Question

我正在尝试添加选项以单击片段中的Gridview中的图像/视频，但它说我无法将我的主要活动转换为我创建的OnClickThumbListener接口... 我认为这是因为我使用片段而不是FragmentActivity。

主：

public class MyPostsScreen extends Fragment implements
    LoaderManager.LoaderCallbacks<Cursor>, MediaStoreAdapter.OnClickThumbListener{

    private OnFragmentInteractionListener mListener;

    private final static int READ_EXTERNAL_STORAGE_PERMMISSION_RESULT = 0;
    private final static int MEDIASTORE_LOADER_ID = 0;
    private RecyclerView mThumbnailRecyclerView;
    private MediaStoreAdapter mMediaStoreAdapter;

    public MyPostsScreen() {
        // Required empty public constructor
    }


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

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_my_posts_screen, container, false);

        mThumbnailRecyclerView = (RecyclerView) v.findViewById(R.id.thumbnailRv);
        GridLayoutManager gridLayoutManager = new GridLayoutManager(this.getContext(), 3);
        mThumbnailRecyclerView.setLayoutManager(gridLayoutManager);
        mMediaStoreAdapter = new MediaStoreAdapter(this.getActivity());
        mThumbnailRecyclerView.setAdapter(mMediaStoreAdapter);

        checkReadExternalStoragePermission();

        // Inflate the layout for this fragment
        return v;
    }
}

MediaStoreAdapter：

public class MediaStoreAdapter extends RecyclerView.Adapter<MediaStoreAdapter.ViewHolder> {
    private Cursor mMediaStoreCursor;
    private final Activity mActivity;
    private OnClickThumbListener mOnClickThumbListener;

    public interface OnClickThumbListener {
        void OnClickImage(Uri imageUri);
        void OnClickVideo(Uri videoUri);
    }
    public MediaStoreAdapter(Activity activity) {
        this.mActivity = activity;
        //TODO: Figure out why this fails Java Class Exception, and FIX.
        this.mOnClickThumbListener = (OnClickThumbListener)activity;
    }
}

ERROR：

致命的例外：主要处理：example.fadysi.fomoapptest2，PID：21631 java.lang.ClassCastException：example.fadysi.fomoapptest2.MainActivity 无法施展 example.fadysi.fomoapptest2.ThumbnailVideoPlay.MediaStoreAdapter $ OnClickThumbListener 在 example.fadysi.fomoapptest2.ThumbnailVideoPlay.MediaStoreAdapter。（MediaStoreAdapter.java:31）在layout.MyPostsScreen.onCreateView（MyPostsScreen.java:65）在 android.support.v4.app.Fragment.performCreateView（Fragment.java:2087）在 android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1113）在 android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1295）在 android.support.v4.app.BackStackRecord.run（BackStackRecord.java:801）在 android.support.v4.app.FragmentManagerImpl.execSingleAction（FragmentManager.java:1643）在 android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss（BackStackRecord.java:679）在 android.support.v4.app.FragmentPagerAdapter.finishUpdate（FragmentPagerAdapter.java:143）在android.support.v4.view.ViewPager.populate（ViewPager.java:1272）在android.support.v4.view.ViewPager.populate（ViewPager.java:1120）在android.support.v4.view.ViewPager.onMeasure（ViewPager.java:1646）在android.view.View.measure（View.java:18794）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5951）在 android.support.design.widget.CoordinatorLayout.onMeasureChild（CoordinatorLayout.java:703）在 android.support.design.widget.HeaderScrollingViewBehavior.onMeasureChild（HeaderScrollingViewBehavior.java:90）在 android.support.design.widget.AppBarLayout $ ScrollingViewBehavior.onMeasureChild（AppBarLayout.java:1367）在 android.support.design.widget.CoordinatorLayout.onMeasure（CoordinatorLayout.java:768）在android.view.View.measure（View.java:18794）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5951）在android.widget.FrameLayout.onMeasure（FrameLayout.java:194）在 android.support.v7.widget.ContentFrameLayout.onMeasure（ContentFrameLayout.java:139）在android.view.View.measure（View.java:18794）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5951）在 android.widget.LinearLayout.measureChildBeforeLayout（LinearLayout.java:1465）在android.widget.LinearLayout.measureVertical（LinearLayout.java:748）在android.widget.LinearLayout.onMeasure（LinearLayout.java:630）在android.view.View.measure（View.java:18794）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5951）在android.widget.FrameLayout.onMeasure（FrameLayout.java:194）在android.view.View.measure（View.java:18794）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5951）在 android.widget.LinearLayout.measureChildBeforeLayout（LinearLayout.java:1465）在android.widget.LinearLayout.measureVertical（LinearLayout.java:748）在android.widget.LinearLayout.onMeasure（LinearLayout.java:630）在android.view.View.measure（View.java:18794）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5951）在android.widget.FrameLayout.onMeasure（FrameLayout.java:194）在 com.android.internal.policy.PhoneWindow $ DecorView.onMeasure（PhoneWindow.java:2643）在android.view.View.measure（View.java:18794）在android.view.ViewRootImpl.performMeasure（ViewRootImpl.java:2100）在android.view.ViewRootImpl.measureHierarchy（ViewRootImpl.java:1216）在android.view.ViewRootImpl.performTraversals（ViewRootImpl.java:1452）在android.view.ViewRootImpl.doTraversal（ViewRootImpl.java:1107）在 android.view.ViewRootImpl $ TraversalRunnable.run（ViewRootImpl.java:6013）在 android.view.Choreographer $ CallbackRecord.run（Choreographer.java:858）在android.view.Choreographer.doCallbacks（Choreographer.java:670）在android.view.Choreographer.doFrame（Choreographer.java:606）在 android.view.Choreographer $ FrameDisplayEventReceiver.run（Choreographer.java:844）在android.os.Handler.handleCallback（Handler.java:739）在android.os.Handler.dispatchMessage（Handler.java:95）在android.os.Looper.loop（Looper.java:148）在android.app.ActivityThread.main（ActivityThread.java:5417）在java.lang.refle

Answer 1

将其更改为

private final Context mActivity;
....
....

public MediaStoreAdapter(Context context, OnClickThumbListener onClickThumbListener) {
    this.mActivity = context;
    this.mOnClickThumbListener = onClickThumbListener;

}

在MyPostsScreen片段中，调用适配器构造函数，如下所示，

mMediaStoreAdapter = new MediaStoreAdapter(this.getActivity(), this);
mThumbnailRecyclerView.setAdapter(mMediaStoreAdapter);

这是因为您的界面是由片段实现的，而不是MainActivity。

java.lang.ClassCastException：cast to created interface issue？

1 个答案: