Java 从一个片段移动到另一个片段时出错

错误显示无法将突出显示强制转换为片段，无法将概述强制转换为片段，错误仅出现在selectFrag方法中。请任何人帮我解决这个问题。我想在单击textview项时将一个片段切换到另一个片段

public class MainActivity extends Activity {
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
        }        

     public void selectFrag(View view){      
        Fragment fr;
        if (view == findViewById(R.id.txt_highlite)) {          
        fr = (Fragment) new Highlight();
        }
        else{
            fr = (Fragment) new Overview();
        }       
        FragmentManager fm = getFragmentManager();
        FragmentTransaction fragmentTransaction = fm.beginTransaction();
        fragmentTransaction.replace(R.id.place_holder, fr);
        fragmentTransaction.commit();
}
    }

//重点课程

public class Highlight extends Fragment {   
    @Override
    public View onCreateView(LayoutInflater inflater,
             ViewGroup container, Bundle savedInstanceState) {      
        return inflater.inflate(R.layout.highlight, container, false);
    }
}

//概述类

public class Overview extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater,
             ViewGroup container, Bundle savedInstanceState) 
    {
        return inflater.inflate(R.layout.overview, container, false);
    }
}

//activity_main.xml

<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" >    
      <RelativeLayout
            android:layout_width="fill_parent"
            android:layout_height="100dp" >

        <LinearLayout
            android:id="@+id/lin_projectoverview"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="15dp" >

            <TextView
                android:id="@+id/text_Projectoverview"
                android:layout_width="fill_parent"
                android:layout_height="fill_parent"
                android:gravity="center"
                android:text="Project Overview"
                android:textSize="26sp"
                android:textStyle="bold" />
        </LinearLayout>

        <LinearLayout
            android:id="@+id/project_name"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:layout_marginTop="65dp"          
            android:gravity="center" >

            <TextView
                android:id="@+id/txt_overview"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textSize="18sp"
                android:textStyle="bold"
                android:layout_marginLeft="12dp"
                android:text="Overview" />

            <TextView
                android:id="@+id/txt_highlite"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textSize="18sp"
                android:textStyle="bold"
                android:layout_marginLeft="12dp"
                android:text="Highlight" />            
        </LinearLayout>          
    </RelativeLayout>   

     <fragment 
          android:name="com.example.fragment_move.Overview"
          android:id="@+id/place_holder"
          android:layout_width="fill_parent"
          android:layout_height="fill_parent"/>    
</RelativeLayout>

---

您将fr声明为片段，但创建了一个突出显示

突出显示扩展了片段，但您需要将其强制转换为片段，以便在FragmentTransaction中使用它

所以试试这个：

public void selectFrag(View view){      
        Fragment fr;
        if (view == findViewById(R.id.txt_highlite)) {          
        fr = (Fragment) new Highlight();
        }
        else{
            fr = (Fragment) new Overview();
        }       
        FragmentManager fm = getFragmentManager();
        FragmentTransaction fragmentTransaction = fm.beginTransaction();
        fragmentTransaction.replace(R.id.place_holder, fr);
        fragmentTransaction.commit();
}