前言

我们在上一篇基本上已经实现我们要的效果了，但是还遗留了几个问题，这一篇我们就来解决下

自定义解析器

我们上一篇介绍过NavDestination是通过解析xml生成的，我们不想在xml中写死，通过注解的方式实现，我们接下来就自定义注解和解析器来实现

创建

首先创建两个module

annotation模块的gradle

apply plugin: 'java-library' tasks.withType(JavaCompile) {     options.encoding = "UTF-8" }  dependencies {     implementation fileTree(dir: 'libs', include: ['*.jar']) }  sourceCompatibility = "8" targetCompatibility = "8 " 

compiler模块的gradle

apply plugin: 'java-library' tasks.withType(JavaCompile) {     options.encoding = "UTF-8" }  dependencies {     implementation fileTree(dir: 'libs', include: ['*.jar'])     implementation project(':libnavannotation') //生成json     implementation 'com.alibaba:fastjson:1.2.59' //这俩必须     implementation 'com.google.auto.service:auto-service:1.0-rc6'     annotationProcessor 'com.google.auto.service:auto-service:1.0-rc6' }  sourceCompatibility = "8" targetCompatibility = "8" 

编写注解

我们既想让Fragment使用，也让Activity使用，所以我们创建连个类FragmentDestination和ActivityDestination,我们还要添加几个属性pageUrl,needLogin,asStarter。pageUrl是为了给NavController跳转的时候使用的，asStarter表示是不是第一个页，needLogin这个为了以后要用，点击的时候我们判断是否需要加权限

@Target(ElementType.TYPE) public @interface ActivityDestination {      String pageUrl(); boolean needLogin() default false; boolean asStarter() default false; } 

@Target(ElementType.TYPE) public @interface FragmentDestination {      String pageUrl(); boolean needLogin() default false; boolean asStarter() default false; } 

编写解析器

/**  * APP页面导航信息收集注解处理器  * <p>  * AutoService注解：就这么一标记，annotationProcessor  project()应用一下,编译时就能自动执行该类了。  * <p>  * SupportedSourceVersion注解:声明我们所支持的jdk版本  * <p>  * SupportedAnnotationTypes:声明该注解处理器想要处理那些注解  */ @AutoService(Processor.class) @SupportedSourceVersion(SourceVersion.RELEASE_8) @SupportedAnnotationTypes({"com.hfs.libnavannotation.FragmentDestination", "com.hfs.libnavannotation.ActivityDestination"}) public class NavProcessor extends AbstractProcessor { @Override public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) { return false; } } 

这里我们还需要两个类，一个是Messager,另一个是Filer

• Messager ：打印日志
• Filer： 文件操作相关，我们想把生成的json文件存放在某个文件夹下面

初始化这两个类

 private Messager mMessager; private Filer mFiler; @Override public synchronized void init(ProcessingEnvironment processingEnvironment) { super.init(processingEnvironment);         processingEnvironment.getMessager(); //日志打印,在java环境下不能使用android.util.log.e()         mMessager = processingEnv.getMessager(); //文件处理工具         mFiler = processingEnv.getFiler(); } 

接下来就是process这个方法了

 @Override public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) { //通过处理器环境上下文roundEnv分别获取 项目中标记的FragmentDestination.class 和ActivityDestination.class注解。 //此目的就是为了收集项目中哪些类 被注解标记了         Set<? extends Element> fragmentElements = roundEnvironment.getElementsAnnotatedWith(FragmentDestination.class);         Set<? extends Element> activityElements = roundEnvironment.getElementsAnnotatedWith(ActivityDestination.class); if (!fragmentElements.isEmpty() ||! activityElements.isEmpty()) {             HashMap<String, JSONObject> destMap = new HashMap<>(); //分别 处理FragmentDestination  和 ActivityDestination 注解类型 //并收集到destMap 这个map中。以此就能记录下所有的页面信息了 handleDestination(fragmentElements, FragmentDestination.class, destMap); handleDestination(activityElements, ActivityDestination.class, destMap); //app/src/main/assets             FileOutputStream fos = null;             OutputStreamWriter writer = null; try { //filer.createResource()意思是创建源文件 //我们可以指定为class文件输出的地方， //StandardLocation.CLASS_OUTPUT：java文件生成class文件的位置，/app/build/intermediates/javac/debug/classes/目录下 //StandardLocation.SOURCE_OUTPUT：java文件的位置，一般在/ppjoke/app/build/generated/source/apt/目录下 //StandardLocation.CLASS_PATH 和 StandardLocation.SOURCE_PATH用的不多，指的了这个参数，就要指定生成文件的pkg包名了                 FileObject resource = mFiler.createResource(StandardLocation.CLASS_OUTPUT, "", OUTPUT_FILE_NAME);                 String resourcePath = resource.toUri().getPath();                 mMessager.printMessage(Diagnostic.Kind.NOTE, "resourcePath:" + resourcePath); //由于我们想要把json文件生成在app/src/main/assets/目录下,所以这里可以对字符串做一个截取， //以此便能准确获取项目在每个电脑上的 /app/src/main/assets/的路径                 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(); } //此处就是稳健的写入了                 File outPutFile = new File(file, OUTPUT_FILE_NAME); if (outPutFile.exists()) {                     outPutFile.delete(); }                 outPutFile.createNewFile(); //利用fastjson把收集到的所有的页面信息 转换成JSON格式的。并输出到文件中                 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; } 

真正逻辑都在handleDestination中，我们下面再说这个，我们先看上面那些代码，比较好理解，我们拿到被注解标记的类的结合后，交给handleDestination处理，下面是把文件写在app/src/main/assets目录中，接下来我们就来看下handleDestination方法

private void handleDestination(Set<? extends Element> elements, Class<? extends Annotation> annotationClaz, HashMap<String, JSONObject> destMap) { for (Element element : elements) { //TypeElement是Element的一种。 //如果我们的注解标记在了类名上。所以可以直接强转一下。使用它得到全类名             TypeElement typeElement = (TypeElement) element; //全类名com.hfs.jokevideo.home             String clazName = typeElement.getQualifiedName().toString(); //页面的id.此处不能重复,使用页面的类名做hascode即可 int id = Math.abs(clazName.hashCode()); //页面的pageUrl相当于隐士跳转意图中的host://schem/path格式             String pageUrl = null; //是否需要登录 boolean needLogin = false; //是否作为首页的第一个展示的页面 boolean asStarter = false; //标记该页面是fragment 还是activity类型的 boolean isFragment = false;              Annotation annotation = element.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)) {                 mMessager.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); } } } 

这个方法就是拿到集合周,遍历拿到相应属性,组装成json文件

OK,我们实验下,在我们的Fragment或者Activity类头上添加上注解,然后rebuild下我们的项目

@FragmentDestination(pageUrl = "main/tabs/home" ,asStarter = true) public class HomeFragment extends Fragment { ...... } 

@FragmentDestination(pageUrl = "main/tabs/find", asStarter = false) public class FindFragment extends Fragment { ...... } 

@ActivityDestination(pageUrl = "main/tabs/publish") public class PublishActivity extends AppCompatActivity { ...... } 

@FragmentDestination(pageUrl = "main/tabs/sofa" ,asStarter = false) public class SofaFragment extends Fragment { ...... } 

@FragmentDestination(pageUrl = "main/tabs/my" ,asStarter = false) public class MyFragment extends Fragment { ...... } 

我们重新编译下项目

{ "main/tabs/sofa": { "isFragment": true, "asStarter": false, "needLogin": false, "pageUrl": "main/tabs/sofa", "className": "com.hfs.jokevideo.ui.sofa.SofaFragment", "id": 450947876 }, "main/tabs/home": { "isFragment": true, "asStarter": true, "needLogin": false, "pageUrl": "main/tabs/home", "className": "com.hfs.jokevideo.ui.home.HomeFragment", "id": 347820508 }, "main/tabs/publish": { "isFragment": false, "asStarter": false, "needLogin": false, "pageUrl": "main/tabs/publish", "className": "com.hfs.jokevideo.ui.publish.PublishActivity", "id": 848995203 }, "main/tabs/find": { "isFragment": true, "asStarter": false, "needLogin": false, "pageUrl": "main/tabs/find", "className": "com.hfs.jokevideo.ui.find.FindFragment", "id": 1967098396 }, "main/tabs/my": { "isFragment": true, "asStarter": false, "needLogin": false, "pageUrl": "main/tabs/my", "className": "com.hfs.jokevideo.ui.my.MyFragment", "id": 128686460 } } 

这样我们就可以把xml中写死的部分去掉了,像下面就可以

 <fragment android:id="@+id/nav_host_fragment" android:name="androidx.navigation.fragment.NavHostFragment" android:layout_width="match_parent" android:layout_height="match_parent" app:defaultNavHost="true" app:layout_constraintBottom_toTopOf="@id/nav_view" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" app:layout_constraintTop_toTopOf="parent" /> 

自定义底部导航栏

我们不通过官方的方式添加底部导航,那我们就要自定义一个底部导航,我们只需要继承BottomNavigationView即可,这样BottomNavigationView里面的功能属性我们都能使用

public class AppBottomBar extends BottomNavigationView { private static int[] sIcons = new int[]{R.drawable.icon_tab_home, R.drawable.icon_tab_sofa, R.drawable.icon_tab_publish, R.drawable.icon_tab_find, R.drawable.icon_tab_mine}; private BottomBar config; public AppBottomBar(Context context) { this(context, null); } public AppBottomBar(Context context, AttributeSet attrs) { this(context, attrs, 0); } @SuppressLint("RestrictedApi") public AppBottomBar(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr);          config = AppConfig.getBottomBarConfig(); int[][] state = new int[2][];         state[0] = new int[]{android.R.attr.state_selected};         state[1] = new int[]{}; int[] colors = new int[]{Color.parseColor(config.activeColor), Color.parseColor(config.inActiveColor)};         ColorStateList stateList = new ColorStateList(state, colors); setItemTextColor(stateList); setItemIconTintList(stateList); //LABEL_VISIBILITY_LABELED:设置按钮的文本为一直显示模式 //LABEL_VISIBILITY_AUTO:当按钮个数小于三个时一直显示，或者当按钮个数大于3个且小于5个时，被选中的那个按钮文本才会显示 //LABEL_VISIBILITY_SELECTED：只有被选中的那个按钮的文本才会显示 //LABEL_VISIBILITY_UNLABELED:所有的按钮文本都不显示 setLabelVisibilityMode(LabelVisibilityMode.LABEL_VISIBILITY_LABELED);         List<BottomBar.Tab> tabs = config.tabs; for (BottomBar.Tab tab : tabs) { if (!tab.enable) { continue; } int itemId = getItemId(tab.pageUrl); if (itemId < 0) { continue; }             MenuItem menuItem = getMenu().add(0, itemId, tab.index, tab.title);             menuItem.setIcon(sIcons[tab.index]); } //此处给按钮icon设置大小 int index = 0; for (BottomBar.Tab tab : config.tabs) { if (!tab.enable) { continue; } int itemId = getItemId(tab.pageUrl); if (itemId < 0) { continue; } int iconSize = dp2Px(tab.size);             BottomNavigationMenuView menuView = (BottomNavigationMenuView) getChildAt(0);             BottomNavigationItemView itemView = (BottomNavigationItemView) menuView.getChildAt(index);             itemView.setIconSize(iconSize); if (TextUtils.isEmpty(tab.title)) { int tintColor = TextUtils.isEmpty(tab.tintColor) ? Color.parseColor("#ff678f") : Color.parseColor(tab.tintColor);                 itemView.setIconTintList(ColorStateList.valueOf(tintColor)); //禁止掉点按时 上下浮动的效果                 itemView.setShifting(false); /**                  * 如果想要禁止掉所有按钮的点击浮动效果。                  * 那么还需要给选中和未选中的按钮配置一样大小的字号。                  *                  *  在MainActivity布局的AppBottomBar标签增加如下配置，                  *  @style/active，@style/inActive 在style.xml中                  *  app:itemTextAppearanceActive="@style/active"                  *  app:itemTextAppearanceInactive="@style/inActive"                  */ }             index++; } //底部导航栏默认选中项 if (config.selectTab != 0) {             BottomBar.Tab selectTab = config.tabs.get(config.selectTab); if (selectTab.enable) { int itemId = getItemId(selectTab.pageUrl); //这里需要延迟一下 再定位到默认选中的tab //因为 咱们需要等待内容区域,也就NavGraphBuilder解析数据并初始化完成， //否则会出现 底部按钮切换过去了，但内容区域还没切换过去 post(() -> setSelectedItemId(itemId)); } } } private int dp2Px(int dpValue) {         DisplayMetrics metrics = getContext().getResources().getDisplayMetrics(); return (int) (metrics.density * dpValue + 0.5f); } private int getItemId(String pageUrl) {         Destination destination = AppConfig.getDestConfig().get(pageUrl); if (destination == null) return -1; return destination.id; } } 

AppConfig 主要就是通过解析我们刚才生成的json文件,构建BottomBar

public class AppConfig { private static HashMap<String, Destination> sDestConfig; private static BottomBar sBottomBar; public static HashMap<String, Destination> getDestConfig() { if (sDestConfig == null) {             String content = parseFile("destination.json");             sDestConfig = JSON.parseObject(content, new TypeReference<HashMap<String, Destination>>() { }); } return sDestConfig; } public static BottomBar getBottomBarConfig() { if (sBottomBar == null) {             String content = parseFile("main_tabs_config.json");             sBottomBar = JSON.parseObject(content, BottomBar.class); } return sBottomBar; } private static String parseFile(String fileName) {         AssetManager assets = AppGlobals.getApplication().getAssets();         InputStream is = null;         BufferedReader br = null;         StringBuilder builder = new StringBuilder(); try {             is = assets.open(fileName);             br = new BufferedReader(new InputStreamReader(is));             String line = null; while ((line = br.readLine()) != null) {                 builder.append(line); } } catch (IOException e) {             e.printStackTrace(); } finally { try { if (is != null) {                     is.close(); } if (br != null) {                     br.close(); } } catch (Exception e) { } } return builder.toString(); } } 

Ok,这样我们就把我们的activity_main布局改下,menu也不需要了

<?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="https://schemas.android.com/apk/res/android" xmlns:app="https://schemas.android.com/apk/res-auto" android:id="@+id/container" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingTop="?attr/actionBarSize"> <com.hfs.jokevideo.view.AppBottomBar android:id="@+id/nav_view" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_marginStart="0dp" android:layout_marginEnd="0dp" android:background="?android:attr/windowBackground" app:itemTextAppearanceActive="@style/active" app:itemTextAppearanceInactive="@style/inActive" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" /> <fragment android:id="@+id/nav_host_fragment" android:name="androidx.navigation.fragment.NavHostFragment" android:layout_width="match_parent" android:layout_height="match_parent" app:defaultNavHost="true" app:layout_constraintBottom_toTopOf="@id/nav_view" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" app:layout_constraintTop_toTopOf="parent" /> </androidx.constraintlayout.widget.ConstraintLayout> 

解决点击放大的问题只需要设置这个

 app:itemTextAppearanceActive="@style/active"  app:itemTextAppearanceInactive="@style/inActive" 

 <style name="active" parent="TextAppearance.AppCompat">         <item name="android:textSize">14sp</item>         <item name="android:textColor">@color/color_000</item>     </style> <style name="inActive" parent="TextAppearance.AppCompat">         <item name="android:textSize">14sp</item>         <item name="android:textColor">@color/color_999</item>     </style> 

自定义FragmentNavigator,解决Fragment重建问题

这里主要参考FragmentNavigator代码,重写它的navigate即可

/**  * 定制的Fragment导航器，替换ft.replace(mContainerId, frag);为 hide()/show()  */ @Navigator.Name("fixfragment") public class FixFragmentNavigator extends FragmentNavigator { private static final String TAG = "FixFragmentNavigator"; private Context mContext; private FragmentManager mManager; private int mContainerId; public FixFragmentNavigator(@NonNull Context context, @NonNull FragmentManager manager, int containerId) { super(context, manager, containerId);         mContext = context;         mManager = manager;         mContainerId = containerId; } @Nullable @Override public NavDestination navigate(@NonNull Destination destination, @Nullable Bundle args, @Nullable NavOptions navOptions, @Nullable Navigator.Extras navigatorExtras) { if (mManager.isStateSaved()) {             Log.i(TAG, "Ignoring navigate() call: FragmentManager has already" + " saved its state"); return null; }         String className = destination.getClassName(); if (className.charAt(0) == '.') {             className = mContext.getPackageName() + className; } //final Fragment frag = instantiateFragment(mContext, mManager, //       className, args); //frag.setArguments(args); final FragmentTransaction ft = mManager.beginTransaction(); int enterAnim = navOptions != null ? navOptions.getEnterAnim() : -1; int exitAnim = navOptions != null ? navOptions.getExitAnim() : -1; int popEnterAnim = navOptions != null ? navOptions.getPopEnterAnim() : -1; int popExitAnim = navOptions != null ? navOptions.getPopExitAnim() : -1; if (enterAnim != -1 || exitAnim != -1 || popEnterAnim != -1 || popExitAnim != -1) {             enterAnim = enterAnim != -1 ? enterAnim : 0;             exitAnim = exitAnim != -1 ? exitAnim : 0;             popEnterAnim = popEnterAnim != -1 ? popEnterAnim : 0;             popExitAnim = popExitAnim != -1 ? popExitAnim : 0;             ft.setCustomAnimations(enterAnim, exitAnim, popEnterAnim, popExitAnim); }          Fragment fragment = mManager.getPrimaryNavigationFragment(); if (fragment != null) {             ft.hide(fragment); }          Fragment frag = null;         String tag = String.valueOf(destination.getId());          frag = mManager.findFragmentByTag(tag); if (frag != null) {             ft.show(frag); } else {             frag = instantiateFragment(mContext, mManager, className, args);             frag.setArguments(args);             ft.add(mContainerId, frag, tag); } //ft.replace(mContainerId, frag);         ft.setPrimaryNavigationFragment(frag); final @IdRes int destId = destination.getId();         ArrayDeque<Integer> mBackStack = null; try {             Field field = FragmentNavigator.class.getDeclaredField("mBackStack");             field.setAccessible(true);             mBackStack = (ArrayDeque<Integer>) field.get(this); } catch (NoSuchFieldException e) {             e.printStackTrace(); } catch (IllegalAccessException e) {             e.printStackTrace(); } final boolean initialNavigation = mBackStack.isEmpty(); // TODO Build first class singleTop behavior for fragments final boolean isSingleTopReplacement = navOptions != null && !initialNavigation                 && navOptions.shouldLaunchSingleTop() && mBackStack.peekLast() == destId; boolean isAdded; if (initialNavigation) {             isAdded = true; } else if (isSingleTopReplacement) { // Single Top means we only want one instance on the back stack if (mBackStack.size() > 1) { // If the Fragment to be replaced is on the FragmentManager's // back stack, a simple replace() isn't enough so we // remove it from the back stack and put our replacement // on the back stack in its place                 mManager.popBackStack( generateBackStackName(mBackStack.size(), mBackStack.peekLast()),                         FragmentManager.POP_BACK_STACK_INCLUSIVE);                 ft.addToBackStack(generateBackStackName(mBackStack.size(), destId)); }             isAdded = false; } else {             ft.addToBackStack(generateBackStackName(mBackStack.size() + 1, destId));             isAdded = true; } if (navigatorExtras instanceof Extras) {             Extras extras = (Extras) navigatorExtras; for (Map.Entry<View, String> sharedElement : extras.getSharedElements().entrySet()) {                 ft.addSharedElement(sharedElement.getKey(), sharedElement.getValue()); } }         ft.setReorderingAllowed(true);         ft.commit(); // The commit succeeded, update our view of the world if (isAdded) {             mBackStack.add(destId); return destination; } else { return null; } } private String generateBackStackName(int backStackindex, int destid) { return backStackindex + "-" + destid; } } 

OK,我们验证下