java - 获取和设置首选项值

Question

我的目标是管理我的自定义偏好。为此，我有以下代码:

MainActivity.java

public class MainActivity extends ActionBarActivity implements View.OnTouchListener, GoogleMap.OnInfoWindowClickListener, LocationListener, GoogleMap.OnMapClickListener{

             public boolean onOptionsItemSelected(MenuItem item) {
                int id = item.getItemId();

                if (id == R.id.action_settings) {
                    launchPreferences(null);
                    return true;
                }

                return super.onOptionsItemSelected(item);
            }
            public void launchPreferences(View view) {
                Intent i = new Intent(this, Preferences.class);
                startActivity(i);
            }
    }

Preferences.java

public class Preferences extends PreferenceActivity {

    @Override protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.settings);

        updatePreference();


    }

settings.xml

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:key="@+id/preferencias_principal" >
    <EditTextPreference
        android:key="@+id/perimer"
        android:title="Perimeter to list"
        android:summary="Maximum distance to list"
        android:defaultValue="2"/>
    <ListPreference
        android:key="@+id/leguage"
        android:title="Lenguage"
        android:summary="What language would you apply?"
        android:entries="@array/lenguage"
        android:entryValues="@array/lenguageva"
        android:defaultValue="1"/>

</PreferenceScreen>

arrays.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string-array name="lenguage">
        <item>English</item>
        <item>Basque</item>
        <item>Spanish</item>
    </string-array>
    <string-array name="lenguageva">
        <item>1</item>
        <item>2</item>
        <item>3</item>
    </string-array>

    <string-array name="number">
        <item>1</item>
        <item>2</item>
        <item>3</item>
        <item>4</item>
        <item>5</item>
        <item>6</item>
        <item>7</item>
        <item>8</item>
        <item>9</item>
        <item>10</item>
        <item>11</item>
        <item>12</item>
        <item>13</item>
        <item>14</item>
        <item>15</item>
    </string-array>

</resources>

我想使用以下代码获取此首选项的值:

SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(this);
Integer peri = sharedPref.getInt("@+id/perimer", 1);
Integer leng = sharedPref.getInt("@+id/leguage", 2);

但是此代码返回默认值，peri=1 和 leng=2。

不仅如此，有时首选项 Activity 添加的信息会被更改/删除，或者在 ListPreference 项中不会出现所选的默认项(如图所示)。

当我执行可见代码 here 时，使用调试器，结果如下:

我能做什么？

谢谢!

Answer 1

主要问题是您用于 EditTextPreference 和 的 KEY @+id/perimer 和 @+id/leguage >列表首选项。

SharedPreferences 无法将其识别为首选项 KEY。当您添加资源前缀 @+id 时，它被视为 int 资源 id 这就是为什么它仍然可以使用以下几行，但会出现异常行为并给出你的输出不正确。

    Integer peri = sharedPref.getInt("@+id/perimer", 1); // WRONG
    Integer leng = sharedPref.getInt("@+id/leguage", 2); // WRONG

解决方案:

1. 不要将资源前缀 @+id 与首选项 KEY 一起使用。更新您的 settings.xml，如下所示:

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" >

    <EditTextPreference
        android:key="perimer"
        android:title="Perimeter to list"
        android:summary="Maximum distance to list"
        android:defaultValue="2"/>
    <ListPreference
        android:key="leguage"
        android:title="Lenguage"
        android:summary="What language would you apply?"
        android:entries="@array/lenguage"
        android:entryValues="@array/lenguageva"
        android:defaultValue="1"/>

</PreferenceScreen>

2. 使用 SharedPreferences.getString(KEY_NAME, DEFAULT_VALUE) 获取首选项值。

    // Get current values
    String peri = mSharedPreferences.getString("perimer", "1");
    String leng = mSharedPreferences.getString("leguage", "2");

3. 将 OnPreferenceChangeListener 添加到您的 preferences 以获取更新的 值 并更新首选项 摘要(如果需要)。

    // Required to get the updated value and update summary when you input distance
    mPreferencePerimer.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
        @Override
        public boolean onPreferenceChange(Preference preference, Object value) {
            String peri = value.toString();

            //Update premier summary
            mPreferencePerimer.setSummary(peri);

            return true;
        }
    });

    // Required to get the updated value and update summary when you change language from list
    mPreferenceLeguage.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
        @Override
        public boolean onPreferenceChange(Preference preference, Object value) {

            String leng = value.toString();
            int lengIndex = Integer.parseInt(leng) - 1;

            // Update leguage summary
            mPreferenceLeguage.setSummary(mPreferenceLeguage.getEntries()[lengIndex]);
            return true;
        }
    });

完整代码如下:

public class Preferences extends PreferenceActivity {

    // Preference Keys
    public static final String KEY_PREF_PERIMER = "perimer";
    public static final String KEY_PREF_LEGUAGE = "leguage";

    // Shared preference
    SharedPreferences mSharedPreferences;

    EditTextPreference mPreferencePerimer;
    ListPreference mPreferenceLeguage;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.settings);

        // Shared preference
        mSharedPreferences = PreferenceManager.getDefaultSharedPreferences(getActivity());

        // Perimer
        mPreferencePerimer = (EditTextPreference) getPreferenceScreen().findPreference(KEY_PREF_PERIMER);
        // Leguage
        mPreferenceLeguage = (ListPreference) getPreferenceScreen().findPreference(KEY_PREF_LEGUAGE);

        // Get current values
        String peri = mSharedPreferences.getString(KEY_PREF_PERIMER, "1");
        String leng = mSharedPreferences.getString(KEY_PREF_LEGUAGE, "2");
        int lengIndex = Integer.parseInt(leng) - 1;

        // Set preference summary
        mPreferencePerimer.setSummary(peri);
        mPreferenceLeguage.setSummary(mPreferenceLeguage.getEntries()[lengIndex]);

        // Required to get the updated value and update summary when you input distance
        mPreferencePerimer.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
            @Override
            public boolean onPreferenceChange(Preference preference, Object value) {
                String peri = value.toString();

                //Update premier summary
                mPreferencePerimer.setSummary(peri);

                return true;
            }
        });

        // Required to get the updated value and update summary when you change language from list
        mPreferenceLeguage.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
            @Override
            public boolean onPreferenceChange(Preference preference, Object value) {

                String leng = value.toString();
                int lengIndex = Integer.parseInt(leng) - 1;

                // Update leguage summary
                mPreferenceLeguage.setSummary(mPreferenceLeguage.getEntries()[lengIndex]);
                return true;
            }
        });
    }
}

输出:

默认状态

更改后

希望对你有帮助~