Android-使用RecyclerView的ItemDecoration 实现炫酷的 吸顶效果

开始逐渐领略到ItemDecoration的美~

 

源码已上传至github，感兴趣的同学可以下载：

吸顶效果源码 https://github.com/junmei520/LSY_PullupRecyclerView

 

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：

 

如果你对分类型的RecyclerView还不是太了解，可以参看我前面的文章，让你一分钟征服RecyclerView的基本使用。

如果你对ItemDecoration的使用也不太了解，那就再看下我的另外两篇文章吧：

使用ItemDecoration为RecyclerView的Item设置padding和使用ItemDecoration为RecyclerView的Item设置分割线。

总觉得循序渐进是一个不错的学习方法。

 

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)

 

1. /**
2. * 联网请求所需的url
3. */
4. 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";

1. //联网获取数据
2. getDataFromNet();

1. /**
2. * 使用okhttpUtils进行联网请求数据
3. */
4. private void getDataFromNet() {
5. OkHttpUtils.
6. get()
7. .url(url)
8. .build()
9. .execute( new StringCallback() {
10. @Override
11. public void onError(okhttp3.Call call, Exception e, int id) {
12. Log.e( "TAG", "联网失败" + e.getMessage());
13. }
14.  
15. @Override
16. public void onResponse(String response, int id) {
17. Log.e( "TAG", "联网成功==" + response);
18.  
19. //联网成功后使用fastjson解析
20. processData(response);
21. }
22. });
23. }

1. /**
2. * 使用fastjson进行解析
3. *
4. * @param json
5. */
6. private void processData(String json) {
7. //这里使用GsonFormat生成对应的bean类
8. JSONObject jsonObject = parseObject(json);
9.  
10. String data = jsonObject.getString( "data");
11. JSONObject dataObj = JSON.parseObject(data);
12.  
13. String coming = dataObj.getString( "coming");
14. List<WaitMVBean.DataBean.ComingBean> comingslist = parseArray(coming, WaitMVBean.DataBean.ComingBean.class);
15.  
16. //测试是否解析数据成功
17. // String strTest = comingslist.get(0).getCat();
18. // Log.e("TAG", strTest + "222");
19.  
20. //解析数据成功,设置适配器-->
21.  
22. }
23.  
24. }

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

 

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

适配器：

 

1. public class MyRecyclerAdapter extends RecyclerView.Adapter {
2.  
3. private final List<WaitMVBean.DataBean.ComingBean> comingslist;
4. private final Context mContext;
5. private final LayoutInflater mLayoutInflater;
6.  
7.  
8. public MyRecyclerAdapter(Context mContext, List<WaitMVBean.DataBean.ComingBean> comingslist) {
9. this.mContext = mContext;
10. this.comingslist = comingslist;
11. mLayoutInflater = LayoutInflater.from(mContext);
12. }
13.  
14. @Override
15. public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
16. return new MyViewHolder(mLayoutInflater.inflate(R.layout.date_item, null));
17. }
18.  
19. @Override
20. public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
21. MyViewHolder myholder = (MyViewHolder) holder;
22. myholder.setData(position);
23. }
24.  
25. @Override
26. public int getItemCount() {
27. return comingslist.size();
28. }
29.  
30. class MyViewHolder extends RecyclerView.ViewHolder {
31. private TextView mv_name;
32. private TextView mv_dec;
33. private TextView mv_date;
34. private ImageView imageView;
35.  
36. public MyViewHolder(View itemView) {
37. super(itemView);
38. mv_name = (TextView) itemView.findViewById(R.id.mv_name);
39. mv_dec = (TextView) itemView.findViewById(R.id.mv_dec);
40. mv_date = (TextView) itemView.findViewById(R.id.mv_date);
41. imageView = (ImageView) itemView.findViewById(R.id.image);
42. }
43.  
44. public void setData(int position) {
45. WaitMVBean.DataBean.ComingBean coming = comingslist.get(position);
46.  
47. String name = coming.getNm();
48. mv_name.setText(name);
49.  
50. String date = coming.getShowInfo();
51. mv_date.setText(date);
52.  
53. String dec = coming.getScm();
54. mv_dec.setText(dec);
55.  
56. //注：当你发下图片无法打开是，做个字符串替换即可
57. String imagUrl = coming.getImg();
58. String newImagUrl = imagUrl.replaceAll( "w.h", "50.80");
59.  
60. //使用Glide加载图片
61. Glide.with(mContext)
62. .load(newImagUrl)
63. .into(imageView);
64. }
65. }
66. }

item的布局：

 

1. <?xml version="1.0" encoding="utf-8"?>
2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
3. android:layout_width="wrap_content"
4. android:layout_height="wrap_content"
5. android:background="#ffffff"
6. android:gravity="center_vertical"
7. android:orientation="horizontal">
8.  
9. <ImageView
10. android:id="@+id/image"
11. android:layout_width="70dp"
12. android:layout_height="110dp"
13. android:layout_marginBottom="5dp"
14. android:layout_marginLeft="10dp"
15. android:layout_marginRight="8dp"
16. android:layout_marginTop="5dp" />
17.  
18. <LinearLayout
19. android:layout_width="0dp"
20. android:layout_height="wrap_content"
21. android:layout_marginLeft="6dp"
22. android:layout_weight="1"
23. android:orientation="vertical">
24.  
25. <TextView
26. android:id="@+id/mv_name"
27. android:layout_width="wrap_content"
28. android:layout_height="wrap_content"
29. android:text="神奇動物在哪裏"
30. android:textColor="#000000"
31. android:textSize="15sp" />
32.  
33. <LinearLayout
34. android:layout_width="wrap_content"
35. android:layout_height="wrap_content"
36. android:orientation="horizontal">
37.  
38. <TextView
39. android:layout_width="wrap_content"
40. android:layout_height="wrap_content"
41. android:text="观众"
42. android:textColor="#55000000"
43. android:textSize="14sp" />
44.  
45. <TextView
46. android:id="@+id/tv_people"
47. android:layout_width="wrap_content"
48. android:layout_height="wrap_content"
49. android:text="9.0 "
50. android:textColor="#FFCE42"
51. android:textSize="18sp" />
52.  
53. <TextView
54. android:layout_width="wrap_content"
55. android:layout_height="wrap_content"
56. android:text=" | 专业"
57. android:textColor="#55000000"
58. android:textSize="14sp" />
59.  
60. <TextView
61. android:id="@+id/tv_professional"
62. android:layout_width="wrap_content"
63. android:layout_height="wrap_content"
64. android:text="6.7"
65. android:textColor="#FFCE42"
66. android:textSize="18sp" />
67. </LinearLayout>
68.  
69. <TextView
70. android:id="@+id/mv_dec"
71. android:layout_width="wrap_content"
72. android:layout_height="wrap_content"
73. android:layout_marginTop="8dp"
74. android:text="神奇動物城，法師顯超能"
75. android:textColor="#99000000"
76. android:textSize="11sp" />
77.  
78. <TextView
79. android:id="@+id/mv_date"
80. android:layout_width="wrap_content"
81. android:layout_height="wrap_content"
82. android:layout_marginTop="10dp"
83. android:text="今天165家影院放映2088场"
84. android:textColor="#99000000"
85. android:textSize="11sp" />
86. </LinearLayout>
87.  
88. </LinearLayout>

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

 

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

此时RecyclerView简单的完成效果如下：

 

 

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

 

1. public class NameBean {
2. String name;
3.  
4. public String getName() {
5. return name;
6. }
7.  
8. public void setName(String name) {
9. this.name = name;
10. }
11. }

 

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

 

1. public class SectionDecoration extends RecyclerView.ItemDecoration {
2. private static final String TAG = "SectionDecoration";
3.  
4. private List<NameBean> dataList;
5.  
6. private DecorationCallback callback;
7. private TextPaint textPaint;
8. private Paint paint;
9. private int topGap;
10. private int alignBottom;
11. private Paint.FontMetrics fontMetrics;
12.  
13.  
14. public SectionDecoration(List<NameBean> dataList, Context context, DecorationCallback decorationCallback) {
15. Resources res = context.getResources();
16. this.dataList = dataList;
17. this.callback = decorationCallback;
18. //设置悬浮栏的画笔---paint
19. paint = new Paint();
20. paint.setColor(res.getColor(R.color.colorGray));
21.  
22. //设置悬浮栏中文本的画笔
23. textPaint = new TextPaint();
24. textPaint.setAntiAlias( true);
25. textPaint.setTextSize(DensityUtil.dip2px(context, 14));
26. textPaint.setColor(Color.DKGRAY);
27. textPaint.setTextAlign(Paint.Align.LEFT);
28. fontMetrics = new Paint.FontMetrics();
29. //决定悬浮栏的高度等
30. topGap = res.getDimensionPixelSize(R.dimen.sectioned_top);
31. //决定文本的显示位置等
32. alignBottom = res.getDimensionPixelSize(R.dimen.sectioned_alignBottom);
33. }
34.  
35. @Override
36. public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
37. super.getItemOffsets(outRect, view, parent, state);
38. int pos = parent.getChildAdapterPosition(view);
39. Log.i(TAG, "getItemOffsets：" + pos);
40. String groupId = callback.getGroupId(pos);
41. if (groupId.equals("-1")) return;
42. //只有是同一组的第一个才显示悬浮栏
43. if (pos == 0 || isFirstInGroup(pos)) {
44. outRect.top = topGap;
45. if (dataList.get(pos).getName() == "") {
46. outRect.top = 0;
47. }
48. } else {
49. outRect.top = 0;
50. }
51. }
52.  
53. @Override
54. public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
55. super.onDraw(c, parent, state);
56. int left = parent.getPaddingLeft();
57. int right = parent.getWidth() - parent.getPaddingRight();
58. int childCount = parent.getChildCount();
59. for (int i = 0; i < childCount; i++) {
60. View view = parent.getChildAt(i);
61. int position = parent.getChildAdapterPosition(view);
62. String groupId = callback.getGroupId(position);
63. if (groupId.equals("-1")) return;
64. String textLine = callback.getGroupFirstLine(position).toUpperCase();
65. if (textLine == "") {
66. float top = view.getTop();
67. float bottom = view.getTop();
68. c.drawRect(left, top, right, bottom, paint);
69. return;
70. } else {
71. if (position == 0 || isFirstInGroup(position)) {
72. float top = view.getTop() - topGap;
73. float bottom = view.getTop();
74. //绘制悬浮栏
75. c.drawRect(left, top - topGap, right, bottom, paint);
76. //绘制文本
77. c.drawText(textLine, left, bottom, textPaint);
78. }
79. }
80. }
81. }
82.  
83. @Override
84. public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
85. super.onDrawOver(c, parent, state);
86. int itemCount = state.getItemCount();
87. int childCount = parent.getChildCount();
88. int left = parent.getPaddingLeft();
89. int right = parent.getWidth() - parent.getPaddingRight();
90. float lineHeight = textPaint.getTextSize() + fontMetrics.descent;
91.  
92. String preGroupId = "";
93. String groupId = "-1";
94. for (int i = 0; i < childCount; i++) {
95. View view = parent.getChildAt(i);
96. int position = parent.getChildAdapterPosition(view);
97.  
98. preGroupId = groupId;
99. groupId = callback.getGroupId(position);
100. if (groupId.equals("-1") || groupId.equals(preGroupId)) continue;
101.  
102. String textLine = callback.getGroupFirstLine(position).toUpperCase();
103. if (TextUtils.isEmpty(textLine)) continue;
104.  
105. int viewBottom = view.getBottom();
106. float textY = Math.max(topGap, view.getTop());
107. //下一个和当前不一样移动当前
108. if (position + 1 < itemCount) {
109. String nextGroupId = callback.getGroupId(position + 1);
110. //组内最后一个view进入了header
111. if (nextGroupId != groupId && viewBottom < textY) {
112. textY = viewBottom;
113. }
114. }
115. //textY - topGap决定了悬浮栏绘制的高度和位置
116. c.drawRect(left, textY - topGap, right, textY, paint);
117. //left+2*alignBottom 决定了文本往左偏移的多少（加-->向左移）
118. //textY-alignBottom 决定了文本往右偏移的多少 (减-->向上移)
119. c.drawText(textLine, left + 2 * alignBottom, textY - alignBottom, textPaint);
120. }
121. }
122.  
123.  
124. /**
125. * 判断是不是组中的第一个位置
126. *
127. * @param pos
128. * @return
129. */
130. private boolean isFirstInGroup(int pos) {
131. if (pos == 0) {
132. return true;
133. } else {
134. // 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
135. // 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
136. String prevGroupId = callback.getGroupId(pos - 1);
137. String groupId = callback.getGroupId(pos);
138. //判断前一个字符串 与 当前字符串 是否相同
139. if (prevGroupId.equals(groupId)) {
140. return false;
141. } else {
142. return true;
143. }
144. }
145. }
146.  
147. //定义一个借口方便外界的调用
148. interface DecorationCallback {
149. String getGroupId(int position);
150.  
151. String getGroupFirstLine(int position);
152. }
153. }

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);

1. private void setPullAction(List<WaitMVBean.DataBean.ComingBean> comingslist) {
2. dataList = new ArrayList<>();
3.  
4. for (int i = 0; i < comingslist.size(); i++) {
5. NameBean nameBean = new NameBean();
6. String name0 = comingslist.get(i).getComingTitle();
7. nameBean.setName(name0);
8. dataList.add(nameBean);
9. }
10. }
11.  
12.  

 

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

 

1. recyclerView.addItemDecoration( new SectionDecoration(dataList,mContext, new SectionDecoration.DecorationCallback() {
2. //返回标记id (即每一项对应的标志性的字符串)
3. @Override
4. public String getGroupId(int position) {
5. if(dataList.get(position).getName()!=null) {
6. return dataList.get(position).getName();
7. }
8. return "-1";
9. }
10.  
11. //获取同组中的第一个内容
12. @Override
13. public String getGroupFirstLine(int position) {
14. if(dataList.get(position).getName()!=null) {
15. return dataList.get(position).getName();
16. }
17. return "";
18. }
19. }));

这样就完成了~

再看一眼最终效果感受一下：

 

 

--------------------- 本文来自 李诗雨 的CSDN 博客 ，全文地址请点击：https://blog.csdn.net/cjm2484836553/article/details/53453982?utm_source=copy