Problem Running Chapter 6 Earthquake

Bofur · September 25th, 2010, 06:04 AM

Just want to point out that the solution to this is as described by jadoti in posts 15 and 16.

Another thing worth noticing, is that after these changes to use the built-in XML preferences, the preferences activity no longer return a result Activity.RESULT_OK (there is no OK or CANCEL button, you get back to the main activity by using the back-button). It is therefore necessary to change the on ActivityResult function if you want the quake list to update after changing the preferences:

Code:

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
	super.onActivityResult(requestCode, resultCode, data);
	
	if (requestCode == SHOW_PREFERENCES) {
		//if (resultCode == Activity.RESULT_OK) {
			updateFromPreferences();
			refreshEarthquakes();
		//}
	}
}

Notice the commented-out check for the result code. They should be removed.

Of course, this will probably not be necessary when we learn about adding listeners to preference changes. But for now at least, this is needed if you want your list update.

VJaen · January 18th, 2011, 11:45 AM

Hi I'm new to Android development and I'm having an issue with Earthquake sample . It worked fine until chapter 6, but after that I get an error saying "The application Earthquake has stopped unexpectedly", even if I try with the sample code for the following chapters I get same error. I've being trying to apply the fixes described in this thread but the problems persists.

polilla · January 26th, 2011, 02:07 PM

This issue is mainly related to this:

http://code.google.com/p/android/issues/detail?id=2096

In order to solve it, some things must be done, first, only use string-array in your resource arrays.xml

Code:

<?xml version="1.0" encoding="utf-8"?>
<resources>
	<string-array name="update_freq_options">
		<item>Every Minute</item>
		<item>5 minutes</item>
		<item>10 minutes</item>
		<item>15 minutes</item>
		<item>Every Hour</item>
	</string-array>
	<string-array name="magnitudes">
		<item>3</item>
		<item>5</item>
		<item>6</item>
		<item>7</item>
		<item>8</item>
	</string-array>
	<string-array name="magnitude_options">
		<item>3</item>
		<item>5</item>
		<item>6</item>
		<item>7</item>
		<item>8</item>
	</string-array>
	<string-array name="update_freq_value">
		<item>1</item>
		<item>5</item>
		<item>10</item>
		<item>15</item>
		<item>60</item>
	</string-array>
</resources>

In the Activity Earthquake the method updateFromPreferences should be like this, because using the standard preferences the value selected will be directly returned (and not the index for the array).

Code:

private void updateFromPreferences() {
		Context context = getApplicationContext();
		SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
		
		minimumMagnitude = Integer.parseInt(prefs.getString(Preferences.PREF_MIN_MAG, "0"));
		updateFreq = Integer.parseInt(prefs.getString(Preferences.PREF_UPDATE_FREQ, "0"));
		
		autoUpdate = prefs.getBoolean(Preferences.PREF_AUTO_UPDATE, false);
	}

Another important change is to delete the requestCode check in the onActivityResult method, because we are returning from the preferences screen using the back functionality and this will return us a RESULT_CANCELED.

Code:

public void onActivityResult(int requestCode, int resultCode, Intent data) {
		super.onActivityResult(requestCode, resultCode, data);
		if (requestCode == SHOW_PREFERENCES)
			//if (resultCode == Activity.RESULT_OK) {
				updateFromPreferences();
				refreshEarthquakes();
			//}
	}

Applying all this changes the sample will work perfectly.

Only one last issue, if you have already stored preferences as integers the code will fail because they must be cleaned, I am still looking for the way to clean the preferences without having to add a little trick in the code. Just clear the preferences and then commit.

travisa · April 4th, 2011, 07:05 PM

I just want to say thanks to everyone who contributed in this thread. It was very frustrating to deal with this section, since the problem isn't very clear, the code in the book isn't right, and the "Errata" section on the wrox website doesn't even mention this.

docuk · December 5th, 2011, 07:47 PM

i've inputted the code for the earthquakes part in chapter 6 up to p197 and the app crashes when i select a number of magnitude greater than 5 and it also doesn't update the page and leaves the previous in place.

So the code needs changing quite significantly.

Cheers

P.S. the book seems to have quite a few errors to be honest.

docuk · December 7th, 2011, 04:31 PM

Update: I've got it working by just changing a couple of lines.

In the onActivityResult method i inserted an earthquakes.clear and and aa.notify... so i refresh things with an empty screen before calling the refreshearthquakes (if you call this method with a magnitude greater than any present i think it generate an error and so fails to implement)

P.S. i needed to refresh on result cancelled also.

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
earthquakes.clear();
aa.notifyDataSetChanged();

if (requestCode == SHOW_PREFERENCES)
//putting this clear in to clear the screen for a insight to what is happening
if (resultCode == Activity.RESULT_OK || resultCode == Activity.RESULT_CANCELED) {
updateFromPreferences();
refreshEarthquakes();
}
}

cfljason · June 28th, 2012, 01:33 PM

In case anybody else makes the dumb error I did here. I just spent about an hour looking over everything, and of course not focusing on the simplest thing. When I created the Preferences file in Eclipse, I chose the root element as "Preference" rather than the required "PreferenceScreen" This causes the same forced application close when selecting the preferences menu as did all the other omissions already mentioned in the other posts.