Android RecyclerView 详解(2)---网格布局（支持多种分割线）
上篇Android RecyclerView 详解(1)—线性布局记录了下RecyclerView的使用方法，并且讲述了线性布局列表的使用方法，在此基础上加上了万能分割线，支持颜色分割线和图片分割线，同时支持对分割线设置线宽。这篇是总结一下网格布局的使用，同样也支持两种分割线和线宽的设置。主要的相关类：1. RecyclerView.Adapter2. GridLayoutManager
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上篇Android RecyclerView 详解(1)—线性布局
记录了下RecyclerView的使用方法，并且讲述了线性布局列表的使用方法，在此基础上加上了万能分割线，支持颜色分割线和图片分割线，同时支持对分割线设置线宽。
这篇是总结一下网格布局的使用，同样也支持两种分割线和线宽的设置。
主要的相关类：
1. RecyclerView.Adapter
2. GridLayoutManager 网格布局管理器
3. RecycleView.ItemDecoration 分割线
下面就直接通过一个例子来展示：
先上效果图：
(1) 颜色分割线
看起来还不错吧，根据item的数量去显示格子，当然如果你需要的样式不是三列，这个很简单，只需要在设置
GridLayoutManager的时候设置相应的列数即可，即：
mManagerLayout = new GridLayoutManager(getActivity(), 3);(2) 图片分割线
可能有人会说你的列表四周都有分割线，其实在不做特殊处理时左边和上面默认是没有分割线的。后面我会加上四周没有分割线的，其实这两种形式在实际开发中都是常见的，先来看四周都有边线的。
由于RecycleView是高度解耦的控件，绘制分割线只和 RecycleView.ItemDecoration 有关，所以我们只需关心怎么去继承 RecycleView.ItemDecoration 去实现我们所需的分割线，如下：
这里需要说明的是：颜色分割线和图片分割线原理是完全一样的，图片分割线只是将一张很细的图片传入即可。
public class GridDivider extends RecyclerView.ItemDecoration {
private Drawable mDividerDarwable;
private int mDividerHight = 1;
private Paint mColorPaint;
public final int[] ATRRS = new int[]{android.R.attr.listDivider};
public GridDivider(Context context) {
final TypedArray ta = context.obtainStyledAttributes(ATRRS);
this.mDividerDarwable = ta.getDrawable(0);
ta.recycle();
}
/*
int dividerHight 分割线的线宽
int dividerColor 分割线的颜色
*/
public GridDivider(Context context, int dividerHight, int dividerColor) {
this(context);
mDividerHight = dividerHight;
//绘制颜色分割线的画笔
mColorPaint = new Paint();
mColorPaint.setColor(dividerColor);
}
/*
int dividerHight 分割线的线宽
Drawable dividerDrawable 图片分割线
*/
public GridDivider(Context context, int dividerHight, Drawable dividerDrawable) {
this(context);
mDividerHight = dividerHight;
mDividerDarwable = dividerDrawable;
}
@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
super.onDraw(c, parent, state);
//画水平和垂直分割线
drawHorizontalDivider(c, parent);
drawVerticalDivider(c, parent);
}
public void drawVerticalDivider(Canvas c, RecyclerView parent) {
// 这里传入的parent是recycleview，通过它我们可以获取列表的所有的元素，
// 这里我们遍历列表中的每一个元素，对每一个元素绘制垂直分割线
final int childCount = parent.getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = parent.getChildAt(i);
//获取当前item布局参数，通过它可以知道该item的精确位置，我们通过这个位置去绘制它的分割线
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
final int top = child.getTop() - params.topMargin;
final int bottom = child.getBottom() + params.bottomMargin;
int left = 0;
int right = 0;
//左边第一列，
if ((i % 3) == 0) {
//item左边分割线
left = child.getLeft();
right = left + mDividerHight;
mDividerDarwable.setBounds(left, top, right, bottom);
mDividerDarwable.draw(c);
if (mColorPaint != null) {//如果是颜色分割线
c.drawRect(left, top, right, bottom, mColorPaint);
}
//item右边分割线
left = child.getRight() + params.rightMargin - mDividerHight;
right = left + mDividerHight;
} else {
//非左边第一列
left = child.getRight() + params.rightMargin - mDividerHight;
right = left + mDividerHight;
}
//画分割线
mDividerDarwable.setBounds(left, top, right, bottom);
mDividerDarwable.draw(c);
if (mColorPaint != null) {
c.drawRect(left, top, right, bottom, mColorPaint);
}
}
}
//....水平分割线与垂直分割线类似，完整代码见下。
}下面是完整代码：
1. MainActivity
public class MainActivity extends AppCompatActivity {
private GridFragment mGridFragment;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//网格
mGridFragment = new GridFragment();
getFragmentManager().beginTransaction().replace(R.id.activity_main, mGridFragment).commit();
}activity_main
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent">
</FrameLayout>2. GridFragment
public class GridFragment extends Fragment implements View.OnClickListener{
private RecyclerView mRecycleViewDrawable;
private RecyclerView mRecycleViewColor;
private LinearLayoutManager mManagerColor;
private LinearLayoutManager mManagerDrawable;
private List<String> mData;
private Button mDrawable;
private Button mColor;
private MyRecycleViewAdapter mRecycleViewAdapter;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_grid_layout, container, false);
mRecycleViewDrawable = (RecyclerView) view.findViewById(R.id.recycleview_drawable);
mRecycleViewColor = (RecyclerView) view.findViewById(R.id.recycleview_color);
mDrawable = (Button) view.findViewById(R.id.btn_drawable);
mDrawable.setOnClickListener(this);
mColor = (Button) view.findViewById(R.id.btn_color);
mColor.setOnClickListener(this);
//设置颜色分割线
mManagerColor = new GridLayoutManager(getActivity(), 3);
mRecycleViewColor.setLayoutManager(mManagerColor);
mRecycleViewColor.addItemDecoration(new GridDivider(getActivity(), 20, this.getResources().getColor(R.color.colorAccent)));
//设置图片分割线
mManagerDrawable = new GridLayoutManager(getActivity(), 3);
mRecycleViewDrawable.setLayoutManager(mManagerDrawable);
Drawable drawable = ContextCompat.getDrawable(getActivity(), R.mipmap.divider);
mRecycleViewDrawable.addItemDecoration(new GridDivider(getActivity(), 20, drawable));
//初始化数据
mData = new ArrayList<String>();
initData(mData);
mRecycleViewAdapter = new MyRecycleViewAdapter(getActivity(), R.layout.item_grid_recycleview, mData);
mRecycleViewColor.setAdapter(mRecycleViewAdapter);
mRecycleViewDrawable.setAdapter(mRecycleViewAdapter);
return view;
}
private void initData(List<String> dataList) {
for (int i = 0; i < 16; i++) {
dataList.add("item" + i);
}
}
@Override
public void onClick(View view) {
int id = view.getId();
switch (id){
case R.id.btn_drawable:
mRecycleViewColor.setVisibility(View.INVISIBLE);
mRecycleViewDrawable.setVisibility(View.VISIBLE);
break;
case R.id.btn_color:
mRecycleViewColor.setVisibility(View.VISIBLE);
mRecycleViewDrawable.setVisibility(View.INVISIBLE);
break;
}
}
}3.分割线 GridDivider
直接继承 RecyclerView.ItemDecoration
public class GridDivider extends RecyclerView.ItemDecoration {
private Drawable mDividerDarwable;
private int mDividerHight = 1;
private Paint mColorPaint;
public final int[] ATRRS = new int[]{android.R.attr.listDivider};
public GridDivider(Context context) {
final TypedArray ta = context.obtainStyledAttributes(ATRRS);
this.mDividerDarwable = ta.getDrawable(0);
ta.recycle();
}
/*
int dividerHight 分割线的线宽
int dividerColor 分割线的颜色
*/
public GridDivider(Context context, int dividerHight, int dividerColor) {
this(context);
mDividerHight = dividerHight;
mColorPaint = new Paint();
mColorPaint.setColor(dividerColor);
}
/*
int dividerHight 分割线的线宽
Drawable dividerDrawable 图片分割线
*/
public GridDivider(Context context, int dividerHight, Drawable dividerDrawable) {
this(context);
mDividerHight = dividerHight;
mDividerDarwable = dividerDrawable;
}
@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
super.onDraw(c, parent, state);
//画水平和垂直分割线
drawHorizontalDivider(c, parent);
drawVerticalDivider(c, parent);
}
public void drawVerticalDivider(Canvas c, RecyclerView parent) {
final int childCount = parent.getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = parent.getChildAt(i);
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
final int top = child.getTop() - params.topMargin;
final int bottom = child.getBottom() + params.bottomMargin;
int left = 0;
int right = 0;
//左边第一列
if ((i % 3) == 0) {
//item左边分割线
left = child.getLeft();
right = left + mDividerHight;
mDividerDarwable.setBounds(left, top, right, bottom);
mDividerDarwable.draw(c);
if (mColorPaint != null) {
c.drawRect(left, top, right, bottom, mColorPaint);
}
//item右边分割线
left = child.getRight() + params.rightMargin - mDividerHight;
right = left + mDividerHight;
} else {
//非左边第一列
left = child.getRight() + params.rightMargin - mDividerHight;
right = left + mDividerHight;
}
//画分割线
mDividerDarwable.setBounds(left, top, right, bottom);
mDividerDarwable.draw(c);
if (mColorPaint != null) {
c.drawRect(left, top, right, bottom, mColorPaint);
}
}
}
public void drawHorizontalDivider(Canvas c, RecyclerView parent) {
final int childCount = parent.getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = parent.getChildAt(i);
RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
final int left = child.getLeft() - params.leftMargin - mDividerHight;
final int right = child.getRight() + params.rightMargin;
int top = 0;
int bottom = 0;
// 最上面一行
if ((i / 3) == 0) {
//当前item最上面的分割线
top = child.getTop();
//当前item下面的分割线
bottom = top + mDividerHight;
mDividerDarwable.setBounds(left, top, right, bottom);
mDividerDarwable.draw(c);
if (mColorPaint != null) {
c.drawRect(left, top, right, bottom, mColorPaint);
}
top = child.getBottom() + params.bottomMargin;
bottom = top + mDividerHight;
} else {
top = child.getBottom() + params.bottomMargin;
bottom = top + mDividerHight;
}
//画分割线
mDividerDarwable.setBounds(left, top, right, bottom);
mDividerDarwable.draw(c);
if (mColorPaint != null) {
c.drawRect(left, top, right, bottom, mColorPaint);
}
}
}
}4. Adapter
public class MyRecycleViewAdapter extends RecyclerView.Adapter<MyRecycleViewAdapter.MyViewHolder> {
private LayoutInflater mLayoutInflater;
private List<String> mDataList;
private int mItemLayout;
public MyRecycleViewAdapter(Context context, int itemLayout, List<String> datalist) {
mLayoutInflater = LayoutInflater.from(context);
mItemLayout = itemLayout;
mDataList = datalist;
}
@Override
public MyRecycleViewAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
return new MyViewHolder(mLayoutInflater.inflate(mItemLayout, parent, false));
}
@Override
public void onBindViewHolder(MyRecycleViewAdapter.MyViewHolder holder, int position) {
holder.mTextView.setText(mDataList.get(position));
}
@Override
public int getItemCount() {
return mDataList.size();
}
class MyViewHolder extends RecyclerView.ViewHolder {
private TextView mTextView;
public MyViewHolder(View itemView) {
super(itemView);
mTextView = (TextView) itemView.findViewById(R.id.tv);
}
}
}adapter 的item布局
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="@+id/tv"
android:gravity="center"
android:layout_width="match_parent"
android:layout_height="60dp"/>
</FrameLayout>未完待续……
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