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1.前言

在12.0的系统rom定制化中，在某些时候安装第三方应用，突然会发现应用左右两侧为全屏有黑边显示，所以这时候需要进行
优化，看问题出在哪，然后解决这个问题，接下来分析下相关问题

2.第三方应用左右两侧未全屏有黑边问题解决的核心类

 frameworks\base\core\java\android\content\pm\parsing\component\ParsedActivityUtils.java

3.第三方应用左右两侧未全屏有黑边问题解决的核心功能分析和实现

在android7.0以后，在AndroidManifest.xml中的
<application> 标签隐式添加一个属性，android:resizeableActivity=“true”, 该属性的作用后面将详细说明。
在 标签中增加属性：android:resizeableActivity=“false”，同时在节点下增加一个meta-data标签：

原理说明

在Android 7.0（API 级别 24）或更高版本的应用，android:resizeableActivity属性默认为true（对应适配方式1）。这个属性是控制多窗口显示的，决定当前的应用或者Activity是否支持多窗口。
可以在清单的<activity>或 <application>节点中设置该属性，启用或禁用多窗口显示，配置如下：
android:resizeableActivity=[“true” | “false”]

如果该属性设置为 true，Activity 将能以分屏和自由形状模式启动。 如果此属性设置为 false，Activity 将不支持多窗口模式。 如果该值为 false，且用户尝试在多窗口模式下启动 Activity，该 Activity 将全屏显示。

适配方式2即为设置屏幕的最大长宽比，这是官方提供的设置方式。
如果设置了最大长宽比，必须android:resizeableActivity=“false”。 否则最大长宽比没有任何作用

这是android12开始支持了多窗口和分屏等功能，对一些低版本sdk的应用兼容性有了调整，如果不想改变targetsdk到更高，也可以为Activity增加resizeableActivity属性，同样可以达到去除黑边效果。

   <activityandroid:name=".YourActivity"android:resizeableActivity="true"></activity>

以上两种解决办法适用于自己开发的应用，但对应腾讯视频这种第三方应用就只能从系统层面去解决了。
接下来看下第三方应用如何处理两边黑屏的问题

 ParsedActivityUtils 是Android系统中用于解析 AndroidManifest.xml 文件中的一个类，主要负责解析Activity、Service、Receiver等组件的信息。‌
功能和作用

ParsedActivityUtils类在Android系统中主要用于解析AndroidManifest.xml文件中的Activity、Service和Receiver等组件的信息。它通过读取XML文件中的标签和属性，将这些信息转换为Java对象，以便系统能够正确地管理和调用这些组件。具体功能包括：

    ‌解析Activity信息‌：读取Activity的标签、名称、启动模式等信息。
    ‌解析Service信息‌：读取Service的标签、名称、启动方式等信息。
    ‌解析Receiver信息‌：读取Receiver的标签、名称、接收的Intent等信息。

3.1ParsingPackageUtils.java的相关解析代码分析

    public class ParsingPackageUtils {public ParsingPackageUtils(boolean onlyCoreApps, String[] separateProcesses,DisplayMetrics displayMetrics, @NonNull Callback callback) {mOnlyCoreApps = onlyCoreApps;mSeparateProcesses = separateProcesses;mDisplayMetrics = displayMetrics;mCallback = callback;}

 在ParsingPackageUtils的构造方法中，主要是构造callback参数，供解析的时候回调参数使用的，接下来主要看解析的最主要的方法parseBaseApplication
接下来看parseBaseApplication的具体解析方式方法

   private ParseResult<ParsingPackage> parseBaseApplication(ParseInput input,ParsingPackage pkg, Resources res, XmlResourceParser parser, int flags)throws XmlPullParserException, IOException {final String pkgName = pkg.getPackageName();int targetSdk = pkg.getTargetSdkVersion();TypedArray sa = res.obtainAttributes(parser, R.styleable.AndroidManifestApplication);try {// TODO(b/135203078): Remove this and force unit tests to mock an empty manifest// This case can only happen in unit tests where we sometimes need to create fakes// of various package parser data structures.if (sa == null) {return input.error("<application> does not contain any attributes");}String name = sa.getNonConfigurationString(R.styleable.AndroidManifestApplication_name,0);if (name != null) {String packageName = pkg.getPackageName();String outInfoName = ParsingUtils.buildClassName(packageName, name);if (PackageManager.APP_DETAILS_ACTIVITY_CLASS_NAME.equals(outInfoName)) {return input.error("<application> invalid android:name");} else if (outInfoName == null) {return input.error("Empty class name in package " + packageName);}pkg.setClassName(outInfoName);}....TypedValue v = sa.peekValue(R.styleable.AndroidManifestApplication_fullBackupContent);int fullBackupContent = 0;if (v != null) {fullBackupContent = v.resourceId;if (v.resourceId == 0) {if (PackageParser.DEBUG_BACKUP) {Slog.v(TAG, "fullBackupContent specified as boolean=" +(v.data == 0 ? "false" : "true"));}// "false" => -1, "true" => 0fullBackupContent = v.data == 0 ? -1 : 0;}pkg.setFullBackupContent(fullBackupContent);}if (PackageParser.DEBUG_BACKUP) {Slog.v(TAG, "fullBackupContent=" + fullBackupContent + " for " + pkgName);}}if (sa.getBoolean(R.styleable.AndroidManifestApplication_persistent, false)) {// Check if persistence is based on a feature being presentfinal String requiredFeature = sa.getNonResourceString(R.styleable.AndroidManifestApplication_persistentWhenFeatureAvailable);pkg.setPersistent(requiredFeature == null || mCallback.hasFeature(requiredFeature));}......String classLoaderName = pkg.getClassLoaderName();if (classLoaderName != null&& !ClassLoaderFactory.isValidClassLoaderName(classLoaderName)) {return input.error("Invalid class loader name: " + classLoaderName);}pkg.setGwpAsanMode(sa.getInt(R.styleable.AndroidManifestApplication_gwpAsanMode, -1));} finally {sa.recycle();}boolean hasActivityOrder = false;boolean hasReceiverOrder = false;boolean hasServiceOrder = false;final int depth = parser.getDepth();int type;while ((type = parser.next()) != XmlPullParser.END_DOCUMENT&& (type != XmlPullParser.END_TAG|| parser.getDepth() > depth)) {if (type != XmlPullParser.START_TAG) {continue;}final ParseResult result;String tagName = parser.getName();boolean isActivity = false;switch (tagName) {case "activity":isActivity = true;// fall-throughcase "receiver":ParseResult<ParsedActivity> activityResult =ParsedActivityUtils.parseActivityOrReceiver(mSeparateProcesses, pkg,res, parser, flags, PackageParser.sUseRoundIcon, input);if (activityResult.isSuccess()) {ParsedActivity activity = activityResult.getResult();if (isActivity) {hasActivityOrder |= (activity.getOrder() != 0);pkg.addActivity(activity);} else {hasReceiverOrder |= (activity.getOrder() != 0);pkg.addReceiver(activity);}}result = activityResult;break;case "service":ParseResult<ParsedService> serviceResult =ParsedServiceUtils.parseService(mSeparateProcesses, pkg, res, parser,flags, PackageParser.sUseRoundIcon, input);if (serviceResult.isSuccess()) {ParsedService service = serviceResult.getResult();hasServiceOrder |= (service.getOrder() != 0);pkg.addService(service);}result = serviceResult;break;case "provider":ParseResult<ParsedProvider> providerResult =ParsedProviderUtils.parseProvider(mSeparateProcesses, pkg, res, parser,flags, PackageParser.sUseRoundIcon, input);if (providerResult.isSuccess()) {pkg.addProvider(providerResult.getResult());}result = providerResult;break;case "activity-alias":activityResult = ParsedActivityUtils.parseActivityAlias(pkg, res,parser, PackageParser.sUseRoundIcon, input);if (activityResult.isSuccess()) {ParsedActivity activity = activityResult.getResult();hasActivityOrder |= (activity.getOrder() != 0);pkg.addActivity(activity);}result = activityResult;break;default:result = parseBaseAppChildTag(input, tagName, pkg, res, parser, flags);break;}if (result.isError()) {return input.error(result);}}if (TextUtils.isEmpty(pkg.getStaticSharedLibName())) {// Add a hidden app detail activity to normal apps which forwards user to App Details// page.ParseResult<ParsedActivity> a = generateAppDetailsHiddenActivity(input, pkg);if (a.isError()) {// Error should be impossible here, as the only failure case as of SDK R is a// string validation error on a constant ":app_details" string passed in by the// parsing code itself. For this reason, this is just a hard failure instead of// deferred.return input.error(a);}pkg.addActivity(a.getResult());}if (hasActivityOrder) {pkg.sortActivities();}if (hasReceiverOrder) {pkg.sortReceivers();}if (hasServiceOrder) {pkg.sortServices();}// Must be run after the entire {@link ApplicationInfo} has been fully processed and after// every activity info has had a chance to set it from its attributes.setMaxAspectRatio(pkg);setMinAspectRatio(pkg);setSupportsSizeChanges(pkg);pkg.setHasDomainUrls(hasDomainURLs(pkg));return input.success(pkg);} 

从上述代码中，可以看出在parseBaseApplication中解析xml时可以对tag的值为activity,receiver,service,provider,activity-alias等几种类型的组件进行解析
在activity-alias这种tag，就是对activity的别类的解析，而这里也是今天实现默认启动Launcher的重点部分在解析activity的实现调用的是ParsedActivityUtils.parseActivityOrReceiver
进行解析的,最后代码还是由parseActivityOrAlias来负责解析的，所以接下来看这部分代码

3.2 ParsedActivityUtils相关解析源码分析

@NonNull@VisibleForTesting(visibility = VisibleForTesting.Visibility.PACKAGE)public static ParseResult<ParsedActivity> parseActivityOrReceiver(String[] separateProcesses,ParsingPackage pkg, Resources res, XmlResourceParser parser, int flags,boolean useRoundIcon, ParseInput input)throws XmlPullParserException, IOException {final String packageName = pkg.getPackageName();final ParsedActivityactivity = new ParsedActivity();...//int resizeMode = getActivityResizeMode(pkg, sa, screenOrientation);int resizeMode = ActivityInfo.RESIZE_MODE_RESIZEABLE; //固定开启resizeable属性...}

ParseResult()方法中重写resizeMode值即可。这样就可以从系统层面解决所有应用显示黑边问题，包括安装的第三方应用。