我习惯于在布局文件中放置一个特殊的视图，如ListActivity文档中所述，在没有数据时显示。这个视图的id为“android:id/empty”。
<TextView
android:id="@android:id/empty"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/no_data" />
我想知道这如何能与新的RecyclerView?
当前回答
最简单的解决方案是使用RecyclerView。AdapterDataObserver并在适配器初始化后将其注册到recyclerview中。
val emptyDataObserver = EmptyDataObserver(recycler_view, empty_data_parent)
yourAdapter.registerAdapterDataObserver(emptyDataObserver)
其中，recycler_view & empty_data_parent是布局在你的活动，约束这些视图，你想要的，使其可见性消失。然后用图像和文本创建自己的空数据集视图。
<include
android:id="@+id/empty_data_parent"
layout="@layout/item_empty_dataset"
android:layout_width="match_parent"
android:visibility="gone"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintTop_toBottomOf="parent"
android:layout_height="match_parent"
android:layout_gravity="center" />
下面是empty_data_set_view.xml的示例
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:layout_gravity="center"
android:gravity="center"
android:paddingTop="10dp"
android:paddingBottom="10dp"
tools:ignore="RtlHardcoded">
<ImageView
android:id="@+id/imageView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.498"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.422"
android:src="@drawable/ic_empty_dataset_1" />
<TextView
android:id="@+id/title"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:text="Title is called when title is placed"
android:padding="10dp"
android:fontFamily="@font/normal"
android:textStyle="bold"
android:gravity="center"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/imageView2" />
<TextView
android:id="@+id/sub_title"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:text=" Subtitle is called when title is placed. Subtitle is called when title is placed"
android:padding="5dp"
android:fontFamily="@font/normal"
android:gravity="center"
android:layout_marginStart="10dp"
android:layout_marginEnd="10dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/title" />
</androidx.constraintlayout.widget.ConstraintLayout>
和这个EmptyDataObserver类来做这项工作。
import android.view.View
import androidx.recyclerview.widget.RecyclerView
class EmptyDataObserver constructor(rv: RecyclerView?, ev: View?): RecyclerView.AdapterDataObserver() {
private var emptyView: View? = null
private var recyclerView: RecyclerView? = null
init {
recyclerView = rv
emptyView = ev
checkIfEmpty()
}
private fun checkIfEmpty() {
if (emptyView != null && recyclerView!!.adapter != null) {
val emptyViewVisible = recyclerView!!.adapter!!.itemCount == 0
emptyView!!.visibility = if (emptyViewVisible) View.VISIBLE else View.GONE
recyclerView!!.visibility = if (emptyViewVisible) View.GONE else View.VISIBLE
}
}
override fun onChanged() {
super.onChanged()
checkIfEmpty()
}
override fun onItemRangeChanged(positionStart: Int, itemCount: Int) {
super.onItemRangeChanged(positionStart, itemCount)
}
}
其他回答
我使用ViewSwitcher
<ViewSwitcher
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/switcher"
>
<android.support.v7.widget.RecyclerView
android:id="@+id/list"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
<TextView android:id="@+id/text_empty"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="@string/list_empty"
android:gravity="center"
/>
</ViewSwitcher>
在代码中，您将检查光标/数据集和切换视图。
void showItems(Cursor items) {
if (items.size() > 0) {
mAdapter.switchCursor(items);
if (R.id.list == mListSwitcher.getNextView().getId()) {
mListSwitcher.showNext();
}
} else if (R.id.text_empty == mListSwitcher.getNextView().getId()) {
mListSwitcher.showNext();
}
}
如果你愿意，你也可以用几行代码设置动画
mListSwitcher.setInAnimation(slide_in_left);
mListSwitcher.setOutAnimation(slide_out_right);
对于我的项目，我做了这个解决方案(RecyclerView与setEmptyView方法):
public class RecyclerViewEmptySupport extends RecyclerView {
private View emptyView;
private AdapterDataObserver emptyObserver = new AdapterDataObserver() {
@Override
public void onChanged() {
Adapter<?> adapter = getAdapter();
if(adapter != null && emptyView != null) {
if(adapter.getItemCount() == 0) {
emptyView.setVisibility(View.VISIBLE);
RecyclerViewEmptySupport.this.setVisibility(View.GONE);
}
else {
emptyView.setVisibility(View.GONE);
RecyclerViewEmptySupport.this.setVisibility(View.VISIBLE);
}
}
}
};
public RecyclerViewEmptySupport(Context context) {
super(context);
}
public RecyclerViewEmptySupport(Context context, AttributeSet attrs) {
super(context, attrs);
}
public RecyclerViewEmptySupport(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
@Override
public void setAdapter(Adapter adapter) {
super.setAdapter(adapter);
if(adapter != null) {
adapter.registerAdapterDataObserver(emptyObserver);
}
emptyObserver.onChanged();
}
public void setEmptyView(View emptyView) {
this.emptyView = emptyView;
}
}
你应该使用它来代替RecyclerView类:
<com.maff.utils.RecyclerViewEmptySupport android:id="@+id/list1"
android:layout_height="match_parent"
android:layout_width="match_parent"
/>
<TextView android:id="@+id/list_empty"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Empty"
/>
and
RecyclerViewEmptySupport list =
(RecyclerViewEmptySupport)rootView.findViewById(R.id.list1);
list.setLayoutManager(new LinearLayoutManager(context));
list.setEmptyView(rootView.findViewById(R.id.list_empty));
我添加了RecyclerView和替代ImageView到RelativeLayout:
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/no_active_jobs"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:src="@mipmap/ic_active_jobs" />
<android.support.v7.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</RelativeLayout>
然后在适配器中:
@Override
public int getItemCount() {
if (mOrders.size() == 0) {
mRecyclerView.setVisibility(View.INVISIBLE);
} else {
mRecyclerView.setVisibility(View.VISIBLE);
}
return mOrders.size();
}
如果你想在回收器视图为空时显示一个文本视图，你可以这样做:
ArrayList<SomeDataModel> arrayList = new ArrayList<>();
RecycleAdapter recycleAdapter = new RecycleAdapter(getContext(),project_Ideas);
recyclerView..setAdapter(recycleAdapter);
if(arrayList.isEmpty())
{
emptyTextView.setVisibility(View.VISIBLE);
recyclerView.setVisibility(View.GONE);
}
我假设你有TextView
和这样的XML
android:visibility="gone"
这是如何显示空视图，同时过滤和更新RecyclerView使用LiveData
ViewModel.getInstance().getCustomers?.observe(viewLifecycleOwner, {customerList ->
//assign your adapter with your list then
listAdapter?.notifyDataSetChanged()
isListItemEmpty(customerList?.isEmpty())
}
创建一个接口来在适配器和片段之间通信，并在适配器中注册它
interface EmptyListener {
fun isListEmpty(isEmpty: Boolean)
}
然后在publishResults中调用它:
dataList?.isEmpty()?.let { mListener?.isListEmpty(it) }
最后在Fragment中实现你的接口:
override fun isListEmpty(isEmpty: Boolean) {
if (isEmpty) {
your_list?.visibility = View.GONE
empty_view?.visibility = View.VISIBLE
} else {
empty_view?.visibility = View.GONE
your_list?.visibility = View.VISIBLE
}
}
