An important technique in Android Programming is to make potentially long task run asynchronously in your app, avoid blocking the UI thread, so your app feels more responsive. For example, downloading a file from the Internet, loading a media file from the external storage or applying a filter on an image bitmap etc. I will show you how to implement with AsyncTask, simple java threads and java Executor in Part 1.
Let’s say I want to load a bitmap from the internet, and set it to an ImageView , this might be what you’d write at first:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | //This is a terrible example, the UI thread is blocked when user click the button button.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { try { //DON'T DO THIS!! URL url = new URL("https://www.google.com/images/logos/google_logo_41.png"); URLConnection conn = url.openConnection(); Bitmap bm = BitmapFactory.decodeStream(conn.getInputStream()); imageView.setImageBitmap(bm); } catch (Exception e) { Log.e(TAG, e.getMessage()); } } }); |
The Java way: simple Threads
You can implement it just like any other Java programs, define a Thread that does the job, and run it. Every Java programmer knows how to do that. Remember that if you want to modify the UI, you need to use runOnUiThread()
Continue reading “Patterns for running Asynchronous code in Android (Part 1)”