java 阳光偏好片段第2部分

Posted 2021-05-08

<?xml version="1.0" encoding="utf-8"?>

<!-- COMPLETED (7) Make the SettingsFragment the root layout for SettingsActivity -->
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
          android:name="com.example.android.sunshine.SettingsFragment"
          android:id="@+id/weather_settings_fragment"
          android:layout_width="match_parent"
          android:layout_height="match_parent" />

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
        <!--COMPLETED (6) Add preferenceTheme to AppTheme and set to @style/PreferenceThemeOverlay-->
        <!-- for settings preference theme -->
        <item name="preferenceTheme">@style/PreferenceThemeOverlay</item>
    </style>

</resources>

package com.example.android.sunshine;

import android.content.SharedPreferences;
import android.os.Bundle;
import android.support.v7.preference.CheckBoxPreference;
import android.support.v7.preference.ListPreference;
import android.support.v7.preference.Preference;
import android.support.v7.preference.PreferenceFragmentCompat;
import android.support.v7.preference.PreferenceScreen;

/**
 * The SettingsFragment serves as the display for all of the user's settings. In Sunshine, the
 * user will be able to change their preference for units of measurement from metric to imperial,
 * set their preferred weather location, and indicate whether or not they'd like to see
 * notifications.
 *
 * Please note: If you are using our dummy weather services, the location returned will always be
 * Mountain View, California.
 */
// COMPLETED (4) Create SettingsFragment and extend PreferenceFragmentCompat
public class SettingsFragment extends PreferenceFragmentCompat implements
        // COMPLETED (10) Implement OnSharedPreferenceChangeListener from SettingsFragment
        SharedPreferences.OnSharedPreferenceChangeListener {

    // COMPLETED (8) Create a method called setPreferenceSummary that accepts a Preference and an Object and sets the summary of the preference
    private void setPreferenceSummary(Preference preference, Object value) {
        String stringValue = value.toString();
        String key = preference.getKey();

        if (preference instanceof ListPreference) {
            /* For list preferences, look up the correct display value in */
            /* the preference's 'entries' list (since they have separate labels/values). */
            ListPreference listPreference = (ListPreference) preference;
            int prefIndex = listPreference.findIndexOfValue(stringValue);
            if (prefIndex >= 0) {
                preference.setSummary(listPreference.getEntries()[prefIndex]);
            }
        } else {
            // For other preferences, set the summary to the value's simple string representation.
            preference.setSummary(stringValue);
        }
    }

    // COMPLETED (5) Override onCreatePreferences and add the preference xml file using addPreferencesFromResource
    @Override
    public void onCreatePreferences(Bundle bundle, String s) {
        /* Add 'general' preferences, defined in the XML file */
        addPreferencesFromResource(R.xml.pref_general);

        // COMPLETED (9) Set the preference summary on each preference that isn't a CheckBoxPreference
        SharedPreferences sharedPreferences = getPreferenceScreen().getSharedPreferences();
        PreferenceScreen prefScreen = getPreferenceScreen();
        int count = prefScreen.getPreferenceCount();
        for (int i = 0; i < count; i++) {
            Preference p = prefScreen.getPreference(i);
            if (!(p instanceof CheckBoxPreference)) {
                String value = sharedPreferences.getString(p.getKey(), "");
                setPreferenceSummary(p, value);
            }
        }
    }

    // COMPLETED (13) Unregister SettingsFragment (this) as a SharedPreferenceChangedListener in onStop
    @Override
    public void onStop() {
        super.onStop();
        /* Unregister the preference change listener */
        getPreferenceScreen().getSharedPreferences()
                .unregisterOnSharedPreferenceChangeListener(this);
    }

    // COMPLETED (12) Register SettingsFragment (this) as a SharedPreferenceChangedListener in onStart
    @Override
    public void onStart() {
        super.onStart();
        /* Register the preference change listener */
        getPreferenceScreen().getSharedPreferences()
                .registerOnSharedPreferenceChangeListener(this);
    }

    // COMPLETED (11) Override onSharedPreferenceChanged to update non CheckBoxPreferences when they are changed
    @Override
    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
        Preference preference = findPreference(key);
        if (null != preference) {
            if (!(preference instanceof CheckBoxPreference)) {
                setPreferenceSummary(preference, sharedPreferences.getString(key, ""));
            }
        }
    }
}