java - 如何处理卡片 View 中不同的按钮 onclick 并传递 Intent ？

Question

我有一个卡片 View ，它显示即将举行的 Activity ，包括标题、日期等，并且有两个 ImageView 应充当按钮:如果单击其中一个，则应转到参与确认 Activity ，如果单击另一个，则应转到参与确认 Activity 详细 Activity 。这两者还应该使用 Intent (名称、日期、用户 ID、 token )传递信息。我已关注this tutorial ，因为这是最接近我的问题的解决方案，但它仍然不起作用。无论我如何更改，这些都是我得到的错误:尝试在空对象引用上调用虚拟方法 'void android.widget.ImageView.setOnClickListener(android.view.View$OnClickListener)' (这是我调用 setButtons 函数时给出的) ，或者如果 onclick 以某种方式工作， Intent 不会被传递，并且我得到一个 nullpointerException。我确保我使用了正确的 ID 和名称。附加信息:我正在使用 Laravel 和改造。 Activity Activity :

public class EventsActivity extends AppCompatActivity {
private static final String TAG = "EventsActivity";
private static final int ACTIVITY_NUM = 1;
private static final String PREFS_NAME = "LoginPrefs";
public static final String EVENT_DETAIL = "EVENT_DETAIL";
private Context mContext = EventsActivity.this;
private Event mEvent = new Event();
private String token, name;
private int id;
private EventAdapter adapter;
private RecyclerView recyclerView;
private List<Event> eventList = new ArrayList<>();
private List<Response> result;
private TextView noEvents;
private Button add, more;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_events);

    //Get token and id from shared preferences
    SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
    token = settings.getString("token", "");
    id = settings.getInt("id", 0);
    Log.d(TAG, "onResponse: id " + id + "token " + token);

    noEvents = findViewById(R.id.noEvents);
    recyclerView = findViewById(R.id.event_recyclerview);
    RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(mContext);
    recyclerView.setLayoutManager(layoutManager);
    adapter = new EventAdapter(mContext, eventList);
    recyclerView.setAdapter(adapter);

    adapter.setOnItemClickListener(new EventAdapter.OnItemClickListener() {
        @Override
        public void onAddClicked(int position) {
           addClick(position);
        }

        @Override
        public void onMoreClicked(int position) {
            moreClick(position);
        }
    });

    loadData();
    setButtons();
}

public void addClick(int position){
    final Event event = eventList.get(position);
    Intent i = new Intent(EventsActivity.this, EventInvitationActivity.class);
    i.putExtra("name", event.getName());
    i.putExtra("name", event.getDescription());
    i.putExtra("name", event.getDate());
    i.putExtra("name", event.getLocation());
    Log.i("hello", event.getName());
    startActivity(i);
}

public void moreClick(int position){
    final Event event = eventList.get(position);
    Intent i = new Intent(EventsActivity.this, EventDetailActivity.class);
    i.putExtra("name", event.getName());
    Log.i("hello", event.getName());
    startActivity(i);
}

void setButtons() {
     add = findViewById(R.id.add_icon);
     more = findViewById(R.id.more_icon);
    Log.d(TAG, "setButtons: called");
    add.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Log.d(TAG, "onClick: add onclicklistener");
            int position = Integer.parseInt(v.getTag().toString());
            addClick(position);
        }
    });
    more.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            int position = Integer.parseInt(v.getTag().toString());
            moreClick(position);
        }
    });
}

//Listing events
private void loadData(){
    ApiEvents service = RetrofitBuilder.getRetrofitInstance().create(ApiEvents.class);
    Call<List<Event>> call = service.listEvents("Bearer" + token, id);
    call.enqueue(new Callback<List<Event>>() {
        @Override
        public void onResponse(@NonNull Call<List<Event>> call, @NonNull Response<List<Event>> response) {
            if (response.isSuccessful() && response.body()!=null) {
                Log.d(TAG, "onResponse: loadData called");
                eventList = response.body();
                adapter = new EventAdapter(mContext, eventList);
                recyclerView.setAdapter(adapter);
                adapter.setOnItemClickListener(new EventAdapter.OnItemClickListener() {
                    @Override
                    public void onAddClicked(int position) {
                        addClick(position);
                    }

                    @Override
                    public void onMoreClicked(int position) {
                        moreClick(position);
                    }
                });
            }
            else if(response.body() == null){
                noEvents.setVisibility(View.VISIBLE);
            }
            else{
                Log.d(TAG, "onResponse: " + response.body());
            }
        }

        @Override
        public void onFailure(@NonNull Call<List<Event>> call, @NonNull Throwable t) {
            Log.d("Response", "onFailure: " + t.toString());
        }
    });
}

}

事件适配器

public class EventAdapter extends RecyclerView.Adapter<EventAdapter.MyViewHolder> {
private Context mContext;
private List<Event> eventList;
private static final String TAG = "EventDetailActivity";
private OnItemClickListener clickListener;

public EventAdapter(Context mContext, List<Event> eventList){
    this.mContext = mContext;
    this.eventList = eventList;
}

public interface OnItemClickListener {
    void onAddClicked(int position);
    void onMoreClicked(int position);
}

public void setOnItemClickListener(OnItemClickListener clickListener) {
    this.clickListener = clickListener;
}

@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.event_layout, parent, 
false);
    return new MyViewHolder(view);
}

@Override
public void onBindViewHolder(@NonNull final MyViewHolder holder, int position) {
    Event event = eventList.get(position);
    holder.itemView.setTag(event);
    holder.title.setText(eventList.get(position).getName());
    holder.description.setText(eventList.get(position).getDescription());
    holder.date.setText(eventList.get(position).getDate());
    holder.location.setText(eventList.get(position).getLocation());
    holder.add.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if(clickListener != null){
                int position = (int)v.getTag();
                clickListener.onAddClicked(position);
                final Event event = (Event)v.getTag();
                if(event!= null){
                    Intent i = new Intent(mContext, EventInvitationActivity.class);
                    i.putExtra("EVENT_DETAIL", event);
                    v.getContext().startActivity(i);
                }
            }
        }
    });

    holder.more.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if(clickListener != null){
                int position = (int)v.getTag();
                clickListener.onMoreClicked(position);
                final Event event = (Event)v.getTag();
                if(event!= null){
                    Intent i = new Intent(mContext, EventDetailActivity.class);
                    i.putExtra("EVENT_DETAIL", event);
                    v.getContext().startActivity(i);
                }
            }
        }
    });


@Override
public int getItemCount() {
    return eventList.size();
}

public class MyViewHolder extends RecyclerView.ViewHolder {
    TextView title, description, date, location;
    Button add, more;

    public MyViewHolder(@NonNull View itemView) {
        super(itemView);
        title = itemView.findViewById(R.id.event_name);
        description = itemView.findViewById(R.id.event_description);
        date = itemView.findViewById(R.id.event_date);
        location = itemView.findViewById(R.id.event_location);
        add = itemView.findViewById(R.id.add_icon);

    }

}

这就是我试图在两个 Activity 中获取传递 Intent 的方式:

//Getting resources
    mName = findViewById(R.id.eventName);
    mDescription = findViewById(R.id.description);
    mLocation = findViewById(R.id.location);
    mDate = findViewById(R.id.date);

    mEvent = Objects.requireNonNull(getIntent().getExtras()).getParcelable(EVENT_DETAIL);
   if(mEvent != null){
    mName.setText(mEvent.getName());
    mDescription.setText(mEvent.getDescription());
    mLocation.setText(mEvent.getLocation());
    mDate.setText(mEvent.getDate());
   }

这是卡片 View 中的按钮示例:

<Button
            android:id="@+id/add_icon"
            android:layout_width="80dp"
            android:layout_height="40dp"
            android:layout_below="@+id/image"
            android:layout_gravity="center_horizontal"
            android:layout_marginTop="5dp"
            android:layout_toEndOf="@id/event_description"
            android:drawableStart="@drawable/ic_add_black_24dp"
            android:scaleType="centerCrop"
            android:transitionName="img"
            android:visibility="visible"
            android:textColor="@color/colorAccent"
           />

所以问题是，我怎样才能做到这一点？

编辑我已经弄清楚问题是什么:添加和更多 ImageView 作为 CardView 的一部分位于 event_layout 上，而不是程序正在寻找它们的 Activity_events 上。但是，当这两个按钮放置在 CardView 上时，我真的不知道如何使它们工作。

Answer 1

在您的MyViewHolder构造函数中，您没有初始化more，因此它将为空，因此会抛出空引用异常