20150623----Android-Settings源码分析

</pre><p>Settings的时序图：</p><p><img src="http://img.blog.csdn.net/20150623143540579?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc2hhZGFpb2Rld2FuZ3dlaQ==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center" height="451" width="679" alt="" /></p><p></p><p align="center"><span style="font-weight:bold">1.本文说明</span></p>  <p>    本文主要针对L平台上Settings模块正常启动流程做一个简要分析，并试着分析一下Settings下面Storage选项的实现过程。</p>  <p> </p>  <p> </p>  <p align="center"><strong>2.Settings概览</strong></p>  <p>    在之前的KK平台上Settings模块的第一个Activity名字为Settings，其继承的是PreferenceActivity，设置的每一个选项都是对应的一个Header对象，并且Header对象允许显示switch控件，button控件，checkbox控件等。如下图2.1，WLAN和蓝牙上使用到了switch开关。但在L上面，WLAN和蓝牙的这两个开关已经去掉了，如图2.2，在Settings模块的首个页面似乎就只是一个普通的Listview，那它用的还是不是Header呢？或者说取而代之的是什么呢？下一节详细说明。<img src="http://img.blog.csdn.net/20150623144026713?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc2hhZGFpb2Rld2FuZ3dlaQ==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center" alt="" /> KK Settings首届面                                   <img src="http://img.blog.csdn.net/20150623144058131?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc2hhZGFpb2Rld2FuZ3dlaQ==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center" height="300" width="177" alt="" />L Settings首届面</p><p></p><p></p><p align="center"><strong> 3 .L Settings 模块首界面初始化流程</strong></p>  <p> </p>  <p>L Settings模块首界面为Settings，继承自SettingsActivity，SettingsActivity继承自Activity。</p>  <p> </p>  <p>首先看一下Settings.java代码可以发现它没有重写任何SettingsActiviy的方法，也没有增加任何自己的方法，唯独增加了许多静态内部类，如：</p><p><pre name="code" class="java"> /*    * Settings subclasses for launching independently.    */    public static class BluetoothSettingsActivity extends SettingsActivity { /* empty */ }    public static class WirelessSettingsActivity extends SettingsActivity { /* empty */ }    public static class SimSettingsActivity extends SettingsActivity { /* empty */ }    public static class TetherSettingsActivity extends SettingsActivity { /* empty */ }    public static class VpnSettingsActivity extends SettingsActivity { /* empty */ }    public static class DateTimeSettingsActivity extends SettingsActivity { /* empty */ }    public static class StorageSettingsActivity extends SettingsActivity { /* empty */ }    public static class WifiSettingsActivity extends SettingsActivity { /* empty */ }

看注释可以知道，这些子类是为了启动特定独立的Settings选项而创建的，例如在某个应用里需要设置无线那么只需要启动 WirelessSettingsActivity 就可以了。

 

所以Settings模块的启动流程直接看SettingsActiviy就行了。

 

    3.1 SettingsActivity.onCreate方法

    

onCreate方法是Activity的生命周期第一步，看看 SettingsActivity在这里都做了些什么？

     // Should happen before any call to getIntent()     getMetaData();

这个方法用来获得Activity的额外数据mFragmentClass，如果可以获得这个数据，那么下面会去显示mFragmentClass对应的Activity。直接启动Settings模块不会获得这个数据。

     mIsShowingDashboard = className.equals(Settings.class.getName());

这一步很重要，因为我们是从Settings这个Activity过来的，所以这里的 mIsShowingDashboard 为 true 。

     // This is a "Sub Settings" when:        // - this is a real SubSettings        // - or :settings:show_fragment_as_subsetting is passed to the Intent        final boolean isSubSettings = className.equals(SubSettings.class.getName()) ||                intent.getBooleanExtra(EXTRA_SHOW_FRAGMENT_AS_SUBSETTING, false);这个判断很重要但很明显这时isSubSettings的值是fasle，暂时忽略。         setContentView(mIsShowingDashboard ?                R.layout.settings_main_dashboard : R.layout.settings_main_prefs);

 

由于mIsShowingDashboard为true，直接走到下面这段

       else {                // No UP affordance if we are displaying the main Dashboard                mDisplayHomeAsUpEnabled = false;                // Show Search affordance                mDisplaySearch = true;                mInitialTitleResId = R.string.dashboard_title;                switchToFragment(DashboardSummary.class.getName(), null, false, false,                        mInitialTitleResId, mInitialTitle, false);              } 

这里看到switchToFragment这个方法，可以知道这里是要切换DashboardSummary这个Fragment.

 

接下来就看看DashboardSummary是个什么玩意？

 

dashboard中文意思是仪表盘，这里是指DashboardSummary就是用来显示Settings所有选项的。

在DashboardSummary的onCreateView里加载了这个布局文件R.layout.dashboard：

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"    android:id="@+id/dashboard"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:scrollbarStyle="outsideOverlay"    android:clipToPadding="false">         <LinearLayout                android:id="@+id/dashboard_container"                android:layout_width="match_parent"                android:layout_height="match_parent"                android:layout_gravity="center_horizontal"                android:paddingStart="@dimen/dashboard_padding_start"                android:paddingEnd="@dimen/dashboard_padding_end"                android:paddingTop="@dimen/dashboard_padding_top"                android:paddingBottom="@dimen/dashboard_padding_bottom"                android:orientation="vertical"                /> </ScrollView>

看了上面的布局文件可以知道Settings的选项视图应该就是显示在dashboard_container中了。

DashboardSummary走完onCreateView方法后会走onResume,然后一路下来又会调到SettingsActivity的

loadCategoriesFromResource(R.xml.dashboard_categories, categories);

过程试这样的：DashboardSummary.java中rebuildUI方法：

 private void rebuildUI(Context context) {        if (!isAdded()) {            Log.w(LOG_TAG, "Cannot build the DashboardSummary UI yet as the Fragment is not added");            return;        }        long start = System.currentTimeMillis();        final Resources res = getResources();        mDashboard.removeAllViews();        List<DashboardCategory> categories =                ((SettingsActivity) context).getDashboardCategories(true);......}

SettingsActivity.java中的getDashboardCategories(boolean b)

public List<DashboardCategory> getDashboardCategories(boolean forceRefresh) {        if (forceRefresh || mCategories.size() == 0) {            buildDashboardCategories(mCategories);        }        return mCategories;    }

buildDashboardCategories()方法：

/**     * Called when the activity needs its list of categories/tiles built.     *     * @param categories The list in which to place the tiles categories.     */    private void buildDashboardCategories(List<DashboardCategory> categories) {        categories.clear();        loadCategoriesFromResource(R.xml.dashboard_categories, categories);        updateTilesList(categories);    }

loadCategoriesFromResource()方法：

/**     * Parse the given XML file as a categories description, adding each     * parsed categories and tiles into the target list.     *     * @param resid The XML resource to load and parse.     * @param target The list in which the parsed categories and tiles should be placed.     */    private void loadCategoriesFromResource(int resid, List<DashboardCategory> target) {        XmlResourceParser parser = null;        try {            parser = getResources().getXml(resid);            AttributeSet attrs = Xml.asAttributeSet(parser);            int type;            while ((type=parser.next()) != XmlPullParser.END_DOCUMENT                    && type != XmlPullParser.START_TAG) {                // Parse next until start tag is found            }            String nodeName = parser.getName();            if (!"dashboard-categories".equals(nodeName)) {                throw new RuntimeException(                        "XML document must start with <preference-categories> tag; found"                                + nodeName + " at " + parser.getPositionDescription());            }            Bundle curBundle = null;            final int outerDepth = parser.getDepth();            while ((type=parser.next()) != XmlPullParser.END_DOCUMENT                    && (type != XmlPullParser.END_TAG || parser.getDepth() > outerDepth)) {                if (type == XmlPullParser.END_TAG || type == XmlPullParser.TEXT) {                    continue;                }                nodeName = parser.getName();                if ("dashboard-category".equals(nodeName)) {                    DashboardCategory category = new DashboardCategory();                    TypedArray sa = obtainStyledAttributes(                            attrs, com.android.internal.R.styleable.PreferenceHeader);                    category.id = sa.getResourceId(                            com.android.internal.R.styleable.PreferenceHeader_id,                            (int)DashboardCategory.CAT_ID_UNDEFINED);                    TypedValue tv = sa.peekValue(                            com.android.internal.R.styleable.PreferenceHeader_title);                    if (tv != null && tv.type == TypedValue.TYPE_STRING) {                        if (tv.resourceId != 0) {                            category.titleRes = tv.resourceId;                        } else {                            category.title = tv.string;                        }                    }                    sa.recycle();                    final int innerDepth = parser.getDepth();                    while ((type=parser.next()) != XmlPullParser.END_DOCUMENT                            && (type != XmlPullParser.END_TAG || parser.getDepth() > innerDepth)) {                        if (type == XmlPullParser.END_TAG || type == XmlPullParser.TEXT) {                            continue;                        }                        String innerNodeName = parser.getName();                        if (innerNodeName.equals("dashboard-tile")) {                            DashboardTile tile = new DashboardTile();                            sa = obtainStyledAttributes(                                    attrs, com.android.internal.R.styleable.PreferenceHeader);                            tile.id = sa.getResourceId(                                    com.android.internal.R.styleable.PreferenceHeader_id,                                    (int)TILE_ID_UNDEFINED);                            tv = sa.peekValue(                                    com.android.internal.R.styleable.PreferenceHeader_title);                            if (tv != null && tv.type == TypedValue.TYPE_STRING) {                                if (tv.resourceId != 0) {                                    tile.titleRes = tv.resourceId;                                } else {                                    tile.title = tv.string;                                }                            }                            tv = sa.peekValue(                                    com.android.internal.R.styleable.PreferenceHeader_summary);                            if (tv != null && tv.type == TypedValue.TYPE_STRING) {                                if (tv.resourceId != 0) {                                    tile.summaryRes = tv.resourceId;                                } else {                                    tile.summary = tv.string;                                }                            }                            tile.iconRes = sa.getResourceId(                                    com.android.internal.R.styleable.PreferenceHeader_icon, 0);                            tile.fragment = sa.getString(                                    com.android.internal.R.styleable.PreferenceHeader_fragment);                            sa.recycle();                            if (curBundle == null) {                                curBundle = new Bundle();                            }                            final int innerDepth2 = parser.getDepth();                            while ((type=parser.next()) != XmlPullParser.END_DOCUMENT                                    && (type != XmlPullParser.END_TAG || parser.getDepth() > innerDepth2)) {                                if (type == XmlPullParser.END_TAG || type == XmlPullParser.TEXT) {                                    continue;                                }                                String innerNodeName2 = parser.getName();                                if (innerNodeName2.equals("extra")) {                                    getResources().parseBundleExtra("extra", attrs, curBundle);                                    XmlUtils.skipCurrentTag(parser);                                } else if (innerNodeName2.equals("intent")) {                                    tile.intent = Intent.parseIntent(getResources(), parser, attrs);                                } else {                                    XmlUtils.skipCurrentTag(parser);                                }                            }                            if (curBundle.size() > 0) {                                tile.fragmentArguments = curBundle;                                curBundle = null;                            }                            // Show the SIM Cards setting if there are more than 2 SIMs installed.                            if(tile.id != R.id.sim_settings || Utils.showSimCardTile(this)){                                category.addTile(tile);                            }                        } else {                            XmlUtils.skipCurrentTag(parser);                        }                    }                    target.add(category);                } else {                    XmlUtils.skipCurrentTag(parser);                }            }        } catch (XmlPullParserException e) {            throw new RuntimeException("Error parsing categories", e);        } catch (IOException e) {            throw new RuntimeException("Error parsing categories", e);        } finally {            if (parser != null) parser.close();        }    }

这一步是通过 R.xml.dashboard_categories来加载categories，这里的categorys为ArrayList<DashboardCategory>mCategories。接着来看看dashboard_categories.xml这个文件吧

<dashboard-categories  xmlns:android="http://schemas.android.com/apk/res/android">    <!-- ----------------------------------------WIRELESS and NETWORKS ---------------------------------------->    <dashboard-category            android:id="@+id/wireless_section"            android:title="@string/header_category_wireless_networks" >        <!-- Wifi -->        <dashboard-tile                android:id="@+id/wifi_settings"                android:title="@string/wifi_settings_title"                android:fragment="com.android.settings.wifi.WifiSettings"                android:icon="@drawable/ic_settings_wireless"                />        <!-- Bluetooth -->                    <!-- Hotknot -->        <!-- SIM Cards -->        <!-- Data Usage --><!-- Call Settings -->        <dashboard-tile            android:id="@+id/call_settings"            android:title="@string/call_settings"            android:icon="@drawable/ic_menu_phone">        <intent            android:action="android.intent.action.MAIN"            android:targetPackage="com.android.dialer"            android:targetClass="com.android.dialer.settings.DialerSettingsActivity"            />        </dashboard-tile>        <!-- Operator hook -->        <dashboard-tile                android:id="@+id/operator_settings"                android:fragment="com.android.settings.WirelessSettings" >            <intent android:action="com.android.settings.OPERATOR_APPLICATION_SETTING" />        </dashboard-tile>        <!-- Other wireless and network controls -->        <dashboard-tile                android:id="@+id/wireless_settings"                android:title="@string/radio_controls_title"                android:fragment="com.android.settings.WirelessSettings"                android:icon="@drawable/ic_settings_more"                />    </dashboard-category>    <!--------------------------------------------------------------------------- DEVICE -------------------------------------------------->    <dashboard-category            android:id="@+id/device_section"            android:title="@string/header_category_device" >        <!-- Home -->        <dashboard-tile                android:id="@+id/home_settings"                android:title="@string/home_settings"                android:fragment="com.android.settings.HomeSettings"                android:icon="@drawable/ic_settings_home"                /> 。。。<pre name="code" class="html"> </dashboard-category>。。。。。。</dashboard-categories>

根据这个文件我们可以知道了，所谓的dashboard就是Settings模块首界面的一个抽象。而dashboard-categorys则是设置分类集合的抽象，而dashboard-category是分类的抽象，dashboard-tile就是分类下每个选项的抽象了。代码中的List<DashboardCategory>对应dashboard-categorys， DashboardCategory对应dashboard-category，而dashboard-tile则对因代码中的DashboardTile。

当加载完这些对象后SettingsActivity会将得到的 mCategories 返回给DashboardSummary来初始化Settings的设置选项。

下面这段代码就是DashboardSummary.rebuildUI()中完成界面的初始化

    long start = System.currentTimeMillis();        final Resources res = getResources();         mDashboard.removeAllViews();         List<DashboardCategory> categories =                ((SettingsActivity) context).getDashboardCategories(true);         final int count = categories.size();        for (int n = 0; n < count; n++) {            DashboardCategory category = categories.get(n);             View categoryView = mLayoutInflater.inflate(R.layout.dashboard_category, mDashboard,                    false);             TextView categoryLabel = (TextView) categoryView.findViewById(R.id.category_title);            categoryLabel.setText(category.getTitle(res));             ViewGroup categoryContent =                    (ViewGroup) categoryView.findViewById(R.id.category_content);             final int tilesCount = category.getTilesCount();            for (int i = 0; i < tilesCount; i++) {                DashboardTile tile = category.getTile(i);                 DashboardTileView tileView = new DashboardTileView(context);                updateTileView(context, res, tile, tileView.getImageView(),                        tileView.getTitleTextView(), tileView.getStatusTextView());                 tileView.setTile(tile);                 categoryContent.addView(tileView);            }             // Add the category            mDashboard.addView(categoryView);        }

这段代码我就不具体分析了，逻辑很简单，遍历categories这个列表来获取DashboardCategory对象，将所有DashboardCategory对象和DashboardCategory对象中的DashboardTile对象转化为视图对象并添加到主视图对象mDashboard中。

 

到这里SettingsActivity的onCreate方法就算结束了。总结一下，

    1.onCreate完成的任务是切换DashboardSmmary这个Fragment，然后从dashboard_categories.xml中读取预先配置好的文件来初始化Settings的首界面视图。

    2.L中舍弃了Header类，取而代之的是DashboardCategory和DashboardTile类。