Android实现当下最流行的吸顶效果

开始逐渐领略到ItemDecoration的美~

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今天让我使用 ItemDecoration来完成 可推动的悬浮导航栏的效果，最终实现的效果如下图：

Android 实现当下最流行的吸顶效果

具体实现步骤如下：

根据我前面的文章所讲的RecyclerView的基本使用，我们先来完成基本的recyclerView：

第一步：布局里写一个RecyclerView

第二步：实例化

recyclerView = (RecyclerView) findViewById(R.id.recyclerView);

第三步：获取所需的数据 (这里我们来个真实点的情景，去联网请求数据)

/**
 * 联网请求所需的url
 */ 
 public String url=http://api.meituan.com/mmdb/movie/v2/list/rt/order/coming.json?ci=1&limit=12&token=&__vhost=api.maoyan.com&utm_campaign=AmovieBmovieCD-1&movieBundleVersion=6801&utm_source=xiaomi&utm_medium=android&utm_term=6.8.0&utm_content=868030022327462&net=255&dModel=MI%205&uuid=0894DE03C76F6045D55977B6D4E32B7F3C6AAB02F9CEA042987B380EC5687C43&lat=40.100673&lng=116.378619&__skck=6a375bce8c66a0dc293860dfa83833ef&__skts=1463704714271&__skua=7e01cf8dd30a179800a7a93979b430b2&__skno=1a0b4a9b-44ec-42fc-b110-ead68bcc2824&__skcy=sXcDKbGi20CGXQPPZvhCU3%2FkzdE%3D;

//联网获取数据 
 getDataFromNet();

/**
 * 使用okhttpUtils进行联网请求数据
 */ 
 private void getDataFromNet() { 
 OkHttpUtils. 
 get() 
 .url(url) 
 .build() 
 .execute(new StringCallback() { 
  @Override 
  public void onError(okhttp3.Call call, Exception e, int id) { 
  Log.e("TAG", "联网失败" + e.getMessage()); 
  } 
 
  @Override 
  public void onResponse(String response, int id) { 
  Log.e("TAG", "联网成功==" + response); 
 
  //联网成功后使用fastjson解析 
  processData(response); 
  } 
 }); 
 }

/**
 * 使用fastjson进行解析
 *
 * @param json
 */ 
 private void processData(String json) { 
 //这里使用GsonFormat生成对应的bean类 
 JSONObject jsonObject = parseObject(json); 
 
 String data = jsonObject.getString("data"); 
 JSONObject dataObj = JSON.parseObject(data); 
 
 String coming = dataObj.getString("coming"); 
 List comingslist = parseArray(coming, WaitMVBean.DataBean.ComingBean.class); 
 
 //测试是否解析数据成功 
// String strTest = comingslist.get(0).getCat(); 
// Log.e("TAG", strTest + "222"); 
 
 //解析数据成功,设置适配器--> 
 
 } 
 }

第四步：解析数据成功后，创建并设置适配器,并传递相关数据

//解析数据成功,设置适配器 
 MyRecyclerAdapter adapter = new MyRecyclerAdapter( mContext,comingslist); 
 recyclerView.setAdapter(adapter);

适配器：

public class MyRecyclerAdapter extends RecyclerView.Adapter { 
 private final List comingslist; 
 private final Context mContext; 
 private final LayoutInflater mLayoutInflater; 
 public MyRecyclerAdapter(Context mContext, List comingslist) { 
 this.mContext = mContext; 
 this.comingslist = comingslist; 
 mLayoutInflater = LayoutInflater.from(mContext); 
 } 
 @Override 
 public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
 return new MyViewHolder(mLayoutInflater.inflate(R.layout.date_item, null)); 
 } 
 @Override 
 public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) { 
 MyViewHolder myholder = (MyViewHolder) holder; 
 myholder.setData(position); 
 } 
 @Override 
 public int getItemCount() { 
 return comingslist.size(); 
 } 
 class MyViewHolder extends RecyclerView.ViewHolder { 
 private TextView mv_name; 
 private TextView mv_dec; 
 private TextView mv_date; 
 private ImageView imageView; 
 public MyViewHolder(View itemView) { 
 super(itemView); 
 mv_name = (TextView) itemView.findViewById(R.id.mv_name); 
 mv_dec = (TextView) itemView.findViewById(R.id.mv_dec); 
 mv_date = (TextView) itemView.findViewById(R.id.mv_date); 
 imageView = (ImageView) itemView.findViewById(R.id.image); 
 } 
 public void setData(int position) { 
 WaitMVBean.DataBean.ComingBean coming = comingslist.get(position); 
 String name = coming.getNm(); 
 mv_name.setText(name); 
 String date = coming.getShowInfo(); 
 mv_date.setText(date); 
 String dec = coming.getScm(); 
 mv_dec.setText(dec); 
 //注：当你发下图片无法打开是，做个字符串替换即可 
 String imagUrl = coming.getImg(); 
 String newImagUrl = imagUrl.replaceAll("w.h", "50.80"); 
 
 //使用Glide加载图片 
 Glide.with(mContext) 
  .load(newImagUrl) 
  .into(imageView); 
 } 
 } 
}

item的布局：

<?xml version="1.0" encoding="utf-8"?>

第五步：一定不能忘！！！

recycleView不仅要设置适配器还要设置布局管理者,否则图片不显示

GridLayoutManager manager = new GridLayoutManager(this, 1); 
 recyclerView.setLayoutManager(manager);

此时RecyclerView简单的完成效果如下：

Android 实现当下最流行的吸顶效果

下面开始做可推动的悬浮导航栏：

第一步：首先我们来写一个类，它起标记的作用，来放每一个item的对应的悬浮栏的字符串

public class NameBean { 
 String name; 
 public String getName() { 
 return name; 
 } 
 public void setName(String name) { 
 this.name = name; 
 } 
}

第二步：自定义一个SectionDecoration 类继承 RecyclerView的ItemDecoration

public class SectionDecoration extends RecyclerView.ItemDecoration { 
 private static final String TAG = "SectionDecoration"; 
 private List dataList; 
 private DecorationCallback callback; 
 private TextPaint textPaint; 
 private Paint paint; 
 private int topGap; 
 private int alignBottom; 
 private Paint.FontMetrics fontMetrics; 
 public SectionDecoration(List dataList, Context context, DecorationCallback decorationCallback) { 
 Resources res = context.getResources(); 
 this.dataList = dataList; 
 this.callback = decorationCallback; 
 //设置悬浮栏的画笔---paint 
 paint = new Paint(); 
 paint.setColor(res.getColor(R.color.colorGray)); 
 //设置悬浮栏中文本的画笔 
 textPaint = new TextPaint(); 
 textPaint.setAntiAlias(true); 
 textPaint.setTextSize(DensityUtil.dip2px(context, 14)); 
 textPaint.setColor(Color.DKGRAY); 
 textPaint.setTextAlign(Paint.Align.LEFT); 
 fontMetrics = new Paint.FontMetrics(); 
 //决定悬浮栏的高度等 
 topGap = res.getDimensionPixelSize(R.dimen.sectioned_top); 
 //决定文本的显示位置等 
 alignBottom = res.getDimensionPixelSize(R.dimen.sectioned_alignBottom); 
 } 
 @Override 
 public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) { 
 super.getItemOffsets(outRect, view, parent, state); 
 int pos = parent.getChildAdapterPosition(view); 
 Log.i(TAG, "getItemOffsets：" + pos); 
 String groupId = callback.getGroupId(pos); 
 if (groupId.equals("-1")) return; 
 //只有是同一组的第一个才显示悬浮栏 
 if (pos == 0 || isFirstInGroup(pos)) { 
 outRect.top = topGap; 
 if (dataList.get(pos).getName() == "") { 
 outRect.top = 0; 
 } 
 } else { 
 outRect.top = 0; 
 } 
 } 
 @Override 
 public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) { 
 super.onDraw(c, parent, state); 
 int left = parent.getPaddingLeft(); 
 int right = parent.getWidth() - parent.getPaddingRight(); 
 int childCount = parent.getChildCount(); 
 for (int i = 0; i < childCount; i++) { 
 View view = parent.getChildAt(i); 
 int position = parent.getChildAdapterPosition(view); 
 String groupId = callback.getGroupId(position); 
 if (groupId.equals("-1")) return; 
 String textLine = callback.getGroupFirstLine(position).toUpperCase(); 
 if (textLine == "") { 
 float top = view.getTop(); 
 float bottom = view.getTop(); 
 c.drawRect(left, top, right, bottom, paint); 
 return; 
 } else { 
 if (position == 0 || isFirstInGroup(position)) { 
  float top = view.getTop() - topGap; 
  float bottom = view.getTop(); 
  //绘制悬浮栏 
  c.drawRect(left, top - topGap, right, bottom, paint); 
  //绘制文本 
  c.drawText(textLine, left, bottom, textPaint); 
 } 
 } 
 } 
 } 
 @Override 
 public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) { 
 super.onDrawOver(c, parent, state); 
 int itemCount = state.getItemCount(); 
 int childCount = parent.getChildCount(); 
 int left = parent.getPaddingLeft(); 
 int right = parent.getWidth() - parent.getPaddingRight(); 
 float lineHeight = textPaint.getTextSize() + fontMetrics.descent; 
 String preGroupId = ""; 
 String groupId = "-1"; 
 for (int i = 0; i < childCount; i++) { 
 View view = parent.getChildAt(i); 
 int position = parent.getChildAdapterPosition(view); 
 preGroupId = groupId; 
 groupId = callback.getGroupId(position); 
 if (groupId.equals("-1") || groupId.equals(preGroupId)) continue; 
 String textLine = callback.getGroupFirstLine(position).toUpperCase(); 
 if (TextUtils.isEmpty(textLine)) continue; 
 int viewBottom = view.getBottom(); 
 float textY = Math.max(topGap, view.getTop()); 
 //下一个和当前不一样移动当前 
 if (position + 1 < itemCount) { 
 String nextGroupId = callback.getGroupId(position + 1); 
 //组内最后一个view进入了header 
 if (nextGroupId != groupId && viewBottom < textY) { 
  textY = viewBottom; 
 } 
 } 
 //textY - topGap决定了悬浮栏绘制的高度和位置 
 c.drawRect(left, textY - topGap, right, textY, paint); 
 //left+2*alignBottom 决定了文本往左偏移的多少（加-->向左移） 
 //textY-alignBottom 决定了文本往右偏移的多少 (减-->向上移) 
 c.drawText(textLine, left + 2 * alignBottom, textY - alignBottom, textPaint); 
 } 
 } 
 /**
 * 判断是不是组中的第一个位置
 *
 * @param pos
 * @return
 */ 
 private boolean isFirstInGroup(int pos) { 
 if (pos == 0) { 
 return true; 
 } else { 
 // 因为是根据 字符串内容的相同与否 来判断是不是同意组的，所以此处的标记id 要是String类型 
 // 如果你只是做联系人列表，悬浮框里显示的只是一个字母，则标记id直接用 int 类型就行了 
 String prevGroupId = callback.getGroupId(pos - 1); 
 String groupId = callback.getGroupId(pos); 
 //判断前一个字符串 与 当前字符串 是否相同 
 if (prevGroupId.equals(groupId)) { 
 return false; 
 } else { 
 return true; 
 } 
 } 
 } 
 //定义一个借口方便外界的调用 
 interface DecorationCallback { 
 String getGroupId(int position); 
 String getGroupFirstLine(int position); 
 } 
}

第三步：在向list集合中先把每一个item的起“标记”作用的字符串都加进去

setPullAction(comingslist);

private void setPullAction(List comingslist) { 
 dataList = new ArrayList<>(); 
 for (int i = 0; i < comingslist.size(); i++) { 
 NameBean nameBean = new NameBean(); 
 String name0 = comingslist.get(i).getComingTitle(); 
 nameBean.setName(name0); 
 dataList.add(nameBean); 
 } 
 }

第四步：在setAdapter() 前，为RecyclerView添加ItemDecoration:

recyclerView.addItemDecoration(new SectionDecoration(dataList,mContext, new SectionDecoration.DecorationCallback() { 
 //返回标记id (即每一项对应的标志性的字符串) 
 @Override 
 public String getGroupId(int position) { 
  if(dataList.get(position).getName()!=null) { 
  return dataList.get(position).getName(); 
  } 
  return "-1"; 
 } 
  //获取同组中的第一个内容 
 @Override 
 public String getGroupFirstLine(int position) { 
  if(dataList.get(position).getName()!=null) { 
  return dataList.get(position).getName(); 
  } 
  return ""; 
 } 
 }));

这样就完成了~

再看一眼最终效果感受一下：

Android 实现当下最流行的吸顶效果

以上就是本文的全部内容，希望本文的内容对大家的学习或者工作能带来一定的帮助，同时也希望多多支持创新互联！

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