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

另一种方法是使用addOnChildAttachStateChangeListener来处理RecyclerView中出现/消失的子视图。

recyclerView.addOnChildAttachStateChangeListener(new RecyclerView.OnChildAttachStateChangeListener() {
            @Override
            public void onChildViewAttachedToWindow(@NonNull View view) {
                forEmptyTextView.setVisibility(View.INVISIBLE);
            }

            @Override
            public void onChildViewDetachedFromWindow(@NonNull View view) {
                forEmptyTextView.setVisibility(View.VISIBLE);
            }
        });

其他回答

在自定义RecyclerView中使用AdapterDataObserver

科特林:

RecyclerViewEnum.kt

enum class RecyclerViewEnum {
    LOADING,
    NORMAL,
    EMPTY_STATE
}

RecyclerViewEmptyLoadingSupport.kt

class RecyclerViewEmptyLoadingSupport : RecyclerView {

    var stateView: RecyclerViewEnum? = RecyclerViewEnum.LOADING
        set(value) {
            field = value
            setState()
        }
    var emptyStateView: View? = null
    var loadingStateView: View? = null


    constructor(context: Context) : super(context) {}

    constructor(context: Context, attrs: AttributeSet) : super(context, attrs) {}

    constructor(context: Context, attrs: AttributeSet, defStyle: Int) : super(context, attrs, defStyle) {}


    private val dataObserver = object : AdapterDataObserver() {
        override fun onChanged() {
            onChangeState()
        }

        override fun onItemRangeRemoved(positionStart: Int, itemCount: Int) {
            super.onItemRangeRemoved(positionStart, itemCount)
            onChangeState()
        }

        override fun onItemRangeInserted(positionStart: Int, itemCount: Int) {
            super.onItemRangeInserted(positionStart, itemCount)
            onChangeState()
        }
    }


    override fun setAdapter(adapter: RecyclerView.Adapter<*>?) {
        super.setAdapter(adapter)
        adapter?.registerAdapterDataObserver(dataObserver)
        dataObserver.onChanged()
    }


    fun onChangeState() {
        if (adapter?.itemCount == 0) {
            emptyStateView?.visibility = View.VISIBLE
            loadingStateView?.visibility = View.GONE
            this@RecyclerViewEmptyLoadingSupport.visibility = View.GONE
        } else {
            emptyStateView?.visibility = View.GONE
            loadingStateView?.visibility = View.GONE
            this@RecyclerViewEmptyLoadingSupport.visibility = View.VISIBLE
        }
    }

    private fun setState() {

        when (this.stateView) {
            RecyclerViewEnum.LOADING -> {
                loadingStateView?.visibility = View.VISIBLE
                this@RecyclerViewEmptyLoadingSupport.visibility = View.GONE
                emptyStateView?.visibility = View.GONE
            }

            RecyclerViewEnum.NORMAL -> {
                loadingStateView?.visibility = View.GONE
                this@RecyclerViewEmptyLoadingSupport.visibility = View.VISIBLE
                emptyStateView?.visibility = View.GONE
            }
            RecyclerViewEnum.EMPTY_STATE -> {
                loadingStateView?.visibility = View.GONE
                this@RecyclerViewEmptyLoadingSupport.visibility = View.GONE
                emptyStateView?.visibility = View.VISIBLE
            }
        }
    }
}

layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

    <LinearLayout
        android:id="@+id/emptyView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/white"
        android:gravity="center"
        android:orientation="vertical">

        <TextView
            android:id="@+id/emptyLabelTv"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="empty" />
    </LinearLayout>

    <LinearLayout
        android:id="@+id/loadingView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/white"
        android:gravity="center"
        android:orientation="vertical">

        <ProgressBar
            android:id="@+id/progressBar"
            android:layout_width="45dp"
            android:layout_height="45dp"
            android:layout_gravity="center"
            android:indeterminate="true"
            android:theme="@style/progressBarBlue" />
    </LinearLayout>

    <com.peeyade.components.recyclerView.RecyclerViewEmptyLoadingSupport
        android:id="@+id/recyclerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</LinearLayout>

在活动中使用这种方式:

recyclerView?.apply {
        layoutManager = GridLayoutManager(context, 2)
        emptyStateView = emptyView
        loadingStateView = loadingView
        adapter = adapterGrid
    }

    // you can set LoadingView or emptyView manual
    recyclerView.stateView = RecyclerViewEnum.EMPTY_STATE
    recyclerView.stateView = RecyclerViewEnum.LOADING

在适配器的getItemViewType上检查适配器是否有0个元素,如果是,则返回不同的viewType。

然后在onCreateViewHolder上检查viewType是否为之前返回的视图,并膨胀一个不同的视图。在这种情况下,布局文件与该TextView

编辑

如果这仍然不能工作,那么你可能想通过编程来设置视图的大小,就像这样:

Point size = new Point();
((WindowManager)itemView.getContext().getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay().getSize(size);

然后当你膨胀你的视图调用:

inflatedView.getLayoutParams().height = size.y;
inflatedView.getLayoutParams().width = size.x;

这里是我的类显示空视图,重试视图(当加载api失败时)和加载进度的RecyclerView

public class RecyclerViewEmptyRetryGroup extends RelativeLayout {
    private RecyclerView mRecyclerView;
    private LinearLayout mEmptyView;
    private LinearLayout mRetryView;
    private ProgressBar mProgressBar;
    private OnRetryClick mOnRetryClick;

    public RecyclerViewEmptyRetryGroup(Context context) {
        this(context, null);
    }

    public RecyclerViewEmptyRetryGroup(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public RecyclerViewEmptyRetryGroup(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    public void onViewAdded(View child) {
        super.onViewAdded(child);
        if (child.getId() == R.id.recyclerView) {
            mRecyclerView = (RecyclerView) findViewById(R.id.recyclerView);
            return;
        }
        if (child.getId() == R.id.layout_empty) {
            mEmptyView = (LinearLayout) findViewById(R.id.layout_empty);
            return;
        }
        if (child.getId() == R.id.layout_retry) {
            mRetryView = (LinearLayout) findViewById(R.id.layout_retry);
            mRetryView.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    mRetryView.setVisibility(View.GONE);
                    mOnRetryClick.onRetry();
                }
            });
            return;
        }
        if (child.getId() == R.id.progress_bar) {
            mProgressBar = (ProgressBar) findViewById(R.id.progress_bar);
        }
    }

    public void loading() {
        mRetryView.setVisibility(View.GONE);
        mEmptyView.setVisibility(View.GONE);
        mProgressBar.setVisibility(View.VISIBLE);
    }

    public void empty() {
        mEmptyView.setVisibility(View.VISIBLE);
        mRetryView.setVisibility(View.GONE);
        mProgressBar.setVisibility(View.GONE);
    }

    public void retry() {
        mRetryView.setVisibility(View.VISIBLE);
        mEmptyView.setVisibility(View.GONE);
        mProgressBar.setVisibility(View.GONE);
    }

    public void success() {
        mRetryView.setVisibility(View.GONE);
        mEmptyView.setVisibility(View.GONE);
        mProgressBar.setVisibility(View.GONE);
    }

    public RecyclerView getRecyclerView() {
        return mRecyclerView;
    }

    public void setOnRetryClick(OnRetryClick onRetryClick) {
        mOnRetryClick = onRetryClick;
    }

    public interface OnRetryClick {
        void onRetry();
    }
}

activity_xml

<...RecyclerViewEmptyRetryGroup
        android:id="@+id/recyclerViewEmptyRetryGroup">

        <android.support.v7.widget.RecyclerView
            android:id="@+id/recyclerView"/>

        <LinearLayout
            android:id="@+id/layout_empty">
            ...
        </LinearLayout>

        <LinearLayout
            android:id="@+id/layout_retry">
            ...
        </LinearLayout>

        <ProgressBar
            android:id="@+id/progress_bar"/>

</...RecyclerViewEmptyRetryGroup>

来源在这里https://github.com/PhanVanLinh/AndroidRecyclerViewWithLoadingEmptyAndRetry

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
        }
    }

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"