视图组
视图组参数
可定制项
xml文件
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
ViewHolder
简介
-
ViewHolder有个itemView私有成员，可以从itemView中通过findViewById()找到子View。
- 保留
context注意内存泄漏问题，可以使用Application的Context。
- 此处
context非必要。
简单示例
@SuppressWarnings({"FieldCanBeLocal", "unused"})
class Holder extends RecyclerView.ViewHolder {
private Context mContext;
// Todo: View成员
// Todo: Model成员
Holder(Context context, View itemView) {
super(itemView);
bindView(itemView);
mContext = context;
}
void bindModel(/* Model */) {
// Todo: 初始化Model
// Todo: 绑定View和Model
}
void setOnClickListener(View.OnClickListener onClickListener) {
itemView.setOnClickListener(onClickListener);
}
private void bindView(View itemView) {
// Todo: 初始化View
}
}
Adapter
简介
- 保留
context注意内存泄漏问题，可以使用Application的Context。
- 此处
context非必要。
简单示例
public class Adapter extends RecyclerView.Adapter<Holder> {
private Context mContext;
// Todo: Models
// Todo: 构造
public Adapter(Context context, /* Models */) {
mContext = context;
// 初始化Models
}
@Override
public Holder onCreateViewHolder(ViewGroup parent, int viewType) {
LayoutInflater layoutInflater = LayoutInflater.from(mContext);
// Todo: 载入布局
View view = layoutInflater.inflate(/*View Layout Id*/, parent, false);
return new Holder(mContext, view);
}
@Override
public void onBindViewHolder(Holder holder, int position) {
// Todo: Get Model in Models by Position
// Todo: Bind Model and Holder
}
@Override
public int getItemCount() {
// Todo: return Size
return /* Size */;
}
}
LayoutManager
LinearLayoutManager
RecyclerView mRecyclerView = /* 初始化 */;
mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
GridLayoutManager
RecyclerView mRecyclerView = /* 初始化 */;
mRecyclerView.setLayoutManager(new GridLayoutManager(getActivity(), 2, GridLayoutManager.VERTICAL, false));
StaggeredGridLayoutManager
RecyclerView mRecyclerView = /* 初始化 */;
mRecyclerView.setLayoutManager(new StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL));
ItemDecoration
简介
- 用于定制绘制子项行为
- 绘制顺序：
onDraw()-> 子项 ->onDrawOver()
简单示例
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<size android:height="2dp"/>
<solid android:color="#8b2cab"/>
</shape>
public class DividerItemDecoration extends RecyclerView.ItemDecoration {
private Drawable mDivider;
public DividerItemDecoration(Context context) {
mDivider = context.getResources().getDrawable(R.drawable.d, null);
}
@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
final int left = parent.getPaddingLeft();
final int right = parent.getWidth() - parent.getPaddingRight();
final int childCount = parent.getChildCount();
for (int i = 0; i < childCount - 1; i++) {
View child = parent.getChildAt(i);
RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
int top = child.getBottom() + params.bottomMargin;
int bottom = top + mDivider.getIntrinsicHeight();
// 设置mDivider的绘画区域和宽高，相当于给定左上角和右下角坐标确定一个矩形
mDivider.setBounds(left, top, right, bottom);
// 在画布（Canvas）上画
mDivider.draw(c);
}
}
@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
super.onDrawOver(c, parent, state);
}
// Item偏移
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
if (parent.getAdapter().getItemCount() - 1 == parent.getChildAdapterPosition(view))
outRect.set(0, 0, 0, 0);
else {
outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
}
}
}
ItemAnimator
- 用于定制子项动画增删。
- 通过复制粘贴
DefaultItemAnimator并重写其中的几个函数来控制动画
animateRemoveImplanimateAddImplanimateMoveImplanimateChangeImpl-
endAnimation：恢复原状
-
endAnimations：恢复原状
- 因为复用的原因，子项动画处理完毕后必须恢复原状。
- 【Todo】：可以封装
RecyclerView
RecyclerView mRecyclerView = /* 初始化 */;
mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
mRecyclerView.addItemDecoration(new DividerItemDecoration(getActivity()));
Adapter adapter = new Adapter(getActivity(), /* Models */);
mRecyclerView.setAdapter(adapter);
显示没有内容
注意事项
- 对于因为复用导致索引错乱的问题，使用
ViewHolder.getAdapterPosition()解决。若找不到ViewHolder，会返回-1，注意处理这种情况。
- 项目发生改变时（ 增加 、 删除 、 修改 ），记得调用
notify()系列函数。
ViewPager
xml文件
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.view.ViewPager
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
FragmentStatePagerAdapter
FragmentManager fragmentManager = getSupportFragmentManager();
mViewPager.setAdapter(new FragmentStatePagerAdapter(fragmentManager) {
@Override
public Fragment getItem(int position) {
return /* fragment */;
}
// 获取当前的显示的那一页的Fragment
@Override
public void setPrimaryItem(ViewGroup container, int position, Object object) {
super.setPrimaryItem(container, position, object);
mPageFragment = (PageFragment) object;
}
@Override
public int getCount() {
return /* size */;
}
});
FragmentPagerAdapter
- 相对比于
FragmentStatePagerAdapter，FragmentPagerAdapter不会回收复用。
- 使用方法参见
FragmentStatePagerAdapter。
PagerAdapter
@SuppressWarnings("WeakerAccess")
public class CustomPagerAdapter extends PagerAdapter {
private Context mContext;
public CustomPagerAdapter(Context context) {
mContext = context;
}
@Override
public Object instantiateItem(ViewGroup collection, int position) {
LayoutInflater inflater = LayoutInflater.from(mContext);
ViewGroup layout = (ViewGroup) inflater.inflate(/* Layout */, collection, false);
collection.addView(layout);
return layout;
}
@Override
public void destroyItem(ViewGroup collection, int position, Object view) {
collection.removeView((View) view);
}
@Override
public int getCount() {
return /* size */;
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}
}
常用方法
-
setCurrentItem()：设置当前页数。
-
setOffscreenPageLimit()：预加载页数。
