Java 当RecyclerView为空时,显示单独的视图(图像和文本)
当我的RecyclerView为空时,我需要显示一个包含图像和一些文本的视图。我的代码正在做这项工作,但我认为有更好的方法来做。我看到了一些东西,比如视图的可见性,但大多数示例仅适用于文本视图 这是我的密码: 请注意,对于xml文件,如果我为空的_视图设置了visibility:gone,我将永远看不到空的_视图。如果我删除这一行,我总是看到空的视图Java 当RecyclerView为空时,显示单独的视图(图像和文本),java,android,Java,Android,当我的RecyclerView为空时,我需要显示一个包含图像和一些文本的视图。我的代码正在做这项工作,但我认为有更好的方法来做。我看到了一些东西,比如视图的可见性,但大多数示例仅适用于文本视图 这是我的密码: 请注意,对于xml文件,如果我为空的_视图设置了visibility:gone,我将永远看不到空的_视图。如果我删除这一行,我总是看到空的视图 <?xml version="1.0" encoding="utf-8"?><!--
<?xml version="1.0" encoding="utf-8"?><!--
As recommended by Google, we use a ConstraintLayout
as the root element
We add a padding all around using the padding attribute
-->
<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"
tools:context=".CityActivity"
>
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="0dp"
android:layout_height="0dp"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
/>
<include
android:id="@+id/empty_view"
layout="@layout/activity_city_empty"
/>
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="@+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_add_location"
app:backgroundTint="@color/orange"
app:fabSize="normal"
android:layout_margin="12dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
/>
</androidx.constraintlayout.widget.ConstraintLayout>
以下是我的主要活动:
public class CityActivity extends AppCompatActivity implements OnClickListener {
private RecyclerView recyclerView;
private ConstraintLayout mEmptyLayout;
public static final String TAG = CityActivity.class.getSimpleName();
/*
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
final List<City> cities = CityRepository.getInstance(this).getCities();
/*if(cities.isEmpty())
{
setContentView(R.layout.activity_city_empty);
}
else {
setContentView(R.layout.activity_city);
recyclerView = findViewById(R.id.recyclerView);
recyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL));
//}
mEmptyView = findViewById(R.id.empty_view);
//We configure the click on the fab
findViewById(R.id.fab).setOnClickListener(this);
}*/
@Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_city);
recyclerView = findViewById(R.id.recyclerView);
mEmptyLayout = findViewById(R.id.empty_view);
recyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL));
findViewById(R.id.fab).setOnClickListener(this);
setup();
}
private void setup() {
final List<City> cities = CityRepository.getInstance(this).getCities();
final CitiesAdapter citiesAdapter = new CitiesAdapter(cities);
recyclerView.setAdapter(citiesAdapter);
citiesAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
@Override
public void onChanged() {
super.onChanged();
checkIsEmpty(citiesAdapter);
}
});
}
@Override
protected void onResume()
{
super.onResume();
Log.d(TAG, "test");
//We init the list into the onResume method
//so the list is updated each time the screen goes to foreground
setup();
}
private void initList(){
//We retrieve the list of cities to display
final List<City> cities = CityRepository.getInstance(this).getCities();
//We create the adapter and we attach it to the RecyclerView
final CitiesAdapter citiesAdapter = new CitiesAdapter(cities);
recyclerView.setAdapter(citiesAdapter);
citiesAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
@Override
public void onChanged() {
super.onChanged();
checkIsEmpty(citiesAdapter);
}
});
}
@Override
public void onClick(View v){
final Intent intent = new Intent(this, AddCityActivity.class);
startActivity(intent);
}
private void checkIsEmpty(CitiesAdapter citiesadapter) {
mEmptyLayout.setVisibility(citiesadapter == null || citiesadapter.getItemCount() == 0 ? View.VISIBLE : View.GONE);
}
}
private RecyclerView recyclerView;
private View mEmptyView;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO: Implement this method
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
mEmptyLayout = findViewById(R.id.empty_view);
setup();
}
公共类CityActivity扩展了AppCompatActivity实现了OnClickListener{
私人回收站;
private ConstraintLayout mEmptyLayout;
public static final String TAG=CityActivity.class.getSimpleName();
/*
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
final List cities=CityRepository.getInstance(this.getCities();
/*if(cities.isEmpty())
{
setContentView(R.layout.activity\u city\u empty);
}
否则{
setContentView(R.layout.activity_city);
recyclerView=findViewById(R.id.recyclerView);
recyclerView.addItemDecoration(新的DividerItemDecoration(这个,DividerItemDecoration.VERTICAL));
//}
mEmptyView=findViewById(R.id.empty\u视图);
//我们配置点击晶圆厂
findviewbyd(R.id.fab).setOnClickListener(this);
}*/
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_city);
recyclerView=findViewById(R.id.recyclerView);
mEmptyLayout=findviewbyd(R.id.empty\u视图);
recyclerView.addItemDecoration(新的DividerItemDecoration(这个,DividerItemDecoration.VERTICAL));
findviewbyd(R.id.fab).setOnClickListener(this);
设置();
}
私有无效设置(){
final List cities=CityRepository.getInstance(this.getCities();
最终城市自适应城市自适应=新城市自适应(城市);
recyclerView.setAdapter(CitieAdapter);
citiesAdapter.registerAdapterDataObserver(新的RecyclerView.AdapterDataObserver(){
@凌驾
更改后的公共无效(){
super.onChanged();
checkIsEmpty(citiesAdapter);
}
});
}
@凌驾
受保护的void onResume()
{
super.onResume();
日志d(标签“测试”);
//我们将列表初始化到onResume方法中
//因此,每次屏幕转到前台时,列表都会更新
设置();
}
私有void initList(){
//我们检索要显示的城市列表
final List cities=CityRepository.getInstance(this.getCities();
//我们创建适配器并将其连接到RecyclerView
最终城市自适应城市自适应=新城市自适应(城市);
recyclerView.setAdapter(CitieAdapter);
citiesAdapter.registerAdapterDataObserver(新的RecyclerView.AdapterDataObserver(){
@凌驾
更改后的公共无效(){
super.onChanged();
checkIsEmpty(citiesAdapter);
}
});
}
@凌驾
公共void onClick(视图v){
最终意图=新意图(此,AddCityActivity.class);
星触觉(意向);
}
私人无效支票为空(CitiesAdapter CitiesAdapter){
mEmptyLayout.setVisibility(citiesadapter==null | | citiesadapter.getItemCount()==0?View.VISIBLE:View.GONE);
}
}
注意:这是我为这些类编写的完整代码,但我认为这些是解决这个问题最重要的部分。在include中添加一个id:
<include
android:id="@+id/empty_view"
layout="@layout/activity_city_empty"
/>
设置方法:
private void setup() {
final List<City> cities = CityRepository.getInstance(this).getCities();
final CitiesAdapter citiesAdapter = new CitiesAdapter(cities);
recyclerView.setAdapter(citiesAdapter);
citiesAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
@Override
public void onChanged() {
super.onChanged();
checkIsEmpty();
}
});
}
上一示例的结果:
以上所有答案都可以完成这项工作,但不是以正确和最干净的方式。下面是RecyclerView的扩展,它可以处理空状态
public class ExtendedRecyclerView extends RecyclerView {
private View mEmptyView;
private AdapterDataObserver mDataObserver = new AdapterDataObserver() {
@Override
public void onChanged() {
super.onChanged();
updateEmptyView();
}
};
public ExtendedRecyclerView (Context context) {
super(context);
}
public ExtendedRecyclerView (Context context, AttributeSet attrs) {
super(context, attrs);
}
public ExtendedRecyclerView (Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
/**
* Designate a view as the empty view. When the backing adapter has no
* data this view will be made visible and the recycler view hidden.
*/
public void setEmptyView(View emptyView) {
mEmptyView = emptyView;
}
@Override
public void setAdapter(RecyclerView.Adapter adapter) {
if (getAdapter() != null) {
getAdapter().unregisterAdapterDataObserver(mDataObserver);
}
if (adapter != null) {
adapter.registerAdapterDataObserver(mDataObserver);
}
super.setAdapter(adapter);
updateEmptyView();
}
private void updateEmptyView() {
if (mEmptyView != null && getAdapter() != null) {
boolean showEmptyView = getAdapter().getItemCount() == 0;
mEmptyView.setVisibility(showEmptyView ? VISIBLE : GONE);
setVisibility(showEmptyView ? GONE : VISIBLE);
}
}
}
在活动类中添加以下内容以显示空视图
public class MyActivity extends AppCompatActivity {
ExtendedRecyclerView recycler_view;
View empty_view;
Adapter adapter;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity);
recycler_view = findViewById(R.id.recycler_view);
empty_view = findViewById(R.id.empty_view);
recycler_view.setHasFixedSize(true);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity(), LinearLayoutManager.HORIZONTAL, false);
recycler_view.setLayoutManager(linearLayoutManager);
adapter = new Adapter(getActivity(), myRandomList, false);
recycler_view.setAdapter(adapter);
recycler_view.setEmptyView(empty_view);
}
}
public class MyFragment extends Fragment {
ExtendedRecyclerView recycler_view;
View empty_view;
Adapter adapter;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment, container, false);
recycler_view = view.findViewById(R.id.recycler_view);
empty_view = view.findViewById(R.id.empty_view);
recycler_view.setHasFixedSize(true);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity(), LinearLayoutManager.HORIZONTAL, false);
recycler_view.setLayoutManager(linearLayoutManager);
adapter = new Adapter(getActivity(), myRandomList, false);
recycler_view.setAdapter(adapter);
recycler_view.setEmptyView(empty_view);
return view;
}
}
在fragement类中添加以下内容以显示空视图
public class MyActivity extends AppCompatActivity {
ExtendedRecyclerView recycler_view;
View empty_view;
Adapter adapter;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity);
recycler_view = findViewById(R.id.recycler_view);
empty_view = findViewById(R.id.empty_view);
recycler_view.setHasFixedSize(true);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity(), LinearLayoutManager.HORIZONTAL, false);
recycler_view.setLayoutManager(linearLayoutManager);
adapter = new Adapter(getActivity(), myRandomList, false);
recycler_view.setAdapter(adapter);
recycler_view.setEmptyView(empty_view);
}
}
public class MyFragment extends Fragment {
ExtendedRecyclerView recycler_view;
View empty_view;
Adapter adapter;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment, container, false);
recycler_view = view.findViewById(R.id.recycler_view);
empty_view = view.findViewById(R.id.empty_view);
recycler_view.setHasFixedSize(true);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity(), LinearLayoutManager.HORIZONTAL, false);
recycler_view.setLayoutManager(linearLayoutManager);
adapter = new Adapter(getActivity(), myRandomList, false);
recycler_view.setAdapter(adapter);
recycler_view.setEmptyView(empty_view);
return view;
}
}
希望这能帮助你和任何遇到这个答案的人!祝大家快乐 我知道问题到底出在哪里了。下面是您需要的正确代码,它现在应该可以工作了。您忘记将列表声明为新的ArrayList,这导致应用程序崩溃
public class CityActivity extends AppCompatActivity {
ExtendedRecyclerView recycler_view;
View empty_view;
CitiesAdapter citiesadapter;
List<City> cities;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_city_empty);
recycler_view = findViewById(R.id.recyclerView);
empty_view = findViewById(R.id.empty_view);
cities = new ArrayList<>();
recycler_view.setHasFixedSize(true);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
recycler_view.setLayoutManager(linearLayoutManager);
citiesadapter = new CitiesAdapter(cities);
recycler_view.setAdapter(citiesadapter);
recycler_view.setEmptyView(empty_view);
}
}
公共类城市活动扩展了AppCompatActivity{
ExtendedRecyclerView回收器视图;
查看空视图;
城市适应者城市适应者;
列出城市;
@凌驾
创建时受保护的void(@Nullable Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity\u city\u empty);
回收者视图=findViewById(R.id.recyclerView);
empty_view=findviewbyd(R.id.empty_view);
城市=新阵列列表();
recycler_视图。setHasFixedSize(真);
LinearLayoutManager LinearLayoutManager=新的LinearLayoutManager(此,LinearLayoutManager.VERTICAL,false);
回收器\u视图。setLayoutManager(linearLayoutManager);
citiesadapter=新的citiesadapter(城市);
recycler_view.setAdapter(CitieAdapter);
回收器视图。设置清空视图(清空视图);
}
}
我不确定你的问题是什么,你有什么东西不起作用吗?事实上,这段代码正在发挥作用,我对此没有什么问题,但我认为我的方式似乎不是最好的,只是要确保,我认为有些东西不起作用,而您需要一些具体的帮助:)例如,我不认为在initList()方法中使用setContentView和OnClickListener是实现我想做的事情的最好方法,因为我认为您是新的。我将根据您的代码更新我的答案。因此我必须替换OnCreate方法