有人可以解释一下RecyclerView在android中的工作原理吗？
我使用此网站作为参考：https://developer.android.com/training/material/lists-cards.html#CardView
但是当我编译相同的代码时，我收到了一个错误。
任何帮助将不胜感激。谢谢。
MyAdapter.java
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.ViewGroup;
import android.widget.TextView;
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
TextView v = (TextView) 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;
}
}
RecyclerActivity.java
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import java.util.ArrayList;
public class RecyclerActivity extends AppCompatActivity {
private RecyclerView mRecyclerView;
private RecyclerView.Adapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
private String[] myDataset = {"hellow"};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_recycler);
mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);
// use this setting to improve performance if you know that changes
// in content do not change the layout size of the RecyclerView
mRecyclerView.setHasFixedSize(true);
// use a linear layout manager
mLayoutManager = new LinearLayoutManager(this);
mRecyclerView.setLayoutManager(mLayoutManager);
// specify an adapter (see also next example)
mAdapter = new MyAdapter(myDataset);
mRecyclerView.setAdapter(mAdapter);
}
}
my_text_view.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
</LinearLayout>
activity_recycler.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_recycler"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.bloxofcode.listviewcustom.RecyclerActivity">
<!-- A RecyclerView with some commonly used attributes -->
<android.support.v7.widget.RecyclerView
android:id="@+id/my_recycler_view"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</RelativeLayout>
遇到错误：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.bloxofcode.listviewcustom, PID: 27529
java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to android.widget.TextView
at com.bloxofcode.listviewcustom.MyAdapter.onCreateViewHolder(MyAdapter.java:37)
at com.bloxofcode.listviewcustom.MyAdapter.onCreateViewHolder(MyAdapter.java:12)
答案 0 :(得分：1)
首先改变你的my_text_view.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:
android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:id="@+id/text_view"/>
</LinearLayout>
现在更改您的MyAdapter.java类：
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.ViewGroup;
import android.widget.TextView;
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(View v) {
super(v);
mTextView = (TextView) v.findViewById(R.id.text_view);
}
}
// 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;
}
}
答案 1 :(得分：0)
RecyclerView is more advanced version of ListView with improved performance
和其他好处。首先，你必须创建一个适配器类 onCreateViewHolder（）膨胀布局（my_text_view.xml）和onBindViewHolder（）为每一行设置适当的数据。
so first of all make some changes in your my_text_view.xml file and in adapter class.
1. add a TextView field in my_text_view.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:id="@+id/tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
2. Do following changes in MyAdapter.java
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
private String[] mDataset;
private static final String TAG = "MyAdapter";
public static class ViewHolder extends RecyclerView.ViewHolder {
public TextView mTextView;
// change 1: ViewHolder wants View
public ViewHolder(View view) {
super(view);
// change 2: instanciate the mTextView
/* mTextView = v; delete this line */
mTextView = (TextView) view.findViewById(R.id.tv);
}
}
public MyAdapter(String[] myDataset) {
mDataset = myDataset;
}
@Override
public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
int viewType) {
//Change 3: inflate the layout
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.my_text_view, parent, false);
// return the view
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
holder.mTextView.setText(mDataset[position]);
Log.e(TAG, "data: " + mDataset[position]);
}
@Override
public int getItemCount() {
return mDataset.length;
}
}
3. there is no need to change MyAdapter.java n its xml file.