[英]Add line separator on first item of recyclerview
如何在第一项 (10) 的正上方添加一行?
我正在使用 RecyclerView 和 LinearLayoutManager 来实现我的设计。
活动_main.xml:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<SeekBar
android:id="@+id/timesTablesSeekBar"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="5dp"
android:layout_marginLeft="5dp"
android:layout_marginTop="5dp"
android:layout_marginEnd="5dp"
android:layout_marginRight="5dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="32dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
list_layout.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/linearLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:showDividers="beginning">
<TextView
android:id="@+id/timeTables"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:text=""
android:textSize="70px"
android:textStyle="bold|italic" />
</LinearLayout>
您可以在textView上方的list_layout.xml中添加高度为1dp且背景为黑色的视图,只需删除recyclerView的默认分隔线即可。
首先,使用 LinearLayout 的android:showDividers
来划分项目不是最佳实践。 首先,我会像这样从list_layout.xml
删除外部LinearLayout
:
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/timeTables"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:text=""
android:textSize="70px"
android:textStyle="bold|italic" />
要显示分隔线,最好的方法是使用RecyclerView.ItemDecoration
。 请参阅DividerItemDecoration
绘制分隔线: https : //developer.android.com/reference/androidx/recyclerview/widget/DividerItemDecoration
dividerItemDecoration = new DividerItemDecoration(recyclerView.getContext(),
layoutManager.getOrientation());
recyclerView.addItemDecoration(dividerItemDecoration);
那么唯一缺少的就是绘制顶线。 您可以像这样实现自定义ItemDecoration
:
public class TopLineDecoration extends RecyclerView.ItemDecoration {
private static final int[] ATTRS = new int[]{android.R.attr.listDivider};
private final Drawable divider;
public TopLineDecoration(Context context) {
TypedArray a = context.obtainStyledAttributes(ATTRS);
divider = a.getDrawable(0);
a.recycle();
}
@Override
public void onDraw(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
int childCount = parent.getChildCount();
for (int i = 0; i < childCount; i++) {
View child = parent.getChildAt(i);
if (parent.getChildAdapterPosition(child) == 0) {
RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
int top = child.getTop() - params.topMargin;
int bottom = top + divider.getIntrinsicHeight();
int left = parent.getPaddingLeft();
int right = parent.getWidth() - parent.getPaddingRight();
divider.setBounds(left, top, right, bottom);
divider.draw(c);
}
}
}
}
你的最终实现将是这样的:
dividerItemDecoration = new DividerItemDecoration(recyclerView.getContext(),
layoutManager.getOrientation());
topLineDecoration = new TopLineDecoration(recyclerView.getContext())
recyclerView.addItemDecoration(dividerItemDecoration);
recyclerView.addItemDecoration(topLineDecoration)
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