我需要在我的Android应用程序中实现一个水平列表视图。我做了一些研究，遇到了如何在Android中创建一个水平的ListView ?和横向列表视图在Android?然而，这些问题是在Recyclerview发布之前提出的。有没有更好的方法来实现这个现在与Recyclerview?
有没有更好的方法来实现这个现在与RecyclerView现在?
Yes.
当您使用RecyclerView时，您需要指定一个LayoutManager，该LayoutManager负责布局视图中的每个项。LinearLayoutManager允许你指定一个方向，就像一个正常的LinearLayout一样。
要用RecyclerView创建一个水平列表，你可以这样做:
LinearLayoutManager layoutManager
= new LinearLayoutManager(requireContext(), LinearLayoutManager.HORIZONTAL, false);
RecyclerView myList = (RecyclerView) findViewById(R.id.my_recycler_view);
myList.setLayoutManager(layoutManager);
试图构建一个水平的ListView花费了太多的时间。我用两种方法解决了这个问题。
通过使用一个ViewPager，它的适配器扩展自PagerAdapter。 通过像上面一样使用RecyclerView。我们需要像下面的代码一样应用LayoutManager: LinearLayoutManager layoutManager = new LinearLayoutManager(这个，LinearLayoutManager。水平,假); RecyclerView myList = (RecyclerView) findViewById(R.id.my_recycler_view); myList.setLayoutManager (layoutManager);
如果你想使用RecyclerView和GridLayoutManager，这是实现水平滚动的方法。
recyclerView.setLayoutManager(
new GridLayoutManager(recyclerView.getContext(), rows, GridLayoutManager.HORIZONTAL, false));
<android.support.v7.widget.RecyclerView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layoutManager="android.support.v7.widget.LinearLayoutManager" />
随着RecyclerView库的发布，现在您可以轻松地对齐与文本绑定的图像列表。您可以使用LinearLayoutManager来指定您想要定位列表的方向，可以是垂直的，也可以是水平的，如下所示。
你可以从这篇文章中下载一个完整的工作演示。
如果你想使用水平回收器视图作为ViewPager，那么现在可以使用线性snaphelper的帮助，它是在支持库24.2.0版本中添加的。
首先添加RecyclerView到你的活动/片段
<android.support.v7.widget.RecyclerView
android:layout_below="@+id/sign_in_button"
android:layout_width="match_parent"
android:orientation="horizontal"
android:id="@+id/blog_list"
android:layout_height="match_parent">
</android.support.v7.widget.RecyclerView>
在我的情况下，我已经使用了一个CardView在RecyclerView
blog_row.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_margin="15dp"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="vertical">
<com.android.volley.toolbox.NetworkImageView
android:id="@+id/imageBlogPost"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:adjustViewBounds="true"
android:paddingBottom="15dp"
android:src="@drawable/common_google_signin_btn_text_light_normal" />
<TextView
android:id="@+id/TitleTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="20dp"
android:text="Post Title Here"
android:textSize="16sp" />
<TextView
android:id="@+id/descriptionTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Post Description Here"
android:paddingBottom="15dp"
android:textSize="14sp" />
</LinearLayout>
</android.support.v7.widget.CardView>
在你的活动/片段中
private RecyclerView mBlogList;
LinearLayoutManager layoutManager =
new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false);
mBlogList = (RecyclerView) findViewById(R.id.blog_list);
mBlogList.setHasFixedSize(true);
mBlogList.setLayoutManager(layoutManager);
LinearSnapHelper snapHelper = new LinearSnapHelper() {
@Override
public int findTargetSnapPosition(RecyclerView.LayoutManager lm, int velocityX, int velocityY) {
View centerView = findSnapView(lm);
if (centerView == null)
return RecyclerView.NO_POSITION;
int position = lm.getPosition(centerView);
int targetPosition = -1;
if (lm.canScrollHorizontally()) {
if (velocityX < 0) {
targetPosition = position - 1;
} else {
targetPosition = position + 1;
}
}
if (lm.canScrollVertically()) {
if (velocityY < 0) {
targetPosition = position - 1;
} else {
targetPosition = position + 1;
}
}
final int firstItem = 0;
final int lastItem = lm.getItemCount() - 1;
targetPosition = Math.min(lastItem, Math.max(targetPosition, firstItem));
return targetPosition;
}
};
snapHelper.attachToRecyclerView(mBlogList);
最后一步是将适配器设置为RecyclerView
mBlogList.setAdapter(firebaseRecyclerAdapter);
完整的示例
垂直RecyclerView和水平RecyclerView之间唯一真正的区别是如何设置LinearLayoutManager。下面是代码片段。完整的示例如下。
LinearLayoutManager horizontalLayoutManagaer = new LinearLayoutManager(MainActivity.this, LinearLayoutManager.HORIZONTAL, false);
recyclerView.setLayoutManager(horizontalLayoutManagaer);
这个更完整的例子是模仿我的垂直RecyclerView答案。
更新Gradle依赖项
确保以下依赖项在你的应用程序gradle中。构建文件:
implementation 'com.android.support:appcompat-v7:27.1.1'
implementation 'com.android.support:recyclerview-v7:27.1.1'
您可以将版本号更新为最新的版本号。
创建活动布局
将RecyclerView添加到xml布局中。
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
android:id="@+id/rvAnimals"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</RelativeLayout>
创建项目布局
我们的RecyclerView中的每一项都将在TextView上有一个单独的彩色视图。创建一个新的布局资源文件。
recyclerview_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="10dp">
<View
android:id="@+id/colorView"
android:layout_width="100dp"
android:layout_height="100dp"/>
<TextView
android:id="@+id/tvAnimalName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="20sp"/>
</LinearLayout>
创建适配器
RecyclerView需要一个适配器，用您的数据填充每行(水平项)中的视图。创建一个新的java文件。
MyRecyclerViewAdapter.java
public class MyRecyclerViewAdapter extends RecyclerView.Adapter<MyRecyclerViewAdapter.ViewHolder> {
private List<Integer> mViewColors;
private List<String> mAnimals;
private LayoutInflater mInflater;
private ItemClickListener mClickListener;
// data is passed into the constructor
MyRecyclerViewAdapter(Context context, List<Integer> colors, List<String> animals) {
this.mInflater = LayoutInflater.from(context);
this.mViewColors = colors;
this.mAnimals = animals;
}
// inflates the row layout from xml when needed
@Override
@NonNull
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = mInflater.inflate(R.layout.recyclerview_item, parent, false);
return new ViewHolder(view);
}
// binds the data to the view and textview in each row
@Override
public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
int color = mViewColors.get(position);
String animal = mAnimals.get(position);
holder.myView.setBackgroundColor(color);
holder.myTextView.setText(animal);
}
// total number of rows
@Override
public int getItemCount() {
return mAnimals.size();
}
// stores and recycles views as they are scrolled off screen
public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
View myView;
TextView myTextView;
ViewHolder(View itemView) {
super(itemView);
myView = itemView.findViewById(R.id.colorView);
myTextView = itemView.findViewById(R.id.tvAnimalName);
itemView.setOnClickListener(this);
}
@Override
public void onClick(View view) {
if (mClickListener != null) mClickListener.onItemClick(view, getAdapterPosition());
}
}
// convenience method for getting data at click position
public String getItem(int id) {
return mAnimals.get(id);
}
// allows clicks events to be caught
public void setClickListener(ItemClickListener itemClickListener) {
this.mClickListener = itemClickListener;
}
// parent activity will implement this method to respond to click events
public interface ItemClickListener {
void onItemClick(View view, int position);
}
}
笔记
虽然不是严格必要的，但我包含了监听项目上的单击事件的功能。这在旧的listview中是可用的，是一种常见的需求。如果不需要，可以删除此代码。
在Activity中初始化RecyclerView
将以下代码添加到您的主活动中。
MainActivity.java
public class MainActivity extends AppCompatActivity implements MyRecyclerViewAdapter.ItemClickListener {
private MyRecyclerViewAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// data to populate the RecyclerView with
ArrayList<Integer> viewColors = new ArrayList<>();
viewColors.add(Color.BLUE);
viewColors.add(Color.YELLOW);
viewColors.add(Color.MAGENTA);
viewColors.add(Color.RED);
viewColors.add(Color.BLACK);
ArrayList<String> animalNames = new ArrayList<>();
animalNames.add("Horse");
animalNames.add("Cow");
animalNames.add("Camel");
animalNames.add("Sheep");
animalNames.add("Goat");
// set up the RecyclerView
RecyclerView recyclerView = findViewById(R.id.rvAnimals);
LinearLayoutManager horizontalLayoutManager
= new LinearLayoutManager(MainActivity.this, LinearLayoutManager.HORIZONTAL, false);
recyclerView.setLayoutManager(horizontalLayoutManager);
adapter = new MyRecyclerViewAdapter(this, viewColors, animalNames);
adapter.setClickListener(this);
recyclerView.setAdapter(adapter);
}
@Override
public void onItemClick(View view, int position) {
Toast.makeText(this, "You clicked " + adapter.getItem(position) + " on item position " + position, Toast.LENGTH_SHORT).show();
}
}
笔记
注意，该活动实现了我们在适配器中定义的ItemClickListener。这允许我们在onItemClick中处理项目单击事件。
完成了
就是这样。您现在应该能够运行您的项目，并获得与顶部图像类似的内容。
笔记
我示例中的彩色视图当然可以在实际项目中替换为图像。 Vertical RecyclerView示例
试试这个:
myrecyclerview.setLayoutManager(
new LinearLayoutManager(getActivity(),
LinearLayoutManager.HORIZONTAL,false));
myrecyclerview.setAdapter(recyclerAdapter);
只是以防你有一个带有碎片的回收视图。
XML文件
<HorizontalScrollView
android:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
android:scrollbars="vertical|horizontal" />
</HorizontalScrollView>
Code
import androidx.appcompat.app.AppCompatActivity;
import android.content.Context;
import android.content.ContextWrapper;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
public class MainActivity extends AppCompatActivity{
ImageView mImageView1;
Bitmap bitmap;
String mSavedInfo;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mImageView1 = (ImageView) findViewById(R.id.image);
}
public Bitmap getBitmapFromURL(String src) {
try {
java.net.URL url = new java.net.URL(src);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setDoInput(true);
connection.connect();
InputStream input = connection.getInputStream();
Bitmap myBitmap = BitmapFactory.decodeStream(input);
return myBitmap;
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
public void button2(View view) {
new DownloadImageFromTherad().execute();
}
private class DownloadImageFromTherad extends AsyncTask<String, Integer, String> {
@Override
protected String doInBackground(String... params) {
bitmap = getBitmapFromURL("https://cdn.pixabay.com/photo/2016/08/08/09/17/avatar-1577909_960_720.png");
return null;
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
File sdCardDirectory = Environment.getExternalStorageDirectory();
File image = new File(sdCardDirectory, "test.png");
boolean success = false;
FileOutputStream outStream;
mSavedInfo = saveToInternalStorage(bitmap);
if (success) {
Toast.makeText(getApplicationContext(), "Image saved with success", Toast.LENGTH_LONG).show();
} else {
Toast.makeText(getApplicationContext(), "Error during image saving" + mSavedInfo, Toast.LENGTH_LONG).show();
}
}
}
private String saveToInternalStorage(Bitmap bitmapImage) {
ContextWrapper cw = new ContextWrapper(getApplicationContext());
// path to /data/data/yourapp/app_data/imageDir
File directory = cw.getDir("imageDir", Context.MODE_PRIVATE);
File mypath = new File(directory, "profile.jpg");
FileOutputStream fos = null;
try {
fos = new FileOutputStream(mypath);
bitmapImage.compress(Bitmap.CompressFormat.PNG, 100, fos);
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return directory.getAbsolutePath();
}
private void loadImageFromStorage(String path) {
try {
File f = new File(path, "profile.jpg");
Bitmap b = BitmapFactory.decodeStream(new FileInputStream(f));
mImageView1.setImageBitmap(b);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
public void showImage(View view) {
loadImageFromStorage(mSavedInfo);
}
}
水平方向和垂直方向都适用。
RecyclerView recyclerView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test_recycler);
recyclerView = (RecyclerView)findViewById(R.id.recyclerViewId);
RecyclAdapter adapter = new RecyclAdapter();
//Vertical RecyclerView
RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
recyclerView.setLayoutManager(mLayoutManager);
//Horizontal RecyclerView
//recyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext(),LinearLayoutManager.HORIZONTAL,false));
recyclerView.setAdapter(adapter);
}
水平动态回收视图。
回收器视图实现
RecyclerView musicList = findViewById(R.id.MusicList);
// RecyclerView musiclist = findViewById(R.id.MusicList1);
// RecyclerView musicLIST = findViewById(R.id.MusicList2);
LinearLayoutManager layoutManager = new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false);
musicList.setLayoutManager(layoutManager);
String[] names = {"RAP", "CH SHB", "Faheem", "Anum", "Shoaib", "Laiba", "Zoki", "Komal", "Sultan","Mansoob Gull"};
musicList.setAdapter(new ProgrammingAdapter(names));'
回收器视图的适配器类，其中有一个视图持有者用于持有该回收器的视图
public class ProgrammingAdapter
extendsRecyclerView.Adapter<ProgrammingAdapter.programmingViewHolder> {
private String[] data;
public ProgrammingAdapter(String[] data)
{
this.data = data;
}
@Override
public programmingViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
LayoutInflater inflater = LayoutInflater.from(parent.getContext());
View view = inflater.inflate(R.layout.list_item_layout, parent, false);
return new programmingViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull programmingViewHolder holder, int position) {
String title = data[position];
holder.textV.setText(title);
}
@Override
public int getItemCount() {
return data.length;
}
public class programmingViewHolder extends RecyclerView.ViewHolder{
ImageView img;
TextView textV;
public programmingViewHolder(View itemView) {
super(itemView);
img = itemView.findViewById(R.id.img);
textV = itemView.findViewById(R.id.textt);
}
}
recyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false));
recyclerView.setAdapter(adapter);
您可以在代码或布局xml文件中更改方向。
在xml文件中
在你的布局xml文件中，将orientation设置为水平，layoutManager设置为LinearLayoutManager, GridLayoutManager, StaggeredGridLayoutManager之一。根据您的要求选择。
<androidx.recyclerview.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" />
在代码中
如果希望以编程方式更改方向，请将layoutManager设置为水平方向。
recyclerView.layoutManager = LinearLayoutManager(context, RecyclerView.HORIZONTAL, false)
只需在XML的RecyclerView中添加这些属性
android：orientation=“horizontal” app：layoutManager=“androidx.recyclerview.widget.LinearLayoutManager”
您可以从布局文件或java/kotlin文件中定义方向和layoutManager
使用XML
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/my_recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" />
在Java中
LinearLayoutManager layoutManager
= new LinearLayoutManager(requireContext(), LinearLayoutManager.HORIZONTAL, false);
RecyclerView rv= (RecyclerView) findViewById(R.id.my_recyclerView);
rv.setLayoutManager(layoutManager);
在Kotlin
val layoutManager
= LinearLayoutManager(requireContext(), LinearLayoutManager.HORIZONTAL, false)
my_recyclerView.layoutManager = layoutManager
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