Quickest way of displaying large text in android app

Question

I have written an app which downloads a large txt file using Java URL and BufferedInputStream. The file downloads quite fast in around 4 seconds for a 20 - 30Mb file. The file is actually logs. While reading the file in line by line the data is stored in an ArrayList of String.

I then traverse through the ArrayList and build a TableLayout with rows and textviews for each line. However this process takes forever (more than 8 minutes) to finally complete and update the UI.

Is there a quicker way I can download this text and display it. I have opened the file with the native browser and its very quick but I don't want to use the native browser in my app.

Thanks

Answer 1

You should use a RecyclerView for this. It will only inflate the TextViews that are currently needed, and recycles them, which drastically improves performance.

Add a RecycleView to your layout:

<android.support.v7.widget.RecyclerView
    android:id="@+id/loggingRecyclerView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

Then, you need to define in a layout file how each single item of the RecyclerView should look like, similar to this text_row_item.xml file:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="@dimen/list_item_height"
    android:layout_marginLeft="@dimen/margin_medium"
    android:layout_marginRight="@dimen/margin_medium"
    android:gravity="center_vertical">

    <TextView
        android:id="@+id/logLine"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/element_text"/>
</FrameLayout>

Next, define an adapter class which maps the input data to the individual RecyclerView items:

class CustomAdapter(private val logLines: Array<String>) :
        RecyclerView.Adapter<CustomAdapter.ViewHolder>() {

    /**
     * Provide a reference to the type of views that you are using
     * (custom ViewHolder)
     */
    class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
        val textView: TextView

        init {
            // Define click listener for the ViewHolder's View
            textView = view.findViewById(R.id.logLine)
        }
    }

    // Create new views (invoked by the layout manager)
    override fun onCreateViewHolder(viewGroup: ViewGroup, viewType: Int): ViewHolder {
        // Create a new view, which defines the UI of the list item
        val view = LayoutInflater.from(viewGroup.context)
                .inflate(R.layout.text_row_item, viewGroup, false)

        return ViewHolder(view)
    }

    // Replace the contents of a view (invoked by the layout manager)
    override fun onBindViewHolder(viewHolder: ViewHolder, position: Int) {

        // Get element from your dataset at this position and replace the
        // contents of the view with that element
        viewHolder.textView.text = logLines[position]
    }

    // Return the size of your dataset (invoked by the layout manager)
    override fun getItemCount() = logLines.size

}

Finally, assign the adapter to the RecyclerView in your layout like this:

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val logData = arrayOf("Log Statement 1", "Log Statement 2", "Log Statement 3")
        val customAdapter = CustomAdapter(logData )

        val recyclerView: RecyclerView = findViewById(R.id.loggingRecyclerView)
        recyclerView.layoutManager = LinearLayoutManager(this)
        recyclerView.adapter = customAdapter

    }
}