主目录见：Android高级进阶知识（这是总目录索引）
Launcher3源码地址：Launcher3-master
[This tutorial was written by Ticoo]
省略一万字前奏
主入口Launcher
LauncherAppState
Launcher的onCreate里比较长，我们依次取代码片段来分析，看oncrate方法的这一段,初始化LauncherAppState
public void onCreate() {
...
LauncherAppState app = LauncherAppState.getInstance();
...
}
LauncherAppState是保存一些全局的，核心的对象。主要有整个Launcher的工作台workspace，Launcher的控制器LauncherModel，应用图标的缓存机制IconCache，设备的配置信息InvariantDeviceProfile等。
构造方法，首先初始化内存的追踪器TestingUtils，记录我们app的内存信息，这个工具在我们开发其他app分析内存信息时也是很有用的。
private LauncherAppState() {
...
if (TestingUtils.MEMORY_DUMP_ENABLED) {
TestingUtils.startTrackingMemory(sContext);
}
mInvariantDeviceProfile = new InvariantDeviceProfile(sContext);
mIconCache = new IconCache(sContext, mInvariantDeviceProfile);
mWidgetCache = new WidgetPreviewLoader(sContext, mIconCache);
mAppFilter = AppFilter.loadByName(sContext.getString(R.string.app_filter_class));
mModel = new LauncherModel(this, mIconCache, mAppFilter);
LauncherAppsCompat.getInstance(sContext).addOnAppsChangedCallback(mModel);
// Register intent receivers
IntentFilter filter = new IntentFilter();
filter.addAction(Intent.ACTION_LOCALE_CHANGED);
filter.addAction(SearchManager.INTENT_GLOBAL_SEARCH_ACTIVITY_CHANGED);
// For handling managed profiles
filter.addAction(LauncherAppsCompat.ACTION_MANAGED_PROFILE_ADDED);
filter.addAction(LauncherAppsCompat.ACTION_MANAGED_PROFILE_REMOVED);
filter.addAction(LauncherAppsCompat.ACTION_MANAGED_PROFILE_AVAILABLE);
filter.addAction(LauncherAppsCompat.ACTION_MANAGED_PROFILE_UNAVAILABLE);
sContext.registerReceiver(mModel, filter);
...
}
LauncherAppsCompat里添加了一个应用变化的回调，由LauncherModel实现接口，及时的响应数据变化。LauncherAppsCompat是获取所有应用，监听应用变化的一个抽象，Android 5.0前后的版本获取方式不一样了，这就是Launcher良好适配性的体现了。
LauncherAppsCompat.getInstance(sContext).addOnAppsChangedCallback(mModel);
Android 5.0以前的监听
private void registerForPackageIntents() {
IntentFilter filter = new IntentFilter(Intent.ACTION_PACKAGE_ADDED);
filter.addAction(Intent.ACTION_PACKAGE_REMOVED);
filter.addAction(Intent.ACTION_PACKAGE_CHANGED);
filter.addDataScheme("package");
mContext.registerReceiver(mPackageMonitor, filter);
filter = new IntentFilter();
filter.addAction(Intent.ACTION_EXTERNAL_APPLICATIONS_AVAILABLE);
filter.addAction(Intent.ACTION_EXTERNAL_APPLICATIONS_UNAVAILABLE);
mContext.registerReceiver(mPackageMonitor, filter);
}
Android5.0后的监听
import android.content.pm.LauncherApps;
protected LauncherApps mLauncherApps;
public void addOnAppsChangedCallback(LauncherAppsCompat.OnAppsChangedCallbackCompat callback) {
WrappedCallback wrappedCallback = new WrappedCallback(callback);
synchronized (mCallbacks) {
mCallbacks.put(callback, wrappedCallback);
}
mLauncherApps.registerCallback(wrappedCallback);
}
除了TestingUtils，应用变化监听外，初始化两个核心对象IconCache，LauncherModel。LauncherModel添加了设备变更，用户信息变更的广播，这是因为当用户修改设备信息如语言，区域，用户信息等，LauncherModel会刷新数据，改变图标，标题等信息。
LauncherAppState的初始化到这里基本上就完成了。
DeviceProfile，InvariantDeviceProfile，Launcher的配置
我们继续看，下一步
LauncherAppState app = LauncherAppState.getInstance();
// Load configuration-specific DeviceProfile
mDeviceProfile = getResources().getConfiguration().orientation
== Configuration.ORIENTATION_LANDSCAPE ?
app.getInvariantDeviceProfile().landscapeProfile
: app.getInvariantDeviceProfile().portraitProfile;
通过Configuration获取横屏配置landscapeProfile 或者portraitProfile竖屏配置
DeviceProfile
DeviceProfile的数据都是来自InvariantDeviceProfile，封装一些工具方法，我们直接看重点InvariantDeviceProfile
InvariantDeviceProfile
InvariantDeviceProfile的初始化是在LauncherAppState构造里new出来的，调用的是
InvariantDeviceProfile(Context context) {
...
numRows = closestProfile.numRows;
numColumns = closestProfile.numColumns;
numHotseatIcons = closestProfile.numHotseatIcons;
hotseatAllAppsRank = (int) (numHotseatIcons / 2);
defaultLayoutId = closestProfile.defaultLayoutId;
numFolderRows = closestProfile.numFolderRows;
numFolderColumns = closestProfile.numFolderColumns;
minAllAppsPredictionColumns = closestProfile.minAllAppsPredictionColumns;
iconSize = interpolatedDeviceProfileOut.iconSize;
iconBitmapSize = Utilities.pxFromDp(iconSize, dm);
iconTextSize = interpolatedDeviceProfileOut.iconTextSize;
hotseatIconSize = interpolatedDeviceProfileOut.hotseatIconSize;
fillResIconDpi = getLauncherIconDensity(iconBitmapSize);
// If the partner customization apk contains any grid overrides, apply them
// Supported overrides: numRows, numColumns, iconSize
applyPartnerDeviceProfileOverrides(context, dm);
Point realSize = new Point();
display.getRealSize(realSize);
// The real size never changes. smallSide and largeSide will remain the
// same in any orientation.
int smallSide = Math.min(realSize.x, realSize.y);
int largeSide = Math.max(realSize.x, realSize.y);
landscapeProfile = new DeviceProfile(context, this, smallestSize, largestSize,
largeSide, smallSide, true /* isLandscape */);
portraitProfile = new DeviceProfile(context, this, smallestSize, largestSize,
smallSide, largeSide, false /* isLandscape */);
}
可以看到，通过closestProfile和interpolatedDeviceProfileOut拿到了一系列配置项，如桌面的行，列，Hotseat(桌面底部固定的应用栏)的个数，Hotseat所有应用的位置，布局id，文件夹的行列，图标的大小等等。之后再将这些信息new出我们的DeviceProfile对象。
那问题来了，closestProfile和interpolatedDeviceProfileOut是什么？？怎么计算出来的？
...
WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
Display display = wm.getDefaultDisplay();
DisplayMetrics dm = new DisplayMetrics();
display.getMetrics(dm);
Point smallestSize = new Point();
Point largestSize = new Point();
display.getCurrentSizeRange(smallestSize, largestSize);
// This guarantees that width < height
minWidthDps = Utilities.dpiFromPx(Math.min(smallestSize.x, smallestSize.y), dm);
minHeightDps = Utilities.dpiFromPx(Math.min(largestSize.x, largestSize.y), dm);
ArrayList closestProfiles =
findClosestDeviceProfiles(minWidthDps, minHeightDps, getPredefinedDeviceProfiles());
InvariantDeviceProfile interpolatedDeviceProfileOut =
invDistWeightedInterpolate(minWidthDps, minHeightDps, closestProfiles);
...
可以发现，通过设备的宽高等信息，从各种分辨率的DeviceProfiles列表中找到最合适的配置信息，查找的方法如下，根据
设备的宽高跟列表里的的最小宽高差值的平方根从小到大排序，第一个就是我们期望的配置
/**
* Returns the closest device profiles ordered by closeness to the specified width and height
*/
// Package private visibility for testing.
ArrayList findClosestDeviceProfiles(
final float width, final float height, ArrayList points) {
// Sort the profiles by their closeness to the dimensions
ArrayList pointsByNearness = points;
Collections.sort(pointsByNearness, new Comparator() {
public int compare(InvariantDeviceProfile a, InvariantDeviceProfile b) {
return Float.compare(dist(width, height, a.minWidthDps, a.minHeightDps),
dist(width, height, b.minWidthDps, b.minHeightDps));
}
});
return pointsByNearness;
}
@Thunk float dist(float x0, float y0, float x1, float y1) {
return (float) Math.hypot(x1 - x0, y1 - y0);
}
配置好的InvariantDeviceProfile列表信息如下，构造参数依次是，
配置名称，宽高，行数，列数，文件夹行数列数，图标大小，图标文本大小
hotseat配置资源文件，hotseat图标大小，默认页的资源文件
故，当我们有新机型没有适配，就可以在这里修改或新增配置
ArrayList getPredefinedDeviceProfiles() {
ArrayList predefinedDeviceProfiles = new ArrayList<>();
// width, height, #rows, #columns, #folder rows, #folder columns,
// iconSize, iconTextSize, #hotseat, #hotseatIconSize, defaultLayoutId.
predefinedDeviceProfiles.add(new InvariantDeviceProfile("Super Short Stubby",
255, 300, 2, 3, 2, 3, 3, 48, 13, 3, 48, R.xml.default_workspace_3x3));
predefinedDeviceProfiles.add(new InvariantDeviceProfile("Shorter Stubby",
255, 400, 3, 3, 3, 3, 3, 48, 13, 3, 48, R.xml.default_workspace_3x3));
predefinedDeviceProfiles.add(new InvariantDeviceProfile("Short Stubby",
275, 420, 3, 4, 3, 4, 4, 48, 13, 5, 48, R.xml.default_workspace_4x4));
predefinedDeviceProfiles.add(new InvariantDeviceProfile("Stubby",
255, 450, 3, 4, 3, 4, 4, 48, 13, 5, 48, R.xml.default_workspace_4x4));
predefinedDeviceProfiles.add(new InvariantDeviceProfile("Nexus S",
296, 491.33f, 4, 4, 4, 4, 4, 48, 13, 5, 48, R.xml.default_workspace_4x4));
predefinedDeviceProfiles.add(new InvariantDeviceProfile("Nexus 4",
359, 567, 4, 4, 4, 4, 4, DEFAULT_ICON_SIZE_DP, 13, 5, 56, R.xml.default_workspace_4x4));
predefinedDeviceProfiles.add(new InvariantDeviceProfile("Nexus 5",
335, 567, 5, 4, 5, 4, 4, DEFAULT_ICON_SIZE_DP, 13, 5, 56, R.xml.default_workspace_5x4_no_all_apps));
predefinedDeviceProfiles.add(new InvariantDeviceProfile("Large Phone",
406, 694, 5, 5, 4, 4, 4, 64, 14.4f, 5, 56, R.xml.default_workspace_5x5));
// The tablet profile is odd in that the landscape orientation
// also includes the nav bar on the side
predefinedDeviceProfiles.add(new InvariantDeviceProfile("Nexus 7",
575, 904, 5, 6, 4, 5, 4, 72, 14.4f, 7, 60, R.xml.default_workspace_5x6));
// Larger tablet profiles always have system bars on the top & bottom
predefinedDeviceProfiles.add(new InvariantDeviceProfile("Nexus 10",
727, 1207, 5, 6, 4, 5, 4, 76, 14.4f, 7, 76, R.xml.default_workspace_5x6));
predefinedDeviceProfiles.add(new InvariantDeviceProfile("20-inch Tablet",
1527, 2527, 7, 7, 6, 6, 4, 100, 20, 7, 72, R.xml.default_workspace_5x6));
return predefinedDeviceProfiles;
}
Launcher的配置初始化到这里基本上就完成了。
还有一些其他的对象的初始化，包括workspace状态变化的动画加载控制LauncherStateTransitionAnimation, 应用组件的管理器AppWidgetManagerCompat, 处理组件长按事件的ViewLauncherAppWidgetHost，因为在Launcher的初始化流程里不是特别需要，故后文有机会再做介绍。
LauncherModel加载应用信息
整个流程里比较复杂的就是LauncherModel加载应用了, 在onCreate里
mModel = app.setLauncher(this);
LauncherAppState里调用了LauncherModel的初始化方法 initialize,参数是Launcher
LauncherModel setLauncher(Launcher launcher) {
getLauncherProvider().setLauncherProviderChangeListener(launcher);
mModel.initialize(launcher);
mAccessibilityDelegate = ((launcher != null) && Utilities.ATLEAST_LOLLIPOP) ?
new LauncherAccessibilityDelegate(launcher) : null;
return mModel;
}
LauncherModel的initialize参数是LauncherModel.Callbacks，Launcher里实现了LauncherModel.Callbacks的一系列接口用于绑定获取到的应用信息，文件夹信息，屏幕信息等等
public void initialize(Callbacks callbacks) {
synchronized (mLock) {
// Disconnect any of the callbacks and drawables associated with ItemInfos on the
// workspace to prevent leaking Launcher activities on orientation change.
unbindItemInfosAndClearQueuedBindRunnables();
mCallbacks = new WeakReference(callbacks);
}
}
在加载数据之前先清除正在运行的线程DeferredBindRunnables，清除DeferredHandler里等待执行的任务
，并且将所有ItemInfo unbind
/** Unbinds all the sBgWorkspaceItems and sBgAppWidgets on the main thread */
void unbindWorkspaceItemsOnMainThread() {
// Ensure that we don't use the same workspace items data structure on the main thread
// by making a copy of workspace items first.
final ArrayList tmpItems = new ArrayList();
synchronized (sBgLock) {
tmpItems.addAll(sBgWorkspaceItems);
tmpItems.addAll(sBgAppWidgets);
}
Runnable r = new Runnable() {
@Override
public void run() {
for (ItemInfo item : tmpItems) {
item.unbind();
}
}
};
runOnMainThread(r);
}
接着我们才看到真正开始加载数据了，onCreate里的LauncherModel调用startLoader，创建线程加载数据
...
if (!mRestoring) {
if (DISABLE_SYNCHRONOUS_BINDING_CURRENT_PAGE) {
// If the user leaves launcher, then we should just load items asynchronously when
// they return.
mModel.startLoader(PagedView.INVALID_RESTORE_PAGE);
} else {
// We only load the page synchronously if the user rotates (or triggers a
// configuration change) while launcher is in the foreground
mModel.startLoader(mWorkspace.getRestorePage());
}
}
...
当第一次打开时，会调用 mModel.startLoader(PagedView.INVALID_RESTORE_PAGE)，停止旧的Loader任务，stopLoaderLocked，然后new出一个LoaderTask(mApp.getContext(), loadFlags) Runnable，通过Handler sworker post出去，开始加载任务
public void startLoader(int synchronousBindPage) {
startLoader(synchronousBindPage, LOADER_FLAG_NONE);
}
public void startLoader(int synchronousBindPage, int loadFlags) {
// Enable queue before starting loader. It will get disabled in Launcher#finishBindingItems
InstallShortcutReceiver.enableInstallQueue();
synchronized (mLock) {
// Clear any deferred bind-runnables from the synchronized load process
// We must do this before any loading/binding is scheduled below.
synchronized (mDeferredBindRunnables) {
mDeferredBindRunnables.clear();
}
// Don't bother to start the thread if we know it's not going to do anything
if (mCallbacks != null && mCallbacks.get() != null) {
// If there is already one running, tell it to stop.
stopLoaderLocked();
mLoaderTask = new LoaderTask(mApp.getContext(), loadFlags);
if (synchronousBindPage != PagedView.INVALID_RESTORE_PAGE
&& mAllAppsLoaded && mWorkspaceLoaded && !mIsLoaderTaskRunning) {
mLoaderTask.runBindSynchronousPage(synchronousBindPage);
} else {
sWorkerThread.setPriority(Thread.NORM_PRIORITY);
sWorker.post(mLoaderTask);
}
}
}
}
开始加载应用信息的任务后，由于后续的篇幅比较长，请看下一篇文章的详细介绍。