById(R.id.text_update);
        return view;
    }


    public void updateTextField(String newText){
        updateText.setText(newText);
    }
}

// xml mainactivity

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#574706"
    tools:context=".MainActivity">



    <FrameLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/fragment2"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"/>

    <TextView
        android:id="@+id/tv_main"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="HIHIH"
        android:textSize="30dp"
        android:textColor="#54ffff"
        android:layout_below="@+id/fragment2"
        android:layout_alignParentEnd="true"
        android:layout_marginEnd="94dp"
        android:layout_marginTop="39dp" />


    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tv_main"
        android:onClick="test_btn"

        />

</RelativeLayout>


// xml fragment_second

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/text_update"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="h"
        android:textColor="#ff0000"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:textStyle="bold"
        android:layout_marginTop="32dp" />

</RelativeLayout>

// Logcat：

  Process: com.example.android.settextfromoutfragment, PID: 2536
                                                                                          java.lang.IllegalStateException: Could not execute method for android:onClick
                                                                                              at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
                                                                                              at android.view.View.performClick(View.java:5076)
                                                                                              at android.view.View$PerformClick.run(View.java:20279)
                                                                                              at android.os.Handler.handleCallback(Handler.java:739)
                                                                                              at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                              at android.os.Looper.loop(Looper.java:135)
                                                                                              at android.app.ActivityThread.main(ActivityThread.java:5910)
                                                                                              at java.lang.reflect.Method.invoke(Native Method)
                                                                                              at java.lang.reflect.Method.invoke(Method.java:372)
                                                                                              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1405)
                                                                                              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1200)
                                                                                           Caused by: java.lang.reflect.InvocationTargetException
                                                                                              at java.lang.reflect.Method.invoke(Native Method)
                                                                                              at java.lang.reflect.Method.invoke(Method.java:372)
                                                                                              at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
                                                                                              at android.view.View.performClick(View.java:5076) 
                                                                                              at android.view.View$PerformClick.run(View.java:20279) 
                                                                                              at android.os.Handler.handleCallback(Handler.java:739) 
                                                                                              at android.os.Handler.dispatchMessage(Handler.java:95) 
                                                                                              at android.os.Looper.loop(Looper.java:135) 
                                                                                              at android.app.ActivityThread.main(ActivityThread.java:5910) 
                                                                                              at java.lang.reflect.Method.invoke(Native Method) 
                                                                                              at java.lang.reflect.Method.invoke(Method.java:372) 
                                                                                              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1405) 
                                                                                              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1200) 
                                                                                           Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
                                                                                              at com.example.android.settextfromoutfragment.SecondFragment.updateTextField(SecondFragment.java:27)
                                                                                              at com.example.android.settextfromoutfragment.MainActivity.test_btn(MainActivity.java:36)
                                                                                              at java.lang.reflect.Method.invoke(Native Method) 
                                                                                              at java.lang.reflect.Method.invoke(Method.java:372) 
                                                                                              at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
                                                                                              at android.view.View.performClick(View.java:5076) 
                                                                                              at android.view.View$PerformClick.run(View.java:20279) 
                                                                                              at android.os.Handler.handleCallback(Handler.java:739) 
                                                                                              at android.os.Handler.dispatchMessage(Handler.java:95) 
                                                                                              at android.os.Looper.loop(Looper.java:135) 
                                                                                              at android.app.ActivityThread.main(ActivityThread.java:5910) 
                                                                                              at java.lang.reflect.Method.invoke(Native Method) 
                                                                                              at java.lang.reflect.Method.invoke(Method.java:372) 
                                                                                              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1405) 
                                                                                              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1200)

Answer 1

您可以通过参数和onCreateView方法在第二个片段中传递string，可以检索此参数并在文本视图上进行设置。这是示例代码。

在您的onClick方法上添加以下代码。

 SecondFragment newGamefragment = SecondFragment.newInstance();
        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        transaction.replace(R.id.fragment2 , newGamefragment);
        transaction.addToBackStack(null);
        transaction.commit();


/**
 * Create a new instance of secondFragment, 
 */
public static SecondFragment newInstance(String yourString) {
    secondFragment f = new secondFragment();
    Bundle args = new Bundle();
    args.putStirng("myString", yourString);
    f.setArguments(args);
    return f;
}

通过片段的onCreateView方法检索您的字符串。

Bundle args = getArguments();
String myString = args.getString("myString");

然后，将此字符串设置为您的textview

 updateText.setText(myString);

Answer 2

您不能在MainActivity中访问更改文本，可以通过两种方式执行此操作：

1：

public class MainActivity extends AppCompatActivity {


    private android.view.View mEditText;

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

    }


    public void test_btn(View V){

        SecondFragment newGamefragment = new SecondFragment.newInstance("asdas");
        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        transaction.replace(R.id.fragment2 , newGamefragment);
        transaction.addToBackStack(null);
        transaction.commit();



    }



}

//SecondFragment



public class SecondFragment extends Fragment {

    private TextView updateText;


    public static SecondFragment newInstance(String str) {
        SecondFragment s= new SecondFragment ();
        Bundle args = new Bundle();
        args.putString("str", str);
        signUpFragment.setArguments(args);
        return s;
    }

    public SecondFragment(){

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_second, container, false);
        updateText = (TextView)view.findViewById(R.id.text_update);
        if (getArguments() != null)
            updateTextField( getArguments().getString("str"));
        return view;
    }


    public void updateTextField(String newText){
        updateText.setText(newText);
    }
}

2：EventBus：您会了解更多click this

无法将文本从外部片段放到textview中吗？

2 个答案: