片段管理器事务错误的参数类型

Question

我正在研究一个导航抽屉，有两个不同的片段。不起作用的是fragmentManager.beginTransaction().replace(R.id.fragment, first).commit();中的"first"和"second"以及以下java文件中的另一行。它引发的错误是：

Wrong 2nd argument type. Found: 'com.example.name_of_app.First', required: 'android.support.v4.app.Fragment' 
replace
(int,
android.support.v4.app.Fragment)
in FragmentTransaction cannot be applied
to
(int,
com.example.name_of_app.First)
 

引发问题的 MainActivity.java 文件部分：

public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
setTitle("First Fragment");
First first = new First();
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().replace(R.id.fragment, first).commit();
} else if (id == R.id.nav_gallery) {
setTitle("Second Fragment");
Second second = new Second();
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().replace(R.id.fragment, second).commit();
} 

这是第一个.java片段

import android.os.Bundle;
import android.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

/**
* A simple {@link Fragment} subclass.
*/
public class First extends Fragment {

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

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_first, container, false);
}

}

fragment_first.xml：

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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"
tools:context="First">
<!-- TODO: Update blank fragment layout -->
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textSize="50dp"
android:text="@string/hello_blank_fragment" />
</FrameLayout>

Answer 1

如果您查看错误，您将看到android.support.v4.app.Fragment.但是，您的类First具有import android.app.Fragment;导入。

它们不匹配。将导入更改为import android.support.v4.app.Fragment;