如何在Fragment和适配器之间创建接口？

Question

我有片段ListView,比方说MyListFragment和自定义CursorAdapter.我onClickListener在此适配器中设置列表行中的按钮.

public class MyListAdapter extends CursorAdapter {

    public interface AdapterInterface {
        public void buttonPressed();
    }

    ...

    @Override
    public void bindView(final View view, final Context context, final Cursor cursor) {
        ViewHolder holder = (ViewHolder) view.getTag();

        ...

        holder.button.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                // some action
                // need to notify MyListFragment
            }
        });
    }
}

public MyListFragment extends Fragment implements AdapterInterface {

    @Override
    public void buttonPressed() {
        // some action
    }
}

我需要在按下按钮时通知片段.如何调用此界面？

请帮忙.

Answer 1

创建一个新的构造函数和一个实例变量:

AdapterInterface buttonListener;

public MyListAdapter (Context context, Cursor c, int flags, AdapterInterface buttonListener)
{
  super(context,c,flags);
  this.buttonListener = buttonListener;
}

制作适配器后,实例变量将被赋予适当的保持参考.

要从点击中调用片段:

public void onClick(View v) {
   buttonListener.buttonPressed();
}

制作时Adapter,您还必须将片段传递给适配器.例如

MyListAdapter adapter = new MyListAdapter (getActivity(), myCursor, myFlags, this);

因为this将引用你的碎片,现在是一个AdapterInterface.

请记住,在片段方向更改时,很可能会重新创建.如果未重新创建适配器,则可能会保留对不存在的对象的引用,从而导致错误.

Answer 2

使用Eventbus:

例子:

https://github.com/kaushikgopal/RxJava-Android-Samples/tree/master/app/src/main/java/com/morihacky/android/rxjava/rxbus

要么

https://github.com/greenrobot/EventBus

使用接口:

我理解当前的答案,但需要一个更清晰的例子.这是我与Adapter(RecyclerView.Adapter)和a 一起使用的示例Fragment.

创建Callback界面:

public interface AdapterCallback {
    void onMethodCallback();
}

传入Callback/ Fragment:

这将实现interface我们所拥有的Adapter.在此示例中,将在用户单击中的项目时调用它RecyclerView.

在你的Fragment:

public class MyFragment extends Fragment implements AdapterCallback {

    private MyAdapter mMyAdapter;

    @Override
    public void onMethodCallback() {
       // do something
    }

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

        this.mMyAdapter = new MyAdapter(this); // this class implements callback
    }
}

使用Callback你的适配器:

在Fragment,我们启动了我们Adapter并将其作为构造函数的参数传递.这将启动我们interface的回调方法.您可以看到我们使用回调方法进行用户点击.

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {

    private AdapterCallback mAdapterCallback;

    public MyAdapter(AdapterCallback callback) {
        this.mAdapterCallback = callback;
    }

    @Override
    public void onBindViewHolder(final MyAdapter.ViewHolder viewHolder, final int i) {
        // simple example, call interface here
        // not complete
        viewHolder.itemView.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                mAdapterCallback.onMethodCallback();
            }
        });
    }
}

或使用Fragment您的适配器:

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {

    private AdapterCallback mAdapterCallback;

    public MyAdapter(Fragment fragment) {
        try {
            this.mAdapterCallback = ((AdapterCallback) fragment);
        } catch (ClassCastException e) {
            throw new ClassCastException("Fragment must implement AdapterCallback.");
        }
    }

    @Override
    public void onBindViewHolder(final MyAdapter.ViewHolder viewHolder, final int i) {
        // simple example, call interface here
        // not complete
        viewHolder.itemView.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    mAdapterCallback.onMethodCallback();
                } catch (ClassCastException exception) {
                   // do something
                }
            }
        });
    }
}

Answer 3

按照以下两个步骤接收来自Adapter的回调Fragment (or Activity)

第一:在你的Adapter

public class ListAdapter extends RecyclerView.Adapter < RecyclerListAdapter.ItemViewHolder > {
    ...
    private ListAdapterListener mListener;

    public interface ListAdapterListener { // create an interface
        void onClickAtOKButton(int position); // create callback function
    }

    public RecyclerListAdapter(Context mContext, ArrayList < Items > listItems, ListAdapterListener mListener) { // add the interface to your adapter constructor
        ...
        this.mListener = mListener; // receive mListener from Fragment (or Activity)
    }
    ...
    public void onBindViewHolder(final ItemViewHolder holder, final int position) {

        holder.btnOK.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // use callback function in the place you want
                mListener.onClickAtOKButton(position);
            }
        });
        ...
    }
    ...
}

第二:在你Fragment (or Activity)的实现回调方法中有2种方法

方式1

 public MyListFragment extends Fragment {
     ...
     public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
         ...
         ListAdapter adapter = new ListAdapter(getActivity(), listItems, new ListAdapter.ListAdapterListener() {
             @Override
             public void onClickAtOKButton(int position) {
                 Toast.makeText(getActivity(), "click ok button at" + position, Toast.LENGTH_SHORT).show();
             }
         });
         ...
     }
 }

方式2

public MyListFragment extends Fragment implements ListAdapter.ListAdapterListener {
     ...
     public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        ListAdapter  adapter = new ListAdapter (getActivity(), listItems, this);
        ...   
    }

    @Override
    public void onClickAtOKButton(int position) {  
        Toast.makeText(getActivity(), "click ok button at" + position, Toast.LENGTH_SHORT).show();     
    }          
}