Android：自定义PopupMenu的样式（显示图标/设置RadioButton图标）

PopupMenu是Android中一个十分轻量级的组件。与PopupWindow相比，PopupMenu的可自定义的能力较小，但使用更加方便。

先上效果图：

本例要实现的功能如下：

1.强制显示菜单项的图标。

默认状态下，PopupMenu的图标是不显示的，并且Android没有为我们开放任何API去设置它的显示状态。为了显示菜单项的图标，可以自己重写PopupMenu并修改相关属性，也可以直接使用反射：

try {
            Field field = popupMenu.getClass().getDeclaredField("mPopup");
            field.setAccessible(true);
            MenuPopupHelper mHelper = (MenuPopupHelper) field.get(popupMenu);
            mHelper.setForceShowIcon(true);
        } catch (IllegalAccessException | NoSuchFieldException e) {
            e.printStackTrace();
        }

menu_popup.xml:

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <group android:checkableBehavior="single">
        <item
            android:id="@+id/menu_setting_wifi"
            android:title="使用WIFI"
            android:orderInCategory="80"
            android:icon="@drawable/menu_setting_wifi"
            app:showAsAction="ifRoom" />

        <item
            android:id="@+id/menu_setting_gps"
            android:title="使用GPS"
            android:orderInCategory="90"
            android:icon="@drawable/menu_setting_gps"
            app:showAsAction="ifRoom" />
    </group>

    <group>
        <item
            android:id="@+id/menu_setting_userIcon"
            android:title="设置头像"
            android:icon="@drawable/menu_setting_usericon"
            android:orderInCategory="91"
            app:showAsAction="never" />
    </group>
</menu>

PopupMenu会从当前的context中继承样式，因此可以通过设置Activity的样式来控制PopupMenu的样式。

<!--自定义PopupMenu上的RadioButton的样式-->
    <style name="PopupMenuStyle" parent="AppTheme">
        <item name="android:radioButtonStyle">@style/MenuRadioButtonStyle</item>
    </style>

    <style name="MenuRadioButtonStyle" parent="@android:style/Widget.CompoundButton.RadioButton">
        <item name="android:button">@drawable/selector_menu_rb</item>
    </style>

<activity
            android:name=".PopupMenuActivity"
            android:theme="@style/PopupMenuStyle" />

补充：也可以在初始话PopupMenu的时候直接设置样式。但是这种方式编译器会多次出现警告：Too many attribute references。因此不建议使用。

Context wrapper = new ContextThemeWrapper(activity, R.style.PopupMenuStyle);
PopupMenu popupMenu = new PopupMenu(activity, ancher);

======  ======

Activity部分完整代码：

/**
 * 自定义PopupMenu
 * Created by hanj on 15-3-17.
 */
public class PopupMenuActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        LinearLayout lin = new LinearLayout(this);
        Button btn = new Button(this);
        LinearLayout.LayoutParams p = new LinearLayout.LayoutParams(
                LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
        btn.setLayoutParams(p);
        lin.addView(btn);

        btn.setText("显示PopupMenu");
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showPopupMenu(PopupMenuActivity.this, v);
            }
        });

        setContentView(lin);
    }

    //当前选择的menuItem的id
    private int checkedItemId = R.id.menu_setting_wifi;

    private void showPopupMenu(final Context context, View ancher) {
        PopupMenu popupMenu = new PopupMenu(context, ancher);
        //引入菜单资源
        popupMenu.inflate(R.menu.menu_popup);

        //设置选中
        popupMenu.getMenu().findItem(checkedItemId).setChecked(true);
        //菜单项的监听
        popupMenu.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
            @Override
            public boolean onMenuItemClick(MenuItem menuItem) {
                switch (menuItem.getItemId()) {
                    case R.id.menu_setting_wifi:
                        checkedItemId = R.id.menu_setting_wifi;
                        Toast.makeText(context, "WIFI", Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.menu_setting_gps:
                        checkedItemId = R.id.menu_setting_gps;
                        Toast.makeText(context, "GPS", Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.menu_setting_userIcon:
                        Toast.makeText(context, "USER_ICON", Toast.LENGTH_SHORT).show();
                        break;
                }
                return true;
            }
        });

        //使用反射，强制显示菜单图标
        try {
            Field field = popupMenu.getClass().getDeclaredField("mPopup");
            field.setAccessible(true);
            MenuPopupHelper mHelper = (MenuPopupHelper) field.get(popupMenu);
            mHelper.setForceShowIcon(true);
        } catch (IllegalAccessException | NoSuchFieldException e) {
            e.printStackTrace();
        }

        //显示PopupMenu
        popupMenu.show();
    }
}