Suggestions to load data faster

Question

I'm seeking for solutions to load 20 items from SQLite faster than 5 seconds (which is the seconds that I'm loading right now.) - First of all, I'm using a custom Listview Adapter.

I load 5 items in 1 second. I tried to load 20 items and I load them in 5 seconds. This are the fields I retrieve from database: int, String, String, int, Bytes, float, int.

As you may think, after getting the bytes I convert them into Bitmap.

Bitmap image = convertBlobToImage(cursor.getBlob(4));
// Using this function:
  public Bitmap convertBlobToImage(byte[] value){
        byte[] new_value = Base64.decode(value, 0);
        return BitmapFactory.decodeByteArray(new_value, 0, new_value.length);   
    }

So, in my class fields, they are going to get not the bytes but already the bitmap. One of the reasons of the amount of time to read, is probably the bitmap. I just did a test on Paint. I saved two equal images one in BMP and another in JPG. The JPG image have the size of 2,87KB and the BMP 420KB!!

With the code above, is that result I'm getting? And probably one of the solutions could be: http://www.mkyong.com/java/how-to-convert-byte-to-bufferedimage-in-java/ ?

What do you guys think? Thanks.

---

Edit: I was searching and I found about onDestroy(). Also I didn't have the "runOnUiThread" implemented, and I put that way. But I think it didn't give me any better result. What do you think? Could this increase the performance?

  @Override
    protected void onDestroy() {
        super.onDestroy();
        listView.setAdapter(null);
    }
// And I also tried to put runOnUiThread:
runOnUiThread(new Runnable() {
             @Override
             public void run() {
                 Bundle extras = getIntent().getExtras();
                 if (extras != null) {
                     DatabaseHandler db = new DatabaseHandler(Produtos.this);
                     display_products = db.get_all_oc_product(extras.getString("category_id"));

                     listView = (ListView) findViewById(R.id.product_listview);
                     inputSearch = (EditText) findViewById(R.id.product_inputSearch);

                     adapter = new itemAdapter(Produtos.this,R.layout.row, display_products);
                     listView.setAdapter(adapter);
                 }
             }
         });

---

Edit (2): I managed to decrease the time for 3 seconds on displaying 20 items. I accomplish this by closing all the connections to database after the queries. I was not doing this properly. Correct way:

cursor db.query(...)
try{
 // Code
} finally {
  cursor.close();
  db.close();
}

Edit (3): Further than the solution on Edit (2), one of the issues I had, which I was identified with, was the problem of the images. So, I started to look at them and I saw images the 2000x1800 and 300kb and even more, and I found rapidly that was here the problem.

So, in the PHP webservice I developed a function to resize the images to half and converting them to jpg.

function resize($filePath){
    list($width, $height) = getimagesize($filePath);

    $percent = 0.5;

        $newwidth = $width * $percent;
        $newheight = $height * $percent;

        $thumb = imagecreatetruecolor($newwidth, $newheight);

        $ext = pathinfo($filePath, PATHINFO_EXTENSION);
        $source = null;

        if($ext == "png"){
            $source = imagecreatefrompng($filePath);
        }else if($ext == "jpg" || $ext == "jpeg"){
            $source = imagecreatefromjpeg($filePath);
        }

        // Resize
        imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);

        // Output
        $temporary = "C:\\xampp\\htdocs\\MyExample\\images\\temporary\\" . basename($filePath);
        imagejpeg($thumb, $temporary . ".jpg", 50);
        ImageDestroy($thumb);

        return $temporary . ".jpg";

}

With this solution, I decreased the time for a stunning 1 second loading 47 items!!

Answer 1

Well It's a bit hard to help from the other side of this question, but some generic tips:

1. Use profiling of some sort to determine which part is slowing you down. Is it loading the actual cursor back that's a problem? or is it the byte conversion? It's hard to say unless you measure - otherwise you could waste a lot of time optimizing something that isn't slowing you down. The simplest profiling example:

   long startTime = SystemClock.elapsedRealTime();
   suspectedSlowFunctionCall();
   long endTime = SystemClock.elapsedRealTime();
   Log.d(TAG, "Method duration: " + (endTime - startTime));
   

   As Mr. Murphy mentioned in the comments, there are also tools that help you with this task. The android developers site has a great post showing how to use traceview, which is included in the SDK.

2. General wisdom is to not store Images in the database if you can avoid it. It is a lot easier on you to debug and work with (and for the system to load) if you store a file path instead and save the file.

3. Android's BitmapFactory should be able to handle JPEGs. If you want to use JPG, feel free

4. If something is unfixably slow, don't do it on the UI Thread! use something like an AsyncTask to do the slow operation, and show your results to the user one by one as they get loaded. This is always preferable to an operation that stalls whilst the user waits confused.

Answer 2

I'd recommend checking into one of the java.nio.* packages to load your images. NIO is non-blocking which means you can load images asynchronously, resulting in more work done per time.

NIO also used native buffers on the system (outside the jvm) so it can prevent java from having to read things into it's heap, which again, makes things faster (native). There's a lot more benefits from using NIO here as well.