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AndroidRecyclerView線性布局詳解(1)

RecyclerView是Android 5.0新增的控件，在android-support-v7下面。官方文檔對RecycleView介紹很簡潔到位，如下：

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A flexible view for providing a limited window into a large data set.
大概意思就是說：在有限大小的窗口里顯示大量數據的一個靈活的view。

下面是ReccleView繼承圖：

Android RecyclerView線性布局詳解(1)

看到這里我們自然想到了與之類似的控件ListView，RecyclerView和ListView都是在有限的屏幕區(qū)域里維護少量的View來進行顯示大量的數據，其實RecyclerView是ListView的升級版，功能更加強大，更加靈活，擴展性更強，Google建議使用RecycleView替代ListView。

下面是RecycleView結構圖：

Android RecyclerView線性布局詳解(1)

RecycleView主要包括以下幾個部件：

1. RecyclerView.Adapter

數據和視圖的分離設計是程序解耦和可維護的重要指標，RecycleView作為展示大量數據的view肯定是遵循這個設計的，ListView也不例外。通過繼承RecycleView.Adapter即可輕松實現自己的adapter，主要重寫RecycleView.Adapter的下面三個方法即可實現：

public MyRecycleViewAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) 
public void onBindViewHolder(MyRecycleViewAdapter.MyViewHolder holder, int position)
public int getItemCount()

上面MyRecycleViewAdapter是我自己定義的ViewHolder

2. ViewHolder

ViewHolder用來保存列表中item view引用的類，這樣做的目的是重用item視圖，從而提高性能。
在ListView中，ViewHolder不是ListView自帶的，是需要自己定義的，當然你也可以不使用ViewHolder，這樣的后果就是ListView每次調用getView()方法的時候都會調用findViewById()方法，要知道findViewById()性能很差，它通過遞歸的方式去從view樹中找特定的子view的，最終往往帶來很差的性能體驗，所以使用ViewHolder也成了優(yōu)化ListView最重要的手段。
在RecyclerView中，Android內置了RecyclerView.ViewHolder，這意味著ViewHolder使用成了必須。

3. 分割線 RecycleView.ItemDecoration

ListView添加分割線很簡單，只需在ListView的xml中配置”divider”屬性即可，如：

android:dividerHeight="2dp"
android:divider="@color/red"

但RecycleView添加分割線是比較麻煩的，并且默認是不帶分割線的。但實際開發(fā)中一般都需要分割線，使用RecycleView.ItemDecoration為RecycleView添加分割線

4. 布局管理器 LayoutManager

RecycleView支持多種布局模式：

1、LinearLayoutManager
線性布局管理器，支持水平布局和垂直布局兩種
2、GridLayoutManager
網格布局管理器
3、StaggerdGridLayoutManager
錯列的網格布局管理器，可以實現瀑布流列表

RecycleView使用時和ListView很類似，直接看一個簡單的例子，分別展示一個垂直方向和水平方向上的列表，并且都支持使用顏色和圖片做分割線，效果圖如下：

Android RecyclerView線性布局詳解(1)

Android RecyclerView線性布局詳解(1)

1. MainActivity

package com.cjl.recycleviewtest;
...
public class MainActivity extends AppCompatActivity {

 private VerticalFragment mVerticalFragment;
 private HorizontalFragment mHorizontalFragment;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 //垂直
 mVerticalFragment = new VerticalFragment();
 //水平
 mHorizontalFragment = new HorizontalFragment();
 //默認為設置垂直
 getFragmentManager().beginTransaction().replace(R.id.activity_main, mVerticalFragment).commit();
 }

 @Override
 public boolean onCreateOptionsMenu(Menu menu) {
 MenuInflater inflater = getMenuInflater();
 inflater.inflate(R.menu.menu_recycleview, menu);
 return super.onCreateOptionsMenu(menu);
 }

 @Override
 public boolean onOptionsItemSelected(MenuItem item) {
 int id = item.getItemId();
 switch (id) {
  //垂直方向
  case R.id.vertical:
  VerticalFragment mVerticalFragment = new VerticalFragment();
  getFragmentManager().beginTransaction().replace(R.id.activity_main, mVerticalFragment).commit();
  break;
  //水平方向
  case R.id.horizontal:
 getFragmentManager().beginTransaction().replace(R.id.activity_main, mHorizontalFragment).commit();
  break;
 }
 return super.onOptionsItemSelected(item);
 }
}

MainActivity布局文件 R.layout.activity_main

<?xml version="1.0" encoding="utf-8"?>

2. 垂直方向上 VerticalFragment

public class VerticalFragment extends Fragment implements View.OnClickListener{

 private RecyclerView mRecycleViewDrawable;
 private RecyclerView mRecycleViewColor;
 private LinearLayoutManager mManagerColor;
 private LinearLayoutManager mManagerDrawable;
 private List 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_vertical_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);
 //1. 顏色分割線
 mManagerColor = new LinearLayoutManager(getActivity());
 mManagerColor.setOrientation(LinearLayoutManager.VERTICAL);
 mRecycleViewColor.setLayoutManager(mManagerColor);
 //設置顏色分割線
 mRecycleViewColor.addItemDecoration(new LinearDivider(getActivity(), LinearLayoutManager.VERTICAL, 10, this.getResources().getColor(R.color.colorAccent)));

 //2. 圖片分割線
 mManagerDrawable = new LinearLayoutManager(getActivity());
 mManagerDrawable.setOrientation(LinearLayoutManager.VERTICAL);
 mRecycleViewDrawable.setLayoutManager(mManagerDrawable);
 //設置圖片分割線
 Drawable drawable = ContextCompat.getDrawable(getActivity(), R.mipmap.divider);
 mRecycleViewDrawable.addItemDecoration(new LinearDivider(getActivity(), LinearLayoutManager.VERTICAL, 20, drawable));

 mData = new ArrayList();
 initData(mData);
 //自定義adapter
 mRecycleViewAdapter = new MyRecycleViewAdapter(getActivity(), R.layout.item_vertical_recycleview, mData);
 //設置adapter
 mRecycleViewColor.setAdapter(mRecycleViewAdapter);
 mRecycleViewDrawable.setAdapter(mRecycleViewAdapter);
 return view;
 }

 private void initData(List dataList) {
 for (int i = 0; i < 30; 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;
 }
 }
}

VerticalFragment 的布局文件 R.layout.fragment_vertical_layout

<?xml version="1.0" encoding="utf-8"?>

3. 直接繼承RecyclerView.Adapter

public class MyRecycleViewAdapter extends RecyclerView.Adapter {

 private LayoutInflater mLayoutInflater;
 private List mDataList;
 private int mItemLayout;

 public MyRecycleViewAdapter(Context context, int itemLayout, List 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);
 }
 }
}

item布局文件 item_vertical_recycleview.xml

<?xml version="1.0" encoding="utf-8"?>

4. 分割線 RecyclerView.ItemDecoration

public class LinearDivider extends RecyclerView.ItemDecoration {

 private Drawable mDividerDarwable;
 private int mOrientation;
 private int mDividerHight = 1;
 private Paint mColorPaint;

 public final int[] ATRRS = new int[]{
  android.R.attr.listDivider
 };

 /*
 orientation 方向
 */
 public LinearDivider(Context context, int orientation) {
 final TypedArray ta = context.obtainStyledAttributes(ATRRS);
 this.mDividerDarwable = ta.getDrawable(0);
 ta.recycle();
 setOrientation(orientation);
 }

 /*
 int orientation 方向
 int dividerHight 分割線的線寬
 Drawable dividerDrawable 充當分割線的圖片
 */
 public LinearDivider(Context context, int orientation, int dividerHight, Drawable dividerDrawable) {
 this(context, orientation);
 mDividerHight = dividerHight;
 mDividerDarwable = dividerDrawable;
 }

 /*
 int orientation 方向
 int dividerHight 分割線的線寬
 int dividerColor 分割線的顏色
 */
 public LinearDivider(Context context, int orientation, int dividerHight, int dividerColor) {
 this(context, orientation);
 mDividerHight = dividerHight;
 mColorPaint = new Paint();
 mColorPaint.setColor(dividerColor);
 }

 public void setOrientation(int orientation) {
 if (orientation != LinearLayoutManager.HORIZONTAL && orientation != LinearLayoutManager.VERTICAL) {
  throw new IllegalArgumentException("方向參數錯誤！");
 }
 mOrientation = orientation;
 }

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

 //畫垂直分割線
 public void drawVirticalDivider(Canvas c, RecyclerView parent) {
 int left = parent.getPaddingLeft();
 int right = parent.getWidth() - parent.getPaddingRight();
 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.getBottom() + params.bottomMargin;
  final int bottom = top + mDividerHight;
  if (mDividerDarwable != null) {
  mDividerDarwable.setBounds(left, top, right, bottom);
  mDividerDarwable.draw(c);
  }
  if (mColorPaint != null) {
  c.drawRect(left, top, right, bottom, mColorPaint);
  }
 }
 }

 //畫水平分割線
 public void drawHorizontalDivider(Canvas c, RecyclerView parent) {
 int top = parent.getPaddingTop();
 int bottom = parent.getHeight() - parent.getPaddingBottom();
 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.getRight() + params.rightMargin;
  final int right = left + mDividerHight;
  if (mDividerDarwable != null) {
  mDividerDarwable.setBounds(left, top, right, bottom);
  mDividerDarwable.draw(c);
  }
  if (mColorPaint != null) {
  c.drawRect(left, top, right, bottom, mColorPaint);
  }
 }
 }

 @Override
 public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
 super.getItemOffsets(outRect, view, parent, state);
 if (mOrientation == LinearLayoutManager.HORIZONTAL) {
  outRect.set(0, 0, 0, mDividerHight);
 } else {
  outRect.set(0, 0, mDividerHight, 0);
 }
 }
}

未完待續(xù)……

以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持創(chuàng)新互聯。


本文名稱：AndroidRecyclerView線性布局詳解(1)
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