Android系统 设置第三方应用为默认Launcher实现和原理分析

import android.os.SystemProperties;
import android.text.TextUtils;
import android.content.ComponentName;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.content.pm.ResolveInfo;

// 从系统属性中获取Home包名
String homePackageName = SystemProperties.get("persist.home.package", null);
// 如果没有设置Home包名，则使用默认的"com.android.launcher3"
if (TextUtils.isEmpty(homePackageName)) {
    homePackageName = "com.android.launcher3"; // 默认launcher包名
}
try {
    Intent it = new Intent(Intent.ACTION_MAIN);
    List<ResolveInfo> list = AppGlobals.getPackageManager().queryIntentActivities(homeIntent,
            homeIntent.resolveTypeIfNeeded(mService.mContext.getContentResolver()), ActivityManagerService.STOCK_PM_FLAGS, userId).getList();
    final int count = list.size();
    for (int i = 0; i < count; i++) {
        ResolveInfo r = list.get(i);
        if (homePackageName.equals(r.activityInfo.packageName)) {
            Slog.d(TAG, "3rd launcher: " + r.activityInfo.packageName + "@" + r.activityInfo.name);
            comp = new ComponentName(homePackageName, r.activityInfo.name);
            aInfo = r.activityInfo;
            break;
        }
    }
} catch (Exception e) {
    e.printStackTrace();
}
if (aInfo == null) {
    // 如果指定的Home包名应用未安装或找不到指定的Activity，启动默认的Launcher
    PackageManager packageManager = mService.mContext.getPackageManager();
    homeIntent = new Intent(Intent.ACTION_MAIN).addCategory(Intent.CATEGORY_HOME);
    comp = homeIntent.resolveActivity(packageManager);
    if (comp != null) {
        try {
            aInfo = packageManager.getActivityInfo(comp, flags);
        } catch (PackageManager.NameNotFoundException e) {
            e.printStackTrace();
        }
    }
}
if (aInfo == null) {
    Slog.wtf(TAG, "No home screen found for " + homeIntent, new Throwable());
    return null;
}

/*@VisibleForTesting
ActivityInfo resolveHomeActivity(int userId, Intent homeIntent) {
    final int flags = ActivityManagerService.STOCK_PM_FLAGS;
    final ComponentName comp = homeIntent.getComponent();
    ActivityInfo aInfo;
    if (comp != null) {
        try {
            aInfo = AppGlobals.getPackageManager().getActivityInfo(comp, flags, userId);
        } catch (RemoteException e) {
            return null;
        }
    } else {
        ResolveInfo info = AppGlobals.getPackageManager().resolveIntent(homeIntent,
                homeIntent.resolveTypeIfNeeded(mService.mContext.getContentResolver()), flags, userId);
        if (info != null) {
            aInfo = info.activityInfo;
        } else {
            Slog.wtf(TAG, "No home screen found for " + homeIntent, new Throwable());
            return null;
        }
    }
    aInfo = new ActivityInfo(aInfo);
    aInfo.applicationInfo = mService.getAppInfoForUser(aInfo.applicationInfo, userId);
    return aInfo;
}*/