代碼如下：

// 時間線裝飾器public class TimeLineDecoration extends RecyclerView.ItemDecoration { private Paint mPaint; public TimeLineDecoration() { mPaint = new Paint(); mPaint.setStyle(Paint.Style.FILL); mPaint.setColor(Color.BLUE); mPaint.setStrokeWidth(5); } @Override public void onDraw(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) { super.onDraw(c, parent, state); RecyclerView.LayoutManager layoutManager = parent.getLayoutManager(); // 這里的childcount為可見item的個數(shù)。 與item的個數(shù)不一定相同。 int childCount = parent.getChildCount(); for (int i = 0; i < childCount; i++) { View child = parent.getChildAt(i); // 避免硬編碼，這里通過代碼獲取在getItemOffsets方法中設(shè)置的寬度 int leftDecoWidth = layoutManager.getLeftDecorationWidth(child); // 根據(jù)position獲取當(dāng)前的數(shù)據(jù)，然后根據(jù)數(shù)據(jù)狀態(tài)繪制不同的形狀 int position = parent.getChildAdapterPosition(child); int cx = leftDecoWidth / 2; int cy = child.getTop() + child.getHeight() / 2; int radius = 20; if (position == 2) {c.drawRect(cx - radius, cy - radius, cx + radius, cy + radius, mPaint); } else if (position == 4) {// 繪制外圈為空心圓，內(nèi)圈為實(shí)心圓mPaint.setStyle(Paint.Style.STROKE);c.drawCircle(cx, cy, radius, mPaint);mPaint.setStyle(Paint.Style.FILL);c.drawCircle(cx, cy, radius >> 1, mPaint); } else {c.drawCircle(cx, cy, radius, mPaint); } // 繪制item中間的連接線，第一個item與最后一個item的連接線需單獨(dú)處理一下。 if (position == 0) {c.drawLine(cx, cy + mPaint.getStrokeWidth() + radius, cx, child.getBottom(), mPaint); } else if (position == parent.getAdapter().getItemCount() - 1) {c.drawLine(cx, child.getTop(), cx, cy - mPaint.getStrokeWidth() - radius, mPaint); } else {c.drawLine(cx, cy + mPaint.getStrokeWidth() + radius, cx, child.getBottom(), mPaint);c.drawLine(cx, child.getTop(), cx, cy - mPaint.getStrokeWidth() - radius, mPaint); } } } @Override public void onDrawOver(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) { super.onDrawOver(c, parent, state); // 不受outRect設(shè)置的范圍影響，可以繪制在item上。 } @Override public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) { super.getItemOffsets(outRect, view, parent, state); // 在item左邊留下100像素的空間。 item的布局會在減掉這100像素后處理。 outRect.left = 100; }}

然后將該itemdecoration設(shè)置到recyclerview上。

RecyclerAdapter adapter = new RecyclerAdapter(this, data);mRecyclerView.setLayoutManager(new LinearLayoutManager(this));mRecyclerView.addItemDecoration(new TimeLineDecoration());mRecyclerView.setAdapter(adapter);

實(shí)現(xiàn)效果如下：

之前在其他地方學(xué)習(xí)到，還可以通過在item layout中實(shí)現(xiàn)時間線的效果。

參考：1、啟艦博客。

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