My main activity file
package com.example.custom_listapp;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.os.Bundle;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
ArrayList<row_data>arrContacts;
RecyclerView recyclerView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView=findViewById(R.id.recyclerContact);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
arrContacts.add(new row_data("Christopher","9876513450",R.drawable.peter));
arrContacts.add(new row_data("Rudraksh","9876513450",R.drawable.avatar2));
arrContacts.add(new row_data("Keshav","9873403450",R.drawable.e));
arrContacts.add(new row_data("Bilal","9876523450",R.drawable.d));
arrContacts.add(new row_data("Niris","9876513450",R.drawable.h));
arrContacts.add(new row_data("Ronaldo","9876513450",R.drawable.g));
arrContacts.add(new row_data("Chris","9876513450",R.drawable.f));
arrContacts.add(new row_data("Christopher","9876513450",R.drawable.trevor));
arrContacts.add(new row_data("Christopher","9876513450",R.drawable.peter));
arrContacts.add(new row_data("Rudraksh","9876513450",R.drawable.avatar2));
arrContacts.add(new row_data("Keshav","9873403450",R.drawable.e));
arrContacts.add(new row_data("Bilal","9876523450",R.drawable.d));
arrContacts.add(new row_data("Niris","9876513450",R.drawable.h));
arrContacts.add(new row_data("Ronaldo","9876513450",R.drawable.g));
arrContacts.add(new row_data("Chris","9876513450",R.drawable.f));
arrContacts.add(new row_data("Christopher","9876513450",R.drawable.trevor));
arrContacts.add(new row_data("Christopher","9876513450",R.drawable.peter));
arrContacts.add(new row_data("Rudraksh","9876513450",R.drawable.avatar2));
arrContacts.add(new row_data("Keshav","9873403450",R.drawable.e));
arrContacts.add(new row_data("Bilal","9876523450",R.drawable.d));
arrContacts.add(new row_data("Niris","9876513450",R.drawable.h));
RecyclerAdapter contactAdapter=new RecyclerAdapter(getApplicationContext(),arrContacts);
recyclerView.setAdapter(contactAdapter);
}
}
Activity main xml code
<?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="match_parent"
android:layout_height="wrap_content"
android:id="@ id/recyclerContact" />
</androidx.constraintlayout.widget.ConstraintLayout>
Customised design for list item xml code named as list_row.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="wrap_content"
android:gravity="center">
<androidx.cardview.widget.CardView
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:cardCornerRadius="7dp"
app:cardUseCompatPadding="true">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<ImageView
android:id="@ id/contactimg"
android:layout_width="70dp"
android:layout_height="70dp"
android:src="@drawable/trevor" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="30dp"
android:layout_marginLeft="11dp"
android:layout_marginEnd="40dp"
android:layout_marginRight="40dp"
android:orientation="vertical">
<TextView
android:id="@ id/txtname"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:text="Christpher"
android:textColor="#1D1111"
android:textStyle="bold" />
<TextView
android:id="@ id/txtnumber"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:text="9373547390"
android:textColor="#1D1111"
android:textStyle="bold" />
</LinearLayout>
</LinearLayout>
</androidx.cardview.widget.CardView>
</LinearLayout>
** Row data java class to set type of arraylist to store three types of data**
package com.example.custom_listapp;
public class row_data {
String name,number;
int image;
public row_data(String name,String number,int image){
this.image=image;
this.name=name;
this.number=number;
}
}
**Recycler adapter class **
package com.example.custom_listapp;
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.recyclerview.widget.RecyclerView;
import org.jetbrains.annotations.NotNull;
import java.util.ArrayList;
public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.Viewholder> {
ArrayList<row_data> arrContacts;
Context context;
public RecyclerAdapter(Context context, ArrayList<row_data> arrContacts){
this.context=context;
this.arrContacts=arrContacts;
}
@NotNull
@Override
public Viewholder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View v=LayoutInflater.from(context).inflate(R.layout.list_row,parent,false);
return new Viewholder(v);
}
@Override
public void onBindViewHolder(@NonNull Viewholder holder, int position) {
holder.img.setImageResource(arrContacts.get(position).image);
holder.txtnumber.setText(arrContacts.get(position).number);
holder.txtname.setText(arrContacts.get(position).name);
}
@Override
public int getItemCount() {
return arrContacts.size();
}
public class Viewholder extends RecyclerView.ViewHolder{
TextView txtname,txtnumber;
ImageView img;
public Viewholder(@NonNull View itemView) {
super(itemView);
this.txtname=itemView.findViewById(R.id.txtname);
this.txtnumber=itemView.findViewById(R.id.txtnumber);
this.img=itemView.findViewById(R.id.contactimg);
}
}
}
Android manifest file
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.custom_listapp">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/Theme.Custom_listApp">
<activity android:name=".MainActivity"
android:exported="true">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
Still my App is crashing like app has been stopped dialog appears . I don't know whats the problem.
CodePudding user response:
Init arrContacts = newArrayList<row_data>(); before use it.
CodePudding user response:
Your arrContacts
is probably null
as per the code you've posted.
You've declared the variable as ArrayList<row_data>arrContacts;
but have not initialised it & therefore it crashed the app when you tried adding elements into a null list.
Simply use: ArrayList<row_data> arrContacts = new ArrayList();
or first declare & initialise in onCreate
like below:
public class MainActivity extends AppCompatActivity {
ArrayList<row_data> arrContacts;
RecyclerView recyclerView;
@Override
protected void onCreate(Bundle savedInstanceState) {
// other things...
arrContacts = new ArrayList();
arrContacts.add(...) // Add items here
}
}
On a side note,
you also do not need a Context
parameter in your RecyclerAdapter
to inflate a layout in onCreateViewHolder
. You can use the provided ViewGroup
's context like below:
@NotNull
@Override
public Viewholder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
Context context = parent.getContext();
LayoutInflater inflater = LayoutInflater.from(context);
View view = inflater.inflate(R.layout.list_row, parent, false);
return new Viewholder(view);
}