Myujth

I am following the Android Developer's explanatin on how to set RecyclerView, but I get some errors, for example android.widget.LinearLayout cannot be cast to android.widget.TextView.

The code taken from here : RecyclerView

This is my code, including all necessary files:

MainActivity.java:

package com.example.lastlocation.recyclerviewer;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;

public class MainActivity extends AppCompatActivity 
 private RecyclerView mRecyclerView;
 private RecyclerView.Adapter mAdapter;
 private RecyclerView.LayoutManager mLayoutManager;

 @Override
 protected void onCreate(Bundle savedInstanceState) 
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);

 // use this setting to improve performance if you know that changes
 // in content do not change the layout size of the RecyclerView
 mRecyclerView.setHasFixedSize(true);

 // use a linear layout manager
 mLayoutManager = new LinearLayoutManager(this);
 mRecyclerView.setLayoutManager(mLayoutManager);
 String myDataset = new String[5];
 myDataset[0] = "Data0";
 myDataset[1] = "Data1";
 myDataset[2] = "Data2";
 myDataset[3] = "Data3";
 myDataset[4] = "Data4";

 // specify an adapter (see also next example)
 mAdapter = new MyAdapter(myDataset);
 mRecyclerView.setAdapter(mAdapter);
 

This is MyAdapter.java:

package com.example.lastlocation.recyclerviewer;

import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> 
 private String mDataset;

 // Provide a reference to the views for each data item
 // Complex data items may need more than one view per item, and
 // you provide access to all the views for a data item in a view holder
 public static class MyViewHolder extends RecyclerView.ViewHolder 
 // each data item is just a string in this case
 public TextView mTextView;
 public MyViewHolder(TextView v) 
 super(v);
 mTextView = v;
 
 

 // Provide a suitable constructor (depends on the kind of dataset)
 public MyAdapter(String myDataset) 
 mDataset = myDataset;
 

 // Create new views (invoked by the layout manager)
 @Override
 public MyAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent,
 int viewType) 


 TextView v = (TextView) LayoutInflater.from(parent.getContext())
 .inflate(R.layout.my_text_view, parent, false);

 MyViewHolder vh = new MyViewHolder(v);
 return vh;
 

 // Replace the contents of a view (invoked by the layout manager)
 @Override
 public void onBindViewHolder(MyViewHolder holder, int position) 
 // - get element from your dataset at this position
 // - replace the contents of the view with that element
 holder.mTextView.setText(mDataset[position]);

 

 // Return the size of your dataset (invoked by the layout manager)
 @Override
 public int getItemCount() 
 return mDataset.length;
 

this is activity_main.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"
 tools:context=".MainActivity">

 <View
 android:id="@+id/view"
 android:layout_width="386dp"
 android:layout_height="135dp"
 app:layout_constraintEnd_toEndOf="parent"
 app:layout_constraintStart_toStartOf="parent"
 app:layout_constraintTop_toTopOf="parent" />

 <ImageView
 android:id="@+id/imageView"
 android:layout_width="66dp"
 android:layout_height="64dp"
 android:layout_marginTop="24dp"
 app:layout_constraintEnd_toEndOf="parent"
 app:layout_constraintStart_toStartOf="parent"
 app:layout_constraintTop_toTopOf="@+id/view"
 app:srcCompat="@android:color/holo_orange_dark" />

 <TextView
 android:id="@+id/textView2"
 android:layout_width="68dp"
 android:layout_height="30dp"
 android:layout_marginTop="8dp"
 android:text="John Doe"
 app:layout_constraintEnd_toEndOf="parent"
 app:layout_constraintStart_toStartOf="parent"
 app:layout_constraintTop_toBottomOf="@+id/imageView" />


 <!-- A RecyclerView with some commonly used attributes -->
 <android.support.v7.widget.RecyclerView
 android:id="@+id/my_recycler_view"
 android:layout_width="375dp"
 android:layout_height="367dp"
 android:layout_marginBottom="8dp"
 android:layout_marginEnd="8dp"
 android:layout_marginLeft="8dp"
 android:layout_marginRight="8dp"
 android:layout_marginStart="8dp"
 android:layout_marginTop="4dp"
 android:scrollbars="vertical"
 app:layout_constraintBottom_toBottomOf="parent"
 app:layout_constraintEnd_toEndOf="parent"
 app:layout_constraintHorizontal_bias="0.428"
 app:layout_constraintStart_toStartOf="parent"
 app:layout_constraintTop_toBottomOf="@+id/view"
 app:layout_constraintVertical_bias="1.0" />



</android.support.constraint.ConstraintLayout>

And this is the xml for a single text view called my_text_view.xml:

<?xml version="1.0" encoding="utf-8"?>


<!-- Layout for a single list item -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:orientation="vertical"
 android:padding="16dp">

 <TextView
 android:id="@+id/my_text_view"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 />


 </LinearLayout> 

As you can see I nearly copied the code from the Android Developer's website, but I still don't know where is the problem.

 public static class MyViewHolder extends RecyclerView.ViewHolder 
 // each data item is just a string in this case
 public TextView mTextView;
 public MyViewHolder(TextView v) 
 super(v);
 mTextView = v;
 
 

 // Provide a suitable constructor (depends on the kind of dataset)
 public MyAdapter(String myDataset) 
 mDataset = myDataset;
 

The problem is in your ViewHolder constructor it should be like that

public static class MyViewHolder extends RecyclerView.ViewHolder 
 // each data item is just a string in this case
 public TextView mTextView;
 public MyViewHolder(View v) 
 super(v);
 mTextView = v.findViewById(R.id.your_text_view_id);
 
 


 @Override
 public MyAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent,
 int viewType) 


 View v = (TextView) LayoutInflater.from(parent.getContext())
 .inflate(R.layout.my_text_view, parent, false);

 MyViewHolder vh = new MyViewHolder(v);
 return vh;
 

You are trying to assign LinearLayout which is the View in your constructor to your TextView and it is crashing. This will fix the problem.
The view you receive as a constructor param in your ViewHolder is the root view of your ViewHolder, in your case a LinearLayout, from this root view you can find the other views in it.

You are inflating row view wrongly and thus not assigning views in viewholder in proper manner change your code as below

@Override
 public UserListAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) 
 LayoutInflater inflater = LayoutInflater.from(parent.getContext());
 ViewHolder vh = new ViewHolder((inflater.inflate(R.layout.your_row_layout, parent, false)));
 return vh;
 

and change your viewholder as below

public static class MyViewHolder extends RecyclerView.ViewHolder 
 // each data item is just a string in this case
 public TextView mTextView;
 public MyViewHolder(View v) 
 super(v);
 mTextView = v.findViewById(R.id.my_text_view);
 
 

Just Simply you need to change your onCreateViewHolder method by taking as

View view = LayoutInflater.from(parent.getContext())
 .inflate(R.layout.my_text_view, parent, false);
return view;