Recyclerview使用体验（一）

• 仅作为自己在使用recyclerview过程中一点点记录，

• 使用Recyclerview已经有一定时间，项目中也用了很久，总觉得该亲自整理一下，也算是自己回顾一下Recyclerview的知识，然后尝试去深层次的了解Recyclerview，只会用，不了解，也不算是会用；
• 如果你想尝试Recyclerview，正好又看到这个文章，嗯哼0.0，那你就好好看看吧。

• 废话不多说，直接开整

  首先当然是添加依赖，根据当前sdk版本，选择合适的依赖，Recyclerview是V7包提供的，所以呢？
  compile 'com.android.support:appcompat-v7:24.0.0'
compile 'com.android.support:recyclerview-v7:24.0.0'
  第一个不必说，第二个就是我们需要的导入的包了，rebuild一下，看看是否导入成功，只要根据自己使用的sdk版本，一般是没有意外的，如果有了
  

  
  

  
  很明显是你导入错了。

• 导入成功，接下来就是布局里使用了

  <?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"        android:orientation="vertical">        <android.support.v4.widget.SwipeRefreshLayout                android:id="@+id/swipeRefresh"                android:layout_width="match_parent"               android:layout_height="match_parent">               <android.support.v7.widget.RecyclerView                      android:id="@+id/recyclerview"                       android:layout_width="match_parent"                       android:layout_height="match_parent" />   </android.support.v4.widget.SwipeRefreshLayout> </LinearLayout>

• 布局很简单，SwipeRefreshLayout包裹Recyclerview，实现下拉刷新
  回到代码中

  public class MainActivity extends AppCompatActivity {        @InjectView(R.id.recyclerview)        RecyclerView recyclerview;        @InjectView(R.id.swipeRefresh)       SwipeRefreshLayout swipeRefresh;        @Override        protected void onCreate(Bundle savedInstanceState) {            super.onCreate(savedInstanceState);            setContentView(R.layout.activity_main);            ButterKnife.inject(this);               initData();   }}

  Recyclerview和SwipeRefreshLayout初始化完成，开始加载数据实现Recyclerview的多种实现布局；

先请求到数据.png

有了数据之后，和ListView一样，需要设置适配器，但是Recyclerview得适配器和ListView适配器，不完全一样；假设Recyclerview适配器定义为Adapter

public class Adapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {@Overridepublic RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {    return null;}@Overridepublic void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {}@Overridepublic int getItemCount() {    return 0;}}

我们真正要实现的是重写一个ViewHolder，继承 Recyclerview.ViewHolder；

  public class ItemHolder extends RecyclerView.ViewHolder {    public ItemHolder(View itemView) {        super(itemView);    }}

设置Adapter的布局

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="60dp"    android:paddingLeft="10dp"    android:paddingTop="10dp">    <ImageView        android:id="@+id/imageView"        android:layout_width="40dp"        android:layout_height="40dp" />    <TextView        android:id="@+id/textView"        android:layout_width="match_parent"        android:layout_height="match_parent"        android:layout_gravity="center_vertical"        android:layout_marginLeft="15dp"        android:drawableBottom="@drawable/line"        android:ellipsize="end"        android:gravity="center_vertical"        android:text="123"        android:textColor="@color/colorAccent"        android:textSize="16sp" /></LinearLayout></LinearLayout>

回到Adapter

public class Adapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {    private Context context;    private ArrayList<String> datas;    public Adapter(Context context, ArrayList<String> datas) {        this.context = context;        this.datas = datas;    }    @Override    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        return new ItemHolder(LayoutInflater.from(context).inflate(R.layout.item_adapter, null));    }    @Override    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {    }    @Override    public int getItemCount() {        return datas.size() == 0 ? 0 : datas.size();    }    public class ItemHolder extends RecyclerView.ViewHolder {        private ImageView imageView;        private TextView textView;        public ItemHolder(View itemView) {            super(itemView);            this.imageView = (ImageView) itemView.findViewById(R.id.imageView);            this.textView = (TextView) itemView.findViewById(R.id.textView);        }    }}

最后数据绑定

/** * Creation time   : 2016/11/22 21:01 * Fix time   :  2016/11/22 21:01 */public class Adapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {    private Context context;    private List<String> datas;    public Adapter(Context context, List<String> datas) {        this.context = context;        this.datas = datas;    }    @Override    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        return new ItemHolder(LayoutInflater.from(context).inflate(R.layout.item_adapter, null));    }//绑定数据    @Override    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {        bindViewHolder((ItemHolder) holder);    }    private void bindViewHolder(ItemHolder holder) {        for (int i = 0; i < this.datas.size() - 1; i++) {            holder.textView.setText(datas.get(i));            holder.imageView.setBackgroundResource(R.drawable.musiclogo144);        }    }    @Override    public int getItemCount() {        return datas.size() == 0 ? 0 : datas.size();    }    public class ItemHolder extends RecyclerView.ViewHolder {        private ImageView imageView;        private TextView textView;        public ItemHolder(View itemView) {            super(itemView);            this.imageView = (ImageView) itemView.findViewById(R.id.imageView);            this.textView = (TextView) itemView.findViewById(R.id.textView);        }    }}

回到加载数据部分

    /**     * 请求数据     */    private void initData() {        //假设联网请求数据N条,这里我就用本地数据        data = null;        for (int i = 0; i < 40; i++) {            data.add(i, i + ". 成功请求数据");        }        adapter = new Adapter(MainActivity.this, data);        recyclerview.setAdapter(adapter);    }

编译运行

但是什么都没有，因为我们没有设置LayoutManager，Recyclerview需要设置LayoutManager，才能显示；

public class MainActivity extends AppCompatActivity {    @InjectView(R.id.recyclerview)    RecyclerView recyclerview;    @InjectView(R.id.swipeRefresh)    SwipeRefreshLayout swipeRefresh;    private static final int GET = 1;    private LinearLayoutManager linearLayoutManager;      private GridLayoutManager gridLayoutManager;    private StaggeredGridLayoutManager staggeredGridLayoutManager;    private List<String> data;    private RecyclerView.LayoutManager layoutmanager;    private Adapter adapter;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        ButterKnife.inject(this);           linearLayoutManager = new LinearLayoutManager(MainActivity.this);  //常见纵向布局//        linearLayoutManager = new LinearLayoutManager(MainActivity.this,LinearLayoutManager.HORIZONTAL,true); //水平方向，最后一个参数是否逆向        gridLayoutManager = new GridLayoutManager(MainActivity.this, 2);  //类似GridView的格式，第二个参数为行的item数量，同理，也有水平方向的GridLayoutManager；        staggeredGridLayoutManager = new StaggeredGridLayoutManager(2, StaggeredGridLayoutManager.VERTICAL); //瀑布流，第一个为每行item数量        layoutmanager = linearLayoutManager;  //默认为纵向的Recyclerview；        initData();    }    @Override    public boolean onCreateOptionsMenu(Menu item) {        getMenuInflater().inflate(R.menu.main_menu, item);        return true;    }    @Override    public boolean onOptionsItemSelected(MenuItem item) {        switch (item.getItemId()) {            case R.id.linearlayout:                layoutmanager = linearLayoutManager;                initData();                break;            case R.id.gridlayout:                layoutmanager = gridLayoutManager;                break;            case R.id.staggeredgridlayout:                layoutmanager = staggeredGridLayoutManager;                initData();                break;            default:                layoutmanager = linearLayoutManager;                initData();                break;        }        return super.onOptionsItemSelected(item);    }    /**     * 请求数据     */    private void initData() {        //假设联网请求数据N条,这里我就用本地数据        data = new ArrayList<>();        for (int i = 0; i < 40; i++) {            data.add(i + ". 成功请求数据");        }        recyclerview.setLayoutManager(layoutmanager);        adapter = new Adapter(MainActivity.this, data);        recyclerview.setHasFixedSize(true);        recyclerview.setAdapter(adapter);    }}

默认的LayoutManager

LayoutManager==LinearLayoutManager.png

那么切换LayoutManager为GridLayoutManager，效果会是什么样呢

LayoutManager为GridLayoutManager.png

最后，切换到瀑布流

LayoutManager为StaggeredGridLayoutManager.png

什么效果都没有，这是为什么呢，因为，设置瀑布流，我们需要对item的间隙进行设置，不然没有效果
首先自定义ItemDecoration

public class ItemDecoration extends RecyclerView.ItemDecoration {    private int space;    public ItemDecoration(int space) {        this.space = space;    }    @Override    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {        outRect.left = space;        outRect.right = space;        outRect.bottom = space;        if (parent.getChildAdapterPosition(view) == 0) {            outRect.top = space;        }    }}

设置间隙

     * 请求数据     */    private void initData() {        //假设联网请求数据N条,这里我就用本地数据        data = new ArrayList<>();        for (int i = 0; i < 40; i++) {            data.add(i + ". 成功请求数据");        }        recyclerview.setLayoutManager(layoutmanager);        if(layoutmanager.equals(staggeredGridLayoutManager)) {   //针对瀑布流，设置间隙            recyclerview.addItemDecoration(new ItemDecoration(15));        }        adapter = new Adapter(MainActivity.this, data);        recyclerview.setHasFixedSize(true);        recyclerview.setAdapter(adapter);    }

重新编译运行，搞定

瀑布流效果.png

这算是Recyclerview的简单使用，实现三种模式，已经搞定，还有很多细节，留到下一篇，仔细讲解。