Switch button not showing up in ActionBar?

问题

I have a Switch that I placed into my ActionBar, but it doesn't seem to show up and I don't see why. This was my attempt:

create_post_menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu 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"
    tools:context=".CreatePost">

    <item
        android:id="@+id/toggle_test"
        android:title=""
        app:showAsAction="ifRoom"
        android:orderInCategory="1"
        android:actionViewClass="android.widget.Switch" />

    <item
        android:id="@+id/send_post"
        android:orderInCategory="2"
        android:title="Send"
        app:showAsAction="ifRoom" />

</menu>

CreatePost.java

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.create_post_menu, menu);
    // Get the action view used in your toggleservice item
    final MenuItem toggleservice = menu.findItem(R.id.toggle_test);
    final Switch actionView = (Switch) toggleservice.getActionView();
    actionView.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            // Start or stop your Service
        }
    });
    return super.onCreateOptionsMenu(menu);
}

I tried to instantiate the Switch to see if I can set a listener to see if you click on or off for the switch but I can't seem to instantiate it as I get an error trying to create the actionView variable in CreatePost.java. Can anyone help me with this? Thanks!

回答1:

your are getting error because your actionView is null. change your Switch menu code

<item
     android:id="@+id/toggle_test"
     android:title=""
     app:showAsAction="ifRoom"
     android:orderInCategory="1"
     android:actionViewClass="android.widget.Switch" /> 

to app:actionViewClass="android.widget.Switch" look carefully it would be app not android like this...

<item
      android:id="@+id/toggle_test"
      android:title=""
      app:showAsAction="ifRoom"
      android:orderInCategory="1"
      app:actionViewClass="android.widget.Switch" /> 

and now change your java code like this

final MenuItem toggleservice = menu.findItem(R.id.toggle_test);
Switch actionView=(Switch) MenuItemCompat.getActionView(toggleservice );
actionView.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

    @Override
    public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
        // Start or stop your Service
    }
});

来源：https://stackoverflow.com/questions/34573040/switch-button-not-showing-up-in-actionbar