RecyclerView的简单使用
前言
RecyclerView不仅可以完全取缔ListView和GridView,还可以有很多其他的效果,可以非常炫酷,今天先来记录下最简单的使用.
RecyclerView是自Android 5.0之后才发布的,要使用它要先根据自己sdk的版本进行导包:
compile 'com.android.support:recyclerview-v7:25.3.1'
导包完成后就可以开始使用了.
1.控件使用
RecyclerView是一个控件,它的使用方法跟ListView的用法差不多,直接在布局中使用.
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main2"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="#5555"
tools:context="com.simon.demo.my.Main2Activity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="@+id/add_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="添加item"/>
<Button
android:id="@+id/delete_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="删除item"/>
</LinearLayout>
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:paddingLeft="3dp"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</LinearLayout>
2.Adapter和LayoutManager
在使用RecyclerView时候,必须指定一个适配器Adapter和一个布局管理器LayoutManager。适配器继承RecyclerView.Adapter类,具体实现类似ListView的适配器,取决于数据信息以及展示的UI。布局管理器用于确定RecyclerView中Item的展示方式以及决定何时复用已经不可见的Item,避免重复创建以及执行高成本的findViewById()方法。
①LayoutManager布局管理器
RecyclerView提供了三种布局管理器:
- LinerLayoutManager 以垂直或者水平列表方式展示Item
- GridLayoutManager 以网格方式展示Item
- StaggeredGridLayoutManager 以瀑布流方式展示Item
//这里使用了线性垂直列表
mLinearLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
mRecyclerView.setLayoutManager(mLinearLayoutManager);
②Adapter适配器
创建一个类继承RecyclerView.Adapter
public class RecycleAdapter extends RecyclerView.Adapter<RecycleAdapter.ViewHolder>{
private final Context context;
private final ArrayList<String> mData;
public RecycleAdapter(Context c, ArrayList<String> data){
this.context = c;
this.mData = data;
}
//获取item布局,并创建ViewHolder与之绑定
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
//这里填充的布局root写parent的话,会只显示一个item,改为null后才正常显示
//解决http://blog.csdn.net/fantasiasango/article/details/52188064
//如果用View.inflate填充的布局没有调用到设置的属性
// View view = View.inflate(parent.getContext(), R.layout.view_rv_item, null);
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.view_rv_item, parent, false);
ViewHolder viewHolder = new ViewHolder(view);
return viewHolder;
}
//
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
holder.mTx.setText(mData.get(position));
}
@Override
public int getItemCount() {
return mData.size();
}
public static class ViewHolder extends RecyclerView.ViewHolder{
//有写情况下需要手动设置属性,不然布局会显示不正常
RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
itemView.setLayoutParams(layoutParams);
private final TextView mTx;
public ViewHolder(View itemView) {
super(itemView);
mTx = (TextView) itemView.findViewById(R.id.item_tv);
}
}
}
Activity中使用代码
mRecycleAdapter = new RecycleAdapter(this,getData());
mRecyclerView.setAdapter(mRecycleAdapter);
//模拟数据
private ArrayList<String> getData() {
ArrayList<String> strings = new ArrayList<>();
for(int i = 0; i < 50; i++) {
strings.add("我是超人"+i);
}
return strings;
}
③Decoration修饰器
这是用来自定义RecycleView的样式,decoration的样式可以同时使用多个,不同的decoration效果会重叠起来,从而达到不同的效果.
主要使用的三个方法:
public void onDraw(Canvas c, RecyclerView parent, State state)
public void onDrawOver(Canvas c, RecyclerView parent, State state)
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state)
举例使用:
public class MyItemDecoration extends RecyclerView.ItemDecoration {
private final Paint mPaint;
private final int mDividerHeight;
public MyItemDecoration(Context context) {
mPaint = new Paint();
mPaint.setColor(Color.BLUE);
mDividerHeight = 10;
}
// 这两个方法都是用于绘制间隔样式
@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
super.onDraw(c, parent, state);
}
@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
super.onDrawOver(c, parent, state);
int childCount = parent.getChildCount();
int left = parent.getPaddingLeft();
int right = parent.getWidth() - parent.getPaddingRight();
for (int i = 0; i < childCount - 1; i++) {
View view = parent.getChildAt(i);
int top = view.getBottom();
int bottom = view.getBottom() + 5;
Log.v("cherish233", "left:" + left + "---" + "top:" + top + "---" + "right:" + right + "---" + "bottom:" + bottom + "---");
c.drawRect(left, top, right, bottom, mPaint);
}
// View view = parent.getChildAt(0);
// int top = view.getBottom();
// int bottom = view.getBottom() + mDividerHeight;
// Log.v("cherish233", "left:" + left + "---" + "top:" + top + "---" + "right:" + right + "---" + "bottom:" + bottom + "---");
// c.drawRect(left, top, right, bottom, mPaint);
}
//设置item的偏移量,偏移的部分用于填充间隔样式
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
super.getItemOffsets(outRect, view, parent, state);
outRect.bottom = mDividerHeight;
}
}
在Activity中的使用代码
mMyItemDecoration = new MyItemDecoration(this);
mRecyclerView.addItemDecoration(mMyItemDecoration);
完整的Activity代码:
public class Main2Activity extends AppCompatActivity implements View.OnClickListener {
private Button mAddBtn;
private Button mDeleteBtn;
private RecyclerView mRecyclerView;
private LinearLayout mActivityMain2;
private LinearLayoutManager mLinearLayoutManager;
private RecycleAdapter mRecycleAdapter;
private MyItemDecoration mMyItemDecoration;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
initView();
initData();
}
private void initData() {
mLinearLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
mRecycleAdapter = new RecycleAdapter(this,getData());
mMyItemDecoration = new MyItemDecoration(this);
mRecyclerView.setLayoutManager(mLinearLayoutManager);
mRecyclerView.setAdapter(mRecycleAdapter);
mRecyclerView.addItemDecoration(mMyItemDecoration);
}
//模拟数据
private ArrayList<String> getData() {
ArrayList<String> strings = new ArrayList<>();
for(int i = 0; i < 50; i++) {
strings.add("我是超人"+i);
}
return strings;
}
private void initView() {
mAddBtn = (Button) findViewById(R.id.add_btn);
mAddBtn.setOnClickListener(this);
mDeleteBtn = (Button) findViewById(R.id.delete_btn);
mDeleteBtn.setOnClickListener(this);
mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.add_btn:
break;
case R.id.delete_btn:
break;
}
}
}
最终效果:
3.添加和删除
要想添加和删除数据,只需要在Adapter中添加两个方法
//添加数据
public void addNewItem(){
if(mData == null) {
mData = new ArrayList<>();
}
mData.add(0, "new Item");
//用notifyItemInserted(0)来刷新需要更新的Item,如果用notifyDataSetChanged()没有动画效果
notifyItemInserted(0);
}
//删除数据
public void deleteItem(int position) {
if (mData == null || mData.isEmpty()) {
return;
}
mData.remove(position);
notifyItemRemoved(position);
//删除数据后要进行刷新,否则下次删除的时候position会对应错误
notifyDataSetChanged();
}
然后在你需要的地方进行调用,我是在MainActivity中添加了两个按钮进行简单的添加和删除操作
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.add_btn:
mRecycleAdapter.addNewItem();
//回到第一个Item
mLinearLayoutManager.scrollToPosition(0);
break;
case R.id.delete_btn:
mRecycleAdapter.deleteItem();
mLinearLayoutManager.scrollToPosition(0);
break;
}
}
效果如下:
RecyclerView可以设置列表中Item删除和添加的动画,V7包中提供了一个默认动画,只需设置一下就可以了.
// 设置Item添加和移除的动画
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
效果:
4.点击事件
RecyclerView并没有像ListView一样提供点击事件,需要自己自定义点击事件和长按事件.
通过在绑定ViewHolder的时候设置监听,然后通过Apater回调出去
在Adapter里创建一个监听器,并提供一个方法:
interface OnItemClickListener {
void onClick();
void onLongClick();
}
//设置为全局变量
private OnItemClickListener mOnItemClickListener;
public void setItemClickListener(OnItemClickListener listener) {
mOnItemClickListener = listener;
}
然后对ViewHolder设置监听
@Override
public void onBindViewHolder(ViewHolder holder, final int position) {
Log.v("cherish233","onBindViewHolder:"+position);
holder.mTx.setText(mData.get(position));
holder.itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mOnItemClickListener.onClick(position);
}
});
holder.itemView.setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View v) {
mOnItemClickListener.onLongClick(position);
return true;
}
});
}
设置完监听后,就回到Activity,对Adapter设置监听,并实现方法
//设置点击事件
private void setClickEvent() {
mRecycleAdapter.setItemClickListener(new RecycleAdapter.OnItemClickListener() {
@Override
public void onClick() {
Toast.makeText(getApplicationContext(),"我点击了一下",Toast.LENGTH_SHORT).show();
}
@Override
public void onLongClick() {
Toast.makeText(getApplicationContext(),"我长按了item",Toast.LENGTH_SHORT).show();
}
});
}
现在只是简单睇地介绍了一下,不仅不够完善,而且还有很多效果没有做出来,等有时间再好好研究下.
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