在控件RecyclerView中,分割线DividerItemDecoration类的使用经常见,如果是使用自带的分割线,只需要这样写即可

   RecyclerView mRecyclerView;
mRecyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL));

会出现一条1pd的灰色的分割线,但是我如果想自己写自定义的分割线呢,这个时候需要我们自定义一个shape,在里面进行自定义样式然后进行引用

代码如下:divider.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<solid android:color="#CB8589" />
<size android:height="15dp" />
</shape>

那我怎么在我的java里面用呢,代码如下:

        //添加自定义的分割线
DividerItemDecoration divider = new DividerItemDecoration(this, DividerItemDecoration.VERTICAL);
divider.setDrawable(ContextCompat.getDrawable(this, R.drawable.divider));
mRecyclerView.addItemDecoration(divider);

如此,我的模拟器上就出现了又粗又红的分割线

但是这个时候又有问题,我每个子项都有,那么我如果想最后一个不要分割线呢,这个时候,我打开了DividerItemDecoration类的源码,发现了循环的地方

我只需要把这个地方减1,那么我不就可以删去最后一个子项的分割线了吗,显然,改源码是很不合理的,于是,我新建一个GridItemDecoration的类,修改如下:

GridItemDecoration.java
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
// package com.example.administrator.myapplication; import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.RecyclerView.ItemDecoration;
import android.support.v7.widget.RecyclerView.State;
import android.util.Log;
import android.view.View; public class GridItemDecoration extends ItemDecoration {
public static final int HORIZONTAL = 0;
public static final int VERTICAL = 1;
private static final String TAG = "DividerItem";
private static final int[] ATTRS = new int[]{16843284};
private Drawable mDivider;
private int mOrientation;
private final Rect mBounds = new Rect(); public GridItemDecoration(Context context, int orientation) {
TypedArray a = context.obtainStyledAttributes(ATTRS);
this.mDivider = a.getDrawable(0);
if (this.mDivider == null) {
Log.w("DividerItem", "@android:attr/listDivider was not set in the theme used for this DividerItemDecoration. Please set that attribute all call setDrawable()");
} a.recycle();
this.setOrientation(orientation);
} public void setOrientation(int orientation) {
if (orientation != 0 && orientation != 1) {
throw new IllegalArgumentException("Invalid orientation. It should be either HORIZONTAL or VERTICAL");
} else {
this.mOrientation = orientation;
}
} public void setDrawable(@NonNull Drawable drawable) {
if (drawable == null) {
throw new IllegalArgumentException("Drawable cannot be null.");
} else {
this.mDivider = drawable;
}
} public void onDraw(Canvas c, RecyclerView parent, State state) {
if (parent.getLayoutManager() != null && this.mDivider != null) {
if (this.mOrientation == 1) {
this.drawVertical(c, parent);
} else {
this.drawHorizontal(c, parent);
} }
} private void drawVertical(Canvas canvas, RecyclerView parent) {
canvas.save();
int left;
int right;
if (parent.getClipToPadding()) {
left = parent.getPaddingLeft();
right = parent.getWidth() - parent.getPaddingRight();
canvas.clipRect(left, parent.getPaddingTop(), right, parent.getHeight() - parent.getPaddingBottom());
} else {
left = 0;
right = parent.getWidth();
} int childCount = parent.getChildCount(); //当最后一个子项的时候去除下划线
for (int i = 0; i < childCount - 1; ++i) {
View child = parent.getChildAt(i);
parent.getDecoratedBoundsWithMargins(child, this.mBounds);
int bottom = this.mBounds.bottom + Math.round(child.getTranslationY());
int top = bottom - this.mDivider.getIntrinsicHeight();
this.mDivider.setBounds(left, top, right, bottom);
this.mDivider.draw(canvas);
} canvas.restore();
} private void drawHorizontal(Canvas canvas, RecyclerView parent) {
canvas.save();
int top;
int bottom;
if (parent.getClipToPadding()) {
top = parent.getPaddingTop();
bottom = parent.getHeight() - parent.getPaddingBottom();
canvas.clipRect(parent.getPaddingLeft(), top, parent.getWidth() - parent.getPaddingRight(), bottom);
} else {
top = 0;
bottom = parent.getHeight();
} int childCount = parent.getChildCount(); for (int i = 0; i < childCount; ++i) {
View child = parent.getChildAt(i);
parent.getLayoutManager().getDecoratedBoundsWithMargins(child, this.mBounds);
int right = this.mBounds.right + Math.round(child.getTranslationX());
int left = right - this.mDivider.getIntrinsicWidth();
this.mDivider.setBounds(left, top, right, bottom);
this.mDivider.draw(canvas);
} canvas.restore();
} public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state) {
if (this.mDivider == null) {
outRect.set(0, 0, 0, 0);
} else {
if (this.mOrientation == 1) {
outRect.set(0, 0, 0, this.mDivider.getIntrinsicHeight());
} else {
outRect.set(0, 0, this.mDivider.getIntrinsicWidth(), 0);
} }
}
}

如此,我在activity里面把这个类引进就可以:

  //最后一个不显示分割线且自定义分割线
GridItemDecoration gridItemDecoration = new GridItemDecoration(this, DividerItemDecoration.VERTICAL);
gridItemDecoration.setDrawable(ContextCompat.getDrawable(this, R.drawable.divider));
mRecyclerView.addItemDecoration(gridItemDecoration);

完整代码如下:

package com.example.administrator.myapplication;

import android.content.ContextWrapper;
import android.graphics.Paint;
import android.os.Bundle;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.DividerItemDecoration;
import android.support.v7.widget.RecyclerView; import java.util.List;
import java.util.ArrayList; public class BodyActivity extends AppCompatActivity {
RecyclerView mRecyclerView;
public Paint paint; @Override
protected void onCreate(Bundle saveInstanceState) {
super.onCreate(saveInstanceState);
setContentView(R.layout.activity_body);
//1.获取控件
mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view); //设置布局方式
mRecyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));//线性布局
// mRecyclerView.setLayoutManager(new GridLayoutManager(this,2));//网格布局
mRecyclerView.setHasFixedSize(true); //是否重新计算大小 //3.准备数据
List<News> newsList = new ArrayList<>();
News news;
for (int i = 1; i <= 20; i++) {
news = new News();
news.setNewsTitle("java是世界上最好的语言" + i);
news.setNewsSource("新华网" + i);
news.setPublishTime("2018-8-6");
newsList.add(news);
} //添加Android自带的分割线
// mRecyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL)); //添加自定义的分割线
// DividerItemDecoration divider = new DividerItemDecoration(this, DividerItemDecoration.VERTICAL);
// divider.setDrawable(ContextCompat.getDrawable(this, R.drawable.divider));
// mRecyclerView.addItemDecoration(divider); //最后一个不显示分割线且自定义分割线
GridItemDecoration gridItemDecoration = new GridItemDecoration(this, DividerItemDecoration.VERTICAL);
gridItemDecoration.setDrawable(ContextCompat.getDrawable(this, R.drawable.divider));
mRecyclerView.addItemDecoration(gridItemDecoration); //4.准备适配器
NewsAdapter newsAdapter = new NewsAdapter(newsList);
mRecyclerView.setAdapter(newsAdapter); }
}

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