将点击侦听器添加到 PagerAdpater CardViews 中的两个按钮

Question

在我的项目中，我有一个 PagerAdapter 来扩充 CardViews，这些 CardViews 包含用户创建的文本对象。

在每个 CardView 上，我都有编辑和删除按钮来访问处理 ArrayList 保存文本对象的方法。

我在我的适配器中编写了一个接口来处理文本 object 创建活动中的点击。 但是，我的适配器中的 instatiateItem 方法现在显示在 @Override 注释上“方法不覆盖其超类中的方法”。 当我删除 @Override 注释时，我的 Logcat 中出现错误：

java.lang.UnsupportedOperationException: Required method instantiateItem was not overridden

如何为 PagerAdapter 中 CardView 上的按钮实现点击监听器？

适配器代码：

public class CreateAdapter extends PagerAdapter {

private List<PdfPage> pagesList;
private LayoutInflater layoutInflater;
private Context context;
private onItemClickListener mListener;

public interface onItemClickListener{
    //click method for edit button
    void onEditClick(int position);
    //click method for delete button
    void onDeleteClick(int position);
}

public void setOnItemClickListener(onItemClickListener listener){
    mListener = listener;
}

public CreateAdapter(List<PdfPage> pagesList, Context context) {
    this.pagesList = pagesList;
    this.context = context;
}

@Override
public int getCount() {
    return pagesList.size();
}

@Override
public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
    return view.equals(object);
}

@NonNull
@Override
public Object instantiateItem(@NonNull ViewGroup container, final int position, final onItemClickListener listener) {
    layoutInflater = LayoutInflater.from(context);
    View view = null;

    if(pagesList.get(position).getPageType() == "Text") {
        view = layoutInflater.inflate(R.layout.create_text_cardview, container, false);

        TextView inputText = view.findViewById(R.id.inputTextView);
        ImageButton editButton = view.findViewById(R.id.imageButtonEdit);
        ImageButton deleteButton = view.findViewById(R.id.imageButtonDelete);

        //if this works, see 12:30 of video for image getter
        inputText.setText(pagesList.get(position).getPageText());

        //edit click listener
        editButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (listener != null){
                    int position2 = pagesList.indexOf(pagesList.get(position));
                    listener.onEditClick(position2);
                }
            }
        });

        //delete click listener
        deleteButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (listener != null){
                    int position3 = pagesList.indexOf(pagesList.get(position));
                    listener.onDeleteClick(position3);
                }
            }
        });

        container.addView(view, 0);

    }

    //put else statement here for image cardView

    assert view != null;
    return view;
}

@Override
public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
    container.removeView((View)object);
}

活动代码：

public class CreateActivity extends AppCompatActivity {

ViewPager viewPager;
CreateAdapter createAdapter;
List<PdfPage> pdfPageList;

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

    pdfPageList = new ArrayList<>();
    
    createAdapter = new CreateAdapter(pdfPageList, this);

    viewPager = findViewById(R.id.viewPager);
    viewPager.setAdapter(createAdapter);
    viewPager.setPadding(130, 0, 130, 0);

}

@Override
protected void onStart() {
    super.onStart();

    createAdapter = new CreateAdapter(pdfPageList, this);

    viewPager = findViewById(R.id.viewPager);
    viewPager.setAdapter(createAdapter);
    viewPager.setPadding(130, 0, 130, 0);

    createAdapter.setOnItemClickListener(new CreateAdapter.onItemClickListener() {
        @Override
        public void onEditClick(int position) {

        }

        @Override
        public void onDeleteClick(int position) {
            pdfPageList.remove(position);
        }
    });
}

Answer 1

您的instantiateItem方法不会从它的超类中覆盖，因为您添加了一个额外的参数final onItemClickListener listener 。

由于您对所有条目使用相同的 clickListener 并将项目 position 作为参数传递，因此我建议您在适配器构造函数中传递onItemClickListener ，或者只是通过

public void setOnItemClickListener(onItemClickListener listener){
    mListener = listener;
}

适配器代码：

public class CreateAdapter extends PagerAdapter {

private List<PdfPage> pagesList;
private LayoutInflater layoutInflater;
private Context context;
private onItemClickListener mListener;

public interface onItemClickListener{
    //click method for edit button
    void onEditClick(int position);
    //click method for delete button
    void onDeleteClick(int position);
}

public void setOnItemClickListener(onItemClickListener listener){
    mListener = listener;
}

public CreateAdapter(List<PdfPage> pagesList, Context context) {
    this.pagesList = pagesList;
    this.context = context;
}

@Override
public int getCount() {
    return pagesList.size();
}

@Override
public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
    return view.equals(object);
}

@NonNull
@Override
public Object instantiateItem(@NonNull ViewGroup container, final int position) {
    layoutInflater = LayoutInflater.from(context);
    View view = null;

    if(pagesList.get(position).getPageType() == "Text") {
        view = layoutInflater.inflate(R.layout.create_text_cardview, container, false);

        TextView inputText = view.findViewById(R.id.inputTextView);
        ImageButton editButton = view.findViewById(R.id.imageButtonEdit);
        ImageButton deleteButton = view.findViewById(R.id.imageButtonDelete);

        //if this works, see 12:30 of video for image getter
        inputText.setText(pagesList.get(position).getPageText());

        //edit click listener
        editButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mlistener != null){
                    int position2 = pagesList.indexOf(pagesList.get(position));
                    mlistener.onEditClick(position2);
                }
            }
        });

        //delete click listener
        deleteButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mlistener != null){
                    int position3 = pagesList.indexOf(pagesList.get(position));
                    mlistener.onDeleteClick(position3);
                }
            }
        });

        container.addView(view, 0);

    }

    //put else statement here for image cardView

    assert view != null;
    return view;
}

@Override
public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
    container.removeView((View)object);
}

您的活动代码可以保持原样。