Error when building recycler view in android studio

Error when building recycler view in android studio - java

My problem 1:I'm using android studio to build a recycler view.However,when I run the code,this notification pop up.
My problem 2:In MainActivity.java ,an error that shown cannot find system variable Recyclerview in line 23 pop up.May I know how to solve it?becuz I declared it already.
Below are my codes:
(MainActivity.java:)
package com.example.recyclerviewdemo;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.os.Bundle;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
RecyclerView recyclerView;
List <Details> detailsList;
MyAdapter myAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView=findViewById(R.id.recyclerView);
detailsList=new ArrayList<>();
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setHasFixedSize(true);
//passing data to model class
for (int i=0;i<=10;i++){
Details details=new Details("Java "+i,"This is description " +i);
detailsList.add(details);
}
myAdapter=new MyAdapter(detailsList);
recyclerView.setAdapter(myAdapter);
}
}
(activity_main.xml:)
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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">
<androidx.recyclerview.widget.RecyclerView
android:layout_width="409dp"
android:layout_height="729dp"
tools:layout_editor_absoluteX="1dp"
tools:layout_editor_absoluteY="1dp" />
</androidx.constraintlayout.widget.ConstraintLayout>
MyAdapter.java:
package com.example.recyclerviewdemo;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.core.widget.TextViewOnReceiveContentListener;
import androidx.recyclerview.widget.RecyclerView;
import org.jetbrains.annotations.NotNull;
import java.util.List;
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
private List<Details> detailsList;
public MyAdapter(List<Details> detailsList) {
this.detailsList = detailsList;
}
#NonNull
#NotNull
#Override
public MyViewHolder onCreateViewHolder(#NonNull #NotNull ViewGroup parent, int viewType) {
View view= LayoutInflater.from(parent.getContext()).inflate(
R.layout.rv_item_list,
parent,
false
);
return new MyViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull #NotNull MyAdapter.MyViewHolder holder, int
position) {
holder.tvTitle.setText(detailsList.get(position).getTitle());
holder.tvDesc.setText(detailsList.get(position).getTitle());
}
#Override
public int getItemCount() {
return detailsList.size();
}
public class MyViewHolder extends RecyclerView.ViewHolder {
TextView tvTitle;
TextView tvDesc;
public MyViewHolder(#NonNull #org.jetbrains.annotations.NotNull View itemView) {
super(itemView);
tvTitle=itemView.findViewById(R.id.tvTitle);
tvDesc=itemView.findViewById(R.id.tvDescription);
}
}
}
Details.java:
package com.example.recyclerviewdemo;
public class Details {
private String title;
private String description;
public Details(String title, String description) {
this.title = title;
this.description = description;
}
public String getTitle() {
return title;
}
public String getDescription() {
return description;
}
}
rv_item_list.xml:
<?xml version="1.0" encoding="utf-8"?>
<com.google.android.material.card.MaterialCardView
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
xmlns:app="http://schemas.android.com/apk/res-auto"
app:cardCornerRadius="5dp"
app:cardElevation="5dp"
android:layout_margin="5dp">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="#+id/imageView"
android:layout_width="100dp"
android:layout_height="100dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="#drawable/a" />
<TextView
android:id="#+id/tvTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:layout_marginTop="24dp"
android:text="TextView"
app:layout_constraintStart_toEndOf="#+id/imageView"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="#+id/tvDescription"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:layout_marginEnd="200dp"
android:text="TextView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="#+id/imageView"
app:layout_constraintTop_toBottomOf="#+id/tvTitle" />
</androidx.constraintlayout.widget.ConstraintLayout>
</com.google.android.material.card.MaterialCardView>

You forget to declare the id in the XML file..Add this in your activity xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recyclerView"
android:layout_width="409dp"
android:layout_height="729dp"
tools:layout_editor_absoluteX="1dp"
tools:layout_editor_absoluteY="1dp" />
</androidx.constraintlayout.widget.ConstraintLayout>

Related

Getting duplicated cardviews using SwipeRefresh Layout

So here is my problem, I got an API that gives me the lastest news of many sources. Each one of them goes with a cardview. The problem here is, while I'm using the swipeRefresh, it gets duplicated cardViews with the same news, like if I have 10 news, it duplicates to 20 with the same ones.
Here is my code where I apply the swipeRefresh:
package com.example.newsapp4;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import androidx.swiperefreshlayout.widget.SwipeRefreshLayout;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;
import com.example.newsapp4.Model.Articles;
import com.example.newsapp4.Model.Headlines;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
public class bbcnews extends AppCompatActivity {
Adapter adapter;
Intent intencion;
RecyclerView recyclerView;
public static String source = "My Source";
public static String API_KEY = "My API Key";
SwipeRefreshLayout srl;
List<Articles> articles = new ArrayList<>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_bbcnews);
srl = findViewById(R.id.swipeRefresh);
srl.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
#Override
public void onRefresh() {
retrieveJson(source, API_KEY);
}
});
recyclerView = findViewById(R.id.recyclerView1);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
adapter = new Adapter(bbcnews.this,articles);
recyclerView.setAdapter(adapter);
retrieveJson(source, API_KEY);
}
public void retrieveJson(String source, String apiKey){
srl.setRefreshing(true);
Call<Headlines> call = ApiClient.getInstance().getApi().getHeadlines(source, apiKey);
call.enqueue(new Callback<Headlines>() {
#Override
public void onResponse(Call<Headlines> call, Response<Headlines> response) {
if(response.isSuccessful() && response.body().getArticles() != null){
srl.setRefreshing(false);
articles.clear();
articles = response.body().getArticles();
adapter.setArticles(articles);
}
}
#Override
public void onFailure(Call<Headlines> call, Throwable t) {
srl.setRefreshing(false);
Toast.makeText(bbcnews.this, t.getLocalizedMessage(), Toast.LENGTH_SHORT).show();
}
});
}
public String getCountry(){
Locale locale = Locale.getDefault();
String country = locale.getCountry();
return country.toLowerCase();
}
public void aPerfil(View vista){
intencion = new Intent(this, profile_activity.class);
startActivity(intencion);
}
}
I don't think that I need to put the xml code with the progressbar and the swipeRefresh but here are both:
This one is the Items.xml where I created the cardView:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
xmlns:app="http://schemas.android.com/apk/res-auto">
<androidx.cardview.widget.CardView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
app:cardElevation="4dp"
android:id="#+id/cardView"
app:cardCornerRadius="10dp">
<FrameLayout
android:layout_width="match_parent"
android:layout_height="200dp">
<ProgressBar
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:id="#+id/loader"/>
<ImageView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/image"
android:scaleType="centerCrop"
android:src="#drawable/img"/>
<ImageView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#drawable/gradient" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TITLE"
android:textSize="20dp"
android:padding="10dp"
android:fontFamily="#font/g_bold"
android:textColor="#color/white"
android:id="#+id/tvTitle"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:orientation="horizontal">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Source"
android:textSize="16dp"
android:padding="10dp"
android:ems="15"
android:fontFamily="#font/g_light"
android:textColor="#color/white"
android:id="#+id/tvSource"/>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:fontFamily="#font/g_light"
android:gravity="right"
android:text="Date"
android:textColor="#color/white"
android:padding="10dp"
android:textSize="16dp"
android:id="#+id/tvDate"/>
</LinearLayout>
</FrameLayout>
</androidx.cardview.widget.CardView>
</LinearLayout>
And here the one with the swipeRefresh in the recyclerView:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
android:orientation="vertical"
android:background="#color/white"
tools:context=".bbcnews">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="DINGO BBC NEWS"
android:textColor="#color/black"
android:textSize="20sp"
android:fontFamily="#font/g_bold"
android:background="#color/white"
android:padding="10dp"
android:textAlignment="center"/>
<GridLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:paddingTop="10dp"
android:paddingBottom="10dp"
android:columnCount="2"
android:paddingLeft="20dp"
android:paddingRight="5dp"
android:background="#drawable/black_background"
android:rowCount="2">
<EditText
android:id="#+id/editTextTextPersonName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:ems="10"
android:hint="Search"
android:textColor="#color/grey"
android:textColorHint="#color/grey"
android:padding="5dp"
android:layout_column="0"
android:background="#drawable/black_background"
android:layout_row="0"
android:layout_columnWeight="1"
android:inputType="textPersonName" />
<Button
android:id="#+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingRight="20dp"
android:background="#drawable/black_background"
android:drawableRight="#drawable/ic_baseline_search_24"
android:layout_column="1"
android:layout_row="0"/>
</GridLayout>
<androidx.swiperefreshlayout.widget.SwipeRefreshLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/swipeRefresh">
<androidx.recyclerview.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="5dp"
android:id="#+id/recyclerView1"/>
</androidx.swiperefreshlayout.widget.SwipeRefreshLayout>
</LinearLayout>
Also this is my adapter.java code:
package com.example.newsapp4;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.cardview.widget.CardView;
import androidx.recyclerview.widget.RecyclerView;
import com.example.newsapp4.Model.Articles;
import com.squareup.picasso.Picasso;
import java.util.List;
public class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
Context context;
List<Articles> articles;
public Adapter(Context context, List<Articles> articles) {
this.context = context;
this.articles = articles;
}
#NonNull
#Override
public ViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.items, parent, false);
return new ViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull ViewHolder holder, int position) {
final Articles a = articles.get(position);
String imageUrl = a.getUrlToImage();
holder.tvTitle.setText(a.getTitle());
holder.tvSource.setText(a.getSource().getName());
holder.tvDate.setText(a.getPublishedAt());
Picasso.with(context).load(imageUrl).into(holder.imageView);
}
#Override
public int getItemCount() {
return articles.size();
}
public static class ViewHolder extends RecyclerView.ViewHolder {
TextView tvTitle,tvSource,tvDate;
ImageView imageView;
CardView cardView;
public ViewHolder(#NonNull View itemView) {
super(itemView);
tvTitle = itemView.findViewById(R.id.tvTitle);
tvSource = itemView.findViewById(R.id.tvSource);
tvDate = itemView.findViewById(R.id.tvDate);
imageView = itemView.findViewById(R.id.image);
cardView = itemView.findViewById(R.id.cardView);
}
}
public void setArticles(List<Articles> articles) {
this.articles.addAll(articles);
int count = getItemCount();
notifyItemRangeInserted(count, count + articles.size());
}
}
Thanks for your time!

// Clear adapter list before add to list.
public void setArticles(List<Articles> articles) {
if(this.articles!=null && this.articles.size()>0)
this.articles.clear();
this.articles.addAll(articles);
int count = getItemCount();
notifyItemRangeInserted(count, count + articles.size());
}

From what I can understand in your code is on the success of API call after Swipe Refresh which is this section here
articles.clear();
articles = response.body().getArticles();
adapter.setArticles(articles);
You are here clearing the article inside your activity, but the thing is inside your Adapter there is already another list of articles, you are not clearing them.
And then when you make the adapter.setArticles(articles); call, inside the following function, your articles get added to the already existing list of articles and thus, the duplicate list.
public void setArticles(List<Articles> articles) {
this.articles.addAll(articles);
int count = getItemCount();
notifyItemRangeInserted(count, count + articles.size());
}
To fix this you can make the following modifications to your function.
public void setArticles(List<Articles> articles, boolean clearAll) {
if(clearAll){ this.articles.clear(); }
this.articles.addAll(articles);
notifyDataSetChanged();
}
And then modify your function call as follows
adapter.setArticles(articles, true);
That way when the Boolean is true, it will clear the existing list. Also I would suggest you to replace the insert call with data set change call. Else you can make a separate function all together for adding elements and for clearing existing elements.

Showing xml for correct view

When a user logs in to my app, they can either click the view students button or daily grading button. The view students will display a student's image and their name. The daily grading will display the student's image, name, and two checkboxes that says pass or fail. Now the issue I have is that the checkboxes for pass and fail are showing up in my activity_view_students.xml view when it should not be. It should only show when a user clicks daily grading. I will put images below to make it clearer
What it looks like in the activity_view_students.xml
What it should look like in activity_view_students.xml
I will paste all relevant code below.
ViewStudents.java
package com.example.studenttracker;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.Query;
import com.google.firebase.database.ValueEventListener;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
public class ViewStudents extends AppCompatActivity {
RecyclerView recyclerView;
Button addStudent;
private DatabaseReference myRef;
public ArrayList<Students> students;
private RecyclerAdapter recyclerAdapter;
private Button orderStudents;
private EditText mEditTextAge;
private EditText mEditTextAssignment;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_students);
recyclerView = findViewById(R.id.recyclerView);
addStudent = findViewById(R.id.addStudentButton);
mEditTextAge = findViewById(R.id.EditTextAge);
mEditTextAssignment = findViewById(R.id.EditTextAssignment);
orderStudents = findViewById(R.id.orderStudents);
addStudent.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(ViewStudents.this, AddStudent.class));
}
});
recyclerView.setLayoutManager(new GridLayoutManager(this, 2));
recyclerView.setHasFixedSize(true);
myRef = FirebaseDatabase.getInstance().getReference();
students = new ArrayList<>();
ClearAll();
GetDataFromFirebase();
}
private void GetDataFromFirebase() {
Query query = myRef.child("student");
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
ClearAll();
for(DataSnapshot snapshot: dataSnapshot.getChildren()) {
Students student = new Students();
if (snapshot.child("url").getValue() == null) {
student.setImageUrl(snapshot.child("imageUrl").getValue().toString());
}
else {
student.setImageUrl(snapshot.child("url").getValue().toString());
}
// student.setAge(mEditTextAge.getText().toString());
// student.setAssignment(mEditTextAssignment.getText().toString().trim());
student.setName(snapshot.child("name").getValue().toString());
students.add(student);
}
recyclerAdapter = new RecyclerAdapter(getApplicationContext(), students);
recyclerView.setAdapter(recyclerAdapter);
recyclerAdapter.notifyDataSetChanged();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
private void ClearAll() {
if (students != null) {
students.clear();
if(recyclerAdapter != null) {
recyclerAdapter.notifyDataSetChanged();
}
}
students = new ArrayList<>();
}
public void orderStudents(View view) {
Collections.sort( students, new Comparator<Students>() {
#Override
public int compare( Students o1, Students o2 ) {
return o1.name.compareTo( o2.name );
}
});
recyclerAdapter.notifyDataSetChanged();
}
}
RecyclerAdapter.java
package com.example.studenttracker;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.ImageView;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import com.bumptech.glide.Glide;
import java.util.ArrayList;
public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.ViewHolder> {
private OnItemClickListener mListener;
public interface OnItemClickListener {
void onItemClick(int position);
}
public void setOnItemClickListener(OnItemClickListener listener) {
mListener = listener;
}
private static final String Tag = "RecyclerView";
private Context mContext;
private ArrayList<Students> studentsArrayList;
public RecyclerAdapter(Context mContext, ArrayList<Students> studentsArrayList) {
this.mContext = mContext;
this.studentsArrayList = studentsArrayList;
}
#NonNull
#Override
public RecyclerAdapter.ViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.activity_student_item,parent,false);
return new ViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull ViewHolder holder, int position) {
//TextView
holder.textView.setText(studentsArrayList.get(position).getName());
Glide.with(mContext).load(studentsArrayList.get(position).getImageUrl()).into(holder.imageView);
// if (studentsArrayList.get(position).get) { //check if you need the buttons or not
// holder..setVisibility(View.VISIBLE);
// holder.checkBox2.setVisibility(View.VISIBLE);
// } else {
// holder.checkBox.setVisibility(View.GONE);
// holder.checkBox2.setVisibility(View.GONE);
// }
}
#Override
public int getItemCount() {
return studentsArrayList.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
ImageView imageView;
TextView textView;
public ViewHolder(#NonNull View itemView) {
super(itemView);
imageView = itemView.findViewById(R.id.imageView);
textView = itemView.findViewById(R.id.textView);
itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (mListener != null) {
int position = getAdapterPosition();
}
}
});
}
}
}
activity_view_students.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".ViewStudents">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recyclerView"
android:layout_width="409dp"
android:layout_height="729dp"
android:layout_marginEnd="1dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent" >
</androidx.recyclerview.widget.RecyclerView>
<Button
android:id="#+id/addStudentButton"
android:layout_width="wrap_content"
android:layout_height="50dp"
android:text="Add Students"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="#+id/orderStudents"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="orderStudents"
android:text="Order Students"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
daily_grading.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".DailyGrading">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recyclerView"
android:layout_width="409dp"
android:layout_height="729dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
activity_student_item.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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="wrap_content"
tools:context=".DailyGrading">
<androidx.cardview.widget.CardView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="50dp"
android:foreground="?android:attr/selectableItemBackground"
app:cardElevation="2dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
</androidx.cardview.widget.CardView>
<RelativeLayout
android:id="#+id/relativeLayout2"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="5dp"
tools:layout_editor_absoluteX="0dp"
tools:layout_editor_absoluteY="52dp">
<ImageView
android:id="#+id/imageView"
android:layout_width="match_parent"
android:layout_height="200dp"
android:layout_marginTop="50dp"
android:paddingTop="20dp"
android:scaleType="centerCrop" />
<TextView
android:id="#+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/imageView"
android:layout_margin="10dp"
android:textSize="16sp" />
<CheckBox
android:id="#+id/passc"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#id/textView"
android:text="PASS" />
<CheckBox
android:id="#+id/failc"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#id/textView"
android:layout_toRightOf="#+id/passc"
android:text="FAIL" />
</RelativeLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
GradingRecyclerAdapter
package com.example.studenttracker;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import com.bumptech.glide.Glide;
import java.util.ArrayList;
public class GradingRecyclerAdapter extends RecyclerView.Adapter<GradingRecyclerAdapter.ViewHolder> {
private OnItemClickListener mListener;
public interface OnItemClickListener {
void onItemClick(int position);
}
public void setOnItemClickListener(OnItemClickListener listener) {
mListener = listener;
}
private static final String Tag = "RecyclerView";
private Context mContext;
private ArrayList<Students> studentsArrayList;
public GradingRecyclerAdapter(Context mContext, ArrayList<Students> studentsArrayList) {
this.mContext = mContext;
this.studentsArrayList = studentsArrayList;
}
#NonNull
#Override
public GradingRecyclerAdapter.ViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.activity_grading_student_item,parent,false);
return new ViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull ViewHolder holder, int position) {
//TextView
holder.textView.setText(studentsArrayList.get(position).getName());
Glide.with(mContext).load(studentsArrayList.get(position).getImageUrl()).into(holder.imageView);
}
#Override
public int getItemCount() {
return studentsArrayList.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
ImageView imageView;
TextView textView;
Button passButton;
Button failButton;
public ViewHolder(#NonNull View itemView) {
super(itemView);
imageView = itemView.findViewById(R.id.imageView);
textView = itemView.findViewById(R.id.textView);
passButton = itemView.findViewById(R.id.PASS);
failButton = itemView.findViewById(R.id.FAIL);
// passButton.setVisibility(View.GONE);
// failButton.setVisibility(View.GONE);
itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (mListener != null) {
int position = getAdapterPosition();
}
}
});
}
}
}
activity_grading_student_item
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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="wrap_content"
tools:context=".DailyGrading">
<androidx.cardview.widget.CardView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="50dp"
android:foreground="?android:attr/selectableItemBackground"
app:cardElevation="2dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
</androidx.cardview.widget.CardView>
<RelativeLayout
android:id="#+id/relativeLayout2"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="5dp"
tools:layout_editor_absoluteX="0dp"
tools:layout_editor_absoluteY="52dp">
<ImageView
android:id="#+id/imageView"
android:layout_width="match_parent"
android:layout_height="200dp"
android:layout_marginTop="50dp"
android:paddingTop="20dp"
android:scaleType="centerCrop" />
<TextView
android:id="#+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/imageView"
android:layout_margin="10dp"
android:textSize="16sp" />
<CheckBox
android:id="#+id/PASS"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#id/textView"
android:text="PASS" />
<CheckBox
android:id="#+id/FAIL"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#id/textView"
android:layout_toRightOf="#+id/PASS"
android:text="FAIL" />
</RelativeLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

You can simply use different adapters
create another activity_student_item.xml let's say activity_view_student_item.xml and remove the checkboxes from that one
create another adapter for that recyclerView but change
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.activity_student_item,parent,false);
in the new adapter to
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.activity_view_student_item,parent,false);
and in the ViewStudents activity set the recycler's Adapter to that new adapter

Image is visible but text is not visible in ListView

I am trying to create a custom layout for list view in android studio. I was able to successfully get image in the in ListView on runtime but wasn't able to print text in the list view . When i run my program in emulator it runs without any error but it doesn't show any text it only shows image from drawables.
MainActivity.java
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ListView;
public class MainActivity extends AppCompatActivity {
private final static String[] names={"A","A","A","A","A","A","A","A","A","A","A","A","A","A","A","A","A","A","A","A","A",
"A","A","A","A","A","A","A","A","A","A","A","A","A","A",};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ListView ls = findViewById((R.id.customlistview));
ls.setAdapter(new CustomListAdapter(getApplicationContext(),names,R.drawable.za));
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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">
<ListView
android:id="#+id/customlistview"
android:layout_width="409dp"
android:layout_height="0dp"
android:layout_marginStart="16dp"
android:layout_marginTop="1dp"
android:layout_marginBottom="1dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
CustomListAdapter.java
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
public class CustomListAdapter extends BaseAdapter {
private final Context context;
private final String[] names;
private final int image;
private final LayoutInflater layoutInflater;
public CustomListAdapter(Context context,String[] names,int image) {
this.context=context;
this.image=image;
this.names=names;
layoutInflater= (LayoutInflater) this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
#Override
public int getCount() {
return names.length;
}
#Override
public Object getItem(int position) {
return position;
}
#Override
public long getItemId(int position) {
return position;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
View rootview;
rootview = layoutInflater.inflate(R.layout.list_item_layout, null);
TextView tv= rootview.findViewById(R.id.textView);
ImageView iv=rootview.findViewById(R.id.imageView);
tv.setText(names[position]);
iv.setImageResource(image);
return rootview;
}
}
list_item_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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="match_parent"
android:orientation="horizontal">
<TextView
android:id="#+id/textView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:height="70dp"
android:gravity="center"
android:text="TextView"
android:textSize="18sp" />
<ImageView
android:id="#+id/imageView"
android:layout_width="match_parent"
android:layout_height="70dp"
android:layout_weight="2"
app:srcCompat="#mipmap/ic_launcher" />
</LinearLayout>

The issue is in your list_item_layout file. There is an issue with match_parent in your layout try using below code
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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="wrap_content"
android:weightSum="3"
android:orientation="horizontal">
<TextView
android:id="#+id/textView"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:height="70dp"
android:gravity="center"
android:text="TextView"
android:textSize="18sp" />
<ImageView
android:id="#+id/imageView"
android:layout_width="0dp"
android:layout_height="70dp"
android:layout_weight="2"
app:srcCompat="#mipmap/ic_launcher" />

The problem was caused by the text colour , changing the colour of textview text in list_item_layout resolved the issue.

null object reference on set adapter

I know that there are a lot of question like this, but i can't find one that can help me. Please pay no attention at strings that are hard coded or other things like that, i will fix. I don't see anything wrong in adapter class or in the fragments. I use Disco class for fill a place list, the Place class contains all the methods that after i use in the adapter.Can anyone help me please? Thank you.
Class MainActivity
package com.techmind.tourguideapp;
import android.support.design.widget.TabLayout;
import android.support.v4.app.FragmentManager;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FragmentManager manager = getSupportFragmentManager();
ViewPager pager = findViewById(R.id.tourPager);
pager.setAdapter(new FragmentAdapter(manager));
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(pager);
}
}
class Disco
package com.techmind.tourguideapp;
import java.util.ArrayList;
import java.util.List;
/**
* Created by Nahuel on 31.05.2018.
*/
public class Disco {
public static ArrayList<Places> initDiscoList(ArrayList<Places> places) {
places.add(new Places().
setAddress("via a").
setImage(1).
setName("casino").
setPhone("333").
setPrice("20€").
setHour("10:30"));
return places;
}
}
Class DiscoFragment
package com.techmind.tourguideapp;
import android.support.v4.app.Fragment;
import android.location.Location;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import java.util.ArrayList;
import java.util.List;
/**
* Created by Nahuel on 31.05.2018.
*/
public class DiscoFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
ArrayList<Places> list = new ArrayList<>();
list = Disco.initDiscoList(list);
PlacesAdapter adapter = new PlacesAdapter(getActivity(), list);
View view = inflater.inflate(R.layout.row_item, container, false);
ListView listView = (ListView) view.findViewById(R.id.list_items);
listView.setAdapter(adapter);
return view;
}
}
Class FragmentAdapter
package com.techmind.tourguideapp;
import android.content.Context;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
/**
* Created by Nahuel on 31.05.2018.
*/
public class FragmentAdapter extends FragmentPagerAdapter {
public FragmentAdapter (FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
return new DiscoFragment();
}
#Override
public int getCount() {
return 3;
}
public CharSequence getPageTitle(int position) {
return "Gradara";
}
}
Class Places
package com.techmind.tourguideapp;
/**
* Created by Nahuel on 31.05.2018.
*/
public class Places {
private String name;
private String price;
private String phone;
private String Address;
private String hour;
private int image;
private final int NO_IMAGE = -1;
public Places () {
}
public String getHour() {
return hour;
}
public String getName() {
return name;
}
public String getPrice() {
return price;
}
public String getPhone() {
return phone;
}
public String getAddress() {
return Address;
}
public int getImage() {
return image;
}
public Places setName(String name) {
this.name = name;
return this;
}
public Places setHour(String hour) {
this.hour = hour;
return this;
}
public Places setPrice(String price) {
this.price = price;
return this;
}
public Places setPhone(String phone) {
this.phone = phone;
return this;
}
public Places setAddress(String address) {
Address = address;
return this;
}
public Places setImage(int image) {
this.image = image;
return this;
}
}
Class PlaceAdapter
package com.techmind.tourguideapp;
import android.content.Context;
import android.location.Location;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.List;
public class PlacesAdapter extends ArrayAdapter<Places> {
public PlacesAdapter(Context context, List<Places> places) {
super(context,-1, places);
}
public View getView (int position, ViewGroup parent, View convertView) {
View listView = convertView;
Places place = getItem(position);
if(listView == null) {
listView = LayoutInflater.from(getContext()).inflate(
R.layout.row_item, parent, false);
}
TextView location = listView.findViewById(R.id.locationName);
location.setText("casino");
TextView hour = listView.findViewById(R.id.txthour);
hour.setText("aaa");
TextView address = listView.findViewById(R.id.address);
address.setText("aaaaa");
TextView price = listView.findViewById(R.id.txtmoney);
price.setText("aaaaa");
TextView phone = listView.findViewById(R.id.phone);
phone.setText("aaaaa");
ImageView img = listView.findViewById(R.id.imgRow);
img.setImageResource(R.drawable.ic_launcher_background);
return listView;
}
}
Activity_Main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
android:orientation="vertical"
tools:context="com.techmind.tourguideapp.MainActivity">
<android.support.design.widget.TabLayout
android:id="#+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:tabMaxWidth="0dp"
/>
<android.support.v4.view.ViewPager
android:id="#+id/tourPager"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
List_item.xml
</LinearLayout>
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ListView
android:id="#+id/list_items"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</ListView>
</LinearLayout>
Row_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<ImageView
android:id="#+id/imgRow"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:src="#drawable/gradara" />
<TextView
android:id="#+id/locationName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:textSize="24sp"
android:textStyle="bold"
android:text=""/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
android:layout_weight="0.5">
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="5dp">
<ImageView
android:id="#+id/positionIcon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:src="#mipmap/position"
android:layout_alignParentStart="true"/>
<TextView
android:id="#+id/txtPosition"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toEndOf="#+id/positionIcon"
android:layout_marginTop="5dp"
android:text="" />
<TextView
android:id="#+id/address"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="#+id/positionIcon"
android:layout_toRightOf="#id/positionIcon"
android:text="" />
</RelativeLayout>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="5dp">
<ImageView
android:id="#+id/moneyIcon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:src="#mipmap/money"
android:layout_alignParentStart="true"/>
<TextView
android:id="#+id/txtmoney"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toEndOf="#+id/moneyIcon"
android:layout_marginTop="15dp"
android:text="10€ - 20€" />
</LinearLayout>
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="5dp">
<ImageView
android:id="#+id/hourIcon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:src="#mipmap/hour"
android:layout_alignParentStart="true"/>
<TextView
android:id="#+id/txthour"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toEndOf="#+id/hourIcon"
android:layout_marginTop="15dp"
android:text="09:30 - 23:00" />
</RelativeLayout>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="10dp">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Phone:"
android:layout_marginEnd="5dp"
android:textStyle="bold"/>
<TextView
android:id="#+id/phone"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="3334323560"
/>
</LinearLayout>
</LinearLayout>
</LinearLayout>

You said you got a null pointer on set adapter. Are you talking about
this line in file DiscoFragment?
listView.setAdapter(adapter)
if listView is null then the findViewByID didn't find a view. Or maybe something inside adapter is null. It is hard to tell from what you said.

i found the error in
ArrayList<Places> list = new ArrayList<>();
list = Disco.initDiscoList(list);
PlacesAdapter adapter = new PlacesAdapter(getActivity(), list);
View view = inflater.inflate(R.layout.row_item, container, false);
ListView listView = (ListView) view.findViewById(R.id.list_items);
listView.setAdapter(adapter);
return view;
}
When i use the inflate method the first parameter was wrong, i used the layout of the row instead of the listView layout.
Thank you for your answers, next times i will post logs and less useless code :)

Timetable android application not working

I have made an android application, and its getting successfully compiled without any errors. But when I run app in my android phone, then it does not show the desired output.
This is my MainActivity.java:
package wahab.com.timetabledemo;
import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.support.v7.widget.Toolbar;
public class MainActivity extends AppCompatActivity {
private Toolbar toolbar;
private ListView listView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setupUIViews();
initToolbar();
}
private void setupUIViews(){
toolbar = (Toolbar)findViewById(R.id.ToolbarMain);
listView = (ListView)findViewById(R.id.lvMain);
}
private void initToolbar(){
setSupportActionBar(toolbar);
getSupportActionBar().setTitle("TimeTable App");
}
private void setupListView(){
String[] title = getResources().getStringArray(R.array.Main);
String[] description = getResources().getStringArray(R.array.Description);
SimpleAdaptor simpleAdaptor = new SimpleAdaptor(this, title, description);
listView.setAdapter(simpleAdaptor);
}
public class SimpleAdaptor extends BaseAdapter{
private Context mContext;
private LayoutInflater layoutInflater;
private TextView title, description;
private String[] titleArray;
private String[] descriptionArray;
private ImageView imageView;
public SimpleAdaptor(Context context, String[] title, String[] description){
mContext = context;
titleArray = title;
descriptionArray = description;
layoutInflater = LayoutInflater.from(context);
}
#Override
public int getCount() {
return titleArray.length;
}
#Override
public Object getItem(int i) {
return titleArray[i];
}
#Override
public long getItemId(int i) {
return i;
}
#Override
public View getView(int i, View view, ViewGroup viewGroup) {
if(view == null){
view = layoutInflater.inflate(R.layout.main_activity_single_item,null);
}
title = (TextView)view.findViewById(R.id.tvMain);
description = (TextView)view.findViewById(R.id.tvDescription);
imageView = (ImageView)view.findViewById((R.id.ivMain));
title.setText(titleArray[i]);
description.setText(descriptionArray[i]);
if(titleArray[i].equalsIgnoreCase("Timetable")){
imageView.setImageResource(R.drawable.timetable);
}
else if(titleArray[i].equalsIgnoreCase("Subjects")){
imageView.setImageResource(R.drawable.book);
}
else if(titleArray[i].equalsIgnoreCase("Faculty")){
imageView.setImageResource(R.drawable.contact);
}
else{
imageView.setImageResource(R.drawable.settings);
}
return view;
}
}
}
The given above is a error free code.
This is my activity_main.xml:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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="wrap_content"
tools:context="wahab.com.timetabledemo.MainActivity">
<android.support.v7.widget.Toolbar
android:id="#+id/ToolbarMain"
android:layout_width="match_parent"
android:layout_height="?android:attr/actionBarSize"
android:background="#color/colorPrimary"
app:titleTextColor="#color/white">
</android.support.v7.widget.Toolbar>
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/lvMain"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:layout_marginBottom="10dp"
android:layout_marginTop="10dp"
android:dividerHeight="10dp"
android:layout_below="#+id/ToolbarMain"
android:divider="#null">
</ListView>
</RelativeLayout>
In my activity_main.xml, I have used a RelativeLayout in which I have defined a Toolbar and a ListView. A ListView is defined so that I can add different list of operation.
This is my main_activity_single_item.xml:
<android.support.v7.widget.CardView android:layout_height="wrap_content"
android:layout_width="match_parent"
android:background="#color/colorAccent"
android:elevation="4dp"
xmlns:android="http://schemas.android.com/apk/res/android">
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<ImageView
android:layout_width="80dp"
android:layout_height="105dp"
android:id="#+id/ivMain"
android:layout_marginLeft="10dp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/tvMain"
android:textStyle="bold"
android:text="Timetable"
android:layout_marginTop="6dp"
android:layout_marginLeft="6dp"
android:layout_toRightOf="#+id/ivMain"
android:textSize="25sp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/tvDescription"
android:text="description"
android:layout_marginLeft="6dp"
android:layout_marginTop="3dp"
android:layout_below="#+id/tvMain"
android:layout_toRightOf="#+id/ivMain"
android:textSize="16sp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/tvClick"
android:textSize="12sp"
android:text="click to know more"
android:layout_marginTop="6dp"
android:layout_alignParentRight="true"
android:layout_below="#+id/tvDescription"
android:layout_alignBottom="#+id/ivMain"/>
</RelativeLayout>
In this above xml file, I have created a CardView which will consist of an ImageView and 3 TextView, which is placed using a RelativeLayout.
So, my code is getting compiled properly and my app is also running but am not getting the desired output.

You need to call setupListView() in onCreate to display the list
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setupUIViews();
initToolbar();
setupListView(); // to display list
^^^^^^^^^^
}

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