Jetpack系列组件--皮皮虾客户端

1.Navigation

• 谷歌的野心，页面路由导航框架。支持Fragment、Activity、DialogFragment的导航行为。

2.Navigation关键类

• 下面这张图看一下Navigation关键类图关系
  NavHostFragment：作为内容区域的宿主container.
  NavigationController：作为页面路由导航的控制器
  NavigatorProvider：是导航器提供者。实际上是一个
  HashMap<String,Navigator>
NavGraph：收集了所有的路由节点Destination
NavGrahpNavigator：是个比较特殊的导航器。当解析到navigation资源文件中navigation标签时会由它创建NavGraph对象。另外它的navigate不执行具体的导航行为，而是分发给FragmentNavigator 、DialogFragmentNavigagtor、ActivityNavigator来执行具体的导航行为。
  ActivityNavigator和FragmentNavigator、DialogFragmentNavigagtor倒是一致的，为了创建各自类型的节点Destination和提供导航行为而生。他们都会在NavHostFragment#onCreate中被创建添加到NavigationController#NavigatorProvider中。

以上就是简单地对Navigation框架几个关键类作用的解释。

• Navigation类图关系

3.Navigation高级用法

• 关于Navigation的用法百度上铺天盖地的都是清一色的文章和用法。不过恶心之处在于必须把路由页面写在资源文件中，不利于灵活配置、页面可见的权限控制。基于此皮皮虾客户端采用了注解处理器标记页面节点、手动创建NavGraph的形式来实现页面路由结构图。

• NavProcessor注解处理器生成页面路由JSON文件，文件生成在assets目录下。

@AutoService(Processor.class)
@SupportedSourceVersion(SourceVersion.RELEASE_8)
@SupportedAnnotationTypes({"com.mooc.libnavannotation.FragmentDestination", "com.mooc.libnavannotation.ActivityDestination"})
public class NavProcessor extends AbstractProcessor {
    private Messager messager;
    private Filer filer;
    private static final String OUTPUT_FILE_NAME = "destination.json";

    @Override
    public synchronized void init(ProcessingEnvironment processingEnv) {
        super.init(processingEnv);
        messager = processingEnv.getMessager();
        filer = processingEnv.getFiler();
    }

    @Override
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        Set<? extends Element> fragmentElements = roundEnv.getElementsAnnotatedWith(FragmentDestination.class);
        Set<? extends Element> activityElements = roundEnv.getElementsAnnotatedWith(ActivityDestination.class);

        if (!fragmentElements.isEmpty() || !activityElements.isEmpty()) {
            HashMap<String, JSONObject> destMap = new HashMap<>();
            handleDestination(fragmentElements, FragmentDestination.class, destMap);
            handleDestination(activityElements, ActivityDestination.class, destMap);

            //app/src/main/assets
            FileOutputStream fos = null;
            OutputStreamWriter writer = null;
            try {
                FileObject resource = filer.createResource(StandardLocation.CLASS_OUTPUT, "", OUTPUT_FILE_NAME);
                String resourcePath = resource.toUri().getPath();
                messager.printMessage(Diagnostic.Kind.NOTE, "resourcePath:" + resourcePath);
                String appPath = resourcePath.substring(0, resourcePath.indexOf("app") + 4);
                String assetsPath = appPath + "src/main/assets/";

                File file = new File(assetsPath);
                if (!file.exists()) {
                    file.mkdirs();
                }

                File outPutFile = new File(file, OUTPUT_FILE_NAME);
                if (outPutFile.exists()) {
                    outPutFile.delete();
                }
                outPutFile.createNewFile();
                String content = JSON.toJSONString(destMap);
                fos = new FileOutputStream(outPutFile);
                writer = new OutputStreamWriter(fos, "UTF-8");
                writer.write(content);
                writer.flush();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if (writer != null) {
                    try {
                        writer.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }

                if (fos != null) {
                    try {
                        fos.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }


        return true;
    }

    private void handleDestination(Set<? extends Element> elements, Class<? extends Annotation> annotationClaz, HashMap<String, JSONObject> destMap) {
        for (Element element : elements) {
            TypeElement typeElement = (TypeElement) element;
            String pageUrl = null;
            String clazName = typeElement.getQualifiedName().toString();
            int id = Math.abs(clazName.hashCode());
            boolean needLogin = false;
            boolean asStarter = false;
            boolean isFragment = false;
            Annotation annotation = typeElement.getAnnotation(annotationClaz);
            if (annotation instanceof FragmentDestination) {
                FragmentDestination dest = (FragmentDestination) annotation;
                pageUrl = dest.pageUrl();
                asStarter = dest.asStarter();
                needLogin = dest.needLogin();
                isFragment = true;
            } else if (annotation instanceof ActivityDestination) {
                ActivityDestination dest = (ActivityDestination) annotation;
                pageUrl = dest.pageUrl();
                asStarter = dest.asStarter();
                needLogin = dest.needLogin();
                isFragment = false;
            }

            if (destMap.containsKey(pageUrl)) {
                messager.printMessage(Diagnostic.Kind.ERROR, "不同的页面不允许使用相同的pageUrl：" + clazName);
            } else {
                JSONObject object = new JSONObject();
                object.put("id", id);
                object.put("needLogin", needLogin);
                object.put("asStarter", asStarter);
                object.put("pageUrl", pageUrl);
                object.put("className", clazName);
                object.put("isFragment", isFragment);
                destMap.put(pageUrl, object);
            }
        }
    }
}

• 根据解析出来的json文件生成NavGrahp对象，并绑定到NavController上.这样一来咱们就结局了只能在资源文件中写死路由节点的问题了。

public static void build(NavController controller) {
        NavigatorProvider provider = controller.getNavigatorProvider();
        NavGraph navGraph = new NavGraph(new NavGraphNavigator(provider));

        FragmentNavigator fragmentNavigator = provider.getNavigator(FragmentNavigator.class);
        ActivityNavigator activityNavigator = provider.getNavigator(ActivityNavigator.class);
        HashMap<String, Destination> destConfig = AppConfig.getDestConfig();
        Iterator<Destination> iterator = destConfig.values().iterator();
        while (iterator.hasNext()) {
            Destination node = iterator.next();
            if (node.isFragment) {
                FragmentNavigator.Destination destination = fragmentNavigator.createDestination();
                destination.setId(node.id);
                destination.setClassName(node.className);
                destination.addDeepLink(node.pageUrl);
                navGraph.addDestination(destination);
            } else {
                ActivityNavigator.Destination destination = activityNavigator.createDestination();
                destination.setId(node.id);
                destination.setComponentName(new ComponentName(AppGlobals.getApplication().getPackageName(), node.className));
                destination.addDeepLink(node.pageUrl);
                navGraph.addDestination(destination);
            }

            if (node.asStarter) {
                navGraph.setStartDestination(node.id);
            }
        }

        controller.setGraph(navGraph);
    }

更多Jetpack系列组件 就在皮皮虾客户端