RecyclerView中item點選事件
阿新 • • 發佈:2019-02-10
自從Google推出RecyclerView後,它就成為"寵兒",自定義外掛式的元件用起來很爽。但是很遺憾的是,Google並沒有給我們提供item的點選事件函式,但是我們可以類似ListView的item點選事件來構造出我們自己的RecyclerView item的點選事件。首先我們看ListView如何用setOnItemClickListener()方法實現item的點選事件的呢,搞明白這個問題,我們還得去看ListView原始碼,開啟原始碼發現,查詢該方法,竟然查不到,是不是它父類AbsListView中的函式呢,其實也不是的。原來setOnItemClickListener()是AdapterView類中的方法,終於理清楚了關係:
ListView extends AbsListView
abstract class AbsListView extends AdapterView<ListAdapter> implements XXXXX
abstract class AdapterView<T extends Adapter> extends ViewGroup
abstract class ViewGroup extends View implements ViewParent, ViewManager
上面簡單給出了ListView類"祖宗"幾代的關係圖,原來ListView就是個View,哈哈,廢話不多說了,感興趣的朋友可以自己看原始碼。
那麼我們瞧瞧setOnItemClickListener()是如何實現的呢?
public interface OnItemClickListener { /** * Callback method to be invoked when an item in this AdapterView has * been clicked. * <p> * Implementers can call getItemAtPosition(position) if they need * to access the data associated with the selected item. * * @param parent The AdapterView where the click happened. * @param view The view within the AdapterView that was clicked (this * will be a view provided by the adapter) * @param position The position of the view in the adapter. * @param id The row id of the item that was clicked. */ void onItemClick(AdapterView<?> parent, View view, int position, long id); } /** * Register a callback to be invoked when an item in this AdapterView has * been clicked. * * @param listener The callback that will be invoked. */ public void setOnItemClickListener(@Nullable OnItemClickListener listener) { mOnItemClickListener = listener; }
從上的原始碼中,可以找到,用到的是介面回撥來完成的。上面的註釋說明的太清楚了,不忍心刪除因為我沒有註釋說的好。
下面給出ListView物件變數如何實現item點選事件的:
listView.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> arg0,View view,final int index,long arg3){
/*
*呼叫者具體的實現邏輯
*/
}
});
原來就是這樣實現的啊!現在是不是很明白了呢?
說了那麼多,接下來我們實戰吧!
在開始之前,看下最終demo實現的效果:
上面每一個item都是一個卡片狀,而且點選的時候還有水波紋效果,實現上面的效果用到CardView,下面也會簡單的介紹CardView使用。
我們item佈局檔案list_text.xml:(主要就是顯示文字,佈局比較簡單)
<android.support.v7.widget.CardView xmlns:card_view="http://schemas.android.com/apk/res-auto" android:id="@+id/card_view" android:layout_width="match_parent" android:layout_height="match_parent" card_view:cardBackgroundColor="@color/pink" android:layout_marginLeft="@dimen/activity_horizontal_margin" android:layout_marginRight="@dimen/activity_horizontal_margin" android:layout_marginTop="5dp" android:layout_marginBottom="15dp" card_view:cardCornerRadius="10dp" card_view:cardElevation="10dp" android:foreground="@drawable/rippler" xmlns:android="http://schemas.android.com/apk/res/android"> <TextView android:id="@+id/text" android:layout_width="match_parent" android:gravity="center" android:textSize="50sp" android:layout_height="wrap_content" /> </android.support.v7.widget.CardView>
主佈局檔案activity_main.xml:
<RelativeLayout 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.support.v7.widget.RecyclerView android:id="@+id/recycler_view" android:layout_width="match_parent" android:layout_height="match_parent"/> </RelativeLayout>
下面就是編寫程式碼了,為了方便,全部放在一個類中了:
public class MainActivity extends Activity { private ArrayList<String> array = new ArrayList<String>(); private RecyclerView recycler; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); initdata(); recycler = (RecyclerView)findViewById(R.id.recycler_view); LinearLayoutManager layout = new LinearLayoutManager(this); recycler.setLayoutManager(layout); MyAdapter adapter = new MyAdapter(); recycler.setAdapter(adapter);
<span style="font-size: 11.3pt;"> </span><span style="font-family: Consolas; font-size: 11.3pt;">adapter.setOnItemClickListener(new onRecyclerViewItemClickListener(){</span>
@Override
public void onItemClick(View view,String data){
Toast.makeText(MainActivity.this,"你好,我是"+data, Toast.LENGTH_SHORT).show();
}});
}
public void initdata(){
for(char i='a';i<='z';i++){
array.add(String.valueOf(i));
System.out.print(i);
}
}
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder>{
private onRecyclerViewItemClickListener itemClickListener = null;
@Override
public int getItemCount() {
// TODO 自動生成的方法存根
return array.size();
}
public void onBindViewHolder(ViewHolder viewholder, int position) { //為item佈局中的控制元件設定數值
// TODO 自動生成的方法存根
viewholder.textview.setText(array.get(position));
viewholder.itemView.setTag(viewholder.textview.getText());
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup viewgroup, int position) {
// TODO 自動生成的方法存根
View view = LayoutInflater.from(viewgroup.getContext()).inflate(R.layout.list_text,viewgroup,false); //獲取item的佈局
view.setOnClickListener(new OnClickListener() { //為每一個item繫結監聽
@Override
public void onClick(View v) {
// TODO 自動生成的方法存根
if (itemClickListener != null)<span style="font-family: Consolas; font-size: 11.3pt;"> </span>
itemClickListener.onItemClick(v,(String)v.getTag());
}
}
});
return new ViewHolder(view);
}
public class ViewHolder extends RecyclerView.ViewHolder{ //獲取item中的控制元件
private TextView textview;
public ViewHolder(View itemView) {
super(itemView);
// TODO 自動生成的建構函式存根
textview = (TextView)itemView.findViewById(R.id.text);
}
}
public void setOnItemClickListener(onRecyclerViewItemClickListener listener) {
this.itemClickListener = listener;
// Log.d("ddd", itemClickListener.toString());
}
}
public interface onRecyclerViewItemClickListener {
void onItemClick(View v, String tag);
}
}
看下上面的效果吧:
有朋友會問,怎麼少了item之間的分隔條啊,對,下面我們就把分隔條畫出來。說到這裡感覺本篇介紹的有點多,不過後面也會陸續介紹。
public class Dividerlios extends RecyclerView.ItemDecoration{
private final static int ARRAS[] = {android.R.attr.listDivider};//使用系統提供的分隔條 當然也可以自己繪製
private Drawable drawDivider;
public Dividerlios(Context context){
TypedArray a = context.obtainStyledAttributes(ARRAS);
drawDivider = a.getDrawable(0);
a.recycle();
}
public void onDrawOver(Canvas canvas,RecyclerView recyclerView){ //在canvas上畫分隔條,要獲得分隔條的座標
int left = recyclerView.getPaddingLeft();
int right = recyclerView.getWidth() - recyclerView.getPaddingRight();
int childCount = recyclerView.getChildCount();
for(int i=0;i<childCount;i++){ //繪製全部的分隔條
View child = recyclerView.getChildAt(i);
RecyclerView.LayoutParams parame = (RecyclerView.LayoutParams)child.getLayoutParams();
int top = child.getBottom() + parame.bottomMargin;
int bottom = top + drawDivider.getIntrinsicHeight();
drawDivider.setBounds(left, top, right, bottom);
drawDivider.draw(canvas);
}
}
}
在MainActivity.java中新增:
Dividerlios divider= new Dividerlios(MainActivity.this);
recycler.addItemDecoration(divider);
然後上面的分割線效果就出來了。感興趣朋友可以自己繪製分割線。
下面簡單說明下,item裡實現波紋和前景色變化,可以我們自定義drawable資原始檔。
selecter.xml:
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_pressed="true">
<shape android:shape="rectangle">
<solid android:color="#18ffc400"/>
</shape>
</item>
<item android:state_focused="true"
android:state_enabled="true">
<shape android:shape="rectangle">
<solid android:color="#0f000000"/>
</shape>
</item>
rippler.xml:
<?xml version="1.0" encoding="utf-8"?>
<ripple xmlns:android="http://schemas.android.com/apk/res/android"
android:color="#20000000"
android:drawable="@drawable/<span style="font-family: Consolas; font-size: 15.0667px; white-space: pre;">selecter.xml</span>" />
關於上面drawable資源如何使用,後面的文章會說明。這裡不再說明。
很久沒更新部落格,寫部落格主要為了鞏固知識,如果能幫助到需要的朋友,我會非常開心。
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