标签：android listview recyclerview
RecyclerView是android5.0提供的新组件（最新的support.v7中也提供了该组件），类似于ListView，但是比ListView更灵活、更先进，我觉得主要表现在以下几个方面：
1、 把ViewHolder的实现封装起来，规范了ViewHolder，把item的view写入ViewHolder中，通过复用ViewHolder来实现view的复用。
2、 RecyclerView.Adapter中把view的回收和内容改变等操作分开解耦了，比传统的Adapter更为灵活。
3、 独立的LayoutManager，可以灵活的控制RecyclerView中items的布局：LinearLayoutManager（垂直布局、水平布局）、GridLayoutManager（网格布局）、StaggeredGridLayoutManager（瀑布流布局）；
4、 提供了RecyclerView.ItemAnimator可以设置items增加、删除时的动画（默认已有定义了动画）；
下面通过官方例子来看一下RecyclerView的使用。
1、 布局文件xml的编写，没什么好说的。
<android.support.v7.widget.RecyclerView
android:id="@+id/my_recycler_view"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
2、在activity中使用RecyclerView
public class MyActivity extends Activity {
private RecyclerView mRecyclerView;
private RecyclerView.Adapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.my_activity);
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);
}
...
}
代码很简单，看一下我们使用到RecyclerView的几个地方：首先是mRecyclerView.setHasFixedSize(true)，从上面的注释可以知道，如果item的内容不改变view布局大小，那使用这个设置可以提高RecyclerView的效率。接着再看mLayoutManager = new LinearLayoutManager(this);mRecyclerView.setLayoutManager(mLayoutManager)，这里就使用LayoutManager来控制item的排列方式，这里用的是LinearLayoutManager，也就是线性布局，默认是垂直布局，如果要设置成水平布局，只需在把new LinearLayoutManager(this)改成newLinearLayoutManager(this,LinearLayoutManager.HORIZONTAL,false)就可以了，最后一项如果为true的话，item会反向排列。
3、编写Adapter
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;
}
}
首先看一下ViewHolder，这里不再是自己随便定义的ViewHolder了，而是继承了RecyclerView.ViewHolder，规范了ViewHolder。不同于传统的Adapter，这里没有getView，取而代之的是onCreateViewHolder和onBindViewHolder，把view的复用和数据的绑定解耦开了。
上面就是官方的简单例子，接下来我们来实现两个比较常用的功能，item的点击和上拉加载。
RecyclerView并没有提供item的点击事件，这也让我们有了多种实现方式，不管什么方式，归根到底就是对view的点击事件。我们可以在Adapter中添加对view的点击事件，有两个地方可以添加，大家看哪种方法更好。
1、 在ViewHolder中添加。
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;
v. setOnClickListener….
}
}
2、 在onBindViewHolder中添加。
@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]);
holder.itemView.setOnClickListener…;
}
再来看看上拉加载更多，我觉得最好的方法就是在onBindViewHolder添加对上拉加载事件的判断，因为如果用传统的监听scroll的方法来做的话，那么如果我改变了LayoutManager，从垂直线性布局改成水平线性布局，或者从线性布局改成网格布局，那么对scroll监听的方法又得重新写了。下面看下具体的写法。
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
if (position == list.size() - 1&&onLoadListener!=null&&(list.size()%limit)==0) {
onLoadListener.load();
Log.i("zhuang","触发");
}
}
如果当前绑定的ViewHolder的position是最后一项，则触发加载更多。这里的onLoadListener是我自定义加载接口
public interface OnLoadListener {
public void load();
}
在Adapter中定义OnLoadListener变量，然后生成get和set方法，我们在activity中可以通过adapter.setOnLoadListener来为加载更多设置加载的具体实现。(list.size()%limit)==0)中的limit是每次加载的item数量，如果list.size()%limit)==0，表示每次从服务器加载的item数和我们请求的item数是一样的，证明还有其他记录，再次把list拉到最后面的item时，我们可以继续触发load方法，如果list.size()%limit)!=0，则说明我们从服务器加载过来的item数和我们请求的item数不一样，那么证明数据已经全部都加载完了，没必要再次请求了，就算list拉到最后一项，也不再请求。当然还有一种情况就是加载的数据数和我们请求的数据数是一样的，而刚好也请求完所有数据，这时候我们上拉到最后一项时，还会再触发一次加载。
下面贴上稍微完整的代码
OnLoadListener：
public interface OnLoadListener {
public void load();
}
MyActivity
public class MyActivity extends Activity {
private RecyclerView mRecyclerView;
private RecyclerView.Adapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
private String[] myDataset = {...};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.my_activity);
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,limit);
mAdapter.setOnLoadListener(new OnLoadListener() {
@Override
public void load() {
...
}
});
mRecyclerView.setAdapter(mAdapter);
}
...
}
MyAdapter：
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
private String[] mDataset;
private OnLoadListener onLoadListener;
private int limit;
// 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,int limit) {
this.mDataset = myDataset;
this.limit = limit;
}
// 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]);
holder.itemView.setOnClickListener(...);
if (position == list.size() - 1&&onLoadListener!=null&&(list.size()%limit)==0) {
onLoadListener.load();
Log.i("zhuang","触发");
}
}
// Return the size of your dataset (invoked by the layout manager)
@Override
public int getItemCount() {
return mDataset.length;
}
}
标签：android listview recyclerview
原文地址：http://blog.csdn.net/weihuangcool/article/details/46238063
