Android Tutorial PreferenceActivity tutorial

This tutorial explains how to use the new PreferenceActivity library. This library allows you to create the "standard" settings screen.

The settings screen is hosted in its own activity. As this is an external activity its declaration should be manually added to the manifest file.
I will take this opportunity to give some tips about manual modification of the manifest file which is sometimes required.

Editing AndroidManifest.xml (general overview)
As of Basic4android v1.8 it is no longer required to manually maintain the manifest file. Instead the manifest editor allows you to add extra elements as needed.
See this link for more information: http://www.basic4ppc.com/forum/showthread.php?p=78136
For PreferenceActivity you should add the following code to the manifest editor:
B4X:
AddApplicationText(<activity android:name="anywheresoftware.b4a.objects.preferenceactivity"/>)
Back to PreferenceActivity

preference_1.png


* This image was taken on a Samsung Galaxy Tab device. On other devices the screen will look a bit different based on their default style.

PreferenceActivity library includes two main objects: PreferenceScreen and PreferenceManager.
PreferenceScreen is responsible for building the settings UI. PreferenceManager allows you to read the settings and also modify them by code.
Both these objects should usually be declared in Sub Process_Globals.
The settings are saved in a file in the internal files folder. File handling is done automatically. Note that when you reinstall an application (without uninstalling it) the files are kept so the settings will also be kept.

Each preference entry is stored as a key/value pair. The key is a string (case sensitive) and the value can be either a string or a boolean value.
Each entry must have a unique key.

Building the UI
In order to build the UI we start with a PreferenceScreen object and add entries to this object directly or to PreferenceCategory which can hold other entries.
In the above screenshot you can see a PreferenceScreen with two categories holding other entries.
Note that a PreferenceScreen can also hold secondary PreferenceScreens. In this case when the user presses on the secondary entry a new screen will appear with its entries.
There are three types of preference entries:
- Checkbox
- EditText - Opens an input dialog when the user presses on it.
- List - Open a list dialog when the user presses on it, allowing the user to select a single item.
The code that creates the above UI is:
B4X:
Sub CreatePreferenceScreen
    screen.Initialize("Settings", "")
    'create two categories
    Dim cat1, cat2 As PreferenceCategory
    cat1.Initialize("Category 1")
    cat1.AddCheckBox("check1", "Checkbox1", "This is Checkbox1", True)
    cat1.AddCheckBox("check2", "Checkbox2", "This is Checkbox2", False)
    cat1.AddEditText("edit1", "EditText1", "This is EditText1", "Hello!")
 
    cat2.Initialize("Category 2")
    cat2.AddList("list1", "List1", "This is List1", "Black", _
        Array As String("Black", "Red", "Green", "Blue"))
     
    'add the categories to the main screen
    screen.AddPreferenceCategory(cat1)
    screen.AddPreferenceCategory(cat2)
End Sub
The first string in the Add methods is the entry key followed by the title, summary and default value.
The default value is used if the key does not yet exist.

To show the preferences we use this code:
B4X:
Sub btn_Click
    StartActivity(screen.CreateIntent)
End Sub
Reading the settings
Reading the settings is done with PreferenceManager.
To retrieve the value of a specific key you should use Manager.GetString or Manager.GetBoolean with this key.
You can get a Map with all the stored keys and values by calling Manager.GetAll
If you want to only handle updated settings then you can call Manager.GetUpdatedKeys. This will return a List with the keys that were updated since the last call to this method.
Usually you will want to handle settings updated in Activity_Resume. Activity_Resume will be called right after Activity_Create when you start your program and also when the user closes the preferences screen.
Whether you want to handle all keys or just the updated keys depends on your application.

Tip:
The default values set in the PreferenceScreen.Add calls have no effect till the user actually sees the screen. It is recommended to explicitly set the default values if they do not already exist.
A simple way to do it is with code similar to:
B4X:
Sub Activity_Create(FirstTime As Boolean)
    If FirstTime Then
        CreatePreferenceScreen
        If manager.GetAll.Size = 0 Then SetDefaults
    End If
End Sub

Sub SetDefaults
    'defaults are only set on the first run.
    manager.SetBoolean("check1", True)
    manager.SetBoolean("check2", False)
    manager.SetString("edit1", "Hello!")
    manager.SetString("list1", "Black")
End Sub
This way our code in Activity_Resume will work correctly whether it is the first time the program runs or after the user has closed the settings page.

The program is attached.
 

Attachments

  • PreferenceActivity.zip
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Last edited:

boten

Active Member
Licensed User
no such directory "/data/data/" on my device. Does it have to be rooted? Is he directory hidden?
 

BumForALiving

Member
Licensed User
Can we do an inverse to dependency or can the feature be added? In other words, if a box is checked like "Use default" an edit field is not enabled.

If not and adding it would be considered, my thought is to have a - in the dependency string like:

B4X:
cat1.AddCheckBox("check1", "Checkbox1", "Use default setting", "", True, "")
cat1.AddEditText("edit1", "EditText1", "This is the alternative setting", "", "-check1")
 

Erel

Administrator
Staff member
Licensed User
The problem was that the "Do not overwrite manifest file" option was checked. Therefore the rapid debugger couldn't add the internet permission which is required for it to run properly.

This option should not be used anymore. Changes should only be done with the manifest editor (this is an old example).

I've uploaded a fixed version.
 

mitobobo

Member
Licensed User
Hello everyone! :)

May I ask a question, please? I've been looking for that in the forum but couldn't find anything: is it possible to understand which item/option is clicked? For example: when the "Intents" option is clicked, it should execute some code that I wrote, it shouldn't open an intentScreen. I can't find any events which raises when an item is clicked.

Thank you so much in advance for your precious help.
 

sigster

Active Member
Licensed User
Thanks

Yes show the preference activity to change Widget color and transparent

Regards
Sigster
 

sigster

Active Member
Licensed User
Hi

When I install the widget I open layout with one button if I don't I get black empty window :)
Activity.LoadLayout("start")

and I can open settings = StartActivity(screen.CreateIntent)

but not if I click on label on the widget



Regards
sigster
 

bjf

Member
Licensed User
Can you create an edittext with class password in preference screen?
I would like to use this for storing a password but of course don't want to show it in plain text.
 

SCIS

Active Member
Licensed User
Can I set the input type of an EditText in a PreferenceActivity to be Decimal Numbers (so you only get the numeric keyboard)?

EDIT: Nvm, I can use the AHPreferenceActivity lib for that, I think :)
 
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