增加一个简单的分享功能

Implementing an effective and user friendly share action in your ActionBar is made even easier with the introduction of ActionProvider in Android 4.0 (API Level 14). An ActionProvider, once attached to a menu item in the action bar, handles both the appearance and behavior of that item. In the case of ShareActionProvider, you provide a share intent and it does the rest.

Note:  ShareActionProvider is available starting with API Level 14 and higher.

Figure 1. The ShareActionProvider in the Gallery app.

Update Menu Declarations

To get started with ShareActionProviders, define the android:actionProviderClass attribute for the corresponding <item> in your menu resource file:

<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:id="@+id/menu_item_share"
        android:showAsAction="ifRoom"
        android:title="Share"
        android:actionProviderClass="android.widget.ShareActionProvider" />
    ...
</menu>

This delegates responsibility for the item's appearance and function to ShareActionProvider. However, you will need to tell the provider what you would like to share.

Set the Share Intent

In order for ShareActionProvider to function, you must provide it a share intent. This share intent should be the same as described in the 向其他的App发送内容 lesson, with action ACTION_SEND and additional data set via extras like EXTRA_TEXT and EXTRA_STREAM. To assign a share intent, first find the corresponding MenuItem while inflating your menu resource in your Activity or Fragment. Next, call MenuItem.getActionProvider() to retreive an instance of ShareActionProvider. Use setShareIntent() to update the share intent associated with that action item. Here's an example:

private ShareActionProvider mShareActionProvider;
...

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate menu resource file.
    getMenuInflater().inflate(R.menu.share_menu, menu);

    // Locate MenuItem with ShareActionProvider
    MenuItem item = menu.findItem(R.id.menu_item_share);

    // Fetch and store ShareActionProvider
    mShareActionProvider = (ShareActionProvider) item.getActionProvider();

    // Return true to display menu
    return true;
}

// Call to update the share intent
private void setShareIntent(Intent shareIntent) {
    if (mShareActionProvider != null) {
        mShareActionProvider.setShareIntent(shareIntent);
    }
}

You may only need to set the share intent once during the creation of your menus, or you may want to set it and then update it as the UI changes. For example, when you view photos full screen in the Gallery app, the sharing intent changes as you flip between photos.

For further discussion about the ShareActionProvider object, see the Action Bar guide.