小贝子编程

无法解析 (RecyclerView)findViewById(R.id.xxx) 中的符号



我想通过连接到 firebase 使用 RecycleView 创建食物菜单，我已经将recycler_menu声明为变量，但是当我输入recycler_menu = (RecyclerView)findViewById(R.id.recycler_menu);时出现错误显示无法解析符号R.id.recycler_menu。需要有关解决此错误的帮助。我已经添加了implementation 'com.android.support:recyclerview-v7:27.1.1'支持库，但仍然无法解决此错误。

首页.java 

package com.example.liew.idelivery;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
import android.widget.Toast;
import com.example.liew.idelivery.Common.Common;
import com.example.liew.idelivery.Interface.ItemClickListener;
import com.example.liew.idelivery.Model.Category;
import com.example.liew.idelivery.ViewHolder.MenuViewHolder;
import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.squareup.picasso.Picasso;
public class Home extends AppCompatActivity implements 
NavigationView.OnNavigationItemSelectedListener {
FirebaseDatabase database;
DatabaseReference category;
TextView txtFullName;
RecyclerView recycler_menu;
RecyclerView.LayoutManager layoutManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
toolbar.setTitle("Menu");
setSupportActionBar(toolbar);
//Init Firebase
database = FirebaseDatabase.getInstance();
category = database.getReference("Category");
TextView txtFullName;

FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
//set name for user
View headerView = navigationView.getHeaderView(0);
txtFullName = (TextView)headerView.findViewById(R.id.txtFullName);
txtFullName.setText(Common.currentUser.getName());
// Load menu
recycler_menu = (RecyclerView)findViewById(R.id.recycler_menu);
recycler_menu.setHasFixedSize(true);
layoutManager = new LinearLayoutManager(this);
recycler_menu.setLayoutManager(layoutManager);
loadMenu();
}
private void loadMenu() {
FirebaseRecyclerAdapter<Category,MenuViewHolder> adapter = new FirebaseRecyclerAdapter<Category, MenuViewHolder>(Category.class,R.layout.menu_item,MenuViewHolder.class,category){
@Override
protected void populateViewHolder(MenuViewHolder viewHolder, Category model, int position) {
viewHolder.txtMenuName.setText(model.getName());
Picasso.with(getBaseContext()).load(model.getImage()).into(viewHolder.imageView);
final Category clickItem = model;
viewHolder.setItemClickListener(new ItemClickListener() {
@Override
public void onClick(View view, int position, boolean isLongClick) {
Toast.makeText(Home.this,""+clickItem.getName(), Toast.LENGTH_SHORT).show();
}
});
}
};
recycler_menu.setAdapter(adapter);
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.home, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {

return super.onOptionsItemSelected(item);
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_menu) {
// Handle the camera action
} else if (id == R.id.nav_cart) {
}else if (id == R.id.nav_orders) {
}else if (id == R.id.nav_logout) {
}else if (id == R.id.nav_share) {
}else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}

菜单视图持有人.java

package com.example.liew.idelivery.ViewHolder;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
import com.example.liew.idelivery.Interface.ItemClickListener;
import com.example.liew.idelivery.R;
public class MenuViewHolder extends RecyclerView.ViewHolder implements 
View.OnClickListener {
public TextView txtMenuName;
public ImageView imageView;
private ItemClickListener itemClickListener;
public MenuViewHolder(View itemView){
super(itemView);
txtMenuName = (TextView)itemView.findViewById(R.id.menu_name);
imageView = (ImageView)itemView.findViewById(R.id.menu_image);
itemView.setOnClickListener(this);

}
public void setItemClickListener(ItemClickListener itemClickListener){
this.itemClickListener = itemClickListener;
}
@Override
public void onClick(View view){
itemClickListener.onClick(view,getAdapterPosition(),false);
}
}

menu_item.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="200dp"
app:cardElevation="4dp">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/menu_image"
android:scaleType="centerCrop"
android:src="@drawable/background"
android:layout_width="match_parent"
android:layout_height="match_parent" />

<TextView
android:id="@+id/menu_name"
android:text="Name of Menu"
android:textAlignment="center"
android:textColor="@android:color/white"
android:background="#4f0e0d0e"
android:textSize="20sp"
android:layout_alignParentBottom="true"
android:layout_width="match_parent"
android:layout_height="wrap_content" />

</RelativeLayout>
</android.support.v7.widget.CardView>

activity_home.xml

<?xml version="1.0" encoding="utf-8"? 
<android.support.v4.widget.DrawerLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
android:background="@drawable/background"
tools:openDrawer="start">
<include
layout="@layout/app_bar_home"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<android.support.design.widget.NavigationView
android:id="@+id/nav_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:fitsSystemWindows="true"
app:headerLayout="@layout/nav_header_home"
android:background="@color/overlayBackground"
app:itemTextColor="@android:color/white"
app:itemIconTint="@android:color/white"
app:menu="@menu/activity_home_drawer" />
</android.support.v4.widget.DrawerLayout>

menu_item.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="200dp"
app:cardElevation="4dp">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/menu_image"
android:scaleType="centerCrop"
android:src="@drawable/background"
android:layout_width="match_parent"
android:layout_height="match_parent" />

<TextView
android:id="@+id/menu_name"
android:text="Name of Menu"
android:textAlignment="center"
android:textColor="@android:color/white"
android:background="#4f0e0d0e"
android:textSize="20sp"
android:layout_alignParentBottom="true"
android:layout_width="match_parent"
android:layout_height="wrap_content" />

</RelativeLayout>

content_home.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context=".Home"
tools:showIn="@layout/app_bar_home">
<android.support.v7.widget.RecyclerView>
android:id="@+id/recycler_menu"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
</android.support.v7.widget.RecyclerView>
</android.support.constraint.ConstraintLayout>

在你的content_home.xml试试这个：

<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_menu"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
</android.support.v7.widget.RecyclerView>

你的代码有什么问题，>字符被放在错误的位置，你的原始代码：

<android.support.v7.widget.RecyclerView>
android:id="@+id/recycler_menu"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
</android.support.v7.widget.RecyclerView>

findViewById 在 xml 文件中搜索 ID "recycler_menu"。

如果您的 xml 文件中没有这样的 ID，则会出现此错误。

正如我所看到的，此ID未在您的XML文件中实现。也许您还有一些实现它的 xml 文件？请出示实现此 ID 的 xml 文件

如果你想声明

recycler_menu =(RecyclerView)findViewById(R.id.recycler_menu);

您应该创建一个如下所示的 xml 文件：

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.RecyclerView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/recycler_menu"
android:layout_width="match_parent"
android:layout_height="wrap_content" />

'

获取引用的代码完全没问题

recycler_menu = (RecyclerView)findViewById(R.id.recycler_menu);

转到 activity_home 的 XML，并重新确认回收器视图具有带有名称的 ID

recycler_menu

喜欢这个

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.RecyclerView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/recycler_menu"
android:layout_width="match_parent"
android:layout_height="wrap_content" />

如需更多帮助，请发送 XML 的 activity_home

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