Launcher 源码有关加载应用xml等资源文件研究

主要Launcher这个类，一些可以意会的代码：

一、有关过滤注册了 <category android:name="android.intent.category.LAUNCHER" />的应用

 Intent intent = new Intent(Intent.ACTION_MAIN, null);
            intent.addCategory(Intent.CATEGORY_LAUNCHER);

            PackageManager packageManager = getPackageManager();
            final List<ResolveInfo> apps = packageManager.queryIntentActivities(
                    intent, 0);
            final int count = apps.size();

上面重点是应用注册了“intent.addCategory(Intent.CATEGORY_LAUNCHER);”

即一般应用在AndroidManifest.xml中的应用入口Acitivity中会这样写到如下：

        <activity android:name=".USBActivity"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

重点<category android:name="android.intent.category.LAUNCHER" />而上面的

 intent.addCategory(Intent.CATEGORY_LAUNCHER);

代码就是过滤哪些应用注册了android.intent.category.LAUNCHER

二、获取app的一些相关信息

ResolveInfo这个类我们需要做一个了解

  List<Intent> intentToLaunchList = packageManager
                    .getLaunchIntentListForPackage(packageName);
            if (intentToLaunchList != null) {
                for (int i = 0; i < intentToLaunchList.size(); i++) {
                    Intent intentToLaunch = intentToLaunchList.get(i);

 ComponentName component = intentToLaunch.getComponent();
        PackageManager packageManager = context.getPackageManager();
        ActivityInfo activityInfo = null;
        try {
            activityInfo = packageManager.getActivityInfo(component, 0 /* no flags */);
        } catch (NameNotFoundException e) {
            if (LauncherSettings.LOG_ON) Log.e(LOG_TAG, "Couldn't find ActivityInfo for selected application", e);
        }

补充一个public class ApplicationInfo extends PackageItemInfo implements Parcelable 

public class ActivityInfo extends ComponentInfo
        implements Parcelable 

public class ComponentInfo extends PackageItemInfo 

  public class PackageItemInfo 类中有这么一个方法

  /**
     * Load an XML resource attached to the meta-data of this item.  This will
     * retrieved the name meta-data entry, and if defined call back on the
     * given PackageManager to load its XML file from the application.
     * 
     * @param pm A PackageManager from which the XML can be loaded; usually
     * the PackageManager from which you originally retrieved this item.
     * @param name Name of the meta-date you would like to load.
     * 
     * @return Returns an XmlPullParser you can use to parse the XML file
     * assigned as the given meta-data.  If the meta-data name is not defined
     * or the XML resource could not be found, null is returned.
     */
    public XmlResourceParser loadXmlMetaData(PackageManager pm, String name) {
        if (metaData != null) {
            int resid = metaData.getInt(name);
            if (resid != 0) {
                return pm.getXml(packageName, resid, null);
            }
        }
        return null;
    }

public abstract XmlResourceParser getXml (String packageName, int resid, ApplicationInfo appInfo)

Since: API Level 1
Retrieve an XML file from a package. This is a low-level API used to retrieve XML meta data.
Parameters

packageName	The name of the package that this xml is coming from. Can not be null.
resid	The resource identifier of the desired xml. Can not be 0.
appInfo	Overall information about packageName. This may be null, in which case the application information will be retrieved for you if needed; if you already have this information around, it can be much more efficient to supply it here.
Returns

Returns an XmlPullParser allowing you to parse out the XML data. Returns null if the xml resource could not be found for any reason.

下面实例

ActivityInfo ai = getPackageManager().getActivityInfo(
                    getComponentName(), PackageManager.GET_META_DATA);
            parser = ai.loadXmlMetaData(getPackageManager(),
                    ALIAS_META_DATA);

    public final String ALIAS_META_DATA = "android.app.alias";

    <application android:hasCode="false">
        <activity android:name="android.app.AliasActivity" android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
            <meta-data android:name="android.app.alias" android:resource="@xml/alias" />
        </activity>

三、ResolveInfo与activityInfo关系

public class ResolveInfo implements Parcelable {
    /**
     * The activity that corresponds to this resolution match, if this
     * resolution is for an activity.  One and only one of this and
     * serviceInfo must be non-null.
     */
    public ActivityInfo activityInfo;

从上面流程可以清晰看出是怎么读取应用的资源的。

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

补充：

       Intent intent = new Intent(MAIN_ACTION_NAME);

        ResolveInfo activityInfo = pm.resolveActivity(intent, 0);

 

        intent = new Intent(SERVICE_NAME);

        ResolveInfo serviceInfo = pm.resolveService(intent, PackageManager.GET_RESOLVED_FILTER);

 

public static ComponentName getHomeComponent(PackageManager PM) {
    Intent home_intent = new Intent("android.intent.action.MAIN");
    home_intent.addCategory("android.intent.category.HOME");
    home_intent.addCategory("android.intent.category.DEFAULT");

    ComponentName cn = home_intent.resolveActivity(PM);
    if (cn == null)
        Log.v(TAG, "[Default] package:null");
    else
        Log.v(TAG, "[Default] package:" + cn.getPackageName() + " class:" + cn.getClassName());

    return cn;
}

 List<ResolveInfo> list = pm.queryIntentActivities(intent, PackageManager.GET_META_DATA);
            int listSize = list.size();
            for (int i = 0; i < listSize; i++) {
                ResolveInfo resolveInfo = list.get(i);
                if ((resolveInfo.activityInfo.applicationInfo.flags
                        & ApplicationInfo.FLAG_SYSTEM) != 0) {
                    Drawable icon = null;
                    String title = null;
                    String summary = null;

                    // Get the activity's meta-data
                    try {
                        Resources res = pm
                                .getResourcesForApplication(resolveInfo.activityInfo.packageName);
                        Bundle metaData = resolveInfo.activityInfo.metaData;

                        if (res != null && metaData != null) {
                            icon = res.getDrawable(metaData.getInt(META_DATA_PREFERENCE_ICON));
                            title = res.getString(metaData.getInt(META_DATA_PREFERENCE_TITLE));
                            summary = res.getString(metaData.getInt(META_DATA_PREFERENCE_SUMMARY));
                        }
                    } catch (NameNotFoundException e) {
                        // Ignore
                    } catch (NotFoundException e) {
                        // Ignore
                    }

                    // Set the preference title to the activity's label if no
                    // meta-data is found
                    if (TextUtils.isEmpty(title)) {
                        title = resolveInfo.loadLabel(pm).toString();
                    }

  PackageManager pm = context.getPackageManager();
            List<ResolveInfo> list = pm.queryIntentActivities(intent, 0);
            int listSize = list.size();
            for (int i = 0; i < listSize; i++) {
                ResolveInfo resolveInfo = list.get(i);
                if ((resolveInfo.activityInfo.applicationInfo.flags & ApplicationInfo.FLAG_SYSTEM)
                        != 0) {

                    // Replace the intent with this specific activity
                    preference.setIntent(new Intent().setClassName(
                            resolveInfo.activityInfo.packageName,
                            resolveInfo.activityInfo.name));

                    if ((flags & UPDATE_PREFERENCE_FLAG_SET_TITLE_TO_MATCHING_ACTIVITY) != 0) {
                        // Set the preference title to the activity's label
                        preference.setTitle(resolveInfo.loadLabel(pm));
                    }

//			Resources res = packageManager
//					.getResourcesForApplication(resolveInfo.activityInfo.packageName);
//		    xmlResourceParser = res.getXml(R.xml.voice_recognition);
			
//			ComponentName component = intent.getComponent();  
//			 activityInfo = packageManager.getActivityInfo(component, 0 /* no flags */); 

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

android 特有的XmlResourceParser解析xml文件方式

http://www.ibm.com/developerworks/cn/xml/x-androidxml/

http://www.iteye.com/wiki/blog/1284853

http://blog.csdn.net/kmyhy/article/details/6439794

http://kahweh.blog.sohu.com/147050083.html

http://scrobin.blog.163.com/blog/static/1787064332011547239247/