AndroidPro4_005_Menus

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# A menu item carries the following attributes:

Name: A string title

Menu item ID: An integer

Group ID: An integer representing which group this item should be part of

Sort order: An integer identifying the order of this menu item when it is displayed in the menu

# The sort-order attribute

Secondary: start at 0x30000, defined by the constant Menu.CATEGORY_SECONDARY. such as system menus, alternative menus, and container menus-have different order-number ranges.

System: start at 0x20000 and are defined by the constant Menu.CATEGORY_SYSTEM.

Alternative: starts at 0x40000.defined by the constant Menu.CATEGORY_ALTERNATIVE.They’re usually contributed by external applications that provide alternative ways to deal with the data that is under consideration.

Container: starting at 0x10000, defined by the constant Menu.CATEGORY_CONTAINER.

# Creating a Menu
3.0之前使用了菜单才会激活onCreateOpintionsMenu(), 3.0之后因为 action bar 总是在activity中显示，onCreateOpintionsMenu()总是在activity创建时调用.

@Override
public boolean onCreateOptionsMenu(Menu menu)
{
  //call the base class to include system menus
  super.onCreateOptionsMenu(menu);
    menu.add(0    // Group
,1    // item id
,0    //order
,"append"); // title
    menu.add(0,2,1,"item2");
    menu.add(0,3,2,"clear");
  //It is important to return true to see the menu
  return true;
}

# Menu Group

removeGroup(id)
setGroupCheckable(id, checkable, exclusive)
setGroupEnabled(id,boolean enabled)
setGroupVisible(id,visible)

# Responding to Menu Items Through Listeners

@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch(item.getItemId()) {

..
  //for items handled
  return true;

     //for the rest

return super.onOptionsItemSelected(item);
}
}

\ onMenuClickListener

//Step 1
public class MyResponse implements OnMenuClickListener
{
//some local variable to work on
//

  //Some constructors
    @override
  boolean onMenuItemClick(MenuItem item)
    {
      //do your thing
      return true;
}
}
//Step 2
MyResponse myResponse = new MyResponse(

);
menuItem.setOnMenuItemClickListener(myResponse);

Note: onMenuItemClickListener executes when click, even before onOpintionsItemSelected() method is called.
If onMenuItemClick() return ture, no other callbacks are executed.

# Other Menu Types

# Icon Menu

//add a menu item and remember it so that you can use it
//subsequently to set the icon on it.
MenuItem item = menu.add(

);
item.setIcon(R.drawable.balloons);

#Submenus

private void addSubMenu(Menu menu)
{
  //Secondary items are shown just like everything else
  int base=Menu.FIRST + 100;
    SubMenu sm = menu.addSubMenu(base,base+1,Menu.NONE,"submenu");
    sm.add(base,base+2,base+2,"sub item1");
    sm.add(base,base+3,base+3,"sub item2");
    sm.add(base,base+4,base+4,"sub item3");
  //submenu item icons are not supported
    item1.setIcon(R.drawable.icon48x48_2);
  //the following is ok however
    sm.setIcon(R.drawable.icon48x48_1);
  //This will result in runtime exception
  //sm.addSubMenu("try this");
}

Note: you cannot add additional submenus to a submenu.

# Context Menus

activity.onCreateContextMenu(); // Context menu is owned by a view, the method to populate context menus resides in the Activity class.

@Override
public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    TextView tv = (TextView)this.findViewById(R.id.textViewId);
    registerForContextMenu(tv);
}

不是每个View都必须有Context Menus, 必须为需要的view注册一个context view: activity.registerForContextMenu(view)

@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo)
{
menu.setHeaderTitle("Sample Context Menu");
menu.add(200, 200, 200, "item1");
}

responding to context menu clicks. onContextItemSelected() is also available on the Activity class.

@Override
public boolean onContextItemSelected(MenuItem item)
{
  if (item.getitemId() = some-menu-item-id)
        {
          //handle this menu item
          return true;
        }

other exception processing
}

# Alternative Menus

??

# Loading Menus Through XML Files

\ Structure of an XML Menu Resource File

Inflating XML Menu Resource Files

@Override
public boolean onCreateOptionsMenu(Menu menu)
{
    MenuInflater inflater = getMenuInflater(); //from activity
    inflater.inflate(R.menu.my_menu, menu);
  //It is important to return true to see the menu
  return true;
}

Responding to XML-Based Menu Items

private void onOptionsItemSelected (MenuItem item)
{
  if (item.getItemId() == R.id.menu_clear) // xml生成的menu用 R.id.ooxx, 和前面code生成的 item id 不一样, item id是在menu.add()里第2个参数.
    {
      //do something
    }
  else if (item.getItemId() == R.id.menu_dial)
    {
  //do something
    }

etc
}

3.0之后可以直接在XML中指定Menu callback method:

<item android:id="

"
android:onClick="a-method-name-in-your-activity"

</item>

# Pop-up Menus in 4.0

Then:

//Other activity code goes here

//Invoke the following method to show a popup menu
private void showPopupMenu()
{
  //Get hold of a view to anchor the popup
  //getTextView() can be any method that returns a view
    TextView tv = getTextView();
  //instantiate a popup menu
  //the var "this" stands for activity
    PopupMenu popup = new PopupMenu(this, tv);
  //the following code for 3.0 sdk
  //popup.getMenuInflater().inflate(R.menu.popup_menu, popup.getMenu());
  //Or in sdk 4.0
    popup.inflate(R.menu.popup_menu);
    popup.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener()
    {
      public boolean onMenuItemClick(MenuItem item)
        {
          //some local method to log that item
          //See the sample project to see how this method works
            appendMenuItemText(item);
          return true;
        }
    }
);
popup.show();
}

# XML Menu Tags

Group Category Tag

Checkable Behavior Tags
use the checkableBehavior tag to control checkable behavior at a group level:

use the checked tag to control checkable behavior at an item level:

<item android:id=".."
android:title="

"
android:checked="true" />

Tags to Simulate a Submenu

submenu is represented as a menu element under a menu item:

<item android:title="All without group">
<menu>
<item

>
</menu>
</item>

Menu Icon Tag

Menu Enabling/Disabling Tag

Menu Item Shortcuts

<item android:id="

"
android:alphabeticShortcut="a"

</item>

Menu Visibility

<item android:id="

"
android:visible="true"

</item>