难以跟进 Android "Creating List and Cards tutorial"

Question

我正在努力学习 this 教程。

Google 给出以下代码：

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
    private String[] mDataset;

    // Provide a reference to the views for each data item
    // Complex data items may need more than one view per item, and
    // you provide access to all the views for a data item in a view holder
    public static class ViewHolder extends RecyclerView.ViewHolder {
        // each data item is just a string in this case
        public TextView mTextView;
        public ViewHolder(TextView v) {
            super(v);
            mTextView = v;
        }
    }

    // Provide a suitable constructor (depends on the kind of dataset)
    public MyAdapter(String[] myDataset) {
        mDataset = myDataset;
    }

    // Create new views (invoked by the layout manager)
    @Override
    public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
                                                   int viewType) {
        // create a new view
        View v = LayoutInflater.from(parent.getContext())
                               .inflate(R.layout.my_text_view, parent, false);
        // set the view's size, margins, paddings and layout parameters
        ...
        ViewHolder vh = new ViewHolder(v);
        return vh;
    }

    // Replace the contents of a view (invoked by the layout manager)
    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        // - get element from your dataset at this position
        // - replace the contents of the view with that element
        holder.mTextView.setText(mDataset[position]);

    }

    // Return the size of your dataset (invoked by the layout manager)
    @Override
    public int getItemCount() {
        return mDataset.length;
    }
}

我正在努力使这项工作完全按照示例进行。我创建了一个 my_text_view.xml 文件，如下所示：

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent"
    android:text="testing"
    />

但是，我在这一行收到一个错误：

TextView v = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.my_text_view, parent, false);

Required 是 android.widget.TextView 并且我给出了 android.view.View

我一定是误解了如何传递 textView。通常我会使用 (TextView) R.FindViewById 但是由于教程是从布局中抓取它，我认为它不希望我这样做。

非常感谢能帮助您理解这一点。

Answer 1

方法inflatereturnsView实例。所以你必须投射到适当的观点。这不是 Android 而是 Java.

Answer 2

例子说：

View v = LayoutInflater.from(parent.getContext())
                           .inflate(R.layout.my_text_view, parent, false);

但是你写了

TextView v = LayoutInflater.from(parent.getContext())
            .inflate(R.layout.my_text_view, parent, false);

您无需将 "View" 更改为 "TextView"，只需保持示例中的原样即可。如果在那之后，您在该行中收到一条错误消息：

ViewHolder vh = new ViewHolder(v);

说：ViewHolder中的ViewHolder(android.widget.TextView)无法应用于(android.view.View)。修改如下：

ViewHolder vh = new ViewHolder((TextView)v);

此外：在 myDataset 中发送多个值，如果发送一个值，它可能会隐藏在工具栏下。

难以跟进 Android "Creating List and Cards tutorial"

Difficulty following Android "Creating List and Cards tutorial"

android

android-layout

textview

cardlayout