安卓当下最流行的吸顶效果的实现
QNTJuliane
8年前
<p>开始逐渐领略到 <strong>ItemDecoration</strong> 的美~</p> <p>今天让我 使用 <strong>ItemDecoration</strong> 来完成 <strong>可推动的悬浮导航栏</strong> 的效果，最终实现的效果如下图：</p> <p style="text-align:center"><img src="https://simg.open-open.com/show/476686b398f5ad935b7aae5a9d5f092b.gif"></p> <p>具体实现步骤如下：</p> <p>根据我前面的文章所讲的RecyclerView的基本使用，我们 <strong>先来完成基本的recyclerView</strong> ：</p> <p>第一步：布局里写一个RecyclerView</p> <p>第二步：实例化</p> <pre> <code class="language-java">recyclerView = (RecyclerView) findViewById(R.id.recyclerView); </code></pre> <p>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)</p> <pre> <code class="language-java">/** * 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⪫=40.100673&lng=116.378619&__skck=6a375bce8c66a0dc293860dfa83833ef&__skts=1463704714271&__skua=7e01cf8dd30a179800a7a93979b430b2&__skno=1a0b4a9b-44ec-42fc-b110-ead68bcc2824&__skcy=sXcDKbGi20CGXQPPZvhCU3%2FkzdE%3D"; </code></pre> <pre> <code class="language-java">//联网获取数据 getDataFromNet(); </code></pre> <pre> <code class="language-java">/** * 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.Callcall, 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); } }); } </code></pre> <pre> <code class="language-java">/** * 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 JSONObjectjsonObject = parseObject(json); String data = jsonObject.getString("data"); JSONObjectdataObj = JSON.parseObject(data); String coming = dataObj.getString("coming"); List<WaitMVBean.DataBean.ComingBean> 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--> } } </code></pre> <p>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</p> <pre> <code class="language-java">//解析数据成功,设置适配器 MyRecyclerAdapteradapter = new MyRecyclerAdapter( mContext,comingslist); recyclerView.setAdapter(adapter); </code></pre> <p>适配器：</p> <pre> <code class="language-java">public class MyRecyclerAdapterextends RecyclerView.Adapter { private final List<WaitMVBean.DataBean.ComingBean> comingslist; private final ContextmContext; private final LayoutInflatermLayoutInflater; public MyRecyclerAdapter(ContextmContext, List<WaitMVBean.DataBean.ComingBean> comingslist) { this.mContext = mContext; this.comingslist = comingslist; mLayoutInflater = LayoutInflater.from(mContext); } @Override public RecyclerView.ViewHolderonCreateViewHolder(ViewGroupparent, int viewType) { return new MyViewHolder(mLayoutInflater.inflate(R.layout.date_item, null)); } @Override public void onBindViewHolder(RecyclerView.ViewHolderholder, int position) { MyViewHoldermyholder = (MyViewHolder) holder; myholder.setData(position); } @Override public int getItemCount() { return comingslist.size(); } class MyViewHolderextends RecyclerView.ViewHolder { private TextViewmv_name; private TextViewmv_dec; private TextViewmv_date; private ImageViewimageView; public MyViewHolder(ViewitemView) { 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.ComingBeancoming = 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); } } } </code></pre> <p>item的布局：</p> <pre> <code class="language-java"><?xmlversion="1.0" encoding="utf-8"?> <LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="wrap_content" android:layout_height="wrap_content" android:background="#ffffff" android:gravity="center_vertical" android:orientation="horizontal"> <ImageView android:id="@+id/image" android:layout_width="70dp" android:layout_height="110dp" android:layout_marginBottom="5dp" android:layout_marginLeft="10dp" android:layout_marginRight="8dp" android:layout_marginTop="5dp" /> <LinearLayout android:layout_width="0dp" android:layout_height="wrap_content" android:layout_marginLeft="6dp" android:layout_weight="1" android:orientation="vertical"> <TextView android:id="@+id/mv_name" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="神奇動物在哪裏" android:textColor="#000000" android:textSize="15sp" /> <LinearLayout android:layout_width="wrap_content" android:layout_height="wrap_content" android:orientation="horizontal"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="观众" android:textColor="#55000000" android:textSize="14sp" /> <TextView android:id="@+id/tv_people" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="9.0 " android:textColor="#FFCE42" android:textSize="18sp" /> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text=" | 专业" android:textColor="#55000000" android:textSize="14sp" /> <TextView android:id="@+id/tv_professional" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="6.7" android:textColor="#FFCE42" android:textSize="18sp" /> </LinearLayout> <TextView android:id="@+id/mv_dec" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="8dp" android:text="神奇動物城，法師顯超能" android:textColor="#99000000" android:textSize="11sp" /> <TextView android:id="@+id/mv_date" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="10dp" android:text="今天165家影院放映2088场" android:textColor="#99000000" android:textSize="11sp" /> </LinearLayout> </LinearLayout> </code></pre> <p>第五步：一定不能忘！！！</p> <p>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</p> <pre> <code class="language-java">GridLayoutManagermanager = new GridLayoutManager(this, 1); recyclerView.setLayoutManager(manager); </code></pre> <p>此时RecyclerView简单的完成效果如下：</p> <p style="text-align:center"><img src="https://simg.open-open.com/show/8f7872f2724cb84146bc6edad9e450f6.gif"></p> <p>下面开始做 可推动的 悬浮导航栏：</p> <p>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</p> <pre> <code class="language-java">public class NameBean { String name; public String getName() { return name; } public void setName(String name) { this.name = name; } } </code></pre> <p>第二步：自定义一个 <strong>SectionDecoration 类</strong> 继承 RecyclerView的ItemDecoration</p> <pre> <code class="language-java">public class SectionDecorationextends RecyclerView.ItemDecoration { private static final String TAG = "SectionDecoration"; private List<NameBean> dataList; private DecorationCallbackcallback; private TextPainttextPaint; private Paintpaint; private int topGap; private int alignBottom; private Paint.FontMetricsfontMetrics; public SectionDecoration(List<NameBean> dataList, Contextcontext, DecorationCallbackdecorationCallback) { Resourcesres = 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(RectoutRect, Viewview, RecyclerViewparent, RecyclerView.Statestate) { 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, RecyclerViewparent, RecyclerView.Statestate) { 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++) { Viewview = 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, RecyclerViewparent, RecyclerView.Statestate) { 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++) { Viewview = 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); } } </code></pre> <p>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</p> <pre> <code class="language-java">setPullAction(comingslist); </code></pre> <pre> <code class="language-java">private void setPullAction(List<WaitMVBean.DataBean.ComingBean> comingslist) { dataList = new ArrayList<>(); for (int i = 0; i < comingslist.size(); i++) { NameBeannameBean = new NameBean(); String name0 = comingslist.get(i).getComingTitle(); nameBean.setName(name0); dataList.add(nameBean); } } </code></pre> <p>第四步：在setAdapter() 前，为RecyclerView添加ItemDecoration:</p> <pre> <code class="language-java">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 ""; } })); </code></pre> <p>这样就 <strong>完成</strong> 了~</p> <p>再看一眼最终效果感受一下：</p> <p style="text-align:center"><img src="https://simg.open-open.com/show/476686b398f5ad935b7aae5a9d5f092b.gif"></p> <p> </p> <p>来自：http://android.jobbole.com/85325/</p> <p> </p>