一、概述

本文主要对android M源码中的设置进行分析，此篇文章主要对第一次进入设置的过程进行分析。

二、入口

AndroidManifest.xml中的<intent-filter> 定义apk默认入口如果有很多就默认第一个，设置入口Settings.java

        <activity android:name="Settings"
                android:taskAffinity="com.android.settings"
                ...
            <intent-filter android:priority="1">
                <action android:name="android.settings.SETTINGS" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
            <meta-data android:name="com.android.settings.PRIMARY_PROFILE_CONTROLLED"
                android:value="true" />

Settings.java中只定义了一些静态内部类，接着看Settings的继承 SettingsActivity，SettingsActivity继承自Activity那么我们就可以从SettingsActivity的onCreate函数对这个SettingsActivity进行分析了。

三、SettingsActivity

onCreate()

protected void onCreate(Bundle savedState) {
        super.onCreate(savedState);
        ...
        getMetaData();
        final Intent intent = getIntent();
        //...
        final String initialFragmentName = intent.getStringExtra(EXTRA_SHOW_FRAGMENT);
    //...
        mIsShowingDashboard = className.equals(Settings.class.getName());

        setContentView(mIsShowingDashboard ?
                R.layout.settings_main_dashboard : R.layout.settings_main_prefs);

        mContent = (ViewGroup) findViewById(R.id.main_content);

        getFragmentManager().addOnBackStackChangedListener(this);

        //...

        if (savedState != null) {
            //...
        } else {
            if (!mIsShowingDashboard) {
                ...
                Bundle initialArguments = intent.getBundleExtra(EXTRA_SHOW_FRAGMENT_ARGUMENTS);
                switchToFragment(initialFragmentName, initialArguments, true, false,
                        mInitialTitleResId, mInitialTitle, false);
            } else {
                ...
                switchToFragment(DashboardSummary.class.getName(), null, false, false,
                        mInitialTitleResId, mInitialTitle, false);
            }
        }

        //...
    }

Class判断

第一个函数getMetaData；获得AndroidManifest中activyt的meta-data，给mFragmentClass给个值在getIntent中getStartingFragmentClass，可以看出此函数作用是打开的界面是属于Settings的话就直接返回这个Class

private void getMetaData() {
        try {
            ActivityInfo ai = getPackageManager().getActivityInfo(getComponentName(),
                    PackageManager.GET_META_DATA);
            if (ai == null || ai.metaData == null) return;
            mFragmentClass = ai.metaData.getString(META_DATA_KEY_FRAGMENT_CLASS);
        } catch (NameNotFoundException nnfe) {
            // No recovery
            Log.d(LOG_TAG, "Cannot get Metadata for: " + getComponentName().toString());
        }
    }

布局

接下来布局设置，mIsShowingDashboard = true，所以是settings_main_dashboard，打开可以看到里边的布局里边只有一个FrameLayout，所以可以看出主界面就是一个FrameLayout的容器

状态

addOnBackStackChangedListener为back stack加上监听第一次进入savedState为空，savedState作用是对界面状态的保存在SettingsAcitvity中的onSaveInstanceState对状态保存一些操作，这里就不详述了。

载入

接着走到了switchToFragment(DashboardSummary.class.getName()....switchToFragment的作用就是加载一个fragment。

 private Fragment switchToFragment(String fragmentName, Bundle args, boolean validate,
            boolean addToBackStack, int titleResId, CharSequence title, boolean withTransition) {
        if (validate && !isValidFragment(fragmentName)) {
            throw new IllegalArgumentException("Invalid fragment for this activity: "
                    + fragmentName);
        }
        Fragment f = Fragment.instantiate(this, fragmentName, args);
        FragmentTransaction transaction = getFragmentManager().beginTransaction();
        transaction.replace(R.id.main_content, f);
        if (withTransition) {
            TransitionManager.beginDelayedTransition(mContent);
        }
        if (addToBackStack) {
            transaction.addToBackStack(SettingsActivity.BACK_STACK_PREFS);
        }
        if (titleResId > 0) {
            transaction.setBreadCrumbTitle(titleResId);
        } else if (title != null) {
            transaction.setBreadCrumbTitle(title);
        }
        transaction.commitAllowingStateLoss();
        getFragmentManager().executePendingTransactions();
        return f;
    }

在SettingsActivity中，onCreate基本就走完了，onResume只是一些广播的注册数据的监听，接下来就看看这个载入DashboardSummary.java

四、DashboardSummary

此类主要管理主界面的菜单解析，加载整个创建过程代码很少，onCreateView中看到，布局是一个ViewGroup，在onResume中调用sendRebuildUI方法开始加载界面

 private void sendRebuildUI() {
        if (!mHandler.hasMessages(MSG_REBUILD_UI)) {
            mHandler.sendEmptyMessage(MSG_REBUILD_UI);
        }
    }

接着在mHandler中调用rebuildUI

  private Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case MSG_REBUILD_UI: {
                    final Context context = getActivity();
                    rebuildUI(context);
                } break;
            }
        }
    };

然后看最后的加载函数rebuildUI

        private void rebuildUI(Context context) {
        ...

        List<DashboardCategory> categories =
                ((SettingsActivity) context).getDashboardCategories(true);

        final int count = categories.size();

        for (int n = 0; n < count; n++) {
            ...
            mDashboard.addView(categoryView);
        }
       ...
    }

里边最关键的是调用了SettingsActivity的getDashboardCategories方法而在getDashboardCategories主要调用buildDashboardCategories

private void buildDashboardCategories(List<DashboardCategory> categories) {
        categories.clear();
        loadCategoriesFromResource(R.xml.dashboard_categories, categories, this);
        updateTilesList(categories);
    }

最后，我们打开dashboard_categories这个xml文件就可以到设置菜单的一些配置了

<dashboard-categories
        xmlns:android="http://schemas.android.com/apk/res/android">

    <!-- WIRELESS and NETWORKS -->
    <dashboard-category
            android:id="@+id/wireless_section"
            android:key="@string/category_key_wireless"
            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 -->
        <dashboard-tile
                android:id="@+id/bluetooth_settings"
                android:title="@string/bluetooth_settings_title"
                android:fragment="com.android.settings.bluetooth.BluetoothSettings"
                android:icon="@drawable/ic_settings_bluetooth"
                />

五、总结

设置进入后的初始化流程主要是通过SettingsActvity来加载DashboardSummary
最后再DashboardSummary进行初始化解析加载出界面。