RecyclerView动态添加、删除及点击事件
上一节讲解了RecyclerView的三种显示方式，本节将主要研究一下RecyclerView的动态添加、删除及其单击和长按事件的处理。我们在上一节代码的基础上进行相关操作。
一、修改适配器类MyAdapter，加入添加和删除这两个方法：
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
private Context context;
private List<String> datas;
private List<Integer> mHights;
public MyAdapter(Context context,List<String> datas){
this.context=context;
this.datas=datas;
mHights=new ArrayList<>();
for (int i=0;i<datas.size();i++){
mHights.add((int)(50+Math.random()*300));
}
}
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
MyViewHolder holder = new MyViewHolder(LayoutInflater.from(
context).inflate(R.layout.item, parent,
false));
return holder;
}
@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
ViewGroup.LayoutParams layoutparams= holder.itemView.getLayoutParams();
layoutparams.height=mHights.get(position);
holder.itemView.setLayoutParams(layoutparams);
holder.tv.setText(datas.get(position));
}
@Override
public int getItemCount() {
return datas.size();
}
public void addItem(int position){
datas.add(position,"新加项");
notifyItemInserted(position);
}
public void removeItem(int position){
datas.remove(position);
notifyItemRemoved(position);
}
class MyViewHolder extends RecyclerView.ViewHolder {
TextView tv;
public MyViewHolder(View view) {
super(view);
tv = (TextView) view.findViewById(R.id.id_num);
}
}
}二、在MainActivity中添加两个菜单按钮，对应添加和删除方法：
public class MainActivity extends Activity {
private RecyclerView mRecyclerView;
private List<String> mDatas;
private MyAdapter myAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initData();
mRecyclerView = (RecyclerView) findViewById(R.id.recycleview);
mRecyclerView.setLayoutManager(new StaggeredGridLayoutManager(4,StaggeredGridLayoutManager.VERTICAL));
myAdapter = new MyAdapter(this, mDatas);
mRecyclerView.setAdapter(myAdapter);
mRecyclerView.addItemDecoration(new DividerGridItemDecoration(this));
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
}
protected void initData() {
mDatas = new ArrayList<String>();
for (int i = 1; i < 100; i++) {
mDatas.add("" + i);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
menu.add(1,1,1,"添加");
menu.add(1,2,2,"删除");
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item)
{
switch (item.getItemId())
{
case 1:
myAdapter.addItem(1);
break;
case 2:
myAdapter.removeItem(1);
break;
}
return true;
}
}调用了setItemAnimator方法，传入系统默认的动画对象进行“添加或删除Item”动画的添加。编写了两个菜单按钮，单击添加按钮时，在positon为1的位置添加一个Item，单击删除按钮，删除position为1的Item 。 运行实例如下：
单击添加按钮时，添加了一个新加项，单击删除按钮时，这个新加项被删除。
RecyclerView没有提供单击监听和长按监听，需要我们自己实现，这里采用回调接口的方法实现这两个监听。
修改适配器类文件MyAdapter，添加一个接口，接口中定义两个方法：
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
private Context context;
private List<String> datas;
private List<Integer> mHights;
public interface onItemClickListener{
void onItemClick(View view ,int position);
void onItemLongClick(View view,int position);
}
private onItemClickListener onItemClickListener;
public void setOnItemClickListener(onItemClickListener onItemClickListener){
this.onItemClickListener=onItemClickListener;
}
public MyAdapter(Context context,List<String> datas){
this.context=context;
this.datas=datas;
mHights=new ArrayList<>();
for (int i=0;i<datas.size();i++){
mHights.add((int)(50+Math.random()*300));
}
}
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
MyViewHolder holder = new MyViewHolder(LayoutInflater.from(
context).inflate(R.layout.item, parent,
false));
return holder;
}
@Override
public void onBindViewHolder(final MyViewHolder holder, final int position) {
ViewGroup.LayoutParams layoutparams= holder.itemView.getLayoutParams();
layoutparams.height=mHights.get(position);
holder.itemView.setLayoutParams(layoutparams);
holder.tv.setText(datas.get(position));
if(onItemClickListener!=null){
holder.itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int layoutPos=holder.getLayoutPosition();
onItemClickListener.onItemClick(holder.itemView,layoutPos);
}
});
holder.itemView.setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View v) {
int layoutPos=holder.getLayoutPosition();
onItemClickListener.onItemLongClick(holder.itemView,layoutPos);
return false;
}
});
}
}
@Override
public int getItemCount() {
return datas.size();
}
public void addItem(int position){
datas.add(position,"新加项");
notifyItemInserted(position);
}
public void removeItem(int position){
datas.remove(position);
notifyItemRemoved(position);
}
class MyViewHolder extends RecyclerView.ViewHolder {
TextView tv;
public MyViewHolder(View view) {
super(view);
tv = (TextView) view.findViewById(R.id.id_num);
}
}
}这里采用了回调函数的方法，实现RecyclerView子Item的单击和长按监听。为了保证动态添加和删除时position值的正确性，我们使用了getLayoutPosition方法获得position，这里要注意。
MainActivity中也添加了一些代码如下：
public class MainActivity extends Activity {
private RecyclerView mRecyclerView;
private List<String> mDatas;
private MyAdapter myAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initData();
mRecyclerView = (RecyclerView) findViewById(R.id.recycleview);
mRecyclerView.setLayoutManager(new StaggeredGridLayoutManager(4,StaggeredGridLayoutManager.VERTICAL));
myAdapter = new MyAdapter(this, mDatas);
mRecyclerView.setAdapter(myAdapter);
mRecyclerView.addItemDecoration(new DividerGridItemDecoration(this));
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
myAdapter.setOnItemClickListener(new MyAdapter.onItemClickListener() {
@Override
public void onItemClick(View view, int position) {
Toast.makeText(MainActivity.this,"onClick"+position,Toast.LENGTH_SHORT).show();
}
@Override
public void onItemLongClick(View view, int position) {
Toast.makeText(MainActivity.this,"onLongClick"+position,Toast.LENGTH_SHORT).show();
}
});
}
protected void initData() {
mDatas = new ArrayList<String>();
for (int i = 1; i < 100; i++) {
mDatas.add("" + i);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
menu.add(1,1,1,"添加");
menu.add(1,2,2,"删除");
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item)
{
switch (item.getItemId())
{
case 1:
myAdapter.addItem(1);
break;
case 2:
myAdapter.removeItem(1);
break;
}
return true;
}
}在对应的匿名内部类方法里写入了对应的Toast，用于测试是否正确，运行项目实例：
单击新加项Toast出了onClick1，长按新加项Toast出了onLongClick1。这时可能有同学会注意到一个问题，在Toast出onLongClick1后还Toast了一个onClick1，这时将MyAdapter中的onLongClick方法的返回值改成true即可，这样拦截了单击事件，可以再次运行测试一下。
