问题
I am trying to set default item on activity created but it isn't working? This is my code:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_userhome);
mTextMessage = (TextView) findViewById(R.id.message);
profile = (FrameLayout) findViewById(R.id.profile);
mall = (FrameLayout) findViewById(R.id.mall);
dietplan =(FrameLayout) findViewById(R.id.dietplan);
BottomNavigationView navigation = (BottomNavigationView)
findViewById(R.id.navigation);
navigation.setSelectedItemId(R.id.dietplan);
navigation.setOnNavigationItemSelectedListener
(mOnNavigationItemSelectedListener);
}
But it seems that navigation.setSelectedItemId(R.id.dietplan); is not working. Please help me to set default item of bottom navigation bar:
This is my stack trace(logcat):
FATAL EXCEPTION: main
Process: gym.android.ommsoftware.gym, PID: 1915
java.lang.RuntimeException: Unable to start activity ComponentInfo{gym.android.ommsoftware.gym/gym.android.ommsoftware.gym.Userhome}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2404)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2464)
at android.app.ActivityThread.access$900(ActivityThread.java:172)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5653)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at gym.android.ommsoftware.gym.Userhome.onCreate(Userhome.java:57)
at android.app.Activity.performCreate(Activity.java:5541)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2368)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2464)
at android.app.ActivityThread.access$900(ActivityThread.java:172)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5653)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
at dalvik.system.NativeStart.main(Native Method)
回答1:
Just share my working source code
In Xml,
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.BottomNavigationView
android:background="@color/colorWhite"
android:id="@+id/gfPrlBnvBtmView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="start"
android:layout_alignParentBottom="true"
app:menu="@menu/bottom_navigation_main" />
</LinearLayout>
In Java,
public class TestActivity extends AppCompatActivity implements BottomNavigationView.OnNavigationItemSelectedListener
{
private BottomNavigationView mBtmView;
private int mMenuId;
@Override
public void onCreate(@Nullable Bundle savedInstanceState, @Nullable PersistableBundle persistentState) {
super.onCreate(savedInstanceState, persistentState);
setContentView(R.layout.test);
mBtmView = (BottomNavigationView) findViewById(R.id.gfPrlBnvBtmView);
mBtmView.setOnNavigationItemSelectedListener(this);
mBtmView.getMenu().findItem(R.id.action_yoga).setChecked(true);
}
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
// uncheck the other items.
mMenuId = item.getItemId();
for (int i = 0; i < mBtmView.getMenu().size(); i++) {
MenuItem menuItem = mBtmView.getMenu().getItem(i);
boolean isChecked = menuItem.getItemId() == item.getItemId();
menuItem.setChecked(isChecked);
}
switch (item.getItemId()) {
case R.id.action_food: {
}
break;
case R.id.action_medical: {
}
break;
case R.id.action_yoga: {
}
break;
case R.id.action_postures: {
}
break;
}
return true;
}
}
回答2:
Instead of selected you need to setChecked(true) that item. Try this code
mBottomNavigationView=(BottomNavigationView)findViewById(R.id.bottom_nav);
mBottomNavigationView.getMenu().findItem(R.id.item_id).setChecked(true);
Checked item is highlighted in BottomNavigationView.
回答3:
Kotlin extension version of Abshishek's answer:
internal fun BottomNavigationView.checkItem(actionId: Int) {
menu.findItem(actionId)?.isChecked = true
}
// use
bottom_navigation.checkItem(R.id.navigation_home)
This does not trigger OnNavigationItemSelectedListener.
回答4:
You can use:
navigationView?.menu?.findItem(drawableMenuItem.id)?.isChecked = true
and it will not fire OnNavigationItemSelectedListener events.
回答5:
This works for me
Activity layout:
<android.support.design.widget.BottomNavigationView
android:id="@+id/bottomNavigation"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:itemBackground="@color/colorPrimary"
app:itemIconTint="@color/tabs"
app:itemTextColor="@color/tabs"
app:menu="@menu/bottom_navigation_main" />
color/tabs.xml:
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:color="@color/not_active" android:state_checked="false"/>
<item android:color="@color/active" android:state_checked="true"/>
</selector>
Click callback:
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.action_tab0:
setFragment(f0);
break;
case R.id.action_tab1:
setFragment(f1);
break;
}
return true; // not false!
}
回答6:
You can also set selection in BottomNavigatioView using index like this :
public void selectBottomNavigationOption(int index) {
switch (index) {
case 0:
index = R.id.action_1;
break;
case 1:
index = R.id.action_2;
break;
case 2:
index = R.id.action_3;
break;
case 3:
index = R.id.action_4;
break;
}
bottomNavigationView.setSelectedItemId(index);
}
回答7:
Add android:enabled="true" to your BottomNavigation menu items.
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item
android:id="@+id/menu_id"
android:enabled="true"
android:icon="@drawable/ic_my_icon"
android:title="@string/menu_title"/>
</menu>
And in onCreate() method,
set up listeners by
bottomNavigationView.setOnNavigationItemSelectedListener(mListener).
And set the desired item to be selected by doing bottomNavigationView.selectedItemId = R.id.menu_id.
This will trigger onNavigationItemSelected() from the NavigationItemSelectedListener whenever the activity is created.
回答8:
If what you want is that the clicked element is ignored on the view and is not returned as "selected" you can return false after the click is handled, in some cases and some designs you could need to open an activity instead of a fragment and this will make selected the bottom item after the activity is closed.
private val onNavigationItemSelectedListener = BottomNavigationView.OnNavigationItemSelectedListener { item ->
when (item.itemId) {
R.id.navigation_shipment -> {
currentItem = TAB_INDEX_SHIPMENT
val intent = Intent(this, BookShipmentActivity::class.java)
startActivity(intent)
return@OnNavigationItemSelectedListener false
}
}
false
}
回答9:
FYI: for fragment, onCreateView
BottomNavigationView mBottomNavigationView = getActivity().findViewById(R.id.bottomNavigationView);
mBottomNavigationView.setSelectedItemId(R.id.your_item);
来源：https://stackoverflow.com/questions/43246059/how-to-set-selected-item-in-bottomnavigationview