在中RecyclerView
,我想设置一个空视图以在适配器为空时显示。有相当于ListView.setEmptyView()
吗?
在中RecyclerView
,我想设置一个空视图以在适配器为空时显示。有相当于ListView.setEmptyView()
吗?
Answers:
使用新的数据绑定功能,您还可以在布局中直接实现此目的:
<TextView
android:text="No data to display."
android:visibility="@{dataset.size() > 0 ? View.GONE : View.VISIBLE}" />
在这种情况下,您只需要向XML的数据部分添加变量和导入即可:
<data>
<import type="android.view.View"/>
<variable
name="dataset"
type="java.util.List<java.lang.String>"
/>
</data>
Adapter
而不是数据集,并使用它getItemCount()
或将所有内容包装在中ViewModel
并设置android:visibility
为viewModel.getEmptyViewVisibility()
。
这是一个类似于@dragonborn的类,但是更完整。基于此要点。
public class EmptyRecyclerView extends RecyclerView {
private View emptyView;
final private AdapterDataObserver observer = new AdapterDataObserver() {
@Override
public void onChanged() {
checkIfEmpty();
}
@Override
public void onItemRangeInserted(int positionStart, int itemCount) {
checkIfEmpty();
}
@Override
public void onItemRangeRemoved(int positionStart, int itemCount) {
checkIfEmpty();
}
};
public EmptyRecyclerView(Context context) {
super(context);
}
public EmptyRecyclerView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public EmptyRecyclerView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
void checkIfEmpty() {
if (emptyView != null && getAdapter() != null) {
final boolean emptyViewVisible = getAdapter().getItemCount() == 0;
emptyView.setVisibility(emptyViewVisible ? VISIBLE : GONE);
setVisibility(emptyViewVisible ? GONE : VISIBLE);
}
}
@Override
public void setAdapter(Adapter adapter) {
final Adapter oldAdapter = getAdapter();
if (oldAdapter != null) {
oldAdapter.unregisterAdapterDataObserver(observer);
}
super.setAdapter(adapter);
if (adapter != null) {
adapter.registerAdapterDataObserver(observer);
}
checkIfEmpty();
}
public void setEmptyView(View emptyView) {
this.emptyView = emptyView;
checkIfEmpty();
}
}
setEmptyView
方法,您可以在要定义空视图时调用该方法。ListView.setEmptyView
如果不清楚,请参见文档,这是相同的想法。
该链接中提供的解决方案似乎很完美。它使用viewType标识何时显示emptyView。无需创建自定义RecyclerView
从上面的链接添加代码:
package com.example.androidsampleproject;
import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class RecyclerViewActivity extends Activity {
RecyclerView recyclerView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_recycler_view);
recyclerView = (RecyclerView) findViewById(R.id.myList);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setAdapter(new MyAdapter());
}
private class MyAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
private List<String> dataList = new ArrayList<String>();
public class EmptyViewHolder extends RecyclerView.ViewHolder {
public EmptyViewHolder(View itemView) {
super(itemView);
}
}
public class ViewHolder extends RecyclerView.ViewHolder {
TextView data;
public ViewHolder(View v) {
super(v);
data = (TextView) v.findViewById(R.id.data_view);
}
}
@Override
public int getItemCount() {
return dataList.size() > 0 ? dataList.size() : 1;
}
@Override
public int getItemViewType(int position) {
if (dataList.size() == 0) {
return EMPTY_VIEW;
}
return super.getItemViewType(position);
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder vho, final int pos) {
if (vho instanceof ViewHolder) {
ViewHolder vh = (ViewHolder) vho;
String pi = dataList.get(pos);
}
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v;
if (viewType == EMPTY_VIEW) {
v = LayoutInflater.from(parent.getContext()).inflate(R.layout.empty_view, parent, false);
EmptyViewHolder evh = new EmptyViewHolder(v);
return evh;
}
v = LayoutInflater.from(parent.getContext()).inflate(R.layout.data_row, parent, false);
ViewHolder vh = new ViewHolder(v);
return vh;
}
private static final int EMPTY_VIEW = 10;
}
}
我只喜欢一个简单的解决方案,例如
将RecyclerView置于具有TextView或其他视图的FrameLayout或RelativeLayout内,默认情况下显示可见性为GONE的空数据消息,然后在适配器类中应用逻辑
在这里,我有一个TextView,消息没有数据
@Override
public int getItemCount() {
textViewNoData.setVisibility(data.size() > 0 ? View.GONE : View.VISIBLE);
return data.size();
}
RVEmptyObserver
:这是的实现,AdapterDataObserver
您可以将设置View
为默认的空布局RecylerView
。这样RecyclerView
,您可以轻松地将其与现有代码一起使用,而不必使用自定义方法,使生活更艰辛:
用法示例:
RVEmptyObserver observer = new RVEmptyObserver(recyclerView, emptyView)
rvAdapter.registerAdapterDataObserver(observer);
类:
public class RVEmptyObserver extends RecyclerView.AdapterDataObserver {
private View emptyView;
private RecyclerView recyclerView;
public RVEmptyObserver(RecyclerView rv, View ev) {
this.recyclerView = rv;
this.emptyView = ev;
checkIfEmpty();
}
private void checkIfEmpty() {
if (emptyView != null && recyclerView.getAdapter() != null) {
boolean emptyViewVisible = recyclerView.getAdapter().getItemCount() == 0;
emptyView.setVisibility(emptyViewVisible ? View.VISIBLE : View.GONE);
recyclerView.setVisibility(emptyViewVisible ? View.GONE : View.VISIBLE);
}
}
public void onChanged() { checkIfEmpty(); }
public void onItemRangeInserted(int positionStart, int itemCount) { checkIfEmpty(); }
public void onItemRangeRemoved(int positionStart, int itemCount) { checkIfEmpty(); }
}
我的版本基于https://gist.github.com/adelnizamutdinov/31c8f054d1af4588dc5c
public class EmptyRecyclerView extends RecyclerView {
@Nullable
private View emptyView;
public EmptyRecyclerView(Context context) { super(context); }
public EmptyRecyclerView(Context context, AttributeSet attrs) { super(context, attrs); }
public EmptyRecyclerView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
private void checkIfEmpty() {
if (emptyView != null && getAdapter() != null) {
emptyView.setVisibility(getAdapter().getItemCount() > 0 ? GONE : VISIBLE);
}
}
private final AdapterDataObserver observer = new AdapterDataObserver() {
@Override
public void onChanged() {
checkIfEmpty();
}
@Override
public void onItemRangeInserted(int positionStart, int itemCount) {
checkIfEmpty();
}
@Override
public void onItemRangeRemoved(int positionStart, int itemCount) {
checkIfEmpty();
}
};
@Override
public void setAdapter(@Nullable Adapter adapter) {
final Adapter oldAdapter = getAdapter();
if (oldAdapter != null) {
oldAdapter.unregisterAdapterDataObserver(observer);
}
super.setAdapter(adapter);
if (adapter != null) {
adapter.registerAdapterDataObserver(observer);
}
checkIfEmpty();
}
@Override
public void setVisibility(int visibility) {
super.setVisibility(visibility);
if (null != emptyView && (visibility == GONE || visibility == INVISIBLE)) {
emptyView.setVisibility(GONE);
} else {
checkIfEmpty();
}
}
public void setEmptyView(@Nullable View emptyView) {
this.emptyView = emptyView;
checkIfEmpty();
}
}
setVisibility
。
我希望在Recycler.Adapter中实现此功能
在您覆盖的getItemCount方法上,在此处注入空的检查代码:
@Override
public int getItemCount() {
if(data.size() == 0) listIsEmtpy();
return data.size();
}
setVisibility()
都会被调用。当然,您可以添加一些标志来进行补偿,但这就是当它变得更加复杂时。
如果您想支持更多状态,例如加载状态,错误状态,则可以签出 https://github.com/rockerhieu/rv-adapter-states。否则,可以使用RecyclerViewAdapterWrapper
(https://github.com/rockerhieu/rv-adapter)轻松实现支持空视图的功能。这种方法的主要优点是您可以轻松支持空视图,而无需更改现有适配器的逻辑:
public class StatesRecyclerViewAdapter extends RecyclerViewAdapterWrapper {
private final View vEmptyView;
@IntDef({STATE_NORMAL, STATE_EMPTY})
@Retention(RetentionPolicy.SOURCE)
public @interface State {
}
public static final int STATE_NORMAL = 0;
public static final int STATE_EMPTY = 2;
public static final int TYPE_EMPTY = 1001;
@State
private int state = STATE_NORMAL;
public StatesRecyclerViewAdapter(@NonNull RecyclerView.Adapter wrapped, @Nullable View emptyView) {
super(wrapped);
this.vEmptyView = emptyView;
}
@State
public int getState() {
return state;
}
public void setState(@State int state) {
this.state = state;
getWrappedAdapter().notifyDataSetChanged();
notifyDataSetChanged();
}
@Override
public int getItemCount() {
switch (state) {
case STATE_EMPTY:
return 1;
}
return super.getItemCount();
}
@Override
public int getItemViewType(int position) {
switch (state) {
case STATE_EMPTY:
return TYPE_EMPTY;
}
return super.getItemViewType(position);
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
switch (viewType) {
case TYPE_EMPTY:
return new SimpleViewHolder(vEmptyView);
}
return super.onCreateViewHolder(parent, viewType);
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
switch (state) {
case STATE_EMPTY:
onBindEmptyViewHolder(holder, position);
break;
default:
super.onBindViewHolder(holder, position);
break;
}
}
public void onBindEmptyViewHolder(RecyclerView.ViewHolder holder, int position) {
}
public static class SimpleViewHolder extends RecyclerView.ViewHolder {
public SimpleViewHolder(View itemView) {
super(itemView);
}
}
}
用法:
Adapter adapter = originalAdapter();
StatesRecyclerViewAdapter statesRecyclerViewAdapter = new StatesRecyclerViewAdapter(adapter, emptyView);
rv.setAdapter(endlessRecyclerViewAdapter);
// Change the states of the adapter
statesRecyclerViewAdapter.setState(StatesRecyclerViewAdapter.STATE_EMPTY);
statesRecyclerViewAdapter.setState(StatesRecyclerViewAdapter.STATE_NORMAL);
我已解决此问题:
创建布局layout_recyclerview_with_emptytext.xml文件。
创建EmptyViewRecyclerView.java
---------
EmptyViewRecyclerView emptyRecyclerView =(EmptyViewRecyclerView)findViewById(R.id.emptyRecyclerViewLayout);
emptyRecyclerView.addAdapter(mPrayerCollectionRecyclerViewAdapter,“没有为选定的类别祷告。”);
layout_recyclerview_with_emptytext.xml文件
<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/switcher"
>
<android.support.v7.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
<com.ninestars.views.CustomFontTextView android:id="@+id/recyclerViewEmptyTextView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="Empty Text"
android:layout_gravity="center"
android:gravity="center"
android:textStyle="bold"
/>
</merge>
EmptyViewRecyclerView.java
public class EmptyViewRecyclerView extends ViewSwitcher {
private RecyclerView mRecyclerView;
private CustomFontTextView mRecyclerViewExptyTextView;
public EmptyViewRecyclerView(Context context) {
super(context);
initView(context);
}
public EmptyViewRecyclerView(Context context, AttributeSet attrs) {
super(context, attrs);
initView(context);
}
private void initView(Context context) {
LayoutInflater.from(context).inflate(R.layout.layout_recyclerview_with_emptytext, this, true);
mRecyclerViewExptyTextView = (CustomFontTextView) findViewById(R.id.recyclerViewEmptyTextView);
mRecyclerView = (RecyclerView) findViewById(R.id.recyclerView);
mRecyclerView.setLayoutManager(new LinearLayoutManager(context));
}
public void addAdapter(final RecyclerView.Adapter<?> adapter) {
mRecyclerView.setAdapter(adapter);
adapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
@Override
public void onChanged() {
super.onChanged();
if(adapter.getItemCount() > 0) {
if (R.id.recyclerView == getNextView().getId()) {
showNext();
}
} else {
if (R.id.recyclerViewEmptyTextView == getNextView().getId()) {
showNext();
}
}
}
});
}
public void addAdapter(final RecyclerView.Adapter<?> adapter, String emptyTextMsg) {
addAdapter(adapter);
setEmptyText(emptyTextMsg);
}
public RecyclerView getRecyclerView() {
return mRecyclerView;
}
public void setEmptyText(String emptyTextMsg) {
mRecyclerViewExptyTextView.setText(emptyTextMsg);
}
}
public class EmptyRecyclerView extends RecyclerView {
@Nullable View emptyView;
public EmptyRecyclerView(Context context) { super(context); }
public EmptyRecyclerView(Context context, AttributeSet attrs) { super(context, attrs); }
public EmptyRecyclerView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
void checkIfEmpty() {
if (emptyView != null) {
emptyView.setVisibility(getAdapter().getItemCount() > 0 ? GONE : VISIBLE);
}
}
final @NotNull AdapterDataObserver observer = new AdapterDataObserver() {
@Override public void onChanged() {
super.onChanged();
checkIfEmpty();
}
};
@Override public void setAdapter(@Nullable Adapter adapter) {
final Adapter oldAdapter = getAdapter();
if (oldAdapter != null) {
oldAdapter.unregisterAdapterDataObserver(observer);
}
super.setAdapter(adapter);
if (adapter != null) {
adapter.registerAdapterDataObserver(observer);
}
}
public void setEmptyView(@Nullable View emptyView) {
this.emptyView = emptyView;
checkIfEmpty();
}
}
这样的事情可能会有所帮助
RecyclerView
当emptyView
可见时,您可能需要隐藏(相反)。您还需要调用checkIfEmpty()
上onItemRangeInserted()
和onItemRangeRemoved()
。哦,您可能已经引用了您的出处:gist.github.com/adelnizamutdinov/31c8f054d1af4588dc5c
我认为这与ErrorView和EmptyView都更完整https://gist.github.com/henrytao-me/2f7f113fb5f2a59987e7
您可以只在文本为RecyclerView
空时在其上绘制文本。下面的自定义子类支持empty
,failed
,loading
,和offline
模式。为了成功进行编译recyclerView_stateText
,请为资源添加颜色。
/**
* {@code RecyclerView} that supports loading and empty states.
*/
public final class SupportRecyclerView extends RecyclerView
{
public enum State
{
NORMAL,
LOADING,
EMPTY,
FAILED,
OFFLINE
}
public SupportRecyclerView(@NonNull Context context)
{
super(context);
setUp(context);
}
public SupportRecyclerView(@NonNull Context context, @Nullable AttributeSet attrs)
{
super(context, attrs);
setUp(context);
}
public SupportRecyclerView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);
setUp(context);
}
private Paint textPaint;
private Rect textBounds;
private PointF textOrigin;
private void setUp(Context c)
{
textPaint = new Paint();
textPaint.setAntiAlias(true);
textPaint.setColor(ContextCompat.getColor(c, R.color.recyclerView_stateText));
textBounds = new Rect();
textOrigin = new PointF();
}
private State state;
public State state()
{
return state;
}
public void setState(State newState)
{
state = newState;
calculateLayout(getWidth(), getHeight());
invalidate();
}
private String loadingText = "Loading...";
public void setLoadingText(@StringRes int resId)
{
loadingText = getResources().getString(resId);
}
private String emptyText = "Empty";
public void setEmptyText(@StringRes int resId)
{
emptyText = getResources().getString(resId);
}
private String failedText = "Failed";
public void setFailedText(@StringRes int resId)
{
failedText = getResources().getString(resId);
}
private String offlineText = "Offline";
public void setOfflineText(@StringRes int resId)
{
offlineText = getResources().getString(resId);
}
@Override
public void onDraw(Canvas canvas)
{
super.onDraw(canvas);
String s = stringForCurrentState();
if (s == null)
return;
canvas.drawText(s, textOrigin.x, textOrigin.y, textPaint);
}
private void calculateLayout(int w, int h)
{
String s = stringForCurrentState();
if (s == null)
return;
textPaint.setTextSize(.1f * w);
textPaint.getTextBounds(s, 0, s.length(), textBounds);
textOrigin.set(
w / 2f - textBounds.width() / 2f - textBounds.left,
h / 2f - textBounds.height() / 2f - textBounds.top);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh)
{
super.onSizeChanged(w, h, oldw, oldh);
calculateLayout(w, h);
}
private String stringForCurrentState()
{
if (state == State.EMPTY)
return emptyText;
else if (state == State.LOADING)
return loadingText;
else if (state == State.FAILED)
return failedText;
else if (state == State.OFFLINE)
return offlineText;
else
return null;
}
}