Android中Preferences的基本使用

 在开发应用程序的过程中我们有很大的机会需要用到参数设置功能，那么在Android应用中，我们如何实现参数设置界面及参数存储呢，下面我们来介绍一下Android中的一个特殊Activity–PreferencesActivity。PreferencesActivity是Android中专门用来实现程序设置界面及参数存储的一个Activity，我们用一个实例来简介如何使用PreferencesActivity。

通过查看SDK自带的ApiDemo可以发现，里面有一个类叫PreferenceActivity，里面的第一个例子是通过xml文件来实现的，其它的还没研究（首先通过Eclipse把ApiDemo安装到手机上，然后从手机上打开，选择第一个App，大概在第二页的样子就有一个Preferences，点进去就有了），稍微整理了一下，发出来。。。

按照惯例，还是先发图看看效果，如果不是你们所要的效果，也不浪费你们的时间

效果图就是这样了，现在就开始码代码吧。。。

注意这个界面并非传统的layout布局格式！！！

在res目录下面新建一个文件夹xml，然后在里面新建文件preferences.xml

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

    <PreferenceCategory android:title="@string/inline_preferences" >

        <CheckBoxPreference
            android:key="checkbox_preference"
            android:summary="@string/summary_toggle_preference"
            android:title="@string/title_toggle_preference" />
    </PreferenceCategory>

    <PreferenceCategory android:title="@string/dialog_based_preferences" >

        <EditTextPreference
            android:dialogTitle="@string/dialog_title_edittext_preference"
            android:key="edittext_preference"
            android:summary="@string/summary_edittext_preference"
            android:title="@string/title_edittext_preference" />

        <ListPreference
            android:dialogTitle="@string/dialog_title_list_preference"
            android:entries="@array/entries_list_preference"
            android:entryValues="@array/entryvalues_list_preference"
            android:key="list_preference"
            android:summary="@string/summary_list_preference"
            android:title="@string/title_list_preference" />
    </PreferenceCategory>

    <PreferenceCategory android:title="@string/launch_preferences" >

        <PreferenceScreen
            android:key="screen_preference"
            android:summary="@string/summary_screen_preference"
            android:title="@string/title_screen_preference" >

            <CheckBoxPreference
                android:key="next_screen_checkbox_preference"
                android:summary="@string/summary_next_screen_toggle_preference"
                android:title="@string/title_next_screen_toggle_preference" />
        </PreferenceScreen>

        <PreferenceScreen
            android:summary="@string/summary_intent_preference"
            android:title="@string/title_intent_preference" >

            <intent
                android:action="android.intent.action.VIEW"
                android:data="http://www.baidu.com" />
        </PreferenceScreen>
    </PreferenceCategory>

    <PreferenceCategory android:title="@string/preference_attributes" >

        <CheckBoxPreference
            android:key="parent_checkbox_preference"
            android:summary="@string/summary_parent_preference"
            android:title="@string/title_parent_preference" />

        <CheckBoxPreference
            android:dependency="parent_checkbox_preference"
            android:key="child_checkbox_preference"
            android:layout="?android:attr/preferenceLayoutChild"
            android:summary="@string/summary_child_preference"
            android:title="@string/title_child_preference" />
    </PreferenceCategory>

</PreferenceScreen>

当然里面用到了一些字符串，定义在Strings.xml文件里面的

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

    <string name="hello">Hello World, MainActivity!</string>
    <string name="app_name">Preferences_Demo</string>
    <string name="inline_preferences">In-line preferences</string>
    <string name="title_toggle_preference">Toggle preference</string>
    <string name="summary_toggle_preference">This is a toggle button</string>
    <string name="dialog_based_preferences">Dialog-based preferences</string>
    <string name="title_edittext_preference">Edit text preference</string>
    <string name="dialog_title_edittext_preference">Enter your favorite animal</string>
    <string name="summary_edittext_preference">An example that uses an edit text dialog</string>
    <string name="title_list_preference">List preference</string>
    <string name="summary_list_preference">An example that uses a list dialog</string>
    <string name="preference_attributes">Preference attributes</string>
    <string name="title_parent_preference">Parent toggle</string>
    <string name="summary_parent_preference">This is visually a parent</string>
    <string name="title_child_preference">Child toggle</string>
    <string name="summary_child_preference">This is visually a child</string>
    <string name="title_next_screen_toggle_preference">Toggle preference</string>
    <string name="summary_next_screen_toggle_preference">Preference that is on the next screen but same hierarchy</string>
    <string name="title_intent_preference">Intent preference</string>
    <string name="summary_intent_preference">Launches an Activity from an Intent</string>
    <string name="title_screen_preference">Screen preference</string>
    <string name="summary_screen_preference">Shows another screen of preferences</string>
    <string name="dialog_title_list_preference">Choose one</string>
    <string name="launch_preferences">Launch preferences</string>

</resources>

还有两个array数组，在values文件夹下面建一个arrays.xml

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

    <string-array name="entries_list_preference">
        <item>Alpha Option 01</item>
        <item>Beta Option 02</item>
        <item>Charlie Option 03</item>
    </string-array>
    <string-array name="entryvalues_list_preference">
        <item>alpha</item>
        <item>beta</item>
        <item>charlie</item>
    </string-array>

</resources>

OK，下面写主类MainActivity，它继承自PreferenceActivity

package com.and.preferences;

import android.os.Bundle;
import android.preference.PreferenceActivity;

public class MainActivity extends PreferenceActivity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.preferences);
    }
}

行了，ApiDemo里面好像还提供几种，有待于研究。。。。