android 上划加载 android上拉加载更多

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jordana 2023-08-29 17:30:27

文章标签 android 上划加载 android官方上拉加载加载 ide 数据 文章分类 Android 移动开发

5.0之后推出的RecycleView来代替ListView，可以说RecycleView和ListView比起有过之而无不及，下面这篇博客主要来实现RecyclerView的上拉加载更多功能。

基本思路是让RecyclerView的Adapter加载两种布局，第一个布局来显示主界面，第二个布局来显示上拉加载时的提示信息，让RecyclerView监听是否滑动到最后一个item，如果是，则调用上拉刷新的逻辑，拉取远程数据，并显示第二个布局。等加载完毕时，刷新Adapter，并隐藏第二个布局.

下面主要是针对对RecyclerAdapter的修饰封装，一般我们在使用RecycleView的时候会将RecycleAdapter和RecycleHolder分开进行封装，在使用的时候，就会很方便(这两个类就不贴了，各自有各自的实现)。

先贴两个博客地址翔哥和傻子斌的添加haedView和footVIew的具体操作，因为下拉刷新和上拉加载就是基于添加这个来实现。

1.核心实现

@Override
public int getItemViewType(int position) {
if (position == getItemCount() - 1) {
return TYPE_FOOTER;
} else {
return TYPE_ITEM;
}
}
@Override
public int getItemCount() {
return super.getItemCount() + 1;
}

用过listView的人都知道这两个方法，可以说很大程度上和listView一样，不过ListView有自带的addHead 和 addFoot的方法，RecycleView则没有，所以就需要我们在Adapter中对其进行实现。

2.实现上拉加载更多

public abstract class BasePullUpRecyclerAdapter extends BaseRecyclerAdapter {
public static final int TYPE_FOOTER = 0;//两种状态 footview显示的时候和不显示的一般item
public static final int TYPE_ITEM = 1;
public static final int STATE_INVISIBLE = 0;//footView的四种状态 不可见 加载中 没有更多 没有数据
public static final int STATE_LOADING = 1;
public static final int STATE_NO_MORE = 2;
public static final int STATE_NO_DATA = 3;
protected int state = STATE_LOADING;//默认为加载中
protected FooterView footerView;//footView
private OnPullUpListener pullUpListener;//上拉监听
public BasePullUpRecyclerAdapter(RecyclerView v, Collection datas, int itemLayoutId) {
super(v, datas, itemLayoutId);
v.addOnScrollListener(new BasePullUpScrollListener());//将自定义的监听添加进Adapter
footerView = new FooterView(cxt);//初始化自定义的FootView
}
@Override
public int getItemViewType(int position) {//根据不同的位置设置不同的类型状态
if (position == getItemCount() - 1) {
return TYPE_FOOTER;
} else {
return TYPE_ITEM;
}
}
@Override
public int getItemCount() {//
return super.getItemCount() + 1;
}
@Override
public RecyclerHolder onCreateViewHolder(ViewGroup parent, int viewType) {
if (viewType == TYPE_ITEM) {
return super.onCreateViewHolder(parent, viewType);
} else if (viewType == TYPE_FOOTER) {
refreshFooterView();
return new RecyclerHolder(footerView);
}
return null;
}
@Override
public void onBindViewHolder(RecyclerHolder holder, int position) {
if (position == getItemCount() - 1) {
//因为已经在footerview写死了，所以这里就不用再去设置
//没有数据的时候也不显示footer
if (position == 0) {
getFooterView().setVisibility(View.GONE);
}
} else {
super.onBindViewHolder(holder, position);
}
}
public int getState() {//返回状态
return this.state;
}
public void setState(int state) {//设置不同的状态然后更新footView
this.state = state;
refreshFooterView();
}
/**
* 获取底部的FooterView
*
* @return
*/
public FooterView getFooterView() {
return this.footerView;
}
/**
* 滚动到底部时的监听器
*
* @param l
*/
public void setPullUpListener(OnPullUpListener l) {
this.pullUpListener = l;
}
private void refreshFooterView() {
switch (state) {
case STATE_INVISIBLE:
footerView.setInVisibleState();
break;
case STATE_LOADING:
footerView.setLoadingState();
break;
case STATE_NO_MORE:
footerView.setNoMoreState();
break;
case STATE_NO_DATA:
footerView.setNoDataState();
break;
}
} ········

3.实现对不同的Layout进行适配

/**
* 监听，判断RecyclerView滚动到底部时，加载onBottom方法
*/
public class BasePullUpScrollListener extends RecyclerView.OnScrollListener {
public static final int LINEAR = 0;
public static final int GRID = 1;
public static final int STAGGERED_GRID = 2;
//标识RecyclerView的LayoutManager是哪种
protected int layoutManagerType;
// 瀑布流的最后一个的位置
protected int[] lastPositions;
// 最后一个的位置
protected int lastVisibleItem;
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (newState == RecyclerView.SCROLL_STATE_IDLE && lastVisibleItem + 1 >=
getItemCount() && pullUpListener != null) {
pullUpListener.onBottom(state);//回调加载更多监听
}
}
//根据不同的Layout类型处理FootView
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
if (layoutManager instanceof LinearLayoutManager) {
layoutManagerType = LINEAR;
} else if (layoutManager instanceof GridLayoutManager) {
layoutManagerType = GRID;
} else if (layoutManager instanceof StaggeredGridLayoutManager) {
layoutManagerType = STAGGERED_GRID;
} else {
throw new RuntimeException(
"Unsupported LayoutManager used. Valid ones are " +
"LinearLayoutManager, GridLayoutManager and " +
"StaggeredGridLayoutManager");
}
switch (layoutManagerType) {
case LINEAR:
lastVisibleItem = ((LinearLayoutManager) layoutManager)
.findLastVisibleItemPosition();
break;
case GRID:
lastVisibleItem = ((GridLayoutManager) layoutManager)
.findLastVisibleItemPosition();
break;
case STAGGERED_GRID:
StaggeredGridLayoutManager staggeredGridLayoutManager
= (StaggeredGridLayoutManager) layoutManager;
lastPositions = new int[staggeredGridLayoutManager.getSpanCount()];
staggeredGridLayoutManager.findLastVisibleItemPositions(lastPositions);
lastVisibleItem = findMax(lastPositions);
break;
}
}
private int findMax(int[] lastPositions) {
int max = lastPositions[0];
for (int value : lastPositions) {
if (value > max) {
max = value;
}
}
return max;
}
}

4.自定义的footView(可根据自己需求自定义)

public class FooterView extends LinearLayout {
protected String loadingText = "加载中…";
protected String noMoreText = "已加载全部";
protected String noDataText = "暂无内容";
private final TextView textView;
private final ProgressBar progressBar;
public FooterView(Context context) {
super(context);
textView = new TextView(context);
progressBar = new ProgressBar(context);
init(context);
}
public void init(Context context) {
this.setOrientation(HORIZONTAL);
this.setGravity(Gravity.CENTER);
LayoutParams params = new LayoutParams(LayoutParams.MATCH_PARENT,
LayoutParams.WRAP_CONTENT);
params.gravity = Gravity.CENTER;
params.height = dip2px(23);
this.setLayoutParams(params);
progressBar.setIndeterminate(true);
LayoutParams progressBarparams = new LayoutParams(LayoutParams.WRAP_CONTENT,
LayoutParams.WRAP_CONTENT);
progressBarparams.width = progressBarparams.height = dip2px(22);
progressBar.setLayoutParams(progressBarparams);
LayoutParams textViewparams = new LayoutParams(LayoutParams.WRAP_CONTENT, dip2px(20));
textView.setTextColor(0xff666666);
textView.setTextSize(16);
textView.setLayoutParams(textViewparams);
this.addView(progressBar);
this.addView(textView);
}
public void setText(CharSequence s) {
textView.setText(s);
}
public void setTextColor(int color) {
textView.setTextColor(color);
}
public void setTextSize(float size) {
textView.setTextSize(size);
}
public void setNoDataState() {
this.setVisibility(View.VISIBLE);
progressBar.setVisibility(View.GONE);
textView.setVisibility(View.VISIBLE);
textView.setText(noDataText);
}
public void setNoMoreState() {
this.setVisibility(View.VISIBLE);
progressBar.setVisibility(View.GONE);
textView.setVisibility(View.VISIBLE);
textView.setText(noMoreText);
}
public void setLoadingState() {
this.setVisibility(View.VISIBLE);
progressBar.setVisibility(View.VISIBLE);
textView.setVisibility(View.VISIBLE);
textView.setText(loadingText);
}
public ProgressBar getProgressBar() {
return progressBar;
}
public void setInVisibleState() {
this.setVisibility(View.GONE);
}
public void setLoadingText(String loadingText) {
this.loadingText = loadingText;
}
public void setNoMoreText(String noMoreText) {
this.noMoreText = noMoreText;
}
public void setNoDataText(String noDataText) {
this.noDataText = noDataText;
}
public int dip2px(float dpValue) {
Resources r = getResources();
float px = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,
dpValue, r.getDisplayMetrics());
return (int) px;
}
}

之所以都用代码来写，不用xml布局，为了减少一个xml布局，实际这个View的布局也不复杂，一个RelativeLayout就可以搞定了。就不具体注释来说明了，都看得懂

5.具体使用

1.对适配器进行监听，设置加载中和加载数据

mAdapter.setPullUpListener(new BasePullUpRecyclerAdapter.OnPullUpListener() {
@Override
public void onBottom(int state) {
mAdapter.setState(BasePullUpRecyclerAdapter.STATE_LOADING);
mPresenter.load();
}
});

2.在数据返回的时候对其进行处理

public void onEvent(MessageEventNew event) {
setLoadingIndicator(false);
if (event.code == ModelEvent.SUCCESS) {
if (event.list == null || event.list.size() == 0) {//如果没有数据，就设置为STATE_NO_MORE
onContentEmpty();
mAdapter.setState(BasePullUpRecyclerAdapter.STATE_NO_MORE);
} else {
lastMessageId = event.list.get(event.list.size() - 1).id;

if(lastMessageId==newLastId){//否则加载的数据和上一次加载的数据是否相同来判断是NOMORE还是有数据然后隐藏

mAdapter.setState(BasePullUpRecyclerAdapter.STATE_NO_MORE);
}else {
mAdapter.setState(BasePullUpRecyclerAdapter.STATE_INVISIBLE);
}
showContent(event.list);
newLastId = lastMessageId;
}
} else {
ViewKit.shortToast(event.message);
onNetwork();
}
}

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