Android 下拉刷新 和上拉加载数据

一，简介
实现上拉刷新数据，下拉加载数据


代码如下

/**
* 自定义View继承SwipeRefreshLayout，添加上拉加载更多的布局属性,添加对RecyclerView的支持
*/

public class SwipeRefreshView extends SwipeRefreshLayout{
    private static final String TAG = SwipeRefreshView.class.getSimpleName();
    private final int mScaledTouchSlop;
    private final View mFooterView;
    private ListView mListView;
    private OnLoadMoreListener mListener;

    /**
     * 正在加载状态
     */
    private boolean isLoading;
    private RecyclerView mRecyclerView;
    private int mItemCount;


    public SwipeRefreshView(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);

        // 填充底部加载布局
        mFooterView = View.inflate(context, R.layout.view_footer, null);

        // 表示控件移动的最小距离，手移动的距离大于这个距离才能拖动控件
        mScaledTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        // 获取ListView,设置ListView的布局位置
        if (mListView == null || mRecyclerView == null) {
            // 判断容器有多少个孩子
            if (getChildCount() > 0) {
                // 判断第一个孩子是不是ListView
                if (getChildAt(0) instanceof ListView) {
                    // 创建ListView对象
                    mListView = (ListView) getChildAt(0);

                    // 设置ListView的滑动监听
                    setListViewOnScroll();
                } else if (getChildAt(0) instanceof RecyclerView) {
                    // 创建ListView对象
                    mRecyclerView = (RecyclerView) getChildAt(0);

                    // 设置RecyclerView的滑动监听
                    setRecyclerViewOnScroll();
                }
            }
        }
    }


    /**
     * 在分发事件的时候处理子控件的触摸事件
     */
    private float mDownY, mUpY;

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {

        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN:
                // 移动的起点
                mDownY = ev.getY();
                break;
            case MotionEvent.ACTION_MOVE:
                // 移动过程中判断时候能下拉加载更多
                if (canLoadMore()) {
                    // 加载数据
                    loadData();
                }

                break;
            case MotionEvent.ACTION_UP:
                // 移动的终点
                mUpY = getY();
                break;
        }
        return super.dispatchTouchEvent(ev);
    }

    /**
     * 判断是否满足加载更多条件
     */
    private boolean canLoadMore() {
        // 1. 是上拉状态
        boolean condition1 = (mDownY - mUpY) >= mScaledTouchSlop;
        if (condition1) {
            Log.d(TAG, "------->  是上拉状态");
        }

        // 2. 当前页面可见的item是最后一个条目,一般最后一个条目位置需要大于第一页的数据长度
        boolean condition2 = false;
        if (mListView != null && mListView.getAdapter() != null) {

            if (mItemCount > 0) {
                if (mListView.getAdapter().getCount() < mItemCount) {
                    // 第一页未满，禁止下拉
                    condition2 = false;
                }else {
                    condition2 = mListView.getLastVisiblePosition() == (mListView.getAdapter().getCount() - 1);
                }
            } else {
                // 未设置数据长度，则默认第一页数据不满时也可以上拉
                condition2 = mListView.getLastVisiblePosition() == (mListView.getAdapter().getCount() - 1);
            }

        }

        if (condition2) {
            Log.d(TAG, "------->  是最后一个条目");
        }
        // 3. 正在加载状态
        boolean condition3 = !isLoading;
        if (condition3) {
            Log.d(TAG, "------->  不是正在加载状态");
        }
        return condition1 && condition2 && condition3;
    }

    public void setItemCount(int itemCount) {
        this.mItemCount = itemCount;
    }

    /**
     * 处理加载数据的逻辑
     */
    private void loadData() {
        System.out.println("加载数据...");
        if (mListener != null) {
            // 设置加载状态，让布局显示出来
            setLoading(true);
            mListener.onLoadMore();
        }

    }

    /**
     * 设置加载状态，是否加载传入boolean值进行判断
     *
     * @param loading
     */
    public void setLoading(boolean loading) {
        // 修改当前的状态
        isLoading = loading;
        if (isLoading) {
            // 显示布局
            mListView.addFooterView(mFooterView);
        } else {
            // 隐藏布局
            mListView.removeFooterView(mFooterView);

            // 重置滑动的坐标
            mDownY = 0;
            mUpY = 0;
        }
    }


    /**
     * 设置ListView的滑动监听
     */
    private void setListViewOnScroll() {

        mListView.setOnScrollListener(new AbsListView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
                // 移动过程中判断时候能下拉加载更多
                if (canLoadMore()) {
                    // 加载数据
                    loadData();
                }
            }

            @Override
            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {

            }
        });
    }


    /**
     * 设置RecyclerView的滑动监听
     */
    private void setRecyclerViewOnScroll() {
        mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);
                // 移动过程中判断时候能下拉加载更多
                if (canLoadMore()) {
                    // 加载数据
                    loadData();
                }
            }

            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
            }
        });
    }


    /**
     * 上拉加载的接口回调
     */

    public interface OnLoadMoreListener {
        void onLoadMore();
    }

    public void setOnLoadMoreListener(OnLoadMoreListener listener) {
        this.mListener = listener;
    }
}

/**
* 使用谷歌提供的SwipeRefreshLayout下拉控件进行下拉刷新
*/
public class ShangLaActivity extends AppCompatActivity {
    private List<String> mList;
    private StringAdapter mAdapter;
    private SwipeRefreshView mSwipeRefreshView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_shang_la);
        mSwipeRefreshView = (SwipeRefreshView) findViewById(R.id.srl);
        ListView listView = (ListView) findViewById(R.id.lv);

        mList = new ArrayList<>();
        mAdapter = new StringAdapter();
        listView.setAdapter(mAdapter);


        // 不能在onCreate中设置，这个表示当前是刷新状态，如果一进来就是刷新状态，SwipeRefreshLayout会屏蔽掉下拉事件
        //swipeRefreshLayout.setRefreshing(true);

        // 设置颜色属性的时候一定要注意是引用了资源文件还是直接设置16进制的颜色，因为都是int值容易搞混
        // 设置下拉进度的背景颜色，默认就是白色的
        mSwipeRefreshView.setProgressBackgroundColorSchemeResource(android.R.color.white);
        // 设置下拉进度的主题颜色
        mSwipeRefreshView.setColorSchemeResources(R.color.colorAccent,
                android.R.color.holo_blue_bright, R.color.colorPrimaryDark,
                android.R.color.holo_orange_dark, android.R.color.holo_red_dark, android.R.color.holo_purple);

        mSwipeRefreshView.setItemCount(20);

        // 手动调用,通知系统去测量
        mSwipeRefreshView.measure(0, 0);
        mSwipeRefreshView.setRefreshing(true);

        initEvent();
        initData();
    }

    private void initEvent() {

        // 下拉时触发SwipeRefreshLayout的下拉动画，动画完毕之后就会回调这个方法
        mSwipeRefreshView.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {
                initData();
            }
        });


        // 设置下拉加载更多
        mSwipeRefreshView.setOnLoadMoreListener(new SwipeRefreshView.OnLoadMoreListener() {
            @Override
            public void onLoadMore() {
                loadMoreData();
            }
        });
    }

    private void loadMoreData() {
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {

                mList.clear();
                mList.addAll(DataResource.getMoreData());
                Toast.makeText(ShangLaActivity.this, "加载了" + 20 + "条数据", Toast.LENGTH_SHORT).show();

                // 加载完数据设置为不加载状态，将加载进度收起来
                mSwipeRefreshView.setLoading(false);
            }
        }, 2000);
    }


    private void initData() {
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                mList.clear();
                mList.addAll(DataResource.getData());
                mAdapter.notifyDataSetChanged();

                Toast.makeText(ShangLaActivity.this, "刷新了20条数据", Toast.LENGTH_SHORT).show();

                // 加载完数据设置为不刷新状态，将下拉进度收起来
                if (mSwipeRefreshView.isRefreshing()) {
                    mSwipeRefreshView.setRefreshing(false);
                }
            }
        }, 2000);
    }


    /**
     * 适配器
     */
    private class StringAdapter extends BaseAdapter {

        @Override
        public int getCount() {
            return mList.size();
        }

        @Override
        public Object getItem(int position) {
            return mList.get(position);
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            if (convertView == null) {
                convertView = View.inflate(ShangLaActivity.this, android.R.layout.simple_list_item_1, null);
            }

            TextView tv = (TextView) convertView;
            tv.setGravity(Gravity.CENTER);
            tv.setPadding(0, 20, 0, 20);
            tv.setText(mList.get(position));

            return convertView;
        }
    }


    public static class DataResource {
        private static List<String> datas = new ArrayList<>();
        private static int page = 0;

        public static List<String> getData() {
            page = 0;
            datas.clear();

            for (int i = 0; i < 20; i++) {
                datas.add("我是天才" + i + "号");
            }

            return datas;
        }

        public static List<String> getMoreData() {
            page = page + 1;
            for (int i = 20 * page; i < 20 * (page + 1); i++) {
                datas.add("我是天才" + i + "号");
            }

            return datas;
        }
    }
}

二，布局
activity_shang_la.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ShangLaActivity">

    <!--使用谷歌官方的下拉刷新组件,只有下拉刷新功能-->
    <!--
        <android.support.v4.widget.SwipeRefreshLayout
            android:id="@+id/srl"
            android:layout_width="match_parent"
            android:layout_height="match_parent">
            <ListView
                android:id="@+id/lv"
                android:layout_width="match_parent"
                android:layout_height="match_parent"/>
        </android.support.v4.widget.SwipeRefreshLayout>
    -->


    <!--自定义View实现SwipeRefreshLayout，添加上拉加载更多的功能-->
    <qzjiami.pullrefreshlayout.SwipeRefreshView
        android:id="@+id/srl"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <ListView
            android:id="@+id/lv"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>

    </qzjiami.pullrefreshlayout.SwipeRefreshView>
</RelativeLayout>

view_footer.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="48dp">

        <ProgressBar
            android:id="@+id/load_progress"
            android:layout_width="24dp"
            android:layout_height="24dp"
            android:layout_centerVertical="true"
            android:layout_marginLeft="30dp"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"
            android:text="正在努力加载中..."
            android:textColor="@android:color/black"
            android:textSize="16sp"/>

    </RelativeLayout>

</RelativeLayout>