Sometimes, the application performance on phone is different from emulator. Just like the WatchFootballApp, we found that it takes more time on refreshing the results on device.

Adding debug message and debug your phone in DDMS is useful for locating the bottleneck of the application performance. Please refer to Android – Capture Screenshot to enable the USB Debug on your Android phone.

First of all, we have to add the debug message on the Java class which we would like to look into. To add a debug message, simply use the android.util.Log.

import android.util.Log;

...
Log.v("tag", "message"); // Log level: Verbose
Log.d("tag", "message"); // Log level: Debug
Log.i("tag", "message"); // Log level: Info
Log.w("tag", "message"); // Log level: Warn
Log.e("tag", "message"); // Log level: Error

As shown in the above code snippet, the log is divided into 5 levels and the tag is for better readability of Logcat in DDMS.

For example, i add the following logs in a method and i monitor the application using the DDMS perspective in Eclipse.

Log.v("kit", "*** 1 ***");
...
Log.v("kit", "*** 2 ***");
...
Log.v("kit", "*** 3 ***");
...
...
Log.v("kit", "*** 7 ***");

And this is what i got in the Logcat View. You can filter different log level by pressing the color button.

In addition, there is a filter field at the bottom such that i can display my log easily and now i know that the code between log 1 and 2 is the performance bottleneck.

 

Remember to turn off the debug mode of your phone and unmount the SD card before detached your phone from the computer. By the way, u can also capture the screenshot on your phone using the DDMS perspective in Eclipse.

Done =)