java.lang.RuntimeException:无法在android版本4上启动activity ComponentInfo；

我在安卓版本4.+（特别是在4.1和4.3中）中遇到了这个错误，而在安卓的任何其他版本中都没有。 Manifest.xml文件和gradle文件中引用了活动和库（我使用的是

GooglePlayServices

和

YouTubePlayerAPI

）

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.app.test/com.app.test.DetailActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5039)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.app.test.content.FirstFragment.onCreate(FirstFragment.java:151)
at android.support.v4.app.Fragment.performCreate(Fragment.java:1763)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:913)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1108)
at android.support.v4.app.FragmentManagerImpl.dispatchCreate(FragmentManager.java:1912)
at android.support.v4.app.FragmentActivity.onCreate(FragmentActivity.java:266)
at com.app.test.DetailActivity.onCreate(DetailActivity.java:73)
at android.app.Activity.performCreate(Activity.java:5104)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
... 11 more

导致错误的片段代码（第151行）是附加片段的onCreate（）方法：

 @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setHasOptionsMenu(true);

        if(getArguments() != null && getArguments().containsKey(ARG_ITEM_ID)) {
            // Loads the content specified by the fragment arguments.
            mItem = Items.getInstance().getMap().get(getArguments().getString(ARG_ITEM_ID));
        }

        // Initialize mCustomMediaPlayer
        mCustomMediaPlayer = new CustomMediaPlayer(getActivity().getApplicationContext(), mItem.getTrackId());
    }

其中，点线151为：

mCustomMediaPlayer = new CustomMediaPlayer(VillancicosActivity.getContext(), mItem.getTrackId());

CustomMediaPlayer类：

public class CustomMediaPlayer {

    /////// Constants

    private static final String TAG = "CustomMediaPlayer";

    /////// Fields

    /**
     * The application context.
     * Is used to manage MediaPlayer and async class.
     */
    private Context mContext;

    /**
     * MediaPlayer instance.
     */
    private MediaPlayer mMediaPlayer;

    /**
     * The id representing track used in MediaPlayer create() method
     * where will be played.
     */
    private Integer mTrackId;

    /**
     * A flag indicating if the track is playing or not.
     */
    private Boolean mIsPlaying = false;

    /**
     * Initialize providing the application context and the calling fragment track id.
     *
     * @param context The Context to use.
     * @param trackId The raw resource id to use as datasource.
     */
    public CustomMediaPlayer(Context context, Integer trackId) {
        mContext = context;
        mTrackId = trackId;
    }

.....
}

这是类的一部分，在该类中，从第151行的FirstFragment调用主构造函数

有什么想法吗？ 谢谢大家

试试这个

mCustomMediaPlayer = new CustomMediaPlayer(getActivity(), mItem.getTrackId());

---

并检查是否为

mItem==null

。

您的活动无法识别Villancicos活动。getContext（）您需要传递有效的上下文。

---

请改为尝试getApplicationContext（）。

很可能

mItem

为空

VillancicosActivity.getContext（）

闻起来也很难闻。我尝试过getActivity（）.getApplicationContext（）并报告了相同的错误。我想如果是在Get context中，它在任何android版本中都不起作用，而不仅仅是在4中。+我尝试过getActivity（）.getApplicationContext（）也有同样的错误。你有没有检查mItem=空？我已经试过了，在android 2.3.3和2.3.7的一些设备上mItem是空的，但我不知道是什么原因造成的