RecyclerView - 在特定位置获取视图
Vam*_*lla 123 java android position widget android-recyclerview
我有一个RecyclerView和一个活动ImageView.我正在使用它RecyclerView来水平显示图像列表.当我在点击图片RecyclerView将ImageView在活动中应显示图像的大局观.到目前为止一切正常.
现在活动还有两个ImageButtons:imageButton_left和imageButton_right.当我点击时imageButton_left,该图像ImageView应向左转,并且该缩略图RecyclerView应反映此更改.情况类似imageButton_right.
我能够旋转ImageView.但是,我怎么能旋转缩略图RecyclerView？我如何获得ViewHolder的ImageView？
码:
活动XML:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.v7.widget.RecyclerView
android:id="@+id/recyclerview"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:orientation="vertical">
<ImageView
android:id="@+id/original_image"
android:layout_width="200dp"
android:layout_height="200dp"
android:scaleType="fitXY"
android:src="@drawable/image_not_available_2" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="10dp"
android:gravity="center_horizontal"
android:orientation="horizontal">
<ImageButton
android:id="@+id/imageButton_left"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="20dp"
android:background="@drawable/rotate_left_icon" />
<ImageButton
android:id="@+id/imageButton_right"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@drawable/rotate_right_icon" />
</LinearLayout>
</LinearLayout>
</LinearLayout>
我的活动代码:
public class SecondActivity extends AppCompatActivity implements IRecyclerViewClickListener {
RecyclerView mRecyclerView;
LinearLayoutManager mLayoutManager;
RecyclerViewAdapter mRecyclerViewAdapter;
List<String> urls = new ArrayList<String>();
ImageView mOriginalImageView;
ImageButton mLeftRotate, mRightRotate;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
urls.clear();
mRecyclerView = (RecyclerView) findViewById(R.id.recyclerview);
mLayoutManager = new LinearLayoutManager(this, android.support.v7.widget.LinearLayoutManager.HORIZONTAL, false);
mLayoutManager.setOrientation(android.support.v7.widget.LinearLayoutManager.HORIZONTAL);
mRecyclerView.setLayoutManager(mLayoutManager);
mRecyclerViewAdapter = new RecyclerViewAdapter(this, urls);
mRecyclerView.setAdapter(mRecyclerViewAdapter);
mOriginalImageView = (ImageView) findViewById(R.id.original_image);
mLeftRotate = (ImageButton) findViewById(R.id.imageButton_left);
mLeftRotate.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mOriginalImageView.setRotation(mOriginalImageView.getRotation() - 90);
}
});
mRightRotate = (ImageButton) findViewById(R.id.imageButton_right);
mRightRotate.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mOriginalImageView.setRotation(mOriginalImageView.getRotation() + 90);
}
});
Intent intent = getIntent();
if (intent != null) {
String portfolio = intent.getStringExtra("portfolio");
try {
JSONArray jsonArray = new JSONArray(portfolio);
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject = jsonArray.getJSONObject(i);
String url = jsonObject.getString("url");
urls.add(url);
}
Log.d(Const.DEBUG, "URLs: " + urls.toString());
mRecyclerViewAdapter.notifyDataSetChanged();
} catch (Exception e) {
e.printStackTrace();
}
}
}
@Override
public void onItemClick(int position) {
Picasso.with(this).load(urls.get(position)).into(mOriginalImageView);
}
}
我的RecyclerView自定义适配器:
public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder> {
Context context;
List<String> mUrls = new ArrayList<String>();
IRecyclerViewClickListener mIRecyclerViewClickListener;
public int position;
public int getPosition() {
return position;
}
public void setPosition(int position) {
this.position = position;
}
public RecyclerViewAdapter(Context context, List<String> urls) {
this.context = context;
this.mUrls.clear();
this.mUrls = urls;
Log.d(Const.DEBUG, "Urls Size: " + urls.size());
Log.d(Const.DEBUG, urls.toString());
if (context instanceof IRecyclerViewClickListener)
mIRecyclerViewClickListener = (IRecyclerViewClickListener) context;
else
Log.d(Const.DEBUG, "Implement IRecyclerViewClickListener in Activity");
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(context).inflate(R.layout.item_horizontal_recyclerview, parent, false);
ViewHolder holder = new ViewHolder(view);
return holder;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
Picasso.with(context).load(mUrls.get(position)).into(holder.mImageView);
}
@Override
public int getItemCount() {
return mUrls.size();
}
public void rotateThumbnail() {
}
public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
public ImageView mImageView;
public View v;
public ViewHolder(View v) {
super(v);
v.setTag(getAdapterPosition());
v.setOnClickListener(this);
this.mImageView = (ImageView) v.findViewById(R.id.image);
}
@Override
public void onClick(View v) {
this.v = v;
mIRecyclerViewClickListener.onItemClick(getAdapterPosition());
}
}
}
Sco*_*ggs 216
这就是你要找的东西.
我也有这个问题.和你一样,答案很难找到.但是有一种简单的方法可以将ViewHolder从特定的位置获得(你可能会在适配器中做很多事情).
myRecyclerView.findViewHolderForAdapterPosition(pos);
注意: 如果View已被回收,则会返回null.感谢迈克尔迅速抓住我的重要遗漏.
- 但是,如果你试图引用的`ViewHolder`被"回收",它将返回`null`. (8认同)
- 这正是我在LayoutManager中寻找的东西 (3认同)
- @Michael，赶上！这是对所有人的警告，请先测试null（是的，就像Android中的所有其他功能一样）！ (2认同)
- 我们可以从适配器内部执行此操作吗？ (2认同)
- @Mauker：您可以从任何可以访问RecyclerView实例的对象中使用它。 (2认同)
sta*_*an0 132
我想你用a LinearLayoutManager来显示列表.它有一个叫做不错的方法findViewByPosition是
查找表示给定适配器位置的视图.
您所需要的只是您感兴趣的项目的适配器位置.
编辑:正如Paul Woitaschek在评论中所指出的,它findViewByPosition是一种方法,LayoutManager它可以与所有LayoutManagers(即StaggeredGridLayoutManager等)一起使用
- 这实际上是`LayoutManager`的一种方法,所以这适用于所有LayoutManager子类. (7认同)
- 返回： View--代表给定位置的子视图，如果位置没有布局则为null...recyclerview-->大多数东西返回null (3认同)
Hor*_*tio 22
如果你想要View,请确保访问itemViewViewHolder 的属性,如下所示:myRecyclerView.findViewHolderForAdapterPosition(pos).itemView;
Vik*_*ari 11
你可以使用两者
recyclerViewInstance.findViewHolderForAdapterPosition(adapterPosition) 和
recyclerViewInstance.findViewHolderForLayoutPosition(layoutPosition).确保RecyclerView视图使用两种类型的位置
适配器位置:项目在适配器中的位置.这是从Adapter的角度来看的位置.布局位置:项目在最新布局计算中的位置.这是从LayoutManager的角度来看的位置.你应该使用getAdapterPosition()for findViewHolderForAdapterPosition(adapterPosition)和getLayoutPosition()for findViewHolderForLayoutPosition(layoutPosition).
获取成员变量以保留recyclelerview适配器和其他成员变量中先前选择的项目位置,以检查用户是否第一次单击.
附上示例代码和屏幕截图,以获取更多信息.
public class MainActivity extends AppCompatActivity {
private RecyclerView mRecyclerList = null;
private RecyclerAdapter adapter = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mRecyclerList = (RecyclerView) findViewById(R.id.recyclerList);
}
@Override
protected void onStart() {
RecyclerView.LayoutManager layoutManager = null;
String[] daysArray = new String[15];
String[] datesArray = new String[15];
super.onStart();
for (int i = 0; i < daysArray.length; i++){
daysArray[i] = "Sunday";
datesArray[i] = "12 Feb 2017";
}
adapter = new RecyclerAdapter(mRecyclerList, daysArray, datesArray);
layoutManager = new LinearLayoutManager(MainActivity.this);
mRecyclerList.setAdapter(adapter);
mRecyclerList.setLayoutManager(layoutManager);
}
}
public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.MyCardViewHolder>{
private final String TAG = "RecyclerAdapter";
private Context mContext = null;
private TextView mDaysTxt = null, mDateTxt = null;
private LinearLayout mDateContainerLayout = null;
private String[] daysArray = null, datesArray = null;
private RecyclerView mRecyclerList = null;
private int previousPosition = 0;
private boolean flagFirstItemSelected = false;
public RecyclerAdapter(RecyclerView mRecyclerList, String[] daysArray, String[] datesArray){
this.mRecyclerList = mRecyclerList;
this.daysArray = daysArray;
this.datesArray = datesArray;
}
@Override
public MyCardViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
LayoutInflater layoutInflater = null;
View view = null;
MyCardViewHolder cardViewHolder = null;
mContext = parent.getContext();
layoutInflater = LayoutInflater.from(mContext);
view = layoutInflater.inflate(R.layout.date_card_row, parent, false);
cardViewHolder = new MyCardViewHolder(view);
return cardViewHolder;
}
@Override
public void onBindViewHolder(MyCardViewHolder holder, final int position) {
mDaysTxt = holder.mDaysTxt;
mDateTxt = holder.mDateTxt;
mDateContainerLayout = holder.mDateContainerLayout;
mDaysTxt.setText(daysArray[position]);
mDateTxt.setText(datesArray[position]);
if (!flagFirstItemSelected){
mDateContainerLayout.setBackgroundColor(Color.GREEN);
flagFirstItemSelected = true;
}else {
mDateContainerLayout.setBackground(null);
}
}
@Override
public int getItemCount() {
return daysArray.length;
}
class MyCardViewHolder extends RecyclerView.ViewHolder{
TextView mDaysTxt = null, mDateTxt = null;
LinearLayout mDateContainerLayout = null;
LinearLayout linearLayout = null;
View view = null;
MyCardViewHolder myCardViewHolder = null;
public MyCardViewHolder(View itemView) {
super(itemView);
mDaysTxt = (TextView) itemView.findViewById(R.id.daysTxt);
mDateTxt = (TextView) itemView.findViewById(R.id.dateTxt);
mDateContainerLayout = (LinearLayout) itemView.findViewById(R.id.dateContainerLayout);
mDateContainerLayout.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
LinearLayout linearLayout = null;
View view = null;
if (getAdapterPosition() == previousPosition){
view = mRecyclerList.findViewHolderForAdapterPosition(previousPosition).itemView;
linearLayout = (LinearLayout) view.findViewById(R.id.dateContainerLayout);
linearLayout.setBackgroundColor(Color.GREEN);
previousPosition = getAdapterPosition();
}else {
view = mRecyclerList.findViewHolderForAdapterPosition(previousPosition).itemView;
linearLayout = (LinearLayout) view.findViewById(R.id.dateContainerLayout);
linearLayout.setBackground(null);
view = mRecyclerList.findViewHolderForAdapterPosition(getAdapterPosition()).itemView;
linearLayout = (LinearLayout) view.findViewById(R.id.dateContainerLayout);
linearLayout.setBackgroundColor(Color.GREEN);
previousPosition = getAdapterPosition();
}
}
});
}
}
}
- 在这里，当我尝试更改前一项的颜色时，我在 else 块中收到 NullPointer 异常，所以我添加了空检查，现在如果它有 NullPointer 异常，它永远不会进入该块，所以以前的项目颜色永远不会改变。现在我的 Recycler 视图有多个颜色的项目。我该如何解决这个问题 (2认同)
您可以创建ViewHolder的ArrayList:
ArrayList<MyViewHolder> myViewHolders = new ArrayList<>();
ArrayList<MyViewHolder> myViewHolders2 = new ArrayList<>();
并且,列表中的所有商店ViewHolder如下:
@Override
public void onBindViewHolder(@NonNull final MyViewHolder holder, final int position) {
final String str = arrayList.get(position);
myViewHolders.add(position,holder);
}
并根据您的要求在ArrayList中添加/删除其他ViewHolder.
小智 6
您可以使用以下方法获取回收站视图上特定位置的视图
int position = 2;
RecyclerView.ViewHolder viewHolder = recyclerview.findViewHolderForItemId(position);
View view = viewHolder.itemView;
ImageView imageView = (ImageView)view.findViewById(R.id.imageView);
请记住，您必须等到适配器添加到列表中，然后才能尝试按位置获取视图
final int i = 0;
recyclerView.setAdapter(adapter);
recyclerView.post(new Runnable() {
@Override
public void run() {
View view = recyclerView.getLayoutManager().findViewByPosition(i);
}
});
- 如果您添加多个项目（即：如果您有一个可以添加它们并快速按下的按钮），则这并不总是有效。您应该延迟添加可运行程序。 (2认同)
您可以简单地使用回收者视图的“ findViewHolderForAdapterPosition ”方法，然后从中获得一个viewHolder对象，然后将该视图持有者转换为适配器视图持有者，以便您可以直接访问您的视图持有者的视图
以下是kotlin的示例代码
val viewHolder = recyclerView.findViewHolderForAdapterPosition(position)
val textview=(viewHolder as YourViewHolder).yourTextView
小智 5
要从 recyclerView 的特定位置获取视图，您需要在将返回 RecyclerView.ViewHolder 的 recyclerView 对象上调用 findViewHolderForAdapterPosition(position)
从返回的 RecyclerView.ViewHolder 对象和 itemView 您可以访问该特定位置的所有视图
RecyclerView.ViewHolder rv_view = recyclerView.findViewHolderForAdapterPosition(position);
ImageView iv_wish = rv_view.itemView.findViewById(R.id.iv_item);
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