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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!
Android之RecyclerView简单使用(三)
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