问题
I have a working app with an overflow menu. All the code in the menu works, but no checkmarks are being shown after I click on a single-clickable, grouped menu item.
Am I doing something fundamentally wrong? I thought that this displaying of the checkmark was automatic to Android and that the system would do this for me. Android knows it is in a group, it knows that only one can be selected, and it knows which one I selected! So..... Android should know how to display the checkmarks.
Code
XML
<menu
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context=".Calculator">
<group
android:checkableBehavior="single"
android:visible="true">
<item
android:id="@+id/ui_simple"
android:orderInCategory="100"
app:showAsAction="ifRoom|withText"
android:title="Regular"
android:checkable="true"/>
<item
android:id="@+id/ui_doge"
android:orderInCategory="100"
app:showAsAction="ifRoom|withText"
android:title="Doge"
android:checkable="true"/>
<item
android:id="@+id/ui_static"
android:orderInCategory="100"
app:showAsAction="ifRoom|withText"
android:title="Static"
android:checkable="true"/>
</group>
<item android:title="Display Mode"
android:orderInCategory="101" >
<menu>
<group android:checkableBehavior="single" android:visible="true" >
<item
android:id="@+id/mode_sign"
android:orderInCategory="100"
app:showAsAction="collapseActionView"
android:title="Sign Form"
android:checkable="true"/>
<item
android:id="@+id/mode_noun"
android:orderInCategory="100"
app:showAsAction="collapseActionView"
android:title="Noun Form"
android:checkable="true"/>
<item
android:id="@+id/mode_verb"
android:orderInCategory="100"
app:showAsAction="collapseActionView"
android:title="Verb Form"
android:checkable="true"/>
</group>
</menu>
</item>
</menu>
UI
Note: I have tried switching all the breaks to return true, but nothing happens.
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
switch (item.getItemId()) {
case R.id.ui_simple :
startActivity(new Intent(this, Calculator.class));
break;
case R.id.ui_doge :
startActivity(new Intent(this, CalculatorDoge.class));
break;
case R.id.ui_static :
startActivity(new Intent(this, CalculatorStatic.class));
break;
case R.id.mode_sign : display = BinaryOperation.Display.SIGN; break;
case R.id.mode_verb : display = BinaryOperation.Display.VERB; break;
case R.id.mode_noun : display = BinaryOperation.Display.NOUN; break;
}
return super.onOptionsItemSelected(item);
}
回答1:
While @Elltz provides a valuable solution to a problem in the code, there are a total of 2 issues in the code.
Problem 1
Do not set a checkable XML attribute in both the Menu Group and the individual MenuItems.
since in the XML there is <group android:checkableBehavior="single" it shows that radio buttons are desired; therefore, no item within the group should have android:checkable="true"
<group
android:checkableBehavior="single" <!-- ONLY HERE -->
android:visible="true" >
<item
android:id="@+id/mode_sign"
android:orderInCategory="100"
app:showAsAction="collapseActionView"
android:title="Sign Form" />
<item
android:id="@+id/mode_noun"
android:orderInCategory="100"
app:showAsAction="collapseActionView"
android:title="Noun Form"/>
<item
android:id="@+id/mode_verb"
android:orderInCategory="100"
app:showAsAction="collapseActionView"
android:title="Verb Form"/>
</group>
Problem 2
Again, @Elltz provides a good solution; however, it is slightly more complex than what it needs to be.
For Single Selection Only
switch (item.getItemId()) {
case R.id.ui_simple : startActivity(new Intent(this, Calculator.class)); return true;
case R.id.ui_doge : startActivity(new Intent(this, CalculatorDoge.class)); return true;
case R.id.ui_static : startActivity(new Intent(this, CalculatorStatic.class)); return true;
// Single Selection - Radio Buttons
case R.id.mode_sign :
item.setChecked(true); // ONLY THIS....HERE
display = BinaryOperation.Display.SIGN;
return true;
case R.id.mode_verb :
item.setChecked(true); // HERE
display = BinaryOperation.Display.VERB;
return true;
case R.id.mode_noun :
item.setChecked(true); // AND HERE
display = BinaryOperation.Display.NOUN;
return true;
default : return super.onOptionsItemSelected(item);
}
For Single OR Multi Selection
// Single OR Multi Select - Radio Buttons or CheckBoxes
switch (item.getItemId()) {
case R.id.ui_simple : startActivity(new Intent(this, Calculator.class)); return true;
case R.id.ui_doge : startActivity(new Intent(this, CalculatorDoge.class)); return true;
case R.id.ui_static : startActivity(new Intent(this, CalculatorStatic.class)); return true;
case R.id.mode_sign :
item.setChecked(!item.isChecked()); // LIKE THIS...HERE
display = BinaryOperation.Display.SIGN;
return true;
case R.id.mode_verb :
item.setChecked(!item.isChecked()); // HERE
display = BinaryOperation.Display.VERB;
return true;
case R.id.mode_noun :
item.setChecked(!item.isChecked()); // AND HERE
display = BinaryOperation.Display.NOUN;
return true;
default : return super.onOptionsItemSelected(item);
}
回答2:
No
Menu items in the Icon Menu (from the options menu) cannot display a checkbox or radio button. If you choose to make items in the Icon Menu checkable, you must manually indicate the checked state by swapping the icon and/or text each time the state changes.
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.ui_simple:
if (item.isChecked()){
item.setChecked(false);
}else{
item.setChecked(true);
}
startActivity(new Intent(this, Calculator.class));
break;
case R.id.ui_doge:
//same goes here and everyone
break;
....
}
}
Hope it helps
来源：https://stackoverflow.com/questions/30471846/group-menu-items-work-but-dont-display-checkmark