Question

我想插入一个RecyclerView ItemDecorator分隔符，左边与列表元素内的TextView（项目标题）对齐，该元素被限制为距父项左侧72dp。我们在Google Material Design Docs中看到了here。我假设我需要以某种方式引用titleTextView上的布局参数，但我不知道如何从我的ItemDecorator代码中执行此操作，因为我似乎只能获取ConstraintLayout的参数，而不是textview本身。任何帮助或指示正确的方向将不胜感激！我尝试获取textView参数的相关ItemDecorator代码如下所示：

        for (int i = 0; i < recyclerView.getChildCount() - 1; ++i) {
            View child = recyclerView.getChildAt(i);
            RecyclerView.LayoutParams params =(RecyclerView.LayoutParams) child.getLayoutParams();
//this just gives me the constraint layout, not the TextView params, how to reference the textViewParams!?

RecyclerView看起来像这样：

        <android.support.v7.widget.RecyclerView
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:id="@+id/myList"
        android:name="com.example.Something"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layoutManager="LinearLayoutManager"
        tools:context=".controllers.fragments.ExampleFragment"
        tools:listitem="@layout/fragment_something"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent" />

列表项xml是带有一些TextView的约束布局，相关部分如下所示：

    <android.support.constraint.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="72dp">

    <ImageView
        android:id="@+id/myImageView"
        android:layout_width="32dp"
        android:layout_height="32dp"
        android:layout_marginLeft="16dp"
        app:layout_constraintLeft_toLeftOf="parent"
        tools:src="@drawable/ic_menu_manage"
        android:src="@drawable/ic_menu_manage"
        app:layout_constraintTop_toTopOf="parent"
        android:layout_marginTop="16dp"
        app:layout_constraintBottom_toBottomOf="parent"
        android:layout_marginBottom="16dp" />

    <TextView
        android:id="@+id/titleTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="4dp"
        android:layout_marginLeft="72dp"
        android:layout_marginTop="20dp"
        android:text="MyTitle"
        android:textAppearance="@style/TextAppearance.AppCompat.Subhead"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/textView5"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:text="SampleTitle" />

    ...

    </android.support.constraint.ConstraintLayout>

Answer 1

使用自定义项目装饰器。

Server server = new Server();

        server.Connect("m_server");
        Database db = server.Databases["m_DB"];

        foreach (Table tbl in db.Model.Tables)
        {
            Console.WriteLine("Table: ", tbl.Name.ToString());

        }

你设置它

class CustomItemDecoration(context: Context) : RecyclerView.ItemDecoration()
{

    private val mDivider: Drawable = context.resources.getDrawable(R.drawable.custom_item_divider) // this is a shape   that i want to use

    override fun onDrawOver(c: Canvas,
                            parent: RecyclerView,
                            state: RecyclerView.State)
    {
        val left = parent.paddingLeft // change to how much padding u want to add here .  
        val right = parent.width - parent.paddingRight

        val childCount = parent.childCount
        for (i in 0 until childCount)
        {
            val child = parent.getChildAt(i)

            val params = child.layoutParams as RecyclerView.LayoutParams

            val top = child.bottom + params.bottomMargin
            val bottom = top + mDivider.intrinsicHeight

            mDivider.setBounds(left, top, right, bottom)
            mDivider.draw(c)
        }
    }
}

Answer 2

由于ConstraintLayout是一个ViewGroup，因此只需执行以下操作即可从ItemDecorator内部访问ConstraintLayout的子节点：

public class MyItemDivider extends RecyclerView.ItemDecoration {

....some code here


@Override
public void onDrawOver(Canvas canvas, RecyclerView recyclerView,
                       RecyclerView.State state) {
    super.onDrawOver(canvas, recyclerView, state);

    for (int i = 0; i < recyclerView.getChildCount() - 1; ++i) {
        ViewGroup item = (ViewGroup) recyclerView.getChildAt(i);

        //for now the titleText is at index 1 of constraint layout
        TextView titleChild =  (TextView) item.getChildAt(1);
        int titleTextLeftMargin = titleChild.getLeft();

        //this would probably be less brittle 
        //but I would need to somehow change the context for this to be doable?
        //View titleChild = item.findViewById(R.id.contractListProductNameTextView);
        ...some more code here

            divider.setBounds(titleTextLeftMargin, top, right, bottom);
            divider.draw(canvas);
        }
    }
}

Answer 3

由于你已经知道你需要从左侧插入分频器多少（如果你不知道的话，从你的布局计算它），你需要做的就是将该dp值转换为px，如图所示here并将其设置为自定义ItemDecoration中的左边界。

public class InsetDividerDecoration extends RecyclerView.ItemDecoration {

    private final int insetValueInDp = 72; // in your case

    @Override
    public void onDraw(Canvas canvas, RecyclerView parent, RecyclerView.State state) {
        int dividerLeft = (int) (insetValueInDp * Resources.getSystem().getDisplayMetrics().density);

        ...
    }
}

并在您的回收商视图中使用它 -

recyclerView.addItemDecoration(new InsetDividerDecoration());

Android RecyclerView ItemDecorator：将Inset Divider与List Item TextView对齐

3 个答案: