Android Widget（小部件）添加源码分析三--创建视图
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本文是 Android Widget（小部件） 系列的第七篇，主要从源码角度是对 Android widget 添加过程进行分析 。
本系列的目的是通过对Android 小部件的梳理，了解小部件刷新流程、添加、删除、恢复流程、以及系统发生变化时，小部件是如何适配的，解决在开发小部件过程中遇到的问题。系列文章大部份来自源码的解读，内容非常多，也非常容易遗忘，因此记录分享。
系列文章
一、描述
添加小部件通常是 host 的逻辑，但了解该过程能够帮助我们熟悉小部件体系，分析小部件问题。由于每个 host 对小部件的逻辑处理都不一样，因此本文不梳理 host 中添加逻辑，仅从 ### AppWidgetHost .allocateAppWidgetId 开始。添加 widget 分三步、本篇文章讲解第三步创建视图
1. 申请widgetId
2. 绑定widgetId
3. 创建WidgetHostView
//1、申请
int appWidgetId = mAppWidgetHost.allocateAppWidgetId();
//2、绑定
bound = mAppWidgetManager.bindAppWidgetIdIfAllowed(
appWidgetId, providerInfo.getProfile(), providerInfo.provider,bundle)
//3、创建视图
WidgetHostView hostView = (WidgetHostView) mAppWidgetHost.createView(mContext, appWidgetId ,
appWidgetProviderInfo);
二、创建视图流程
1、Host 进程通过 AIDL 回调到 system_server 中的AppWidgetServiceImpl
2、进行安全校验和小部件加载确定
3、找到对应的 widget ,返回对应的 RemoteView
4、将RemoteView 中的 action 转换成对应的视图
三、详细流程
1、AppWidgetServiceImpl.getAppWidgetViews()
描述：通过AIDL 访问系统服务获取 RemoteView 详细代码：
class AppWidgetServiceImpl{
@Override
public RemoteViews getAppWidgetViews(String callingPackage, int appWidgetId) {
final int userId = UserHandle.getCallingUserId();
if (DEBUG) {
Slog.i(TAG, "getAppWidgetViews() " + userId);
}
// Make sure the package runs under the caller uid.
// 确认安全性，前面已经分析
mSecurityPolicy.enforceCallFromPackage(callingPackage);
synchronized (mLock) {
// 确定小部件已经加载，前面已经分析
ensureGroupStateLoadedLocked(userId);
// NOTE: The lookup is enforcing security across users by making
// sure the caller can only access widgets it hosts or provides.
// 找到对应的widget 前面已经分析
Widget widget = lookupWidgetLocked(appWidgetId,
Binder.getCallingUid(), callingPackage);
// 找到对应的widget,clone RemoteView 进行返回
if (widget != null) {
return cloneIfLocalBinder(widget.getEffectiveViewsLocked());
}
return null;
}
}
2、AppWidgetHostView. updateAppWidget()
描述：根据RemoteView 设置视图 详细代码
class AppWidgetHostView{
public void updateAppWidget(RemoteViews remoteViews) {
mLastInflatedRemoteViews = remoteViews;
applyRemoteViews(remoteViews, true);
}
protected void applyRemoteViews(@Nullable RemoteViews remoteViews, boolean useAsyncIfPossible) {
boolean recycled = false;
View content = null;
Exception exception = null;
// Block state restore until the end of the apply.
mLastInflatedRemoteViewsId = -1;
if (mLastExecutionSignal != null) {
mLastExecutionSignal.cancel();
mLastExecutionSignal = null;
}
if (remoteViews == null) {
// remoteView 为null 加载默认视图apk 升级、组件状态改变，触发
if (mViewMode == VIEW_MODE_DEFAULT) {
// We've already done this -- nothing to do.
return;
}
content = getDefaultView();
mLayoutId = -1;
mViewMode = VIEW_MODE_DEFAULT;
} else {
// Select the remote view we are actually going to apply.
//找到合适的RemoteView ，方法内部会屏幕方向，以及尺寸去找合适的RemoteView
RemoteViews rvToApply = remoteViews.getRemoteViewsToApply(mContext, mCurrentSize);
if (mOnLightBackground) {
rvToApply = rvToApply.getDarkTextViews();
}
// 异步加载，如果没有设置异步线程池的话，不会走该逻辑
if (mAsyncExecutor != null && useAsyncIfPossible) {
inflateAsync(rvToApply);
return;
}
int layoutId = rvToApply.getLayoutId();
// 判断是否可以重新使用用之前的view，这里是比较布局id 及viewID与之前的是否相同。widget 是可以添加一个RemoteView
// 的，因此这里需要比较viewID。
if (rvToApply.canRecycleView(mView)) {
try {
// 将Remote action 设置在 HostView 上。
rvToApply.reapply(mContext, mView, mInteractionHandler, mCurrentSize,
mColorResources);
content = mView;
mLastInflatedRemoteViewsId = rvToApply.computeUniqueId(remoteViews);
recycled = true;
if (LOGD) Log.d(TAG, "was able to recycle existing layout");
} catch (RuntimeException e) {
exception = e;
}
}
// Try normal RemoteView inflation
if (content == null) {
try {
// 该方法会inflate view ,然后将RemoteView 设置到view上
content = rvToApply.apply(mContext, this, mInteractionHandler,
mCurrentSize, mColorResources);
mLastInflatedRemoteViewsId = rvToApply.computeUniqueId(remoteViews);
if (LOGD) Log.d(TAG, "had to inflate new layout");
} catch (RuntimeException e) {
exception = e;
}
}
mLayoutId = layoutId;
mViewMode = VIEW_MODE_CONTENT;
}
applyContent(content, recycled, exception);
}
}
3、AppWidgetHostView. getDefaultView()
描述：获取配置文件中的 initialLayout 视图，如果没有设置，将返回错误视图 详细代码
class AppWidgetHostView{
protected View getDefaultView() {
if (LOGD) {
Log.d(TAG, "getDefaultView");
}
View defaultView = null;
Exception exception = null;
try {
if (mInfo != null) {
Context theirContext = getRemoteContext();
mRemoteContext = theirContext;
LayoutInflater inflater = (LayoutInflater)
theirContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
inflater = inflater.cloneInContext(theirContext);
inflater.setFilter(INFLATER_FILTER);
AppWidgetManager manager = AppWidgetManager.getInstance(mContext);
Bundle options = manager.getAppWidgetOptions(mAppWidgetId);
int layoutId = mInfo.initialLayout;
if (options.containsKey(AppWidgetManager.OPTION_APPWIDGET_HOST_CATEGORY)) {
int category = options.getInt(AppWidgetManager.OPTION_APPWIDGET_HOST_CATEGORY);
if (category == AppWidgetProviderInfo.WIDGET_CATEGORY_KEYGUARD) {
int kgLayoutId = mInfo.initialKeyguardLayout;
// If a default keyguard layout is not specified, use the standard
// default layout.
layoutId = kgLayoutId == 0 ? layoutId : kgLayoutId;
}
}
defaultView = inflater.inflate(layoutId, this, false);
if (!(defaultView instanceof AdapterView)) {
// AdapterView does not support onClickListener
defaultView.setOnClickListener(this::onDefaultViewClicked);
}
} else {
Log.w(TAG, "can't inflate defaultView because mInfo is missing");
}
} catch (RuntimeException e) {
exception = e;
}
if (exception != null) {
Log.w(TAG, "Error inflating AppWidget " + mInfo, exception);
}
if (defaultView == null) {
if (LOGD) Log.d(TAG, "getDefaultView couldn't find any view, so inflating error");
defaultView = getErrorView();
}
return defaultView;
}
}
4、RemoteViews. apply()
- 描述：inflate view ，并且将 RemoteView 中的 action 转化成相应属性，设置到view 上。
- 详细代码
class RemoteViews{
public View apply(@NonNull Context context, @NonNull ViewGroup parent,
@Nullable InteractionHandler handler, @Nullable SizeF size) {
// 找到合适的RemoteView
RemoteViews rvToApply = getRemoteViewsToApply(context, size);
// 加载视图
View result = inflateView(context, rvToApply, parent);
rvToApply.performApply(result, parent, handler, null);
return result;
}
}
5、RemoteViews.getRemoteViewsToApply()
- 描述：找到适合尺寸的widget,这里的 widgetSize 为null,只会根据横竖屏去选择对应的视图
- 详细代码
class RemoteViews{
public RemoteViews getRemoteViewsToApply(@NonNull Context context,
@Nullable SizeF widgetSize) {
if (!hasSizedRemoteViews() || widgetSize == null) {
// If there isn't multiple remote views, fall back on the previous methods.
return getRemoteViewsToApply(context);
}
return findBestFitLayout(widgetSize);
}
// 找到尺寸最合适的remoteview ，更近宽高的差距判断，寻找差距最小的
private RemoteViews findBestFitLayout(@NonNull SizeF widgetSize) {
// Find the better remote view
RemoteViews bestFit = null;
float bestSqDist = Float.MAX_VALUE;
for (RemoteViews layout : mSizedRemoteViews) {
SizeF layoutSize = layout.getIdealSize();
if (layoutSize == null) {
throw new IllegalStateException("Expected RemoteViews to have ideal size");
}
if (fitsIn(layoutSize, widgetSize)) {
if (bestFit == null) {
bestFit = layout;
bestSqDist = squareDistance(layoutSize, widgetSize);
} else {
float newSqDist = squareDistance(layoutSize, widgetSize);
if (newSqDist < bestSqDist) {
bestFit = layout;
bestSqDist = newSqDist;
}
}
}
}
if (bestFit == null) {
Log.w(LOG_TAG, "Could not find a RemoteViews fitting the current size: " + widgetSize);
return findSmallestRemoteView();
}
return bestFit;
}
}
6、RemoteViews. inflateView()
- 描述：LayoutInflater加载视图。这里的context 通过 小部件宿主包名创建，因此可以获取对应资源文件。详细可看
application.getBaseContext().createPackageContextAsUser - 详细代码：
class RemoteViews {
private Context getContextForResources(Context context) {
if (mApplication != null) {
// 如果是同一应用，就用该context
if (context.getUserId() == UserHandle.getUserId(mApplication.uid)
&& context.getPackageName().equals(mApplication.packageName)) {
return context;
}
try {
// remoteview 创建时，会根据packgeName 创建相应的appliction,后面有详细代码
return context.createApplicationContext(mApplication,
Context.CONTEXT_RESTRICTED);
} catch (NameNotFoundException e) {
Log.e(LOG_TAG, "Package name " + mApplication.packageName + " not found");
}
}
return context;
}
public RemoteViews(String packageName, int layoutId) {
this(getApplicationInfo(packageName, UserHandle.myUserId()), layoutId);
}
private static ApplicationInfo getApplicationInfo(@Nullable String packageName, int userId) {
if (packageName == null) {
return null;
}
// Get the application for the passed in package and user.
Application application = ActivityThread.currentApplication();
if (application == null) {
throw new IllegalStateException("Cannot create remote views out of an aplication.");
}
ApplicationInfo applicationInfo = application.getApplicationInfo();
if (UserHandle.getUserId(applicationInfo.uid) != userId
|| !applicationInfo.packageName.equals(packageName)) {
try {
// 创建相应的context，用于访问相应的资源
Context context = application.getBaseContext().createPackageContextAsUser(
packageName, 0, new UserHandle(userId));
applicationInfo = context.getApplicationInfo();
} catch (NameNotFoundException nnfe) {
throw new IllegalArgumentException("No such package " + packageName);
}
}
return applicationInfo;
}
}
7、RemoteViews. performApply()
- 描述：根据action 对view进行设置
- 详细代码：
class RemoteViews{
private void performApply(View v, ViewGroup parent, InteractionHandler handler,
ColorResources colorResources) {
if (mActions != null) {
handler = handler == null ? DEFAULT_INTERACTION_HANDLER : handler;
final int count = mActions.size();
for (int i = 0; i < count; i++) {
Action a = mActions.get(i);
// 将action 设置在view 上,
a.apply(v, parent, handler, colorResources);
}
}
}
}
8、BaseReflectionAction.apply()
- 描述：将action 进行设置，转成相应行为
- 详细代码：
class BaseReflectionAction{
@Override
public final void apply(View root, ViewGroup rootParent, InteractionHandler handler,
ColorResources colorResources) {
final View view = root.findViewById(viewId);
if (view == null) return;
Class<?> param = getParameterType(this.type);
if (param == null) {
throw new ActionException("bad type: " + this.type);
}
Object value = getParameterValue(view);
try {
// getMethod 找到具体的方法，invoke 反射调用
getMethod(view, this.methodName, param, false /* async */).invoke(view, value);
} catch (Throwable ex) {
throw new ActionException(ex);
}
}
}
9、AppWidgetHostView.applyContent()
- 描述：将生成好的view添加到AppWidgetHostView中
- 详细代码
class AppWidgetHostView {
private void applyContent(View content, boolean recycled, Exception exception) {
if (content == null) {
if (mViewMode == VIEW_MODE_ERROR) {
// We've already done this -- nothing to do.
return ;
}
if (exception != null) {
Log.w(TAG, "Error inflating RemoteViews", exception);
}
// 设置错误视图，之前已经分析过
content = getErrorView();
mViewMode = VIEW_MODE_ERROR;
}
// 没有复用的case
if (!recycled) {
prepareView(content);
addView(content);
}
if (mView != content) {
removeView(mView);
mView = content;
}
}
}
10、AppWidgetHostView. prepareView()
描述：设置布局参数 详细代码：
/** * Prepare the given view to be shown. This might include adjusting * { @link FrameLayout.LayoutParams} before inserting. */ protected void prepareView(View view) {
// Take requested dimensions from child, but apply default gravity.
FrameLayout.LayoutParams requested = (FrameLayout.LayoutParams)view.getLayoutParams();
if (requested == null) {
requested = new FrameLayout.LayoutParams(LayoutParams.MATCH_PARENT,
LayoutParams.MATCH_PARENT);
}
requested.gravity = Gravity.CENTER;
view.setLayoutParams(requested);
}
到这里，添加 widget 创建视图流程就分析完了，也是添加 widget的最后一篇文章。添加 widget 可以简单的分为三步：申请widgetId -> 绑定widgetId-> 创建视图。总体流程比较长，拆解以后就会发现有很多校验、状态逻辑都是相同的，也就不那么难了。