Android Launcher3安装应用后，控制应用图标显示位置（显示在第一页上，默认是第二页）

最近在搞Android的Launcher开发，去掉应用列表后，每次安装应用应用图标都会放在第二页。查看源码后，发现安装应用会走LauncherModel的addAndBindAddedWorkspaceApps方法，添加绑定一个应用图标到workspace中。

public void addAndBindAddedWorkspaceApps(final Context context,
                                         final ArrayList<ItemInfo> workspaceApps) {

而addAndBindAddedWorkspaceApps方法又是通过findNextAvailableIconSpace方法寻找一个空位置存放应用图标。这里如果找不到，就会把页数++。

// Add this icon to the db, creating a new page if necessary.  If there
// is only the empty page then we just add items to the first page.
// Otherwise, we add them to the next pages.
int startSearchPageIndex = workspaceScreens.isEmpty() ? 0 : 1;
Pair<Long, int[]> coords = LauncherModel.findNextAvailableIconSpace(context,
        name, launchIntent, startSearchPageIndex, workspaceScreens);

在findNextAvailableIconSpace方法中，我发现总是从我Launcher的第二个页面开始往下寻找空位置。所以我修改了这个方法，让他从第一页开始寻找。这样就完美地解决了安装应用后，应用图标放置位置的问题。

static Pair<Long, int[]> findNextAvailableIconSpace(Context context, String name,
                                                    Intent launchIntent,
                                                    int firstScreenIndex,
                                                    ArrayList<Long> workspaceScreens) {
    // Lock on the app so that we don't try and get the items while apps are being added
    LauncherAppState app = LauncherAppState.getInstance();
    LauncherModel model = app.getModel();
    boolean found = false;
    synchronized (app) {
        if (sWorkerThread.getThreadId() != Process.myTid()) {
            // Flush the LauncherModel worker thread, so that if we just did another
            // processInstallShortcut, we give it time for its shortcut to get added to the
            // database (getItemsInLocalCoordinates reads the database)
            model.flushWorkerThread();
        }
        final ArrayList<ItemInfo> items = LauncherModel.getItemsInLocalCoordinates(context);

        // Try adding to the workspace screens incrementally, starting at the default or center
        // screen and alternating between +1, -1, +2, -2, etc. (using ~ ceil(i/2f)*(-1)^(i-1))

        //修改控制安装后图标位置
        firstScreenIndex = Math.min(firstScreenIndex, workspaceScreens.size());
        int count = workspaceScreens.size();
        firstScreenIndex = firstScreenIndex >= 1 ? firstScreenIndex - 1 : firstScreenIndex;
        for (int screen = firstScreenIndex; screen < count && !found; screen++) {
            int[] tmpCoordinates = new int[2];
            if (findNextAvailableIconSpaceInScreen(items, tmpCoordinates,
                    workspaceScreens.get(screen))) {
                // Update the Launcher db
                return new Pair<Long, int[]>(workspaceScreens.get(screen), tmpCoordinates);
            }
        }
    }
    return null;
}