參考資源:http://blog.csdn.net/developer_jiangqq/article/details/49992269?hmsr=toutiao.io&utm_medium=toutiao.io&utm_source=toutiao.io
一、為什麼叫RecyclerView?
- 不關注item是否顯示在正确位置,是否顯示正确
- 不關注item是如何分割的,即不關注分割線
- 不關注item增加和删除的動畫效果
- 僅僅關注如何回收和複用itemView
備注
- item的位置是由 LayoutManager 決定的
- item的分割線是由ItemDecoration 決定的
- item的動畫效果是由ItemAnimator 決定的
二、RecyclerView能幹什麼?
![](https://img.laitimes.com/img/9ZDMuAjOiMmIsIjOiQnIsIiN2UTNyczM2EzMyIDM2EDMy8CX0Vmbu4GZzNmLn9Gbi1yZtl2Lc9CX6MHc0RHaiojIsJye.jpg)
三、RecyclerView的相關配置
步驟:Files -> Project Structure ->app(需要關聯的Module) -> Dependencies ->”+”(加号) ->recyclerview-v7(選擇該依賴) -> ok -> ok
備注:使用RecyclerView的時候一定要把包名寫完整,如:
否則不會識别RecyclerView。
四、RecyclerView的實作
1、Just Like ListView(無下拉重新整理和加載更多)
①定義一個分割線:DividerItemDecoration.java
public class DividerItemDecoration extends RecyclerView.ItemDecoration
{
private static final int[] ATTRS = new int[] { android.R.attr.listDivider };
public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;
public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL;
private Drawable mDivider;
private int mOrientation;
public DividerItemDecoration(Context context, int orientation)
{
final TypedArray a = context.obtainStyledAttributes(ATTRS);
mDivider = a.getDrawable();
a.recycle();
setOrientation(orientation);
}
public void setOrientation(int orientation)
{
if (orientation != HORIZONTAL_LIST && orientation != VERTICAL_LIST)
{
throw new IllegalArgumentException("invalid orientation");
}
mOrientation = orientation;
}
@Override
public void onDraw(Canvas c, RecyclerView parent)
{
Log.v("itemdecoration", "onDraw()");
if (mOrientation == VERTICAL_LIST) {
drawVertical(c, parent);
} else {
drawHorizontal(c, parent);
}
}
public void drawVertical(Canvas c, RecyclerView parent)
{
final int left = parent.getPaddingLeft();
final int right = parent.getWidth() - parent.getPaddingRight();
final int childCount = parent.getChildCount();
for (int i = ; i < childCount; i++)
{
final View child = parent.getChildAt(i);
RecyclerView v = new RecyclerView(
parent.getContext());
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
.getLayoutParams();
final int top = child.getBottom() + params.bottomMargin;
final int bottom = top + mDivider.getIntrinsicHeight();
mDivider.setBounds(left, top, right, bottom);
mDivider.draw(c);
}
}
public void drawHorizontal(Canvas c, RecyclerView parent)
{
final int top = parent.getPaddingTop();
final int bottom = parent.getHeight() - parent.getPaddingBottom();
final int childCount = parent.getChildCount();
for (int i = ; i < childCount; i++)
{
final View child = parent.getChildAt(i);
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
.getLayoutParams();
final int left = child.getRight() + params.rightMargin;
final int right = left + mDivider.getIntrinsicHeight();
mDivider.setBounds(left, top, right, bottom);
mDivider.draw(c);
}
}
@Override
public void getItemOffsets(Rect outRect, int itemPosition,
RecyclerView parent)
{
if (mOrientation == VERTICAL_LIST)
{
outRect.set(, , , mDivider.getIntrinsicHeight());
} else
{
outRect.set(, , mDivider.getIntrinsicWidth(), );
}
}
}
②定義Adapter和ViewHolder:
MyViewHolder
public class MyViewHolder extends RecyclerView.ViewHolder {
protected TextView textView;
public MyViewHolder(View itemView) {
super(itemView);
textView = (TextView) itemView.findViewById(R.id.text_view);
}
}
擴充卡:RecyclerViewAdapter
public class RecyclerViewAdapter extends RecyclerView.Adapter<MyViewHolder>{
private Context mContext;
private LayoutInflater mInflater;
private List<String> mDatas;
public RecyclerViewAdapter(Context context,List<String> datas) {
this.mContext = context;
this.mDatas = datas;
mInflater = LayoutInflater.from(mContext);
}
@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
holder.textView.setText(mDatas.get(position));
}
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = mInflater.inflate(R.layout.item,parent,false);
MyViewHolder mMyViewHolder = new MyViewHolder(view);
return mMyViewHolder;
}
@Override
public int getItemCount() {
return mDatas.size();
}
}
③布局檔案:
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#ffffff"
>
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
></android.support.v7.widget.RecyclerView>
</RelativeLayout>
item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="70dp"
android:background="#d1da1b"
>
<TextView
android:id="@+id/text_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textSize="15sp"
android:textColor="#ffffff"
android:gravity="center"
/>
</LinearLayout>
④界面Activity:MainActivity.java
public class MainActivity extends Activity {
private RecyclerView mRecyclerView;
private List<String> mDatas;
private RecyclerViewAdapter mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initDatas();
initView();
mAdapter = new RecyclerViewAdapter(this,mDatas);
mRecyclerView.setAdapter(mAdapter);
LinearLayoutManager mLinearLayoutManager = new LinearLayoutManager(this,LinearLayoutManager.VERTICAL,false);
mRecyclerView.setLayoutManager(mLinearLayoutManager);
mRecyclerView.addItemDecoration(new DividerItemDecoration(this,DividerItemDecoration.VERTICAL_LIST));
}
private void initDatas(){
mDatas = new ArrayList<>();
for (int i = 'A';i<='z';i++){
mDatas.add(""+(char)i);
}
}
private void initView(){
mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);
}
}
到此,ListView的效果就成功地實作了
備注:實作自定義分割線
①在drawable檔案夾下建立一個xml檔案,shape類型的,如下:
divider.xml的内容如下:
②android每個工程都會有一個預設的主題,如:
③在這個主題的styles.xml檔案中添加一個item,如下紅線部分:
android:listDivider與分割線DividerItemDecoration.java檔案中的ATTRS中的元素相對應,android.R.attr.listDivider是android自帶的屬性。
最終效果圖如下:
其他添加分割線:在子布局中添加android:layout_margin=”5dp”屬性,如下:
item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="70dp"
android:background="#d1da1b"
android:layout_margin="5dp"
>
<TextView
android:id="@+id/text_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textSize="15sp"
android:textColor="#ffffff"
android:gravity="center"
/>
</LinearLayout>
這種方法的結果是RecyclerView的背景是什麼顔色,分割線就是什麼顔色,而且item的背景有重複的顔色,性能不太好
RecyclerView使用總結的全部代碼下載下傳請點我
下篇将介紹有下拉重新整理和加載更多的仿ListView的RecyclerView