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通过导入第三方库实现ListView的上拉加载和下拉刷新比较简单，今天我要讲的是自定义RecyclerView实现下拉刷新和上拉加载。首先，自定义下拉刷新上拉加载是通过给RecyclerView添加头部和尾部实现的。而问题是RecyclerView并没有addHeaderView(View v)和addFooterView(View v)方法。

     第一步：自定义HeaderAndFooterWrapper（装饰者模式）实现给RecyclerView添加头部和尾部
    方法：public void addHeaderView(View v)
              public void addFooterView(View v)
     代码参照张鸿洋：Android 优雅的为RecyclerView添加HeaderView和FooterView 
     链接：

      第二步：定义类RefreshRecyclerView并抽取为库

1) 头部布局：refresh_recyclerview_header.xml

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

2. <!--下拉刷新控件-->

3. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

4. android:layout_width="match_parent"

5. android:layout_height="wrap_content"

6. android:gravity="center"

7. android:orientation="horizontal">

8.  

9. <FrameLayout

10. android:layout_width="wrap_content"

11. android:layout_height="wrap_content"

12. android:padding="10dp">

13.  

14. <ImageView

15. android:id="@+id/iv_header_refresh"

16. android:layout_width="wrap_content"

17. android:layout_height="wrap_content"

18. android:layout_gravity="center"

19. android:src="@drawable/headview_red_arrow" />

20.  

21. <ProgressBar

22. android:id="@+id/pb_header_refresh"

23. android:layout_width="wrap_content"

24. android:layout_height="wrap_content"

25. android:layout_gravity="center"

26. android:indeterminateDrawable="@drawable/custom_progressbar"

27. android:visibility="gone" />

28. </FrameLayout>

29.  

30. <LinearLayout

31. android:layout_width="wrap_content"

32. android:layout_height="wrap_content"

33. android:layout_gravity="center_vertical"

34. android:orientation="vertical">

35.  

36. <TextView

37. android:id="@+id/tv_status"

38. android:layout_width="match_parent"

39. android:layout_height="wrap_content"

40. android:gravity="center_horizontal"

41. android:text="下拉刷新"

42. android:textColor="#ff0000"

43. android:textSize="18sp" />

44.  

45. <TextView

46. android:id="@+id/tv_time"

47. android:layout_width="match_parent"

48. android:layout_height="wrap_content"

49. android:layout_marginTop="5dp"

50. android:gravity="center_horizontal"

51. android:text="上次更新时间：2016-10-31"

52. android:textColor="#55000000"

53. android:textSize="16sp" />

54.  

55. </LinearLayout>

56.  

57. </LinearLayout>

2）尾部布局（上拉加载部分）：refresh_recyclerview_footer.xml

1. <span style="font-size:14px;"><?xml version="1.0" encoding="utf-8"?>

2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

3. android:layout_width="match_parent"

4. android:gravity="center"

5. android:layout_height="wrap_content"

6. android:orientation="horizontal">

7. <ProgressBar

8. android:indeterminateDrawable="@drawable/custom_progressbar"

9. android:layout_margin="5dp"

10. android:layout_width="wrap_content"

11. android:layout_height="wrap_content" />

12. <TextView

13. android:text="加载更多中...."

14. android:textColor="#ff0000"

15. android:textSize="25sp"

16. android:layout_marginLeft="10dp"

17. android:layout_width="wrap_content"

18. android:layout_height="wrap_content" />

19. </LinearLayout></span>

3）自定义ProgressBar样式custom_progressbar.xml

1. <span style="font-size:14px;"><?xml version="1.0" encoding="utf-8"?>

2. <rotate xmlns:android="http://schemas.android.com/apk/res/android"

3. android:fromDegrees="0"

4. android:toDegrees="360"

5. android:pivotX="50%"

6. android:pivotY="50%">

7. <shape android:shape="ring"

8. android:innerRadiusRatio="2.5"

9. android:thicknessRatio="15"

10. android:useLevel="false"

11. >

12. <gradient android:startColor="#ff0000"

13. android:endColor="#ffffff"

14. android:centerColor="#88ff0000"

15. android:type="sweep"></gradient>

16. </shape>

17. </rotate></span>

代码如下：
 

1. public class RefreshRecyclerView extends RecyclerView {

2.  

3. private final Context mContext;

4. // 顶部视图，下拉刷新控件

5. private LinearLayout headerView;

6. // 正在刷新状态的进度条

7. private ProgressBar pb_header_refresh;

8. // 刷新箭头

9. private ImageView iv_header_refresh;

10. // 显示刷新状态

11. private TextView tv_status;

12. // 显示最近一次的刷新时间

13. private TextView tv_time;

14. // 转到下拉刷新状态时的动画

15. private RotateAnimation downAnima;

16. // 转到释放刷新状态时的动画

17. private RotateAnimation upAnima;

18. //触摸事件中按下的Y坐标，初始值为-1，为防止ACTION_DOWN事件被抢占

19. private float startY = -1;

20. // 下拉刷新控件的高度

21. private int pulldownHeight;

22. // 刷新状态：下拉刷新

23. private final int PULL_DOWN_REFRESH = 0;

24. // 刷新状态：释放刷新

25. private final int RELEASE_REFRESH = 1;

26. // 刷新状态：正常刷新

27. private final int REFRESHING = 2;

28.  

29. // 当前头布局的状态-默认为下拉刷新

30. private int currState = PULL_DOWN_REFRESH;

31. //

32. private RefreshRecyclerView.OnRefreshListener mOnRefreshListener;

33. // 尾部视图

34. private View footerView;

35. // 尾部试图（上拉加载控件）的高度

36. private int footerViewHeight;

37. // 判断是否是加载更多

38. private boolean isLoadingMore;

39.  

40. public RefreshRecyclerView(Context context) {

41. this(context, null);

42. }

43.  

44. public RefreshRecyclerView(Context context, AttributeSet attrs) {

45. this(context, attrs, 0);

46. }

47.  

48. public RefreshRecyclerView(Context context, AttributeSet attrs, int defStyleAttr) {

49. super(context, attrs, defStyleAttr);

50. mContext = context;

51. initHeaderView();

52. initFooterView();

53. }

54. /**

55. * 返回尾部布局，供外部调用

56. * @return

57. */

58. public View getFooterView(){

59. return footerView;

60. }

61. /**

62. * 返回头部布局，供外部调用

63. * @return

64. */

65. public View getHeaderView(){

66. return headerView;

67. }

68.  

69. /**

70. * 通过HeaderAndFooterWrapper对象给RecyclerView添加尾部

71. * @param footerView 尾部视图

72. * @param headerAndFooterWrapper RecyclerView.Adapter的包装类对象，通过它给RecyclerView添加尾部视图

73. */

74. public void addFooterView(View footerView, HeaderAndFooterWrapper headerAndFooterWrapper) {

75. headerAndFooterWrapper.addFooterView(footerView);

76. }

77.  

78. /**

79. * 通过HeaderAndFooterWrapper对象给RecyclerView添加头部部

80. * @param headerView 尾部视图

81. * @param headerAndFooterWrapper RecyclerView.Adapter的包装类对象，通过它给RecyclerView添加头部视图

82. */

83. public void addHeaderView(View headerView,HeaderAndFooterWrapper headerAndFooterWrapper) {

84. headerAndFooterWrapper.addHeaderView(headerView);

85. }

初始化头部布局和尾部布局

1. private void initHeaderView() {

2. headerView = (LinearLayout) View.inflate(mContext, R.layout.refresh_recyclerview_header, null);

3. tv_time = (TextView) headerView.findViewById(R.id.tv_time);

4. tv_status = (TextView) headerView.findViewById(R.id.tv_status);

5. iv_header_refresh = (ImageView) headerView.findViewById(R.id.iv_header_refresh);

6. pb_header_refresh = (ProgressBar) headerView.findViewById(R.id.pb_header_refresh);

7. headerView.measure(0, 0);

8. pulldownHeight = headerView.getMeasuredHeight();

9. headerView.setPadding(0, -pulldownHeight, 0, 0);

10. //初始化头部布局的动画

11. initAnimation();

12. }

13. /**

14. * 刷新状态改变时的动画

15. */

16. private void initAnimation() {

17. // 从下拉刷新状态转换为释放刷新状态

18. upAnima = new RotateAnimation(0, -180, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);

19. upAnima.setFillAfter(true);

20. upAnima.setDuration(500);

21. // 转到下拉刷新的动画

22. downAnima = new RotateAnimation(-180, -360, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);

23. downAnima.setFillAfter(true);

24. downAnima.setDuration(500);

25. }

26.  

1. private void initFooterView() {

2. footerView = View.inflate(mContext, R.layout.refresh_recyclerview_footer, null);

3. footerView.measure(0, 0);

4. //得到控件的高

5. footerViewHeight = footerView.getMeasuredHeight();

6. //默认隐藏下拉刷新控件

7. // View.setPadding(0,-控件高，0,0);//完全隐藏

8. //View.setPadding(0, 0，0,0);//完全显示

9. footerView.setPadding(0, -footerViewHeight, 0, 0);

10. // addFooterView(footerView);

11. // 自己监听自己

12. this.addOnScrollListener(new MyOnScrollListener());

13. }

重写onTouchEvent()方法，startY表示按下时的坐标，但是有可能ACTION_DOWN事件被强占，那么case MotionEvent.ACTION_DOWN:就没机会执行。所以case MotionEvent.ACTION_MOVE:子句时首先判断startY是否为-1，是的话把第一次移动的坐标当作按下时的坐标。然后判断当前的状态，如果正在刷新就不必再次执行下面的刷新代码，直接跳出。dY>0表示用户正在执行下拉操作，因为头部视图初始坐标为-pulldownHeight,所以手指在屏幕上滑动多少距离，顶部视图的y坐标就应该增加相应值。paddingTop==0是一个状态分界线，paddingTop < 0 是下拉刷新状态，大于0是释放刷新状态。根据paddingTop的值跳转相应的状态。最后在手指抬起的时候,首先重置startY = -1;然后判断刷新状态，如果是下拉刷新（头部视图没有完全显示）就设置下拉控件为默认隐藏状态，如果是释放刷新状态（paddingTop > 0）,就跳转到正在刷新状态，并让下拉控件完全显示同时调用用户的回调事件，刷新页面数据。

1. @Override

2. public boolean onTouchEvent(MotionEvent ev) {

3. switch (ev.getAction()) {

4. case MotionEvent.ACTION_DOWN:

5. startY = ev.getY();

6. break;

7. case MotionEvent.ACTION_MOVE:

8. //防止ACTION_DOWN事件被抢占，没有执行

9. if (startY == -1) {

10. startY = ev.getY();

11. }

12. float endY = ev.getY();

13. float dY = endY - startY;

14. //判断当前是否正在刷新中

15. if (currState == REFRESHING) {

16. //如果当前是正在刷新，不执行下拉刷新了，直接break;

17. break;

18. }

19. // 如果是下拉

20. if (dY > 0) {

21. int paddingTop = (int) (dY - pulldownHeight);

22. if (paddingTop > 0 && currState != RELEASE_REFRESH) {

23. //完全显示下拉刷新控件，进入松开刷新状态

24. currState = RELEASE_REFRESH;

25. refreshViewState();

26. } else if (paddingTop < 0 && currState != PULL_DOWN_REFRESH) {

27. //没有完全显示下拉刷新控件，进入下拉刷新状态

28. currState = PULL_DOWN_REFRESH;

29. refreshViewState();

30. }

31. headerView.setPadding(0, paddingTop, 0, 0);

32. }

33. break;

34. case MotionEvent.ACTION_UP:

35. //5.重新记录值

36. startY = -1;

37. if (currState == PULL_DOWN_REFRESH) {

38. //设置默认隐藏

39. headerView.setPadding(0, -pulldownHeight, 0, 0);

40. } else if (currState == RELEASE_REFRESH) {

41. //当前是释放刷新，进入到正在刷新状态，完全显示

42. currState = REFRESHING;

43. refreshViewState();

44. headerView.setPadding(0, 0, 0, 0);

45. //调用用户的回调事件，刷新页面数据

46. if (mOnRefreshListener != null) {

47. mOnRefreshListener.onPullDownRefresh();

48. }

49. }

50. break;

51. }

52. return super.onTouchEvent(ev);

53. }

54. /**

55. * 跳转刷新状态

56. */

57. private void refreshViewState() {

58. switch (currState) {

59. // 跳转到下拉刷新

60. case PULL_DOWN_REFRESH:

61. iv_header_refresh.startAnimation(downAnima);

62. tv_status.setText("下拉刷新");

63. break;

64. // 跳转到释放刷新

65. case RELEASE_REFRESH:

66. iv_header_refresh.startAnimation(upAnima);

67. tv_status.setText("释放刷新");

68. break;

69. // 跳转到正在刷新

70. case REFRESHING:

71. iv_header_refresh.clearAnimation();

72. iv_header_refresh.setVisibility(GONE);

73. pb_header_refresh.setVisibility(VISIBLE);

74. tv_status.setText("正在刷新中.....");

75. break;

76. }

77. }

定义接口

1. /**

2. * 定义下拉刷新和上拉加载的接口

3. */

4. public interface OnRefreshListener {

5. /**

6. * 当下拉刷新时触发此方法

7. */

8. void onPullDownRefresh();

9.  

10. /**

11. * 当加载更多的时候回调这个方法

12. */

13. void onLoadingMore();

14.  

15. }

16. public void setOnRefreshListener(RefreshRecyclerView.OnRefreshListener listener) {

17. this.mOnRefreshListener = listener;

18. }

19.  

20. /**

21. * 当刷新完数据之后，调用此方法，把头文件隐藏，并且状态设置为初始状态

22. * @param isSuccess

23. */

24. public void onFinishRefresh(boolean isSuccess) {

25. if (isLoadingMore) {

26. footerView.setPadding(0, -footerViewHeight, 0, 0);

27. isLoadingMore = false;

28. } else {

29. headerView.setPadding(0, -pulldownHeight, 0, 0);

30. currState = PULL_DOWN_REFRESH;

31. iv_header_refresh.setVisibility(VISIBLE);

32. pb_header_refresh.setVisibility(GONE);

33. tv_status.setText("下拉刷新");

34. if (isSuccess) {

35. //设置更新时间

36. tv_time.setText(getSystemTime());

37. }

38. }

39. }

40.  

41. private String getSystemTime() {

42. SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

43. return dateFormat.format(new Date());

44. }

上拉加载逻辑的实现，重写onScrollStateChanged()方法。如果newState为空闲状态或者是快速滑动状态就判断RecyclerView的最后一个可见Item的索引是否 >= getChildCount()-1。是的话就触发加载更多事件，完全显示上拉加载控件并调用回调事件。这里要注意：ListView是SCROLL_STATE_FLING而RecyclerView是SCROLL_STATE_SETTLING，ListView得到最后一个可见Item索引直接

getLastVisiblePosition()方法就行了。RecyclerView比较麻烦：首先要判断布局管理器是否是线性布局管理器，因为只有LinearLayoutManager才有查找第一个和最后一个可见View位置的方法。

1. private class MyOnScrollListener extends OnScrollListener {

2. @Override

3. public void onScrollStateChanged(RecyclerView recyclerView, int newState) {

4. // super.onScrollStateChanged(recyclerView, newState);

5. if (newState == SCROLL_STATE_IDLE || newState == SCROLL_STATE_SETTLING) {

6. //判断是当前layoutManager是否为LinearLayoutManager

7. // 只有LinearLayoutManager才有查找第一个和最后一个可见view位置的方法

8. LayoutManager layoutManager = recyclerView.getLayoutManager();

9. if (layoutManager instanceof LinearLayoutManager) {

10. LinearLayoutManager linearLayoutManager = (LinearLayoutManager) layoutManager;

11. //当停止滚动时或者惯性滚动时，RecyclerView的最后一个显示的条目：getCount()-1

12. // 注意是findLastVisibleItemPosition()而不是getLastVisiblePosition

13. if (linearLayoutManager.findLastVisibleItemPosition() >= getChildCount() - 1) {

14. isLoadingMore = true;

15. //把底部加载显示

16. footerView.setPadding(0, 0, 0, 0);

17. if (mOnRefreshListener != null) {

18. mOnRefreshListener.onLoadingMore();

19. }

20. }

21. }

22. }

23. }

24. }

     第三步：使用 自定义的RecyclerView
首先上布局

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

2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

3. android:layout_width="match_parent"

4. android:layout_height="match_parent"

5. android:orientation="vertical">

6.  

7. <com.example.refreshrecyclerview_library.RefreshRecyclerView

8. android:id="@+id/custom_recyclerview"

9. android:layout_width="match_parent"

10. android:layout_height="0dp"

11. android:layout_weight="1"

12. android:cacheColorHint="@android:color/transparent"

13. android:divider="@null"

14. android:fadingEdge="none" />

15.  

16. </LinearLayout>

测试代码

1. public class MainActivity extends Activity {

2.  
3.  

4. private static final int REFRESH = 0;

5. private static final int LOADMORE = 1;

6. private HeaderAndFooterWrapper headerAndFooterWrapper;

7. private RefreshRecyclerViewAdapter recyclerAdapter;

8. private RefreshRecyclerView custom_recyclerview;

9. private Handler handler = new Handler(){

10. public void handleMessage(Message msg){

11. switch (msg.what) {

12. case REFRESH:

13. custom_recyclerview.onFinishRefresh(true);

14. break;

15. case LOADMORE:

16. custom_recyclerview.onFinishRefresh(false);

17. break;

18. }

19. }

20. };

21. @Override

22. protected void onCreate(Bundle savedInstanceState) {

23. super.onCreate(savedInstanceState);

24. setContentView(R.layout.activity_main);

25. custom_recyclerview = (RefreshRecyclerView) findViewById(R.id.custom_recyclerview);

26. initRefreshRecyclerView();

27. }

28.  

29. private void initRefreshRecyclerView() {

30. // 给Recycler设置分割线

31. custom_recyclerview.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL_LIST));

32. recyclerAdapter = new RefreshRecyclerViewAdapter(this);

33. headerAndFooterWrapper = new HeaderAndFooterWrapper(recyclerAdapter);

34. // 不要忘记设置布局管理器

35. custom_recyclerview.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));

36. custom_recyclerview.setAdapter(headerAndFooterWrapper);

37. custom_recyclerview.addHeaderView(custom_recyclerview.getHeaderView(), headerAndFooterWrapper);

38. custom_recyclerview.addFooterView(custom_recyclerview.getFooterView(), headerAndFooterWrapper);

39. custom_recyclerview.setOnRefreshListener(new OnRecyclerRefreshListener());

40. }

41.  

42. private class OnRecyclerRefreshListener implements RefreshRecyclerView.OnRefreshListener {

43. @Override

44. public void onPullDownRefresh() {

45. // 执行下拉刷新操作，一般是联网更新数据

46. new Thread(new Runnable() {

47. @Override

48. public void run() {

49. SystemClock.sleep(2000);

50. handler.sendEmptyMessage(REFRESH);

51. }

52. }).start();

53. }

54.  

55. @Override

56. public void onLoadingMore() {

57. // 执行上拉加载操作，一般是联网请求更多分页数据

58. new Thread(new Runnable() {

59. @Override

60. public void run() {

61. SystemClock.sleep(2000);

62. handler.sendEmptyMessage(LOADMORE);

63. }

64. }).start();

65. }

66. }

67. }

68. <pre name="code" class="java">

69. public class RefreshRecyclerViewAdapter extends RecyclerView.Adapter<RefreshRecyclerViewAdapter.ViewHolder> {

70.  

71. private Context mContext;

72. private List<String> datas;

73.  

74. public RefreshRecyclerViewAdapter(Context mContext) {

75. this.mContext = mContext;

76. datas = new ArrayList<>();

77. for(int i = 1; i <= 20; i++) {

78. datas.add("我是Content ："+i);

79. }

80. }

81.  

82. @Override

83. public RefreshRecyclerViewAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

84.  

85. View convertView = View.inflate(mContext, R.layout.item_recycler, null);

86. return new ViewHolder(convertView);

87. }

88.  

89. @Override

90. public void onBindViewHolder(RefreshRecyclerViewAdapter.ViewHolder holder, final int position) {

91. String data = datas.get(position);

92. holder.tv_content.setText(data);

93. }

94.  

95. @Override

96. public int getItemCount() {

97. return datas.size();

98. }

99.  

100. public class ViewHolder extends RecyclerView.ViewHolder {

101.  

102. TextView tv_content;

103.  

104. public ViewHolder(final View itemView) {

105. super(itemView);

106. tv_content = (TextView) itemView.findViewById(R.id.tv);

107. }

108. }

109. }

这里还用到一个分割线的类，RecyclerView默认是没有分割线的，这段代码可以直接粘贴使用

1. public class DividerItemDecoration extends RecyclerView.ItemDecoration {

2.  

3. public final static int VERTICAL_LIST = LinearLayoutManager.VERTICAL;

4. public final static int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;

5. private int mOrientation;

6. private Drawable mDivider;

7. private static final int[] ATTRS = new int[]{android.R.attr.listDivider};

8.  

9. public DividerItemDecoration(Context context, int mOrientation) {

10. final TypedArray a = context.obtainStyledAttributes(ATTRS);

11. mDivider = a.getDrawable(0);

12. a.recycle();

13. setOrientation(mOrientation);

14.  

15. }

16.  

17. private void setOrientation(int mOrientation) {

18. if (mOrientation != VERTICAL_LIST && mOrientation != HORIZONTAL_LIST) {

19. throw new IllegalArgumentException("Invalid orientation");

20. } else {

21. this.mOrientation = mOrientation;

22. }

23. }

24.  

25. @Override

26. public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {

27. super.onDraw(c, parent, state);

28. if (mOrientation == VERTICAL_LIST) {

29. drawVertical(c, parent);

30. } else if (mOrientation == HORIZONTAL_LIST) {

31. drawHorizontal(c, parent);

32. }

33. }

34.  

35. private void drawVertical(Canvas c, RecyclerView parent) {

36. int left = parent.getPaddingLeft();

37. int right = parent.getWidth() - parent.getPaddingRight();

38. int childCount = parent.getChildCount();

39. for (int i = 0; i < childCount; i++) {

40. View child = parent.getChildAt(i);

41. RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();

42. int top = child.getBottom() + params.bottomMargin;

43. int bottom = top + mDivider.getIntrinsicHeight();

44. mDivider.setBounds(left, top, right, bottom);

45. mDivider.draw(c);

46. }

47. }

48.  

49. private void drawHorizontal(Canvas c, RecyclerView parent) {

50. int top = parent.getPaddingTop();

51. int bottom = parent.getHeight() - parent.getPaddingBottom();

52. int childCount = parent.getChildCount();

53. for (int i = 0; i < childCount; i++) {

54. View child = parent.getChildAt(i);

55. RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();

56. int left = child.getRight() + params.rightMargin;

57. int right = left + mDivider.getIntrinsicHeight();

58. mDivider.setBounds(left,top,right,bottom);

59. mDivider.draw(c);

60. }

61.  

62. }

63.  

64. @Override

65. public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {

66. // super.getItemOffsets(outRect, view, parent, state);

67. if(mOrientation == VERTICAL_LIST) {

68. outRect.set(0,0,0,mDivider.getIntrinsicHeight());

69. }else{

70. outRect.set(0,0,mDivider.getIntrinsicHeight(),0);

71. }

72. }

73. }