这个问题肯定经常出现。
当用户在Android应用程序中编辑首选项时，我希望他们能够在首选项摘要中看到当前设置的首选项值。
例如:如果我有“丢弃旧消息”的首选项设置，该设置指定了需要清理消息的天数。在PreferenceActivity中，我想让用户看到:
"丢弃旧消息" <- title
“x天后清理消息”<- summary，其中x是当前首选项值
额外的学分:使此可重用，所以我可以很容易地将它应用到我的所有首选项，而不管它们的类型(使它与EditTextPreference, ListPreference等工作，只需最少的编码)。
当前回答
我解决了这个问题与以下后代的ListPreference:
public class EnumPreference extends ListPreference {
public EnumPreference(Context aContext, AttributeSet attrs) {
super(aContext,attrs);
}
@Override
protected View onCreateView(ViewGroup parent) {
setSummary(getEntry());
return super.onCreateView(parent);
}
@Override
protected boolean persistString(String aNewValue) {
if (super.persistString(aNewValue)) {
setSummary(getEntry());
notifyChanged();
return true;
} else {
return false;
}
}
}
从1.6到4.0.4，我似乎工作得很好。
其他回答
因为我使用了一个自定义PreferenceDataStore，我不能添加一个监听器到一些SharedPreference，所以我不得不写一个有点hack的解决方案，监听每个偏好:
class SettingsFragment : PreferenceFragmentCompat(), Preference.OnPreferenceChangeListener {
private val handler: Handler by lazy { Handler(Looper.getMainLooper()) }
override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
preferenceManager.preferenceDataStore = prefs
addPreferencesFromResource(R.xml.app_preferences)
onPreferenceChange(preferenceScreen, null)
}
override fun onPreferenceChange(preference: Preference, newValue: Any?): Boolean {
preference.onPreferenceChangeListener = this
when (preference) {
is PreferenceGroup -> for (i in 0 until preference.preferenceCount) {
onPreferenceChange(preference.getPreference(i), null)
}
is ListPreference -> {
if (preference.value == null) {
preference.isPersistent = false
preference.value = Preference::class.java.getDeclaredField("mDefaultValue")
.apply { isAccessible = true }
.get(preference).toString()
preference.isPersistent = true
}
postPreferenceUpdate(Runnable { preference.summary = preference.entry })
}
}
return true
}
/**
* We can't directly update the preference summary update because [onPreferenceChange]'s result
* is used to decide whether or not to update the pref value.
*/
private fun postPreferenceUpdate(r: Runnable) = handler.post(r)
}
根据Android文档，你可以在ListPreference和EditTextPreference组件中使用app:useSimpleSummaryProvider="true"。
这是我的解决方案……就其价值而言
package com.example.PrefTest;
import android.content.SharedPreferences;
import android.content.SharedPreferences.OnSharedPreferenceChangeListener;
import android.os.Bundle;
import android.preference.EditTextPreference;
import android.preference.ListPreference;
import android.preference.Preference;
import android.preference.PreferenceActivity;
import android.preference.PreferenceGroup;
import android.preference.PreferenceManager;
public class Preferences extends PreferenceActivity implements
OnSharedPreferenceChangeListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.preferences);
PreferenceManager.setDefaultValues(Preferences.this, R.xml.preferences,
false);
initSummary(getPreferenceScreen());
}
@Override
protected void onResume() {
super.onResume();
// Set up a listener whenever a key changes
getPreferenceScreen().getSharedPreferences()
.registerOnSharedPreferenceChangeListener(this);
}
@Override
protected void onPause() {
super.onPause();
// Unregister the listener whenever a key changes
getPreferenceScreen().getSharedPreferences()
.unregisterOnSharedPreferenceChangeListener(this);
}
public void onSharedPreferenceChanged(SharedPreferences sharedPreferences,
String key) {
updatePrefSummary(findPreference(key));
}
private void initSummary(Preference p) {
if (p instanceof PreferenceGroup) {
PreferenceGroup pGrp = (PreferenceGroup) p;
for (int i = 0; i < pGrp.getPreferenceCount(); i++) {
initSummary(pGrp.getPreference(i));
}
} else {
updatePrefSummary(p);
}
}
private void updatePrefSummary(Preference p) {
if (p instanceof ListPreference) {
ListPreference listPref = (ListPreference) p;
p.setSummary(listPref.getEntry());
}
if (p instanceof EditTextPreference) {
EditTextPreference editTextPref = (EditTextPreference) p;
if (p.getTitle().toString().toLowerCase().contains("password"))
{
p.setSummary("******");
} else {
p.setSummary(editTextPref.getText());
}
}
if (p instanceof MultiSelectListPreference) {
EditTextPreference editTextPref = (EditTextPreference) p;
p.setSummary(editTextPref.getText());
}
}
}
谢谢你的建议!
我有一个首选项屏幕，并希望显示每个列表首选项的值作为摘要。
这就是我现在的方式:
public class Preferences extends PreferenceActivity implements OnSharedPreferenceChangeListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.preferences);
}
@Override
protected void onResume() {
super.onResume();
// Set up initial values for all list preferences
Map<String, ?> sharedPreferencesMap = getPreferenceScreen().getSharedPreferences().getAll();
Preference pref;
ListPreference listPref;
for (Map.Entry<String, ?> entry : sharedPreferencesMap.entrySet()) {
pref = findPreference(entry.getKey());
if (pref instanceof ListPreference) {
listPref = (ListPreference) pref;
pref.setSummary(listPref.getEntry());
}
}
// Set up a listener whenever a key changes
getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);
}
@Override
protected void onPause() {
super.onPause();
// Unregister the listener whenever a key changes
getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this);
}
public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
Preference pref = findPreference(key);
if (pref instanceof ListPreference) {
ListPreference listPref = (ListPreference) pref;
pref.setSummary(listPref.getEntry());
}
}
这对我来说是可行的，但我想知道最好的解决方案(性能、稳定性、可伸缩性)是Koem展示的那个还是这个?
以下是我的解决方案:
构建一个首选项类型“getter”方法。
protected String getPreference(Preference x) {
// http://stackoverflow.com/questions/3993982/how-to-check-type-of-variable-in-java
if (x instanceof CheckBoxPreference)
return "CheckBoxPreference";
else if (x instanceof EditTextPreference)
return "EditTextPreference";
else if (x instanceof ListPreference)
return "ListPreference";
else if (x instanceof MultiSelectListPreference)
return "MultiSelectListPreference";
else if (x instanceof RingtonePreference)
return "RingtonePreference";
else if (x instanceof SwitchPreference)
return "SwitchPreference";
else if (x instanceof TwoStatePreference)
return "TwoStatePreference";
else if (x instanceof DialogPreference) // Needs to be after ListPreference
return "DialogPreference";
else
return "undefined";
}
构建一个'setSummaryInit'方法。
public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
Log.i(TAG, "+ onSharedPreferenceChanged(prefs:" + prefs + ", key:" + key + ")");
if( key != null ) {
updatePreference(prefs, key);
setSummary(key);
} else {
Log.e(TAG, "Preference without key!");
}
Log.i(TAG, "- onSharedPreferenceChanged()");
}
protected boolean setSummary() {
return _setSummary(null);
}
protected boolean setSummary(String sKey) {
return _setSummary(sKey);
}
private boolean _setSummary(String sKey) {
if (sKey == null) Log.i(TAG, "Initializing");
else Log.i(TAG, sKey);
// Get Preferences
SharedPreferences sharedPrefs = PreferenceManager
.getDefaultSharedPreferences(this);
// Iterate through all Shared Preferences
// http://stackoverflow.com/questions/9310479/how-to-iterate-through-all-keys-of-shared-preferences
Map<String, ?> keys = sharedPrefs.getAll();
for (Map.Entry<String, ?> entry : keys.entrySet()) {
String key = entry.getKey();
// Do work only if initializing (null) or updating specific preference key
if ( (sKey == null) || (sKey.equals(key)) ) {
String value = entry.getValue().toString();
Preference pref = findPreference(key);
String preference = getPreference(pref);
Log.d("map values", key + " | " + value + " | " + preference);
pref.setSummary(key + " | " + value + " | " + preference);
if (sKey != null) return true;
}
}
return false;
}
private void updatePreference(SharedPreferences prefs, String key) {
Log.i(TAG, "+ updatePreference(prefs:" + prefs + ", key:" + key + ")");
Preference pref = findPreference(key);
String preferenceType = getPreference(pref);
Log.i(TAG, "preferenceType = " + preferenceType);
Log.i(TAG, "- updatePreference()");
}
初始化
创建一个公共类PreferenceActivity并实现OnSharedPreferenceChangeListener
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
PreferenceManager.setDefaultValues(this, R.xml.global_preferences,
false);
this.addPreferencesFromResource(R.xml.global_preferences);
this.getPreferenceScreen().getSharedPreferences()
.registerOnSharedPreferenceChangeListener(this);
}
protected void onResume() {
super.onResume();
setSummary();
}
