Group menu items work but don't display checkmark

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:

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

回答2:

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);     }

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