【Android】使RecyclerView 支持setEmptyView

自定义一个RecyclerView 的子类，使其支持EmptyView机制。

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();

if (emptyView.getParent() == null) {
//如果emptyView没有父布局，则添加至当前RecyclerView的父View中
ViewParent parent = getParent();
if (parent instanceof RelativeLayout) {
//相对布局
RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(
LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
ViewGroup parentView = (ViewGroup) getParent();
layoutParams.addRule(RelativeLayout.CENTER_IN_PARENT);
parentView.addView(emptyView, layoutParams);
} else if (getParent() instanceof ViewGroup) {
ViewGroup parentView = (ViewGroup) getParent();
parentView.addView(emptyView);
}
}
}
}

如果你使用的IRecyclerView，那么如果要支持setEmptyView，可以参照如下代码：

IRecyclerView项目地址在这里，IRecyclerView on GitHUb

package com.xxx;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.widget.RelativeLayout;

import com.aspsine.irecyclerview.IRecyclerView;

/**
* Created by Administrator on 2016/7/28.
*/
public class EmptyRecyclerView extends IRecyclerView {
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() {
Adapter adapter = getMyAdapter();
if (emptyView != null && adapter != null) {
final boolean emptyViewVisible = adapter.getItemCount() == 0;
emptyView.setVisibility(emptyViewVisible ? VISIBLE : GONE);
setVisibility(emptyViewVisible ? GONE : VISIBLE);
}
}

/**
* 对getIAdapter做些简单处理，避免跟getAdapter重名，叫getMyAdapter。
*
* @return
*/
private Adapter getMyAdapter() {
Adapter adapter = null;
try {
adapter = getIAdapter();
} catch (Exception e) {

}
return adapter;
}

@Override
public void setIAdapter(Adapter adapter) {
final Adapter oldAdapter = getMyAdapter();
if (oldAdapter != null) {
oldAdapter.unregisterAdapterDataObserver(observer);
}
super.setIAdapter(adapter);
if (adapter != null) {
adapter.registerAdapterDataObserver(observer);
}

checkIfEmpty();
}

public void setEmptyView(View emptyView) {
this.emptyView = emptyView;
checkIfEmpty();

if (emptyView.getParent() == null) {
//如果emptyView没有父布局，则添加至当前RecyclerView的父View中
ViewParent parent = getParent();
if (parent instanceof RelativeLayout) {
//相对布局
RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(
LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
ViewGroup parentView = (ViewGroup) getParent();
layoutParams.addRule(RelativeLayout.CENTER_IN_PARENT);
parentView.addView(emptyView, layoutParams);
} else if (getParent() instanceof ViewGroup) {
ViewGroup parentView = (ViewGroup) getParent();
parentView.addView(emptyView);
}
}
}
}