Remove/hide a preference from the screen

问题:

I have an activity which extends PreferenceActivity. I'm loading preferences from the xml file. But in some cases i need completely hide one of the preferences from the screen based on my app state. There is a setEnabled method, but it's not exactly what i want. I want to remove that preference from the screen completely. Is it possible ?

回答1:

Yes, if you have a reference to both the Preference, and its parent (a PreferenceCategory, or PreferenceScreen)

myPreferenceScreen.removePreference(myPreference);

回答2:

If your Preference is within a PreferenceCategory, you have to do this:

XML:

<PreferenceCategory
    android:key="category_foo"
    android:title="foo">

    <CheckBoxPreference
        android:key="checkPref" />

Java:

CheckBoxPreference mCheckBoxPref = (CheckBoxPreference) findPreference("checkPref");
PreferenceCategory mCategory = (PreferenceCategory) findPreference("category_foo");
mCategory.removePreference(mCheckBoxPref);

回答3:

In the case where the Preference is a direct child of the preference screen, here is some stand-alone code:

PreferenceScreen screen = getPreferenceScreen();
Preference pref = getPreferenceManager().findPreference("mypreference");
screen.removePreference(pref);

回答4:

If you want something that will dynamically change the prefs for example on a SwitchPreference, I have found the best way is to put all my sub options into two category containers. Initially you'll have everything shown, then you just remove the bits you don't want. The clever bit, is you just trigger recreate when something changes and then you don't have to manually create anything or worry about putting things back in in the correct order.

protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  addPreferencesFromResource(R.xml.preferences);
  PreferenceCategory prefCatOne= (PreferenceCategory)findPreference("prefCatOne");
  PreferenceCategory prefCatTwo= (PreferenceCategory)findPreference("prefCatTwo");
  SwitchPreference mySwitchPref= (SwitchPreference)findPreference("mySwitchPref");
  PreferenceScreen screen = getPreferenceScreen();
  if (mySwitchPref.isChecked()) {
    screen.removePreference(prefCatOne);
  } else {
    screen.removePreference(prefCatTwo);
  }
}

public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
    if (key.equals("mySwitchPref")) {
        this.recreate();
    }
}

The only downside that I can see with this, is there is a flash as the screen is recreated from scratch.

回答5:

In your XML file:

<PreferenceScreen 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    android:key="preferenceScreen">

    <PreferenceCategory
        android:key="personalisation"
        android:title="your title here">

        <ThemedPreference
            android:key="animation" />

</PreferenceScreen>

In your code:

PreferenceScreen pPreferenceScreen = (PreferenceScreen) findPreference("preferenceScreen");

PreferenceCategory pCategory = (PreferenceCategory) findPreference("personalisation");
ThemedPreference pThemePref = (ThemedPreference) findPreference("animation");

pPreferenceScreen.removePreference(pCategory); //remove category
pCategory.removePreference(pThemePref);   // remove preference

回答6:

If you are using PreferenceFragmentCompat you can set the visiblity in xml.

The preferences in your xml will be converted to AppCompat versions automatically. You can then use the 'app:isPreferenceVisible' attribute in your xml

preferences.xml

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <CheckBoxPreference
        android:defaultValue="false"
        android:key="show.navigation"
        android:title="Show navigation"
        app:isPreferenceVisible="false" />

...

The attribute is documented at https://developer.android.com/guide/topics/ui/settings/components-and-attributes

Adding PreferenceFragmentCompat is documented at https://developer.android.com/guide/topics/ui/settings/#inflate_the_hierarchy

Example:

public class MySettingsActivity extends AppCompatActivity {

    public static class MySettingsFragment extends PreferenceFragmentCompat {
        @Override
        public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
            setPreferencesFromResource(R.xml.preferences, rootKey);
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getSupportFragmentManager()
                .beginTransaction()
                .replace(R.id.settings_container, new MySettingsFragment())
                .commit();
    }
} 

回答7:

I recommend using v7 preference, it has setVisible() method. But I have not tried it yet. Accordingly you have to use PreferenceFragment instead of PreferenceActivity.

• https://developer.android.google.cn/reference/android/support/v7/preference/Preference.html#setVisible(boolean)

回答8:

In the XML file you can make a hidden preference by leaving the title and summary tags empty.

<EditTextPreference
    android:defaultValue="toddlerCam"
    android:key="save_photo_dir"
/>

回答9:

Here's a generic way to do this that works regardless of whether the preference is under a PreferenceCategory or PreferenceScreen.

private void removePreference(Preference preference) {
    PreferenceGroup parent = getParent(getPreferenceScreen(), preference);
    if (parent == null)
        throw new RuntimeException("Couldn't find preference");

    parent.removePreference(preference);
}

private PreferenceGroup getParent(PreferenceGroup groupToSearchIn, Preference preference) {
    for (int i = 0; i < groupToSearchIn.getPreferenceCount(); ++i) {
        Preference child = groupToSearchIn.getPreference(i);

        if (child == preference)
            return groupToSearchIn;

        if (child instanceof PreferenceGroup) {
            PreferenceGroup childGroup = (PreferenceGroup)child;
            PreferenceGroup result = getParent(childGroup, preference);
            if (result != null)
                return result;
        }
    }

    return null;
}

回答10:

Since Android API 26 getParent() method is available: https://developer.android.com/reference/android/preference/Preference.html#getParent()

Though you can do the following:

preference.getParent().removePreference(preference);

回答11:

You can do this in 2 ways:

1.If you use support library, you can build a map of the tree of preferences and their parents, and then remove a preference by using its parent. Here's a function to generate such a map:

public static Map<Preference, PreferenceGroup> buildPreferenceParentTree(@NonNull final PreferenceScreen preferenceScreen) {
    final Map<Preference, PreferenceGroup> result = new HashMap<>();
    final Stack<PreferenceGroup> curParents = new Stack<>();
    curParents.add(preferenceScreen);
    while (!curParents.isEmpty()) {
        final PreferenceGroup parent = curParents.pop();
        final int childCount = parent.getPreferenceCount();
        for (int i = 0; i < childCount; ++i) {
            final Preference child = parent.getPreference(i);
            result.put(child, parent);
            if (child instanceof PreferenceGroup)
                curParents.push((PreferenceGroup) child);
        }
    }
    return result;
}

2. If you use the new android-x preference API, you can just set the visibility, by using setVisible function on it.

回答12:

If you want to evaluate, and based on that mask, an alternative may be

SwitchPreference autenticacionUsuario = 
    (SwitchPreference) findPreference("key_autenticacion_usuario");

final EditTextPreference Username = 
    (EditTextPreference) findPreference("key_username_mqtt");
final EditTextPreference Password = 
    (EditTextPreference) findPreference("key_password_mqtt");

if (!autenticacionUsuario.isChecked()) {
    PreferenceCategory preferenceCategory = 
        (PreferenceCategory) findPreference("category_mqtt");
    preferenceCategory.removePreference(Username);
    preferenceCategory.removePreference(Password);
}

All this must be within

public static class PrefsFragment extends PreferenceFragment {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

回答13:

If you're doing what I think you're trying to do (because I'm trying to do it now) it might be better to enable/disable the preference. Because removing it takes it out of the preference screen and you might not be able to add it back where you want it if you made the screen programmatically.

pref.setEnabled(false); pref.setEnabled(true);

although this might be deprecated. It works for the use case that I'm going through right now.