Android开发之实现水平滚动效果—RecyclerView

ListView由于其强大的功能，在过去的Android开发中有着卓越的贡献，然而使用ListView，如果不使用一些技巧来提升其效率的话，那么ListView的性能会很差。

为此，Android提供了一个更加强大的滚动控件–RecyclerView。下面来讲一下其基本用法。

1.打开app/build.gradle文件，在dependencies闭包中添加如下内容：

dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
testCompile 'junit:junit:4.12'
**compile 'com.android.support:recyclerview-v7:24.2.1'**
compile 'com.android.support:appcompat-v7:24.2.1'
}

添加完后，要记得Sync Now来进行同步。

然后修改main_activity.xml代码：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.gyq.recyclerviewtest.MainActivity">

<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent">

</android.support.v7.widget.RecyclerView>

</LinearLayout>

2，准备fruit_item.xml布局，实现左右滑动效果：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:orientation="vertical">

<ImageView
android:id="@+id/iv_item_icon"
android:layout_width="60dp"
android:layout_height="60dp"
android:layout_gravity="center_horizontal"
android:src="@drawable/apple"/>

<TextView
android:id="@+id/tv_item_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginTop="10dp"
android:text="apple"
android:textSize="20sp"/>

</LinearLayout>

3，为RecyclerView准备一个适配器：

package com.gyq.recyclerviewtest.adapter;

import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import com.gyq.recyclerviewtest.R;
import com.gyq.recyclerviewtest.bean.Fruit;

import java.util.List;

/**
* ${DESC}
* author: gyq
* create at 2016/12/12 18:51
*/
public class FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder> {
private List<Fruit> mFruitList;

static class ViewHolder extends RecyclerView.ViewHolder {
// View fruitView;
ImageView fruitImage;
TextView fruitName;

public ViewHolder(View itemView) {
super(itemView);
//fruitView = itemView;
fruitImage = (ImageView)itemView.findViewById(R.id.iv_item_icon);
fruitName = (TextView)itemView.findViewById(R.id.tv_item_name);
}
}

public FruitAdapter(List<Fruit> fruitInfo) {
mFruitList = fruitInfo;
}

@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.fruit_item,parent,false);
ViewHolder holder = new ViewHolder(view);

return holder;
}

@Override
public void onBindViewHolder(ViewHolder holder, int position) {
Fruit fruit = mFruitList.get(position);
holder.fruitImage.setImageResource(fruit.getImageId());
holder.fruitName.setText(fruit.getName());
}

@Override
public int getItemCount() {
return mFruitList.size();
}

}

解释一下上面代码：首先定义了一个内部类ViewHolder，其继承RecyclerView.ViewHolder。然后ViewHolder的构造函数中需要传入一个view参数；

4，适配器准备好了，接下来我们就来使用RecyclerView：

package com.gyq.recyclerviewtest;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager;

import com.gyq.recyclerviewtest.adapter.FruitAdapter;
import com.gyq.recyclerviewtest.bean.Fruit;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class MainActivity extends AppCompatActivity {
private List<Fruit> fruitInfo = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

initFruit();

RecyclerView recyclerView = (RecyclerView)findViewById(R.id.recycler_view);
LinearLayoutManager layoutManager = new LinearLayoutManager(this);

//设置水平滚动
layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
recyclerView.setLayoutManager(layoutManager);

FruitAdapter adapter = new FruitAdapter(fruitInfo);
recyclerView.setAdapter(adapter);
}

private void initFruit() {
for (int i = 0; i < 2;i++) {
Fruit apple = new Fruit("apple",R.drawable.apple);
fruitInfo.add(apple);
Fruit apricot = new Fruit("apricot"),R.drawable.apricot);
fruitInfo.add(apricot);
Fruit banana = new Fruit("banana"),R.drawable.banana);
fruitInfo.add(banana);
Fruit cherry = new Fruit("cherry"),R.drawable.cherry);
fruitInfo.add(cherry);
Fruit kiwi = new Fruit("kiwi"),R.drawable.kiwi);
fruitInfo.add(kiwi);
Fruit lemon = new Fruit("lemon"),R.drawable.lemon);
fruitInfo.add(lemon);
Fruit mango = new Fruit("mango"),R.drawable.mango);
fruitInfo.add(mango);
Fruit orange = new Fruit("orange"),R.drawable.orange);
fruitInfo.add(orange);
Fruit peach = new Fruit("peach"),R.drawable.peach);
fruitInfo.add(peach);
Fruit pear = new Fruit("pear"),R.drawable.pear);
fruitInfo.add(pear);
Fruit strawberry = new Fruit("strawberry"),R.drawable.strawberry);
fruitInfo.add(strawberry);
Fruit tomato = new Fruit("tomato"),R.drawable.tomato);
fruitInfo.add(tomato);
}

}
}

5,还有一个bean类

package com.gyq.recyclerviewtest.bean;

/**
* ${DESC}
* author: gyq
* create at 2016/12/12 17:02
*/
public class Fruit {
private String name;
private int ImageId;

public Fruit(String name, int imageId) {
this.name = name;
this.ImageId = imageId;
}

public String getName() {
return name;
}

public int getImageId() {
return ImageId;
}

}

本篇博客只是实现了水平滚动的效果；但是没有设置item中控件的点击事件；由于不像listview中有个setOnItemonClick点击事件。下篇博客，我将给大家带了一个瀑布流效果，并设置点击事件。