Android之RecyclerView简单使用(三)

使用过ListView滴小伙伴都知道。ListView有这样一个属性android:divider，用来设置每一个item之间切割线滴属性。问题来了，那么RecyclerView这个控件有没有这个属性呢，尝试了一下，没有这个属性。可是RecyclerView有这种方法mLinearRecycler.addItemDecoration()，用来加入切割线滴。以下是这部分源代码：

public static abstract class ItemDecoration {

public void onDraw(Canvas c, RecyclerView parent, State state)
{
            onDraw(c, parent);
}

public void onDrawOver(Canvas c, RecyclerView parent, State state)
{
            onDrawOver(c, parent);
}
 @Deprecated
public void getItemOffsets(Rect outRect, int itemPosition,RecyclerView parent)
{
            outRect.set(0, 0, 0, 0);
}

public void getItemOffsets(Rect outRect, View view,RecyclerView parent, State state)
{
     getItemOffsets(outRect, ((LayoutParams)view.getLayoutParams()).getViewLayoutPosition(), parent);
}
    }

RecyclerView在调用addItemDecoration()滴时候就会去绘制decoration，通过源代码我们会发现，会调用里面的onDraw()和onDrawOver()方法。而getItemOffsets()，是为每一个Item设置一定的偏移量。主要用于绘制decorator。

以下我们来看一下该类的实现，代码例如以下：

    package recyclerview.hy.com.myrecyclerview.decoration;

    import android.content.Context;
    import android.graphics.Canvas;
    import android.graphics.Rect;
    import android.graphics.drawable.Drawable;
    import android.support.v7.widget.LinearLayoutManager;
    import android.support.v7.widget.RecyclerView;
    import android.view.View;

    import recyclerview.hy.com.myrecyclerview.R;

    /**
     * Created by Ying on 2016/2/16.
     */
    public class ListItemDecoration extends RecyclerView.ItemDecoration {

    private Drawable mDrawable;

    private final static int DEFAULT_ORENTATION = LinearLayoutManager.VERTICAL;

    private int mOrientation;

    public ListItemDecoration(Context context, int orientation) {
        if (orientation != LinearLayoutManager.HORIZONTAL && orientation != LinearLayoutManager.VERTICAL) {
            //方法一：假设没设置布局显示方向，默认设置为垂直方向
            this.mOrientation = DEFAULT_ORENTATION;
            //方法二：抛出异常，提示设置布局方向
           // throw new IllegalArgumentException("invalid orientation");
        } else {
            this.mOrientation = orientation;
        }
        //设置切割线样式
        mDrawable = context.getResources().getDrawable(R.drawable.divider);
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        if (mOrientation == LinearLayoutManager.HORIZONTAL) {
            drawHorizontal(c, parent);
        } else {
            drawVertical(c, parent);
        }
    }

    private void drawHorizontal(Canvas c, RecyclerView parent) {
        int top = parent.getPaddingTop();
        int bottom = parent.getHeight() - parent.getPaddingBottom();
        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = parent.getChildAt(i);
            RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)child.getLayoutParams();
            int left = child.getRight() + params.rightMargin;
            int right = left + mDrawable.getIntrinsicHeight();
            mDrawable.setBounds(left, top, right, bottom);
            mDrawable.draw(c);
        }
    }

    private void drawVertical(Canvas c, RecyclerView parent) {
        int left = parent.getPaddingLeft();
        int right = parent.getWidth() - parent.getPaddingRight();
        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = parent.getChildAt(i);
            android.support.v7.widget.RecyclerView v = new android.support.v7.widget.RecyclerView(parent.getContext());
            RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                    .getLayoutParams();
            int top = child.getBottom() + params.bottomMargin;
            int bottom = top + mDrawable.getIntrinsicHeight();
            mDrawable.setBounds(left, top, right, bottom);
            mDrawable.draw(c);
        }
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        if (mOrientation == DEFAULT_ORENTATION) {
            outRect.set(0, 0, 0, mDrawable.getIntrinsicHeight());
        } else {
            outRect.set(0, 0, mDrawable.getIntrinsicWidth(), 0);
        }
    }
    }

这样就实现了切割线的类，我们仅仅要在Activity中加入这样一句话就可以：

mLinearRecycler.addItemDecoration(new ListItemDecoration(this, LinearLayoutManager.VERTICAL));

看一下效果图：

假设你想设置其他样式滴切割线仅仅需在这句话进行改动：

 mDrawable = context.getResources().getDrawable(R.drawable.divider);

关于RecyclerView实现GridView和瀑布流效果就不在贴代码了。这些代码demo里面有。

看一下效果图：

GridView：

瀑布流：

关于瀑布流背景点击变色，假设有疑惑，能够參考我滴还有一篇博客Android之简单改变button颜色方案。

项目代码：demo下载地址

如有疑问。记得给我留言哦~技术交流嘛~~喜欢滴，顶一下呗！