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size of recycler view item changes when user scrolls down and up

I am working on a chat functionality to implement in my app. The purpose is that when a message comes from another user, the message item will align parent's start and when the user sends a message, it will align to the end. The send button on upper left corner simulates the other user sending a message. The problem is that when items recycles, some of them mathes the width of parent layout. I do not really understand why this happens and how to fix it. Thanks in advance...
package com.example.messageapp;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.app.Activity;
import android.content.Context;
import android.database.Observable;
import android.os.Bundle;
import android.view.View;
import android.view.inputmethod.InputMethodManager;
import android.widget.Button;
import android.widget.EditText;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
Button sendBtn;
Button otherSendBtn;
EditText editText;
RecyclerView recyclerView;
MessagesAdapter adapter;
List<ChatMessage> messageList;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
messageList=new ArrayList<>();
sendBtn=findViewById(R.id.sendBtn);
otherSendBtn=findViewById(R.id.otherSendBtn);
editText=findViewById(R.id.editText);
recyclerView=findViewById(R.id.recyclerView);
adapter=new MessagesAdapter(this,messageList);
recyclerView.setAdapter(adapter);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setHasFixedSize(true);
for(int i=0; i<4; i++){
if(i%2==0){
messageList.add(new ChatMessage("from him","self"));
}else{
messageList.add(new ChatMessage("from me","other"));
}
adapter.notifyItemInserted(messageList.size()-1);
}
otherSendBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
messageList.add(new ChatMessage("random","other"));
adapter.notifyItemInserted(messageList.size()-1);
}
});
sendBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
String txt=editText.getText().toString();
messageList.add(new ChatMessage(txt, "self"));
adapter.notifyItemInserted(messageList.size()-1);
editText.setText("");
hideKeyboardFrom(MainActivity.this, view);
}
});
}
public static void hideKeyboardFrom(Context context, View view) {
InputMethodManager imm = (InputMethodManager) context.getSystemService(Activity.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(view.getWindowToken(), 0);
}
}
model class for messages
package com.example.messageapp;
public class ChatMessage {
public String text;
public String user;
public ChatMessage(String text, String user) {
this.text = text;
this.user = user;
}
}
recycler view adapter
package com.example.messageapp;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.RelativeLayout;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import java.util.List;
public class MessagesAdapter extends RecyclerView.Adapter {
Context context;
List<ChatMessage> messages;
public void setMessages(List<ChatMessage> messages) {
this.messages = messages;
}
public MessagesAdapter(Context context, List<ChatMessage> messages) {
this.context = context;
this.messages = messages;
}
private static class MessageViewHolder extends RecyclerView.ViewHolder{
TextView textView;
RelativeLayout relativeLayout;
public MessageViewHolder(#NonNull View itemView) {
super(itemView);
textView=itemView.findViewById(R.id.messageTextView);
relativeLayout=itemView.findViewById(R.id.item_parent);
}
}
#NonNull
#Override
public RecyclerView.ViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View v= LayoutInflater.from(context).inflate(R.layout.message_item,parent,false);
return new MessageViewHolder(v);
}
#Override
public void onBindViewHolder(#NonNull RecyclerView.ViewHolder holder, int position) {
ChatMessage message=messages.get(position);
((MessageViewHolder) holder).textView.setText(message.text);
RelativeLayout.LayoutParams params= (RelativeLayout.LayoutParams) ((MessageViewHolder) holder).relativeLayout.getLayoutParams();
if(message.user.equals("self")){
params.addRule(RelativeLayout.ALIGN_PARENT_END);
((MessageViewHolder) holder).relativeLayout.setBackgroundColor(context.getResources().getColor(R.color.teal_200));
}else{
params.addRule(RelativeLayout.ALIGN_PARENT_START);
((MessageViewHolder) holder).relativeLayout.setBackgroundColor(context.getResources().getColor(R.color.purple_200));
}
((MessageViewHolder) holder).relativeLayout.setLayoutParams(params);
}
#Override
public int getItemCount() {
return messages.size();
}
}
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_margin="10dp">
<RelativeLayout
android:id="#+id/item_parent"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#color/teal_700">
<TextView
android:padding="10dp"
android:id="#+id/messageTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RelativeLayout>
</RelativeLayout>
<?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="match_parent"
tools:context=".MainActivity">
<Button
android:id="#+id/otherSendBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="send"
android:layout_centerHorizontal="true"/>
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="#id/otherSendBtn"
tools:listitem="#layout/message_item"/>
<RelativeLayout
android:id="#+id/linear"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:orientation="horizontal">
<EditText
android:id="#+id/editText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_toStartOf="#+id/sendBtn"
android:layout_marginEnd="5dp"/>
<Button
android:background="#drawable/ic_baseline_send_24"
android:id="#+id/sendBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentEnd="true"/>
</RelativeLayout>
</RelativeLayout>

Android Studio Grid View doesn't show when I run the app

I created a Java class that should display something like this:
But this is what I get when I run the app:
It doesn't show what I wanted and Android Studio doesn't show any error in Logcat, so I don't know why it's not working.
This is the code for the class SetsActivity:
package com.example.myquiz;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MenuItem;
import android.widget.GridView;
import android.widget.Toolbar;
public class SetsActivity extends AppCompatActivity {
private GridView sets_grid;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sets);
androidx.appcompat.widget.Toolbar toolbar = findViewById(R.id.set_toolbar);
//setSupportActionBar(toolbar);
String title = getIntent().getStringExtra("CATEGORY");
getSupportActionBar().setTitle(title);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
sets_grid = findViewById(R.id.sets_gridview);
SetsAdapter adapter = new SetsAdapter(2);
sets_grid.setAdapter(adapter);
}
#Override
public boolean onOptionsItemSelected(#NonNull MenuItem item) {
if(item.getItemId() == android.R.id.home)
{
SetsActivity.this.finish();
}
return super.onOptionsItemSelected(item);
}
}
I also created an adapter class SetsAdapter so I'm gonna post the code for it as well:
package com.example.myquiz;
import android.content.Intent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
public class SetsAdapter extends BaseAdapter {
private int numOfSets;
public SetsAdapter(int numOfSets) {
this.numOfSets = numOfSets;
}
#Override
public int getCount() {
return 0;
}
#Override
public Object getItem(int position) {
return null;
}
#Override
public long getItemId(int position) {
return 0;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
View view;
if (convertView == null) {
view = LayoutInflater.from(parent.getContext()).inflate(R.layout.set_item_layout, parent, false);
} else {
view = convertView;
}
view.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(parent.getContext(),QuestionActivity.class);
parent.getContext().startActivity(intent);
}
});
((TextView) view.findViewById(R.id.setNo_tv)).setText(String.valueOf(position + 1));
return view;
}
}
And here is the code for the XML file:
<?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"
tools:context=".SetsActivity"
android:orientation="vertical">
<androidx.appcompat.widget.Toolbar
android:id="#+id/set_toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#color/colorPrimary"
android:theme="#style/ThemeOverlay.AppCompat.Dark"
></androidx.appcompat.widget.Toolbar>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Sets"
android:textSize="26sp"
android:textStyle="bold"
android:padding="16dp" />
<GridView
android:layout_width="match_parent"
android:layout_height="0dp"
android:id="#+id/sets_gridview"
android:layout_weight="1"
android:gravity="center"
android:horizontalSpacing="16dp"
android:verticalSpacing="16dp"
android:padding="16dp"
android:columnWidth="100dp"
android:numColumns="auto_fit"
></GridView>
</LinearLayout>
Here is the code for the XML file set_item_layout:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="100dp"
android:layout_height="100dp"
android:orientation="vertical"
android:gravity="center"
android:background="#drawable/round_corner"
android:backgroundTint="#FFC3C3"
>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="1"
android:id="#+id/setNo_tv"
android:textStyle="bold"
android:textColor="#android:color/black"
android:textSize="45sp"></TextView>
</LinearLayout>

The getCount() method in the SetsAdapter should return numOfSets not 0.
#Override
public int getCount() {
return numOfSets;
}

in RecyclerView i want onclicklistner operation

Code is for recyclerview I want to implement click operation in child option separately.
how should i implement the given code below this code?
this my project code with adapter,child,parent
adapter.java
package com.blipclap.engineering_solution.Adapter;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.bignerdranch.expandablerecyclerview.Adapter.ExpandableRecyclerAdapter;
import com.bignerdranch.expandablerecyclerview.Model.ParentObject;
import com.blipclap.engineering_solution.Models.TitleChild;
import com.blipclap.engineering_solution.Models.TitleParent;
import com.blipclap.engineering_solution.R;
import com.blipclap.engineering_solution.ViewHolder.TitleChildViewHolder;
import com.blipclap.engineering_solution.ViewHolder.TitleParentViewHolder;
import java.util.List;
public class adapter extends ExpandableRecyclerAdapter<TitleParentViewHolder,TitleChildViewHolder> {
LayoutInflater inflater;
public adapter(Context context, List<ParentObject> parentItemList) {
super(context, parentItemList);
inflater=LayoutInflater.from(context);
}
#Override
public TitleParentViewHolder onCreateParentViewHolder(ViewGroup viewGroup) {
View view=inflater.inflate(R.layout.list_parent,viewGroup,false);
return new TitleParentViewHolder(view);
}
#Override
public TitleChildViewHolder onCreateChildViewHolder(ViewGroup viewGroup) {
View view=inflater.inflate(R.layout.list_child,viewGroup,false);
return new TitleChildViewHolder(view); }
#Override
public void onBindParentViewHolder(TitleParentViewHolder titleParentViewHolder, int i, Object o) {
TitleParent title =(TitleParent)o;
titleParentViewHolder._textview.setText(title.getTitle());
}
#Override
public void onBindChildViewHolder(TitleChildViewHolder titleChildViewHolder, int i, Object o) {
TitleChild title =(TitleChild)o;
titleChildViewHolder.op1.setText(title.getop1());
titleChildViewHolder.op2.setText(title.getop2());
titleChildViewHolder.op3.setText(title.getop3());
titleChildViewHolder.op4.setText(title.getop4());
titleChildViewHolder.op5.setText(title.getop5());
}
}
TitleChild.java
package com.blipclap.engineering_solution.Models;
public class TitleChild {
public String op1;
public String op2;
public String op3;
public String op4;
public String op5;
public TitleChild(String op1, String op2, String op3, String op4,String op5) {
this.op1 = op1;
this.op2 = op2;
this.op3 = op3;
this.op4 = op4;
this.op5 = op5;
}
public String getop1() {return op1;}
public void setop1(String op1) {this.op1 = op1;}
public String getop2() {return op2;}
public void setop2(String op2) {this.op2 = op2;}
public String getop3() {return op3;}
public void setop3(String op3) {this.op3 = op3;}
public String getop4() {return op4;}
public void setop4(String op4) {this.op4 = op4;}
public String getop5() {return op5;}
public void setop5(String op5) {this.op5 = op5;}
}
TitleCreator.java
package com.blipclap.engineering_solution.Models;
import android.content.Context;
import java.util.ArrayList;
import java.util.List;
public class TitleCreator {
static TitleCreator _titleCreator;
List<TitleParent> _titleParents;
public TitleCreator(Context context) {
_titleParents = new ArrayList<>();
for (int i=1;i<=8;i++)
{
TitleParent title = new TitleParent(String.format("SEM%d",i));
_titleParents.add(title);
}
}
public static TitleCreator get(Context context)
{
if (_titleCreator==null)
_titleCreator=new TitleCreator(context);
return _titleCreator;
}
public List<TitleParent> getall() {
return _titleParents;
}
}
**TitleParent.java**
package com.blipclap.engineering_solution.Models;
import com.bignerdranch.expandablerecyclerview.Model.ParentObject;
import java.util.List;
import java.util.UUID;
public class TitleParent implements ParentObject {
private List<Object> mChildrenList;
private UUID _id;
private String title;
public TitleParent(String title) {
this.title = title;
_id=UUID.randomUUID();
}
public UUID get_id() {
return _id;
}
public void set_id(UUID _id) {
this._id = _id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
#Override
public List<Object> getChildObjectList() {
return mChildrenList;
}
#Override
public void setChildObjectList(List<Object> list) {
mChildrenList=list;
}
}
TitleChildViewHolder.java
package com.blipclap.engineering_solution.ViewHolder;
import android.view.View;
import android.widget.TextView;
import com.bignerdranch.expandablerecyclerview.ViewHolder.ChildViewHolder;
import com.blipclap.engineering_solution.R;
public class TitleChildViewHolder extends ChildViewHolder {
public TextView op1,op2,op3,op4,op5;
public TitleChildViewHolder(View itemView) {
super(itemView);
op1 =(TextView)itemView.findViewById(R.id.op1);
op2 =(TextView)itemView.findViewById(R.id.op2);
op3 =(TextView)itemView.findViewById(R.id.op3);
op4 =(TextView)itemView.findViewById(R.id.op4);
op5 =(TextView)itemView.findViewById(R.id.op5);
}
}
TitleParentViewHolder.java
package com.blipclap.engineering_solution.ViewHolder;
import android.view.View;
import android.widget.ImageButton;
import android.widget.TextView;
import com.bignerdranch.expandablerecyclerview.ViewHolder.ParentViewHolder;
import com.blipclap.engineering_solution.R;
public class TitleParentViewHolder extends ParentViewHolder {
public TextView _textview;
public ImageButton _imagebutton;
public TitleParentViewHolder(View itemView) {
super(itemView);
_textview = (TextView)itemView.findViewById(R.id.parentTitle);
_imagebutton =(ImageButton) itemView.findViewById(R.id.expandArrow);
}
}
SYFragment.java
package com.blipclap.engineering_solution;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.bignerdranch.expandablerecyclerview.Model.ParentObject;
import com.blipclap.engineering_solution.Adapter.adapter;
import com.blipclap.engineering_solution.Models.TitleChild;
import com.blipclap.engineering_solution.Models.TitleCreator;
import com.blipclap.engineering_solution.Models.TitleParent;
import java.util.ArrayList;
import java.util.List;
public class SYFragment extends Fragment {
RecyclerView recyclerView;
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
((adapter)recyclerView.getAdapter()).onSaveInstanceState(outState);
}
private List<ParentObject> initData() {
TitleCreator titleCreator =TitleCreator.get(getActivity());
List<TitleParent> titles = titleCreator.getall();
List<ParentObject> parentObjects =new ArrayList<>();
for (TitleParent title:titles)
{
List<Object> childList =new ArrayList<>();
childList.add(new TitleChild("I.T","C.E","EXTC","MECH","CIVIL" ));
title.setChildObjectList(childList);
parentObjects.add(title);
}
return parentObjects;
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
//returning our layout file
//change R.layout.yourlayoutfilename for each of your fragments
super.onCreate(savedInstanceState);
View rootView =inflater.inflate(R.layout.fragment_sy, container, false);
recyclerView =(RecyclerView)rootView.findViewById(R.id.recyclerview);
recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
adapter adapter =new adapter(getActivity(),initData());
adapter.setParentClickableViewAnimationDefaultDuration();
adapter.setParentAndIconExpandOnClick(true);
recyclerView.setAdapter(adapter);
return rootView;
}
#Override
public void onViewCreated(View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
//you can set the title for your toolbar here for different fragments different titles
getActivity().setTitle("Syllabus");
}
}
list_child.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginTop="5dp">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="#+id/op1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="8dp"
android:text="op1" />
<TextView
android:id="#+id/op2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/op1"
android:padding="8dp"
android:text="op2" />
<TextView
android:id="#+id/op3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/op2"
android:padding="8dp"
android:text="op3" />
<TextView
android:id="#+id/op4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/op3"
android:padding="8dp"
android:text="op4" />
<TextView
android:id="#+id/op5"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/op4"
android:padding="8dp"
android:text="op5" />
</RelativeLayout>
</android.support.v7.widget.CardView>
**list_parent.xml**
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="#+id/parentTitle"
android:padding="16dp"
android:textStyle="bold"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<ImageButton
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/expandArrow"
android:visibility="gone"
android:layout_alignParentRight="true"
android:layout_margin="8dp"
android:src="#android:drawable/arrow_down_float"/>
</RelativeLayout>
</android.support.v7.widget.CardView>
fragment_sy.xml
<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="com.blipclap.engineering_solution.SYFragment">
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/recyclerview"></android.support.v7.widget.RecyclerView>
</FrameLayout>
click code
How should i implement this code in my project it should be like whenever i click clid option specific pdf should open
Anyone can help with this.
whenever i add this i end up with errors.
#Override
public void onBindChildViewHolder(IssueViewHolder issueViewHolder, int position, Object childListItem) {
Issue issue = (Issue) childListItem;
issueViewHolder.bind(issue);
issueViewHolder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//your code
}
});
}

Define interface in your adapter class
public interface onItemClickListener {
void onItemClicked(View view, int position);
}
public void setOnItemClickListener(onItemClickListener listener) {
this.onItemClickListener = listener;
}
On your Custom View Holder Implement View.OnClickListner and set Click Listener for required view.
public static class CustomViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
CustomViewHolder(View itemView){
super(itemView);
yourview.setOnClickListener(this);
}
#Override
public void onClick(View view) {
onItemClickListener.onItemClicked(view, getAdapterPosition());
}
}
Now in the Adapter object just add setOnItemClickListener and you can bifurcate click event using the id of the view.
yourAdapter.setOnItemClickListener(new YourAdapter.onItemClickListener() {
#Override
public void onItemClicked(View view, int position) {
// view.getId()
});

Viewpager in Dialog?

I'm trying to have a dialog where you can click a "next" button to swipe right to the next screen. I am doing that with a ViewPager and adapter:
final Dialog dialog = new Dialog(this);
dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
dialog.setContentView(R.layout.voicedialog);
dialog.setCanceledOnTouchOutside(false);
MyPageAdapter adapter = new MyPageAdapter();
ViewPager pager = (ViewPager) findViewById(R.id.viewpager);
pager.setAdapter(adapter);
However, I get a NullPointerException saying that pager is null. Why is this happening? Here is the Page Adapter class:
public class MyPageAdapter extends PagerAdapter {
public Object instantiateItem(ViewGroup collection, int position) {
int resId = 0;
switch (position) {
case 0:
resId = R.id.voice1;
break;
case 1:
resId = R.id.voice2;
break;
}
return collection.findViewById(resId);
}
#Override
public int getCount() {
return 2;
}
#Override
public boolean isViewFromObject(View arg0, Object arg1) {
return arg0 == arg1;
}
}
Here's my layout for the DIALOG:
<android.support.v4.view.ViewPager
android:id="#+id/viewpager"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
Let me know on how to avoid this situation.
PS: Each of the layouts that should be in the view pager look like this, just diff. text:
<RelativeLayout android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/voice2"
xmlns:android="http://schemas.android.com/apk/res/android">
<TextView
android:text="Slide 1!"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/textView2"
android:layout_gravity="center"
android:textSize="50sp" />
</RelativeLayout>

Without Using Enum Class
You should call findViewById on dialog. so for that you have to add dialog before findViewById..
Like this,
ViewPager pager = (ViewPager) dialog.findViewById(R.id.viewpager);
After solving your null pointer exception the other problem's solution here, if you wont use enum class you can use below code...
MainActivity.java
package demo.com.pager;
import android.app.Dialog;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
Button btn;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn= (Button) findViewById(R.id.btn);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
final Dialog dialog = new Dialog(MainActivity.this);
dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
dialog.setContentView(R.layout.voicedialog);
dialog.setCanceledOnTouchOutside(false);
MyPageAdapter adapter = new MyPageAdapter(MainActivity.this);
ViewPager pager = (ViewPager) dialog.findViewById(R.id.viewpager);
pager.setAdapter(adapter);
dialog.show();
}
});
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="demo.com.pager.MainActivity">
<Button
android:id="#+id/btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!" />
</RelativeLayout>
MyPageAdapter.java
package demo.com.pager;
import android.app.FragmentManager;
import android.content.Context;
import android.support.v4.app.Fragment;
import android.support.v4.view.PagerAdapter;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
/**
* Created by rucha on 26/12/16.
*/
public class MyPageAdapter extends PagerAdapter {
Context mContext;
int resId = 0;
public MyPageAdapter(Context context) {
mContext = context;
}
public Object instantiateItem(ViewGroup collection, int position) {
/* int resId = 0;
switch (position) {
case 0:
resId = R.id.voice1;
break;
case 1:
resId = R.id.voice2;
break;
}
return collection.findViewById(resId);*/
LayoutInflater inflater = LayoutInflater.from(mContext);
switch (position) {
case 0:
resId = R.layout.fragment_blue;
break;
case 1:
resId = R.layout.fragment_pink;
break;
}
ViewGroup layout = (ViewGroup) inflater.inflate(resId, collection, false);
collection.addView(layout);
return layout;
}
#Override
public int getCount() {
return 2;
}
#Override
public boolean isViewFromObject(View arg0, Object arg1) {
return arg0 == arg1;
}
}
FragmentBlue.java
package demo.com.pager;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;
import android.support.v4.app.Fragment;
public class FragmentBlue extends Fragment {
private static final String TAG = FragmentBlue.class.getSimpleName();
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_blue, container, false);
return view;
}
}
fragment_blue.xml
<RelativeLayout 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"
android:background="#4ECDC4">
</RelativeLayout>
voicedialog.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v4.view.ViewPager
android:id="#+id/viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</RelativeLayout>
Please check and reply.

Using Enum Class
Try this code, This is working if any doubt ask again. Happy to help.
MainActivity.java
package demo.com.dialogdemo;
import android.app.Dialog; import android.graphics.Color; import android.graphics.drawable.ColorDrawable; import android.os.Bundle; import android.support.v4.view.ViewPager; import android.support.v7.app.AppCompatActivity; import android.view.View; import android.view.Window; import android.widget.Button;
public class MainActivity extends AppCompatActivity {
Button button;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setupUIComponents();
setupListeners();
}
private void setupUIComponents() {
button = (Button) findViewById(R.id.button);
}
private void setupListeners() {
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
final Dialog dialogItemDetails = new Dialog(MainActivity.this);
dialogItemDetails.requestWindowFeature(Window.FEATURE_NO_TITLE);
dialogItemDetails.setContentView(R.layout.dialoglayout);
dialogItemDetails.getWindow().setBackgroundDrawable(
new ColorDrawable(Color.TRANSPARENT));
ViewPager viewPager = (ViewPager) dialogItemDetails.findViewById(R.id.viewPagerItemImages);
viewPager.setAdapter(new CustomPagerAdapter(MainActivity.this));
dialogItemDetails.show();
}
});
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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">
<Button
android:id="#+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="dialog" />
</RelativeLayout>
ModelObject1.java
public enum ModelObject1 {
RED(R.string.red, R.layout.fragment_one),
BLUE(R.string.blue, R.layout.fragment_two);
private int mTitleResId;
private int mLayoutResId;
ModelObject1(int titleResId, int layoutResId) {
mTitleResId = titleResId;
mLayoutResId = layoutResId;
}
public int getTitleResId() {
return mTitleResId;
}
public int getLayoutResId() {
return mLayoutResId;
}
}
CustomPagerAdapter.java
package demo.com.dialogdemo;
import android.content.Context;
import android.support.v4.view.PagerAdapter;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
/**
* Created by rucha on 26/12/16.
*/
public class CustomPagerAdapter extends PagerAdapter {
private Context mContext;
public CustomPagerAdapter(Context context) {
mContext = context;
}
#Override
public Object instantiateItem(ViewGroup collection, int position) {
ModelObject1 modelObject = ModelObject1.values()[position];
LayoutInflater inflater = LayoutInflater.from(mContext);
ViewGroup layout = (ViewGroup) inflater.inflate(modelObject.getLayoutResId(), collection, false);
collection.addView(layout);
return layout;
}
#Override
public void destroyItem(ViewGroup collection, int position, Object view) {
collection.removeView((View) view);
}
#Override
public int getCount() {
return ModelObject1.values().length;
}
#Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}
#Override
public CharSequence getPageTitle(int position) {
ModelObject1 customPagerEnum = ModelObject1.values()[position];
return mContext.getString(customPagerEnum.getTitleResId());
}
}
dailoglayout.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="#+id/txtHeaderTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:gravity="center"
android:text="ITEM IMAGES"
android:textStyle="bold" />
<android.support.v4.view.ViewPager
android:id="#+id/viewPagerItemImages"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#android:color/white" />
</RelativeLayout>
fragmentone.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="one"/>
</LinearLayout>

RecyclerView with CardView does not work

I am really sorry for such an abstract question but I am loosing my mind here. HERE is my code for RecyclerView activity.
Please tell me what am I missing, because I am new to Android and I've tried for 4 days to figure the CardView out.
The error is
02-26 13:17:36.570 1138-1138/com.parse.starter E/CrashReporting﹕ ParseCrashReporting caught a NullPointerException exception for com.parse.starter. Building report.
02-26 13:17:36.580 1138-1138/com.parse.starter E/CrashReporting﹕ Handling exception for crash
java.lang.NullPointerException
at com.misha.adaptor.ContactAdapter.onBindViewHolder(ContactAdapter.java:31)
at com.misha.adaptor.ContactAdapter.onBindViewHolder(ContactAdapter.java:14)
The main Activity class
package com.parse.starter;
import android.app.Activity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
import com.misha.adaptor.ContactAdapter;
import com.misha.to.ContactInfo;
import com.parse.FindCallback;
import com.parse.GetCallback;
import com.parse.ParseException;
import com.parse.ParseObject;
import com.parse.ParseQuery;
import java.util.ArrayList;
import java.util.List;
public class CardActivity extends Activity {
String column;
TextView name;
String result;
List<ContactInfo> resultContacts;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_card);
// getContacts()
List<ContactInfo> list = new ArrayList<>();
ContactInfo ci = new ContactInfo();
ci.name = "Mihail";
ci.gender = "male";
ci.email = "test#gmail.com";
ci.phone = "4152346153";
list.add(ci);
RecyclerView recList = (RecyclerView) findViewById(R.id.cardList);
recList.setHasFixedSize(true);
LinearLayoutManager llm = new LinearLayoutManager(this);
llm.setOrientation(LinearLayoutManager.VERTICAL);
recList.setLayoutManager(llm);
ContactAdapter adapter = new ContactAdapter(list);
recList.setAdapter(adapter);
// name = (TextView) findViewById(R.id.txtName);
// getMessage("fevK9QPFUW", "Message");
}
public void getMessage(String key, String columnName) {
this.column = columnName;
ParseQuery<ParseObject> query = ParseQuery.getQuery("Messages");
query.getInBackground(key, new GetCallback<ParseObject>() {
public void done(ParseObject object, ParseException e) {
if (e == null) {
name.setText(object.getString(column).toString());
} else {
result = "did not work";
}
}
});
}
public List<ContactInfo> getContacts() {
resultContacts = new ArrayList<>();
ParseQuery<ParseObject> contacts = ParseQuery.getQuery("Messages");
List<ParseQuery<ParseObject>> queries = new ArrayList<>();
queries.add(contacts);
ParseQuery<ParseObject> mainQuery = ParseQuery.or(queries);
mainQuery.findInBackground(new FindCallback<ParseObject>() {
public void done(List<ParseObject> results, ParseException e) {
if (e == null) {
for (ParseObject obj : results) {
String s = obj.getString("Message");
ContactInfo ci = new ContactInfo();
ci.name = s;
ci.email = "email";
ci.phone = "phone";
ci.gender = "gender";
resultContacts.add(ci);
}
}
}
});
return resultContacts;
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_card, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
The Adaptor
package com.misha.adaptor;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import com.misha.to.ContactInfo;
import com.parse.starter.R;
import java.util.List;
public class ContactAdapter extends RecyclerView.Adapter<ContactAdapter.ContactViewHolder> {
private List<ContactInfo> contactList;
public ContactAdapter(List<ContactInfo> contactList) {
this.contactList = contactList;
}
#Override
public int getItemCount() {
return contactList.size();
}
#Override
public void onBindViewHolder(ContactViewHolder contactViewHolder, int i) {
ContactInfo ci = contactList.get(i);
System.out.println("The ContactInfo = " + ci);
contactViewHolder.vName.setText(ci.name);
contactViewHolder.vPhone.setText(ci.phone);
contactViewHolder.vEmail.setText(ci.email);
contactViewHolder.vGender.setText(ci.gender);
}
#Override
public ContactViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
View itemView = LayoutInflater.
from(viewGroup.getContext()).
inflate(R.layout.activity_card, viewGroup, false);
return new ContactViewHolder(itemView);
}
public class ContactViewHolder extends RecyclerView.ViewHolder {
protected TextView vName;
protected TextView vPhone;
protected TextView vEmail;
protected TextView vGender;
public ContactViewHolder(View v) {
super(v);
vName = (TextView) v.findViewById(R.id.txtName);
vPhone = (TextView) v.findViewById(R.id.txtPhone);
vEmail = (TextView) v.findViewById(R.id.txtEmail);
vGender = (TextView) v.findViewById(R.id.txtGender);
}
}
}
and Here are my layOuts:
activity_card.xml
<RelativeLayout 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"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin"
tools:context=".CardActivity">
<android.support.v7.widget.RecyclerView
android:id="#+id/cardList"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</RelativeLayout>
card_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:card_view="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/card_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
card_view:cardCornerRadius="4dp"
android:layout_margin="5dp">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/txtName"
android:layout_width="match_parent"
android:layout_height="20dp"
android:background="#color/bkg_card"
android:text="Name"
android:gravity="center_vertical"
android:textColor="#android:color/white"
android:textSize="14dp" />
<TextView
android:id="#+id/txtPhone"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Phone"
android:gravity="center_vertical"
android:textSize="10dp"
android:layout_below="#id/txtName"
android:layout_marginTop="10dp"
android:layout_marginLeft="5dp" />
<TextView
android:id="#+id/txtEmail"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Email"
android:gravity="center_vertical"
android:textSize="10dp"
android:layout_below="#id/txtPhone"
android:layout_marginTop="10dp"
android:layout_marginLeft="5dp" />
<TextView
android:id="#+id/txtGender"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Gender"
android:textSize="10dp"
android:layout_marginTop="10dp"
android:layout_alignParentRight="true"
android:layout_marginRight="150dp"
android:layout_alignBaseline="#id/txtEmail" />
</RelativeLayout>
</android.support.v7.widget.CardView>

contactViewHolder.vName is null in your example.
You need to call the constructor for ContactViewHolder in the ContactAdapter constructor.

Got it
#Override
public ContactViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
View itemView = LayoutInflater.
from(viewGroup.getContext()).
inflate(R.layout.card_layout, viewGroup, false);
return new ContactViewHolder(itemView);
}
the R.layout.card_layout was set to R.layout.my_activity