Android架构组件-Navigation的使用(二)
秋向阳
这篇主要介绍navigation和BottomNavigationView的使用，可以实现底部导航栏。
如果你的viewpager+tab是非滚动不左右滑动切换页面，可以更换了。
新建activity，选择Bottom Navigation Activity:
Bottom Navigation activity
如果新建activity没有该选项的话，请升级Android studio
代码自动产生activity，xml，menu，drawable。创建4个fragment，此处代码忽略，然后创建navigation，如何创建参考使用一
nav_bottom_navagation.xml代码如下：
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
app:startDestination="@id/nav_home"
android:id="@+id/nav_bottom_navagation">
<fragment
android:id="@+id/nav_home"
android:name="com.ghp.demo.databindingdemoproject.navigation.bottomNavigationView.HomeFragment"
android:label="@string/title_home"
tools:layout="@layout/fragment_home">
</fragment>
<fragment
android:id="@+id/nav_dashboard"
android:name="com.ghp.demo.databindingdemoproject.navigation.bottomNavigationView.DashboardFragment"
android:label="@string/title_dashboard"
tools:layout="@layout/fragment_dashboard">
</fragment>
<fragment
android:id="@+id/nav_notifications"
android:name="com.ghp.demo.databindingdemoproject.navigation.bottomNavigationView.NotificationsFragment"
android:label="@string/title_notifications"
tools:layout="@layout/fragment_notifications">
</fragment>
</navigation>
接着我们修改activity的XML，将自动产生的TextView替换为fragment
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<android.support.constraint.ConstraintLayout
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".navigation.bottomNavigationView.BottomNavigationActivity">
<fragment
android:id="@+id/frag_nav_bottom_navigation"
android:layout_width="0dp"
android:layout_height="0dp"
android:name="androidx.navigation.fragment.NavHostFragment"
app:defaultNavHost="true"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintBottom_toTopOf="@id/navigation"
app:navGraph="@navigation/nav_bottom_navagation"
/>
<android.support.design.widget.BottomNavigationView
android:id="@+id/navigation"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="0dp"
android:layout_marginEnd="0dp"
android:background="?android:attr/windowBackground"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:menu="@menu/bottom_navigation" />
</android.support.constraint.ConstraintLayout>
</layout>
fragment的地方需要注意：
- 添加：android:name="androidx.navigation.fragment.NavHostFragment"，如果自定义了NavHostFragment，就替换为自定义的路径+NavHostFragment
- 配置 app:defaultNavHost 和 app:navGraph属性：app:defaultNavHost="true"
app:navGraph="@navigation/nav_bottom_navagation"
需要注意：navigation里fragment的id需要和menu里item的id对应
下面就是修改activity：
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_bottom_navigation)
var navHostFragment: NavHostFragment = supportFragmentManager.findFragmentById(R.id.frag_nav_bottom_navigation) as NavHostFragment
var navController: NavController = navHostFragment.navController
NavigationUI.setupWithNavController(navigation, navController)
// bottom_navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener)
}
//需要重写onSupportNavigateUp方法
override fun onSupportNavigateUp(): Boolean {
return Navigation.findNavController(this, R.id.frag_nav_bottom_navigation).navigateUp()
}
需要将该自动产生的代码里的listener去掉，因为setupWithNavController里set了,可以看下面的源码
public static void setupWithNavController(
@NonNull final BottomNavigationView bottomNavigationView,
@NonNull final NavController navController) {
bottomNavigationView.setOnNavigationItemSelectedListener(
new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
return onNavDestinationSelected(item, navController, true);
}
});
navController.addOnNavigatedListener(new NavController.OnNavigatedListener() {
@Override
public void onNavigated(@NonNull NavController controller,
@NonNull NavDestination destination) {
Menu menu = bottomNavigationView.getMenu();
for (int h = 0, size = menu.size(); h < size; h++) {
MenuItem item = menu.getItem(h);
if (matchDestination(destination, item.getItemId())) {
item.setChecked(true);
}
}
}
});
}
运行试试看，一个简单的类似tabview+viewpager的效果。
点击BottomNavigationView的时候，发现当menu的数量>3的时候，出现了动画的效果，跟设计完全不符，查看源码会发现：
* support:design:27.1.1版本的：
BottomNavigationMenuView里有个Boolean变量mShiftingMode，他的值是根据mShiftingMode = mMenu.size() > 3;控制的，让人苦恼的他是private，且menu的布局在onMeasure时是根据他的值设置的，当他为false的时候，没有那个动画效果。那就想办法设置他为false吧
@SuppressLint("RestrictedApi")
fun BottomNavigationView.disableShiftMode() {
val menuView = this.getChildAt(0) as BottomNavigationMenuView
try {
val shiftingMode = menuView.javaClass.getDeclaredField("mShiftingMode")
shiftingMode.isAccessible = true
shiftingMode.setBoolean(menuView, false)
shiftingMode.isAccessible = false
for (i in 0 until menuView.childCount) {
val item = menuView.getChildAt(i) as BottomNavigationItemView
item.setShiftingMode(false)
// set once again checked value, so view will be updated
item.setChecked(item.itemData.isChecked)
}
} catch (e: NoSuchFieldException) {
Timber.e("Unable to get shift mode field: $e")
} catch (e: IllegalAccessException) {
Timber.e("Unable to change value of shift mode: $e")
}
}
需要代码设置
bottomNavigationView.disableShiftMode()
运行看看，是不是4个menu均匀的分布了，这是27.1.1下的源码。
注意：27和28版本下navigation的源码是不一样的
如果你设置了4个menu均匀分布后，还会发现，他们带有选中变大的动画，这是因为，源码其实是2个view，他们有各自的大小值控制动画，附上源码：
public BottomNavigationItemView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
final Resources res = getResources();
int inactiveLabelSize =
res.getDimensionPixelSize(R.dimen.design_bottom_navigation_text_size);
int activeLabelSize = res.getDimensionPixelSize(
R.dimen.design_bottom_navigation_active_text_size);
mDefaultMargin = res.getDimensionPixelSize(R.dimen.design_bottom_navigation_margin);
mShiftAmount = inactiveLabelSize - activeLabelSize;
mScaleUpFactor = 1f * activeLabelSize / inactiveLabelSize;
mScaleDownFactor = 1f * inactiveLabelSize / activeLabelSize;
LayoutInflater.from(context).inflate(R.layout.design_bottom_navigation_item, this, true);
setBackgroundResource(R.drawable.design_bottom_navigation_item_background);
mIcon = findViewById(R.id.icon);
mSmallLabel = findViewById(R.id.smallLabel);
mLargeLabel = findViewById(R.id.largeLabel);
}
inactiveLabelSize和activeLabelSize，
如果不想要这样的动画的话，我们只需要将这2个值设为一样就可以了。在自己项目里添加：<dimen name="design_bottom_navigation_active_text_size">14dp</dimen> <dimen name="design_bottom_navigation_text_size">14dp</dimen>
* support:design:28版本的：
可能是意识到BottomNavigationView的问题，他新添加了方法setLabelVisibilityMode，可以设置不同的LabelVisibilityMode，看源码有4种
@Retention(RetentionPolicy.SOURCE)
public @interface LabelVisibilityMode {
int LABEL_VISIBILITY_AUTO = -1;
int LABEL_VISIBILITY_SELECTED = 0;
int LABEL_VISIBILITY_LABELED = 1;
int LABEL_VISIBILITY_UNLABELED = 2;
}
可以在代码里设置：
navigation.labelVisibilityMode = LabelVisibilityMode.LABEL_VISIBILITY_SELECTED
也可以在xml里设置：
app:labelVisibilityMode="labeled"
每种效果不一样，具体的你可以每个运行看看。
有的同学的menu图片使用了PNG，也是可以的，但需要图片四周是透明的，不然会是整块都是颜色值。
如果不想使用他的特性，就想使用自己彩色的图片，可以代码设置：
bottomNavigationView.itemIconTintList = null
运行的过程中发现，每次点击切换menu的时候，fragment都会重新oncreate。
如何避免fragment被回收重新创建呢？
还有印象我前面提到的自定义NavHostFragment吗？
查看源码发现NavHostFragment在create的时候，会在NavigatorProvider里添加创建的FragmentNavigator，而在FragmentNavigator里的navigate方法里对fragment做了处理
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
final Context context = requireContext();
mNavController = new NavController(context);
mNavController.getNavigatorProvider().addNavigator(createFragmentNavigator());
...
}
我们自定义个FragmentNavigator，重写NavHostFragment的createFragmentNavigator
@Navigator.Name("tab_fragment") // Use as custom tag at navigation.xml
class TabNavigator (
private val context: Context,
private val manager: FragmentManager,
private val containerId: Int
) : FragmentNavigator(context, manager, containerId) {
override fun navigate(destination: Destination, args: Bundle?, navOptions: NavOptions?) {
val tag = destination.id.toString()
val transaction = manager.beginTransaction()
val currentFragment = manager.primaryNavigationFragment
if (currentFragment != null) {
transaction.hide(currentFragment)
}
var fragment = manager.findFragmentByTag(tag)
if (fragment == null) {
fragment = destination.createFragment(args)
transaction.add(containerId, fragment, tag)
} else {
transaction.show(fragment)
}
transaction.setPrimaryNavigationFragment(fragment)
transaction.setReorderingAllowed(true)
transaction.commit()
dispatchOnNavigatorNavigated(destination.id, BACK_STACK_DESTINATION_ADDED)
}
}
class TabNavHostFragment: NavHostFragment() {
override fun createFragmentNavigator(): Navigator<out FragmentNavigator.Destination> {
return TabNavigator(requireContext(), childFragmentManager, id)
}
}
TabNavigator我们重命名了@Navigator.Name("tab_fragment")，在
navigation里我们需要更改fragment为tab_fragment
<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
app:startDestination="@id/nav_home"
android:id="@+id/nav_bottom_navagation">
<tab_fragment
android:id="@+id/nav_home"
android:name="com.ghp.demo.databindingdemoproject.navigation.bottomNavigationView.HomeFragment"
android:label="@string/title_home"
tools:layout="@layout/fragment_home">
</tab_fragment>
...
</navigation>
同时我们需要将xml里的fragment修改：
<fragment
...
android:name="com.ghp.demo.databindingdemoproject.navigation.bottomNavigationView.TabNavHostFragment"
...
/>
activity里在获取NavHostFragment也需要修改：
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_bottom_navigation)
//使用自定义的TabNavHostFragment，优化fragment每次重新create问题
var navHostFragment: TabNavHostFragment = supportFragmentManager.findFragmentById(R.id.frag_nav_bottom_navigation) as TabNavHostFragment
var navController: NavController = navHostFragment.navController
NavigationUI.setupWithNavController(navigation, navController)
在每个fragment的oncreate方法添加log，运行查看是不是在点击menu的时候，不会每次都执行oncreate了，而且只有在点击menu的时候才会创建fragment，实现了类似懒加载的方式。
如果你想动态的手动添加menu和fragment，不妨往下继续看。
在xml里将fragment去除app:navGraph的配置，
BottomNavigationView去除app:menu的配置
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".navigation.bottomNavigationView.BtNavShiftingActivity">
<fragment
android:id="@+id/fragment"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:name="androidx.navigation.fragment.NavHostFragment"
app:defaultNavHost="true"
/>
<android.support.design.widget.BottomNavigationView
android:id="@+id/bottomNavigationView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="0dp"
android:layout_marginEnd="0dp"
android:background="?android:attr/windowBackground"
app:labelVisibilityMode="labeled"
/>
</LinearLayout>
</layout>
代码手动的添加：
class BtNavTransactionActivity : AppCompatActivity() {
var homeFragment: HomeFragment? = null
var notificationsFragment: NotificationsFragment? = null
var dashboardFragment: DashboardFragment? = null
var testFragment: DashboardFragment? = null
var currentFragment: Fragment? = null
private val mOnNavigationItemSelectedListener = BottomNavigationView.OnNavigationItemSelectedListener { item ->
when (item.itemId) {
0 -> {
if (homeFragment == null) {
homeFragment = HomeFragment()
}
settingFragment(homeFragment!!)
}
1 -> {
if (notificationsFragment == null) {
notificationsFragment = NotificationsFragment()
}
settingFragment(notificationsFragment!!)
}
2 -> {
if (dashboardFragment == null) {
dashboardFragment = DashboardFragment()
}
settingFragment(dashboardFragment!!)
}
3 -> {
if (testFragment == null) {
testFragment = DashboardFragment()
}
settingFragment(testFragment!!)
}
}
true
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_bt_nav_transaction)
bottomNavigationView.menu.add(0, 0, 0, resources.getString(R.string.title_home)).setIcon(R.drawable.ic_home_black_24dp)
bottomNavigationView.menu.add(0, 1, 1, resources.getString(R.string.title_dashboard)).setIcon(R.drawable.ic_dashboard_black_24dp)
bottomNavigationView.menu.add(0, 2, 2, resources.getString(R.string.title_notifications)).setIcon(R.drawable.ic_notifications_black_24dp)
bottomNavigationView.menu.add(0, 3, 3, resources.getString(R.string.title_test)).setIcon(R.drawable.ic_notifications_black_24dp)
if (homeFragment == null) {
homeFragment = HomeFragment()
}
fragmentAdd(R.id.fragment, homeFragment!!)
currentFragment = homeFragment
// bottomNavigationView.itemIconTintList = null //如果使用的是自己的彩色png图片，需要设置
bottomNavigationView.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener)
}
/**
*用FragmentTransaction控制fragment的show和hide
*避免每次的oncreate
**/
private fun settingFragment(fragment: Fragment) {
if (currentFragment != fragment) {
val transaction = supportFragmentManager.beginTransaction()
if(!fragment.isAdded){
transaction.hide(currentFragment!!).add(R.id.fragment, fragment).commit()
} else {
transaction.hide(currentFragment!!).show(fragment).commit()
}
currentFragment = fragment
}
}
fun fragmentAdd(viewId: Int, fragment: Fragment) {
supportFragmentManager
.beginTransaction()
.add(viewId, fragment)
.commitAllowingStateLoss()
}
}
OK，算是这几天navigation的使用总结吧。
补充注意:
按照上面步骤写代码的话，会出现fragment重叠的bug，可以重写onSaveInstanceState处理，这里就不介绍相关fragment重叠问题了。
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