android - 添加媒体路由器转换按钮时出错

Question

我尝试使用 CastCompanionLibrary 为我的应用程序实现一个转换函数. 当它尝试将 Media Router Cast Button 添加到 ActionBar 时，出现此错误:

10-03 19:33:20.098  11781-11781/de.resper.e2cast W/MenuItemCompat﹕ getActionProvider: item does not implement SupportMenuItem; returning null
10-03 19:33:20.098  11781-11781/de.resper.e2cast W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41ebde18)
10-03 19:33:20.098  11781-11781/de.resper.e2cast E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: de.resper.e2cast, PID: 11781
java.lang.NullPointerException
at com.google.sample.castcompanionlibrary.cast.BaseCastManager.addMediaRouterButton(BaseCastManager.java:355)
at de.resper.e2cast.ChannelCastActivity.onCreateOptionsMenu(ChannelCastActivity.java:655)

在CahnnelCastActivity中的位置是:

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    super.onCreateOptionsMenu(menu);
    getMenuInflater().inflate(R.menu.main, menu);
    mCastManager.addMediaRouterButton(menu, R.id.media_route_menu_item); <--- ERROR
    return true;
}

我已经包括:

import android.support.v7.app.ActionBarActivity;

并扩展为:

public class ChannelCastActivity extends ActionBarActivity

在 BaseCastManager 中是错误行:

public MenuItem addMediaRouterButton(Menu menu, int menuResourceId) {
    MenuItem mediaRouteMenuItem = menu.findItem(menuResourceId);
    MediaRouteActionProvider mediaRouteActionProvider = (MediaRouteActionProvider) MenuItemCompat.getActionProvider(mediaRouteMenuItem);
    mediaRouteActionProvider.setRouteSelector(mMediaRouteSelector); <--- ERROR
    if (null != getMediaRouteDialogFactory()) {
        mediaRouteActionProvider.setDialogFactory(getMediaRouteDialogFactory());
    }
    return mediaRouteMenuItem;
}

在 AndroidManifest.xml 中:

    <activity
        android:name=".ChannelCastActivity"
        android:label="@string/title_activity_channel_cast"
        android:theme="@style/Theme.AppCompat.Light"
        android:parentActivityName=".MainActivity" >
        <meta-data
            android:name="android.support.PARENT_ACTIVITY"
            android:value="de.resper.e2cast.MainActivity" />
        <meta-data
            android:name="com.google.android.gms.version"
            android:value="@integer/google_play_services_version" />
    </activity>

Answer 1

确保您的菜单项具有 android.support.v7.app.MediaRouteActionProvider 的操作 View 而不是 android.app.MediaRouteActionProvider - Chromecast 需要 support-v7 版本。