将数据从一个设计选项卡传递到另一选项卡

Question

I am using material design tabs as follows :

Following is my MainActivity.class :

 public class MainActivity extends AppCompatActivity implements ViewPager.OnPageChangeListener {

    private TabLayout tabLayout;
    private ViewPager viewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        tabLayout = (TabLayout) findViewById(R.id.tabs);
        viewPager = (ViewPager) findViewById(R.id.viewpager);
        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
        viewPager.setAdapter(adapter);
        viewPager.addOnPageChangeListener(this);
        tabLayout.setupWithViewPager(viewPager);

    }

    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

    }

    @Override
    public void onPageSelected(int position) {
        System.out.println("onPageSelected Called");
    }

    @Override
    public void onPageScrollStateChanged(int state) {

    }
}

My ViewPagerAdapter is as follows :

    public class ViewPagerAdapter extends FragmentPagerAdapter {

    private static int count = 2;

    public ViewPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {

        switch (position) {
            case 0:
                 return new FragmentOne();
            case 1:
                return new FragmentTwo();
        }
        return null;
    }

    @Override
    public int getCount() {
        return count;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        switch (position)
        {
            case 0 :
                return "Tab One";
            case 1 :
                return "Tab Two";
        }
        return null;
    }
}

and here are my Fragments :

This is my first fragment name is FragmentOne :

    public class FragmentOne extends Fragment {

    private EditText editText;
    private Button btnSendData;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        System.out.println("IN FRAGMENT ONE");
        View view = inflater.inflate(R.layout.fragment_one,container,false);

        editText = (EditText) view.findViewById(R.id.et_name);
        btnSendData = (Button) view.findViewById(R.id.btn_send);

        btnSendData.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                FragmentTwo fragment = new FragmentTwo();
                Bundle bundle = new Bundle();
                bundle.putString("username",editText.getText().toString());
                fragment.setArguments(bundle);
                getFragmentManager.beginTransaction.replace(R.id.frag_second,fragment).commit();

            }
        });

        return view;
    }
}

and here is another fragment with name FragmentTwo :

 public class FragmentTwo extends Fragment {

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        System.out.println("IN FRAGMENT TWO");
        View view = inflater.inflate(R.layout.fragment_two,container,false);
        Bundle bundle = getArguments();
        if(bundle!= null)
        {
            String value = getArguments().getString("username");
        }
        return  view;
    }

    @Override
    public void onResume() {
        super.onResume();
        System.out.println("onResume gets called");
    }
}

In the second fragment i am getting data buts its adding another view with previous one. see the image :

so I want to pass data from FragmentOne to FragmentTwo in two scenario :
1. I want to pass the data when i click on button and
2. When I swipe to FragmentTwo data should be passed

Also when I try to swipe to FragmentTwo nothing gets called in FragmentTwo ? why is it so ? Also when I click to second tab nothing gets called . Please help me how should i pass data to FragmentTwo on button click ?

following are layout files: here is fragment_one

<LinearLayout 
       xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:gravity="center"
       android:orientation="vertical">
           <EditText
               android:layout_marginLeft="16dp"
               android:layout_marginRight="16dp"
               android:id="@+id/et_name"
               android:hint="Username"

               android:layout_width="match_parent"
               android:layout_height="wrap_content"/>

           <Button
                android:padding="16dp"
                android:text="Send Data"
                android:layout_marginLeft="16dp"
                android:layout_marginRight="16dp"
                android:id="@+id/btn_send"
                android:layout_height="wrap_content"
                android:layout_width="match_parent"/>

and second fragment , fragment_second.xml :

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/second_frag"
android:gravity="center">
<TextView
    android:textSize="24sp"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:text="Fragment Two"
    android:id="@+id/textView2" />

Answer 1

Each fragment is associated with the parent activity. so you can't directly communicate from one fragment to another fragment. You will need to go through Parent Activity using interface.

Check this docs : https://developer.android.com/training/basics/fragments/communicating.html

On button click pass the value to methods in your custom interface and access those methods in second fragment.

when I try to swipe to FragmentTwo nothing gets called in FragmentTwo

For this you need to implement fragment life cycle - https://developer.android.com/reference/android/app/Fragment.html

UPDATE

Done with some modification in you code, just look at the foll. code -

Manifex.xml

<application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity"
            android:theme="@style/Theme.AppCompat.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

MainActivity.java

package com.app.onkar.tabdemo;

import android.support.v4.app.Fragment;
import android.support.design.widget.TabLayout;

import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity implements ViewPager.OnPageChangeListener {

    private Toolbar toolbar;
    private TabLayout tabLayout;
    private ViewPager viewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        viewPager = (ViewPager) findViewById(R.id.viewpager);
        tabLayout = (TabLayout) findViewById(R.id.tabs);


        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());

        adapter.addFragment(new FragmentOne(), "ONE");
        adapter.addFragment(new FragmentTwo(), "TWO");
        viewPager.setAdapter(adapter);

        viewPager.addOnPageChangeListener(this);
        tabLayout.setupWithViewPager(viewPager);
    }

    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

    }

    @Override
    public void onPageSelected(int position) {
        System.out.println("onPageSelected Called");
    }

    @Override
    public void onPageScrollStateChanged(int state) {

    }

    public static class ViewPagerAdapter extends FragmentPagerAdapter {
        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<String> mFragmentTitleList = new ArrayList<>();
        private static int count = 2;

        public void addFragment(Fragment fragment, String title) {
            mFragmentList.add(fragment);
            mFragmentTitleList.add(title);
        }

        public ViewPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {

            switch (position) {
                case 0:
                    return new FragmentOne();
                case 1:
                    return new FragmentTwo();
            }
            return null;
        }

        @Override
        public int getCount() {
            return count;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            switch (position) {
                case 0:
                    return "Tab One";
                case 1:
                    return "Tab Two";
            }
            return null;
        }
    }
}

FragmentOne.java

package com.app.onkar.tabdemo;

import android.content.Context;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;

public class FragmentOne extends Fragment {
    private EditText editText;
    private Button btnSendData;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        System.out.println("IN FRAGMENT ONE");
        View view = inflater.inflate(R.layout.fragment_one,container,false);

        editText = (EditText) view.findViewById(R.id.et_name);
        btnSendData = (Button) view.findViewById(R.id.btn_send);

        btnSendData.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                FragmentTwo fragment = new FragmentTwo();
                Bundle bundle = new Bundle();
                bundle.putString("username",editText.getText().toString());
                fragment.setArguments(bundle);
                getActivity().getSupportFragmentManager().beginTransaction().replace(R.id.second_frag,fragment).commit();
            }
        });

        return view;
    }
}

FragmentTwo.java

package com.app.onkar.tabdemo;


import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;


public class FragmentTwo extends Fragment {

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        System.out.println("IN FRAGMENT TWO");
        View view = inflater.inflate(R.layout.fragment_two,container,false);
        TextView txt2 = (TextView) view.findViewById(R.id.textView2);
        Bundle bundle = getArguments();
        if(bundle!= null)
        {
            String value = getArguments().getString("username");
            txt2.setText(value);
        }
        return  view;
    }

    @Override
    public void onResume() {
        super.onResume();
        System.out.println("onResume gets called");
    }

}

No change in Layout files. Just try above code - it is working exactly as you want. Hope it will help!

SCREENS

Answer 2

ViewPagerAdapter class

public class ViewPagerAdapter extends FragmentPagerAdapter {

private static int count = 2;


public ViewPagerAdapter(FragmentManager fm) {
super(fm);
}

@Override
public Fragment getItem(int position) {

switch (position) {
    case 0:
         Fragment fragmentone = new FragmentOne();
         Bundle args = new Bundle();
         args.putInt("code", 1);
         fragmentone.setArguments(args);
         return fragmentone;
    break;
    case 1:
        Fragment fragmenttwo = new FragmentTwo();
         Bundle args = new Bundle();
         args.putInt("code", 2);
         fragmenttwo.setArguments(args);
         return fragmenttwo ;
      break;
}
return null;
}

@Override
public int getCount() {
return count;
}

@Override
public CharSequence getPageTitle(int position) {
switch (position)
{
    case 0 :
        return "Tab One";
    case 1 :
        return "Tab Two";
}
return null;
}
}

args is the bundle object, you can put String int and other values to use these values in fragment use below code in onCreateView method of Fragment.

int codeForthisFragment = getArguments().getInt("code");

for button click: FragmentTransaction ft = getFragmentManager().beginTransaction(); Fragment secondFragment = new FragmentTwo();

                    Bundle args = new Bundle();
                    args.putInt("code", 2);
                    secondFragment.setArguments(args);
                    ft.replace(R.id.content_frame, secondFragment);
                    ft.commit();

Answer 3

In the second fragment i am getting data buts its adding another view with previous one. see the image

With reference to the answer by @Roy Miller( https://stackoverflow.com/users/5255021/roy-miller ), you can solve it by doing the follwing changes:

In MainActivity.java ,replace the follwing switch:

 @Override
    public Fragment getItem(int position) {

        switch (position) {
            case 0:
                return new FragmentOne();
            case 1:
                return new FragmentTwo();
        }
        return null;
    }

With:

@Override
public Fragment getItem(int position) {

    switch (position){
        case 0:
            return mFragmentList.get(0);
        case 1:
            return mFragmentList.get(1);
        case 2:
            return mFragmentList.get(2);
        default:
            return null;
    }

}

And then, in FragmentOne.java

Replace this:

btnSendData.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            FragmentTwo fragment = new FragmentTwo();
            Bundle bundle = new Bundle();
            bundle.putString("username",editText.getText().toString());
            fragment.setArguments(bundle);
            getActivity().getSupportFragmentManager().beginTransaction().replace(R.id.second_frag,fragment).commit();
        }
    });

With:

btnSendData.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

/*This one FragmentCollection is a Singleton class that contains list of fragments, set it during initialization itself(code is attached below this code)*/
FragmentCollection fragmentCollection=FragmentCollection.getInstance();

            FragmentTwo fragment = (FragmentTwo) FragmentCollection.getmFragmentList().get(2); //getting the second fragment

             fragment.setText(editText.getText().toString());  //add this method in fragment two             

        }
    });

Now inside FragmentTwo.java Add the method:

public void updateTextView(String data){
    Log.d("TabTwo","Update Text view");
    TextView txt = (TextView)view.findViewById(R.id.textView2);
    txt.setText(data);
}

At last, the singleton class i mentioned above:

public class FragmentCollection {
static FragmentCollection fragmentCollection=new FragmentCollection();
private final List<Fragment> mFragmentList = new ArrayList<>();    
private FragmentCollection(){}
public static FragmentCollection getInstance(){
    if(fragmentCollection!=null) {
        return fragmentCollection;
    }else {
        return new FragmentCollection();
    }
}
public void setmFragmentList(List<Fragment> mFragmentList){
    this.mFragmentList.addAll(mFragmentList);
}
public List<Fragment> getmFragmentList(){
    return mFragmentList;
}
}

The issue of getting older views overlapping is because of initializing the fragment again and again

like new FragmentTwo(); in more than one place.

So here we put it in a list and access it so only a single fragment is altered.