如何在回收站视图中回收视图

Question

I am using Recycler view to create List View. With in the List View, Each of the item has Horizontal Scroll bar. In the horizontal scroll bar, I display either one item or 3 items based on particular business logic. When listed, the first 2 scrolls display exactly what I wanted. But for further scrolls, I am having problem with the items that I display in the Horizontal Scroll view. It displays multiple items where only one item should be there. When investigated, I came to know that its because, the view is not recycled.

After searching, I override this function, onViewRecycled. This function is called when the issue starts (third and further on scrolls). I don't know how to fix this issue. I am passing List of History to adapter at the beginning itself.

Kindly help me to resolve this.

public class HistoryAdapter(users:List<HistoryItem>): RecyclerView.Adapter<HistoryAdapter.ViewHolder>() {

    val TAG = "HistoryAdapter"

    var historyList:List<HistoryItem>? =null
    var context: Context? =null

    init {
        historyList = users

    }

    override fun onViewRecycled(holder: ViewHolder?) {
        super.onViewRecycled(holder)
        Log.d(TAG,"********************************************************************************************************************************Views are recycled****************************")

        if (holder is HistoryAdapter.ViewHolder) {

            val handler = Handler()
            handler.post(Runnable { () -> notifyItemRemoved(holder.getOldPosition()) })
            //notifyItemRangeChanged(holder.getAdapterPosition(),historyList!!.size())
        }

    }

    override fun getItemId(position: Int): Long {
        return super.getItemId(position)
    }

    override fun onBindViewHolder(holder: ViewHolder?, position: Int) {
        var lung: Boolean? = false
        var tag: String? = null
        val historyItem: HistoryItem = historyList!!.get(position)

        holder!!.profileImg.setImageBitmap(BitmapFactory.decodeFile(File(Environment.getDataDirectory().getAbsolutePath(), "data/" + context!!.getPackageName() + "/files/users/" + historyItem.uuidVal + "/portrait.png").getAbsolutePath()))

        holder!!.notesTxt.setText(historyItem.sessionVal!!.getNote())

        val date = historyItem.sessionVal!!.getDate()
        var formatDayOfMonth  = SimpleDateFormat("dd");
        val day = Integer.parseInt(formatDayOfMonth.format(date));
        val dayStr = day.toString();

        formatDayOfMonth  = SimpleDateFormat("MMM")
        val month = formatDayOfMonth.format(date)

        formatDayOfMonth = SimpleDateFormat("yyyy")
        val year = formatDayOfMonth.format(date)

        formatDayOfMonth = SimpleDateFormat("hh:mm a")
        val currentTime = formatDayOfMonth.format(date)


        val dateStr = month+" "+dayStr+", "+year

        holder!!.dateTxt.setText(dateStr)
        holder!!.timeTxt.setText(currentTime)

        Log.d(TAG,"********************************************************************************************************************************************user =>"+historyItem.uuidVal);
        Log.d(TAG,"********************************************************************************************************************************************current time =>"+currentTime);

        var ambientTemp: Double? = null
        var surfaceTemp: Double? = null
        var coreBodyTemp: Double? = null

        var heartRate: Int? = null
        var lungAvailable: Boolean = false
        var heartAvailable: Boolean = false
        var tempAvailable: Boolean = false

        try {
            val tempRecording:TemperatureRecording = checkNotNull(historyItem.sessionVal!!.getTemperature())
            tempAvailable = true
            ambientTemp = tempRecording.getAmbientTemp()
            surfaceTemp = tempRecording.getSurfaceTemp()
            coreBodyTemp = TemperatureRecording.CalculateCoreBodyTemperature.getCoreBodyTemp(ambientTemp,surfaceTemp)
        } catch(i: IllegalStateException) {
            Log.w(TAG,"Temperature not available for user session")
            tempAvailable = false
        }

        try {
            val heartRecording:HeartRecording = checkNotNull(historyItem.sessionVal!!.getHeart())
            heartAvailable = true
            heartRate = heartRecording.getHeartRate()
        } catch(i: IllegalStateException) {
            Log.w(TAG,"Heart not available for user session")
            heartAvailable = false
        }

        try {
            val lungRecording:LungsRecording = checkNotNull(historyItem.sessionVal!!.getLungs())
            lungAvailable = true
        } catch(i: IllegalStateException) {
            Log.w(TAG,"Lung not available for user session")
            lungAvailable = false
        }



        Log.d(TAG,"********************************************************************************************************************************************temperature =>"+tempAvailable)
        Log.d(TAG,"********************************************************************************************************************************************heart =>"+heartAvailable)
        Log.d(TAG,"********************************************************************************************************************************************lung =>"+lungAvailable)

        //Log.d(TAG,"********************************************************************************************************************************************ambient temp val =>"+ambientTemp)
        //Log.d(TAG,"********************************************************************************************************************************************surface temp val =>"+surfaceTemp)
        //Log.d(TAG,"********************************************************************************************************************************************heart val =>"+heartRate)
        //Log.d(TAG,"********************************************************************************************************************************************lung val =>"+historyItem.sessionVal!!.getLungs())

        val parentLinearLayout = holder!!.readingsView
        //createLayout(holder!!.readingsView,tag,coreBodyTemp,heartRate)
        var childLinearLayout: LinearLayout? = null

        if(tempAvailable == true && heartAvailable == true && lungAvailable == true) {
            for(i in 1..3) {
                if(i == 1) {
                    val df = DecimalFormat("#.##");
                    childLinearLayout = createChildView(BitmapFactory.decodeResource(context!!.getResources(),R.drawable.temperature), df.format(coreBodyTemp).toString(), context!!.getString(R.string.temperatureStr))
                    parentLinearLayout.addView(childLinearLayout)
                    childLinearLayout = null
                } else if(i == 2) {
                    childLinearLayout = createChildView(BitmapFactory.decodeResource(context!!.getResources(),R.drawable.heart), heartRate.toString(), context!!.getString(R.string.heartRate))
                    parentLinearLayout.addView(childLinearLayout)
                    childLinearLayout = null
                } else if(i == 3) {
                    childLinearLayout = createChildView(BitmapFactory.decodeResource(context!!.getResources(),R.drawable.lung), "", "")
                    parentLinearLayout.addView(childLinearLayout)
                    childLinearLayout = null
                }
            }
        } else if (tempAvailable) {
            val df = DecimalFormat("#.##");
            childLinearLayout = createChildView(BitmapFactory.decodeResource(context!!.getResources(),R.drawable.temperature), df.format(coreBodyTemp).toString(), context!!.getString(R.string.temperatureStr))
            parentLinearLayout.addView(childLinearLayout)
            childLinearLayout = null
        } else if (heartAvailable) {
            childLinearLayout = createChildView(BitmapFactory.decodeResource(context!!.getResources(),R.drawable.heart), heartRate.toString(), context!!.getString(R.string.heartRate))
            parentLinearLayout.addView(childLinearLayout)
            childLinearLayout = null
        } else if (lungAvailable) {
            childLinearLayout = createChildView(BitmapFactory.decodeResource(context!!.getResources(),R.drawable.lung), "", "")
            parentLinearLayout.addView(childLinearLayout)
            childLinearLayout = null
        }



    }

    fun createChildView(icon: Bitmap,readingVal: String, readingTag: String) : LinearLayout {
        val lp = LinearLayout.LayoutParams(0, ViewGroup.LayoutParams.WRAP_CONTENT)
        lp.weight = 1f
        val parent: LinearLayout = LinearLayout(context!!)
        parent.setOrientation(LinearLayout.HORIZONTAL)
        parent.setLayoutParams(lp)

        val imageView = ImageView(context!!)
        val layoutParams = LinearLayout.LayoutParams(0, ViewGroup.LayoutParams.WRAP_CONTENT)
        layoutParams.weight = 0.4f
        layoutParams.leftMargin = 10
        layoutParams.rightMargin = 10
        layoutParams.topMargin = 10
        layoutParams.bottomMargin =10

        imageView.setLayoutParams(layoutParams)
        imageView.setImageBitmap(icon)
        parent.addView(imageView)


        val readingLayout = LinearLayout(context!!)
        readingLayout.setOrientation(LinearLayout.VERTICAL)
        val lp1 = LinearLayout.LayoutParams(0, ViewGroup.LayoutParams.WRAP_CONTENT)
        lp1.weight = 0.6f
        lp1.topMargin = 10
        readingLayout.setLayoutParams(lp)

        val displayValue = TextView(context!!)
        val layoutParams1 = LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, 0)
        layoutParams1.weight = 0.7f
        displayValue.setLayoutParams(layoutParams1)
        displayValue.setText(readingVal)
        readingLayout.addView(displayValue)

        val displayTag = TextView(context!!)
        layoutParams1.weight = 0.3f
        displayTag.setLayoutParams(layoutParams1)
        displayTag.setText(readingTag)
        readingLayout.addView(displayTag)


        parent.addView(readingLayout)

        return parent


    }

override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): ViewHolder? {
        context = parent!!.getContext()
        // create a new view
        val v: View = LayoutInflater.from(parent!!.getContext())
                .inflate(R.layout.layout_history_row, parent, false);

        return ViewHolder(v)
    }

    override fun getItemCount(): Int {
        return historyList!!.size()

    }

    public class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        public var profileImg: ImageView
        public var dateTxt: TextView
        public var timeTxt: TextView
        public var locationTxt: TextView
        public var notesTxt: TextView
        //public var icon: ImageView
        //public var readingTxt: TextView
        //public var readingDescTxt: TextView

        public var readingsView: LinearLayout


        init {
            profileImg = itemView.findViewById(R.id.profileImage) as ImageView
            dateTxt = itemView.findViewById(R.id.date) as TextView
            timeTxt = itemView.findViewById(R.id.time) as TextView
            locationTxt = itemView.findViewById(R.id.location) as TextView
            notesTxt = itemView.findViewById(R.id.notes) as TextView
            //readingTxt = itemView.findViewById(R.id.readings) as TextView
            //readingDescTxt = itemView.findViewById(R.id.readingsDesc) as TextView
//            icon = itemView.findViewById(R.id.icon) as ImageView
            readingsView = itemView.findViewById(R.id.readingsView) as LinearLayout
        }
    }
}

Activity code

val history = findViewById(R.id.history) as RecyclerView
for(user in allUsers) {
            val uuid: String? = user.getId()
            Log.d(TAG,"*****************************************************************************************************************UUID=>"+uuid+"FirstName=>"+user.getFirstName()+",sessions size =>"+user.getSessions().size())
            for(session in user.getSessions()) {
                historyItems.add(HistoryItem(user.getId(),session))
            }
        }

history.setHasFixedSize(true);
        history.setAdapter(HistoryAdapter(historyItems))
        history.setLayoutManager(LinearLayoutManager(this))

Answer 1

I don't know what kind of "recycling" you're expecting, but what the RecyclerView does is that it will call onCreateViewHolder() until it has enough viewholders to cover slightly more than what is visible on the screen. It will then call onBindViewHolder() to populate the data in the created viewholders.

When you start scrolling, it will grab one of the already created viewholders and feed it back into onBindViewHolder() with a new position . It doesn't do any magic resetting of the viewholder.

In your case, you're never resetting the readingsView , so the adapter keeps adding children to it (which is why it contains more children than expected as you scroll further through the data). In onBindViewHolder() you'll need to remove all existing children from readingsView before you start adding new ones.