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androidandroid-tablayout

Andoid: handle data change in TabLayout

I have a layout with TabLayout and ViewPager (file refuel_order_configuration.xml):

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/refuel_order_configuration"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/layout_corners_only_top"
android:gravity="center_vertical|start"
android:orientation="vertical">

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginLeft="20dp"
    android:layout_marginTop="10dp"
    android:layout_marginRight="20dp"
    android:gravity="center_vertical|end"
    android:orientation="horizontal">

    <include layout="@layout/gas_station_info_back" />

    <TextView
        android:id="@+id/refuel_order_column_name"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginTop="9dp"
        android:layout_weight="1"
        android:textAlignment="center"
        android:textColor="#545B6E"
        android:textSize="24sp"
        android:textStyle="bold"
        tools:text="FUEL TYPE"
        android:text="FUEL TYPE"/>
</LinearLayout>

<com.google.android.material.tabs.TabLayout
    android:id="@+id/refuelOrderTabLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginStart="16dp"
    app:tabTextColor="#00C2CA"
    app:tabIndicatorColor="#00C2CA"
    android:layout_marginEnd="16dp">

</com.google.android.material.tabs.TabLayout>

<androidx.viewpager.widget.ViewPager
    android:id="@+id/refuelOrderViewPager"
    android:layout_width="wrap_content"
    android:layout_height="330dp"

    />
</LinearLayout>

And then in code I add two fragments with adapter. This is the code of one of the fragments (file refuel_order_configuration_tab.xml)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/refuel_order_configuration_tab"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@drawable/layout_corners_only_top"
    android:gravity="center_vertical|start"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="10dp"
        android:layout_marginRight="16dp"
        android:gravity="center_vertical|end"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/tv_order_sum"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:textColor="#212121"
            android:textSize="24sp"
            tools:text="1050 P" />

        <TextView
            android:id="@+id/tv_order_litres"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:gravity="end"
            android:textColor="@color/taxi_text"
            android:textSize="24sp"
            tools:text="22.9 л" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="4dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="4dp"
        android:orientation="vertical">

        <androidx.appcompat.widget.AppCompatSeekBar
            android:id="@+id/params_seek_bar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:progress="500"
            android:max="5000"
            android:progressBackgroundTint="#000000"
            android:progressTint="#00C2CA"
            android:thumbTint="#00C2CA" />

        <HorizontalScrollView
            android:id="@+id/order_info_view"
            android:layout_width="match_parent"
            android:layout_marginStart="12dp"
            android:layout_marginEnd="12dp"
            android:layout_height="70dp"
            android:layout_marginTop="16dp"
            android:scrollbars="none">

            <LinearLayout
                android:id="@+id/sum_params_container"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:orientation="horizontal" />

<!--                        <include layout="@layout/gas_column_number"/>-->

        </HorizontalScrollView>
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginEnd="16dp"
        android:baselineAligned="false"
        android:orientation="horizontal">

        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="vertical">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/payment_account_label_text"
                android:textColor="#666666" />

            <LinearLayout
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginTop="8dp"
                android:gravity="bottom"
                android:orientation="horizontal">

                <ImageButton
                    android:layout_width="20dp"
                    android:layout_height="20dp"
                    android:adjustViewBounds="true"
                    android:background="#00000000"
                    android:scaleType="centerCrop"
                    android:src="@mipmap/ic_wallet" />

                <TextView
                    android:id="@+id/wallet_name"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginStart="10dp"
                    android:textColor="#000000"
                    android:textSize="18sp"
                    tools:text="Bill" />
            </LinearLayout>

        </LinearLayout>

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_marginEnd="10dp"
            android:orientation="vertical">

            <TextView
                android:id="@+id/order_count_litres"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textColor="#666666"
                android:textSize="18sp"
                tools:text="50 " />
        </LinearLayout>

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:orientation="vertical">

            <ImageButton
                android:id="@+id/bill_configuration"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:background="#FFFFFF"
                android:minWidth="20dp"
                android:minHeight="26dp"
                android:src="@mipmap/arrow_right_gray" />
        </LinearLayout>
    </LinearLayout>

    <View
        android:layout_width="match_parent"
        android:layout_height="2dp"
        android:layout_marginStart="16dp"
        android:layout_marginTop="12dp"
        android:layout_marginEnd="16dp"
        android:layout_marginBottom="24dp"
        android:background="#E6E6E6" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginBottom="16dp"
        android:orientation="horizontal">

        <Button
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:width="56dp"
            android:background="@drawable/empty_corner_background"
            android:text="@string/finish_button_text"
            android:textColor="#FFFFFF" />
    </LinearLayout>
</LinearLayout>

When data changes in AppCompatSeekBar, I handle it and change data in TextView in current layout

My question: How I may handle data change in first tab and pass it changes into TextView on second tab?

There may be a mechanism with saving the state of the tab when switching tabs and transferring this state to another tab,but I don’t know about it

Update: I solved the problem in the following way

  1. In kotlin class which initialize container Fragment (file refuel_order_configuration.xml) I initialize adapter

    refuelOrderViewPager.adapter = RefuelOrderConfigAdapter(fragmentManager, view.context)
    refuelOrderTabLayout.setupWithViewPager(refuelOrderViewPager)

  2. In adapter class I initialize so-called DataManager and pass it into each kotlin class of tab.

    class RefuelOrderConfigAdapter(fragmentManager: FragmentManager?,
                           val context: Context) : FragmentStatePagerAdapter(fragmentManager) {
private val titles: List<String> = listOf(SUM_TAB_HEADER, LITRES_TAB_HEADER)
private val dataManager = DataManager()
private val items: List<BaseFragment> = listOf(SumOrderConfigurationTab.instance(TabType.SUM, dataManager),
        LitresOrderConfigurationTab.instance(TabType.LITRES, dataManager))
init {
    dataManager.registerObserver(items)
}
//...other adapter methods
}

  3. There is the code of DataManager. It is essentially part of the pattern Observer.

    class DataManager {

private val observers: ArrayList<BaseFragment> = ArrayList()

fun registerObserver(observerList: List<BaseFragment>) {
    observers.addAll(observerList)
}

fun notifyObservers(data: String, tabType: TabType) {
    observers.forEach { observer -> observer.handleNotify(data, tabType) }
}

    }

  4. In each class of fragment when seekBar changed I notify observers about data changed and in method handleNotify I handle data changes.

    class SumOrderConfigurationTab : BaseFragment() {

    companion object {
    private lateinit var tabType: TabType
    private lateinit var dataManager: DataManager
    fun instance(tabType: TabType, dataManager: DataManager): SumOrderConfigurationTab {
        this.tabType = tabType
        this.dataManager = dataManager
        return SumOrderConfigurationTab()
    }
}

    //initializers, logic et.c.

    override fun bindListeners(view: View) {
    seekBar.setOnSeekBarChangeListener(object : SeekBar.OnSeekBarChangeListener {
        override fun onProgressChanged(seekBar: SeekBar?, progress: Int, fromUser: Boolean) {
            leftVariable.text = seekBar?.progress.toString()
            dataManager.notifyObservers(seekBar?.progress.toString(), tabType)
        }

        override fun onStartTrackingTouch(seekBar: SeekBar?) {
            leftVariable.text = seekBar?.progress.toString()
            dataManager.notifyObservers(seekBar?.progress.toString(), tabType)
        }

        override fun onStopTrackingTouch(seekBar: SeekBar?) {
            leftVariable.text = seekBar?.progress.toString()
            dataManager.notifyObservers(seekBar?.progress.toString(), tabType)
        }
    })
}

override fun handleNotify(data: String, type: TabType) {
    if (type != tabType) {
        rightVariable.text = data
    }
}

    }

It works. Works as expected. But

  1. I think this is not the right and elegant solution.
  2. There is little scope for expansion in this implementation. The solution is not flexible.
Solution

  • I found a solution.

    This solution based on popular library EventBus (source code here)

    Algorithm is very simple.

    1. In tab Fragments in method onCreateView I register widget for listen events

      override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
    EventBus.getDefault().register(this)
    return inflater.inflate(R.layout.refuel_order_configuration_tab, container, false)
}

    2. Later in Fragment I create a method for receive events

      @Subscribe(threadMode = ThreadMode.MAIN)
fun handleEvent(event: ChangeSumEvent) {
    // set data from event
}

@Subscribe(threadMode = ThreadMode.MAIN)
fun handleEvent(event: ChangeLitresEvent) {
    // set data from event
}

    3. Create simple POJO classes for events

      class ChangeSumEvent(val data: Int?)
class ChangeLitresEvent(val data: Int?)

    4. In Seekbar listener i send event

      seekBar.setOnSeekBarChangeListener(object : SeekBar.OnSeekBarChangeListener {
    override fun onProgressChanged(seekBar: SeekBar?, progress: Int, fromUser: Boolean) {
        return
    }

    override fun onStartTrackingTouch(seekBar: SeekBar?) {
        return
    }

    override fun onStopTrackingTouch(seekBar: SeekBar?) {
        //...logic for current fragment

        EventBus.getDefault().post(ChangeLitresEvent(progress)) //send event to another fragment
    }
})

    5. Finally, in method onDestroyView unregister listener.

      override fun onDestroyView() {
    super.onDestroyView()
    EventBus().unregister(this)
}