基于SwipeRefreshLayout的上拉加载控件

大家好，又见面了，我是你们的朋友全栈君。

距离上一篇博客，居然已经过了大半年的时间，时间过得真快啊！CSDN最近大改版，各种用户体验也是被无数人吐槽，让人提不起任何写博客的兴趣，不过，该写的博客还是必须得写，话不多话，直接进入正题。
现在项目中用列表来展示数据比比皆是，ListView和RecyclerView大家也是耳熟能详。实际项目中，后台肯定的接口肯定都是分页的，那么，分页加载也是自然而然的事，下面基于Google原生的下拉刷新控件SwipeRefreshLayout，实现上拉加载更多的功能。直接上代码:
CustomSwipeRefreshLayout.java

package com.jackie.sample.custom_view;
import android.content.Context;
import android.support.v4.widget.SwipeRefreshLayout;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ListView;
import com.jackie.sample.R;
import com.jackie.sample.utils.LogUtils;
/** * Created by Jackie on 2018/1/11 * 自定义下拉刷新上拉加载控件 目前只支持ListView */
public class CustomSwipeRefreshLayout extends SwipeRefreshLayout implements OnScrollListener { 

private Context mContext;
// 滑动到最下面时的上拉操作
private int mTouchSlop;
// ListView
private ListView mListView;
// 上拉监听器, 到了最底部的上拉加载操作
private OnLoadListener mOnLoadListener;
private OnScrollListener mOnScrollListener;
private OnScrollStateChangeListener mOnScrollStateChangeListener;
// ListView的加载中FooterView
private View mFooterView;
// 按下时的y坐标
private int mDownY;
// 移动时的y坐标, 与mDownY一起用于滑动到底部时判断是上拉还是下拉
private int mMoveY;
// 是否在加载中 (上拉加载更多)
private boolean mIsLoading = false;
private int mCanLoadCount = 6;
private int mStartLoadCount = 3;
public CustomSwipeRefreshLayout(Context context) {
this(context, null);
}
public CustomSwipeRefreshLayout(Context context, AttributeSet attrs) {
super(context, attrs);
initView(context);
}
private void initView(Context context) {
mContext = context;
// 表示滑动的时候，手的移动要大于这个距离才开始移动控件。如果小于这个距离就不触发移动控件，如ViewPager就是用这个距离来判断用户是否翻页
mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
// 设置下拉progress的开始位置和结束位置
// setProgressViewOffset(false, DensityUtils.dp2px(context, 20), DensityUtils.dp2px(context, 80));
}
@Override  
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {  
super.onLayout(changed, left, top, right, bottom);
// 初始化ListView对象 
if (mListView == null) {
getListView();
}
}  
/** * 获取ListView对象 */  
private void getListView() {  
int childCount = getChildCount();
if (childCount > 0) {
for (int i = 0; i < childCount; i++) {
View childView = getChildAt(i);
if (childView instanceof ListView) {
mListView = (ListView) childView;
// 设置滚动监听器给ListView, 使得滚动的情况下也可以自动加载
mListView.setOnScrollListener(this);
}
}
}  
}
/** * @param event * @return */
@Override
public boolean dispatchTouchEvent(MotionEvent event) {  
final int action = event.getAction();  
switch (action) {  
case MotionEvent.ACTION_DOWN:
// 按下
mDownY = (int) event.getRawY();
break;
case MotionEvent.ACTION_MOVE:
// 移动
mMoveY = (int) event.getRawY();
break;
case MotionEvent.ACTION_UP:  
// 抬起
if (canLoad()) {  
loadData();  
}
break;  
default:  
break;  
}  
return super.dispatchTouchEvent(event);  
}  
// 是否可以加载更多, 条件是到了最底部, ListView不在加载中, 且为上拉操作.
private boolean canLoad() {
if (mListView == null) {
LogUtils.showLog("不能加载");
return false;
}
return isBottom() && !mIsLoading && isPullUp() && mListView.getAdapter().getCount() > mCanLoadCount && !isRefreshing();
}
/** * 设置列表的数目达到多少条才能上拉加载更多 * @param canLoadCount */
public void setCanLoadCount(int canLoadCount) {
this.mCanLoadCount = canLoadCount;
}
// 判断是否到了最底部
private boolean isBottom() {
if (mListView != null && mListView.getAdapter() != null) {  
return mListView.getLastVisiblePosition() >= (mListView.getAdapter().getCount() - mStartLoadCount);
}
return false;  
}
/** * 设置上拉到列表倒数第几条的时候开始加载更多 * @param startLoadCount */
public void setStartLoadCount(int startLoadCount) {
this.mStartLoadCount = startLoadCount;
}
// 是否是上拉操作
private boolean isPullUp() {  
return (mDownY - mMoveY) >= mTouchSlop;
}  
// 如果到了最底部,而且是上拉操作.那么执行onLoad方法
private void loadData() {  
if (mOnLoadListener != null) {  
// 设置状态 
setLoading(true);
mOnLoadListener.onLoad();
}  
}  
private void setLoading(boolean loading) {
mIsLoading = loading;
if (mIsLoading) {
mFooterView = LayoutInflater.from(mContext).inflate(R.layout.listview_footer, null, false);
// if (mListView.getFooterViewsCount() <= 0) { 

// mListView.addFooterView(mFooterView);
// }
//
// mFooterView.setVisibility(View.VISIBLE);
mListView.addFooterView(mFooterView);
} else {
if (mListView == null || mListView.getFooterViewsCount() <= 0 || mListView.getAdapter() == null || mFooterView == null) {
return;
}
// mFooterView.setVisibility(View.GONE);
mListView.removeFooterView(mFooterView);
// ObjectAnimator animation = ObjectAnimator.ofFloat(mFooterView, "scaleY", 1, 0);
// animation.setDuration(100);
// animation.start();
// animation.addListener(new Animator.AnimatorListener() { 

// public void onAnimationStart(Animator arg0) { 

//
// }
//
// public void onAnimationRepeat(Animator arg0) { 

//
// }
//
// public void onAnimationEnd(Animator arg0) { 

// mListView.removeFooterView(mFooterView);
//
// }
//
// public void onAnimationCancel(Animator arg0) { 

//
// }
// });
mDownY = 0;
mMoveY = 0;
}  
}  
// 设置上拉加载的监听
public void setOnLoadListener(OnLoadListener loadListener) {  
mOnLoadListener = loadListener;  
}
// 滑动状态改变的代理
@Override  
public void onScrollStateChanged(AbsListView view, int scrollState) {
if (mOnScrollStateChangeListener != null) {
mOnScrollStateChangeListener.onScrollStateChanged(view, scrollState);
}
}  
@Override  
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
if (mOnScrollListener != null) {
mOnScrollListener.onScroll(view, firstVisibleItem, visibleItemCount, totalItemCount);
}
// 滚动时到了最底部也可以加载更多 
if (canLoad()) {  
loadData();  
}
}  
// 加载更多的监听器
public interface OnLoadListener { 

void onLoad();
}
public interface OnScrollListener { 

void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount);
}
public interface OnScrollStateChangeListener { 

void onScrollStateChanged(AbsListView listView, int state);
}
public void onRefreshComplete() {
setLoading(false);
setRefreshing(false);
// if (isPullUp()) { 

// setLoading(false);
// } else { 

// setRefreshing(false);
// }
}
public void setOnScrollListener(OnScrollListener onScrollListener) {
this.mOnScrollListener = onScrollListener;
}
public void setOnScrollStateChangeListener(OnScrollStateChangeListener onScrollStateChangeListener) {
this.mOnScrollStateChangeListener = onScrollStateChangeListener;
}
}

listview_footer.xml

<?xml version="1.0" encoding="utf-8"?>  
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center" android:paddingBottom="8dp" android:paddingTop="5dp" >
<ProgressBar android:layout_width="wrap_content" android:layout_height="wrap_content" style="?android:attr/progressBarStyleSmall" android:layout_centerVertical="true" android:layout_centerHorizontal="true" android:paddingRight="100dp" android:indeterminate="true" />  
<TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_gravity="center" android:gravity="center" android:paddingTop="5dip" android:text="加载更多..." android:textAppearance="?android:attr/textAppearanceMedium" android:textColor="@android:color/darker_gray" android:textSize="14sp" android:textStyle="bold" />  
</RelativeLayout>

可以看出代码很简单，注释很清楚，这里就不作赘述。由于SwipeRefreshLayout本身就是下拉加载控件，这样封装后，该控件就具备了下拉刷新上拉加载更多的功能，用法没有任务变化：

<com.jackie.sample.custom_view.CustomSwipeRefreshLayout
android:id="@+id/swipe_refresh_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ListView
android:id="@+id/list_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="none" />
</com.jackie.sample.custom_view.CustomSwipeRefreshLayout>

唯一的不足之处，该控件只支持ListView，不支持RecyclerView，有兴趣的同学可以自行优化。
SwipeRefreshLayoutActivity .java

package com.jackie.sample.material_design;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.widget.SwipeRefreshLayout;
import android.support.v7.app.AppCompatActivity;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import com.jackie.sample.R;
import com.jackie.sample.custom_view.CustomSwipeRefreshLayout;
import com.jackie.sample.utils.ThreadUtils;
import java.util.ArrayList;
import java.util.List;
/** * Created by Jackie on 2018/1/11. * 自定下拉刷新上拉加载控件 */
public class SwipeRefreshLayoutActivity extends AppCompatActivity { 

private CustomSwipeRefreshLayout mSwipeRefreshLayout;
private ListView mListView;
private ArrayAdapter mAdapter;
private List<String> mList;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_swipe_refresh_layout);
initView();
initData();
initEvent();
}
private void initView() {
mSwipeRefreshLayout = (CustomSwipeRefreshLayout) findViewById(R.id.swipe_refresh_layout);
mListView = (ListView) findViewById(R.id.list_view);
mList = new ArrayList<>();
}
private void initData() {
for (int i = 0; i < 20; i++) {
mList.add("第" + (i + 1) + "条数据");
}
mAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, mList);
mListView.setAdapter(mAdapter);
}
private void refreshData() {
ThreadUtils.newThread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
runOnUiThread(new Runnable() {
@Override
public void run() {
for (int i = 0; i < 5; i++) {
mList.add("第" + (i + 1) + "条数据");
}
mAdapter.notifyDataSetChanged();
mSwipeRefreshLayout.onRefreshComplete();
}
});
}
});
}
private void initEvent() {
mSwipeRefreshLayout.setColorSchemeResources(R.color.colorPrimary);
/** * 下拉刷新 */
mSwipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
@Override
public void onRefresh() {
refreshData();
}
});
/** * 上拉加载更多 */
mSwipeRefreshLayout.setOnLoadListener(new CustomSwipeRefreshLayout.OnLoadListener() {
@Override
public void onLoad() {
refreshData();
}
});
}
}

效果图如下：
README

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基于SwipeRefreshLayout的上拉加载控件

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