android之OnScrollListener 下拉刷新

1.首先创建一个头部xml文件 

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

<!-- ListView的头部 -->
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
 >

  <!-- 内容 -->
  <RelativeLayout
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:id="@+id/head_contentLayout"
  android:paddingLeft="30dp"
  >

  <!-- 箭头图像、进度条 -->
  <FrameLayout
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:layout_alignParentLeft="true"
  android:layout_centerVertical="true"
  >

  <!-- 箭头 -->
  <ImageView
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:layout_gravity="center"
  android:src="@drawable/pull_down_arrow"
  android:id="@+id/head_arrowImageView"
  />

  <!-- 进度条 -->
  <ProgressBar
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  style="?android:attr/progressBarStyleSmall"
  android:layout_gravity="center"
  android:id="@+id/head_progressBar"

  android:visibility="gone"
  />

  </FrameLayout>

  <!-- 提示、最近更新 -->
  <LinearLayout
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:layout_centerHorizontal="true"
  android:orientation="vertical"
  android:gravity="center_horizontal"
  >

  <!-- 提示 -->
  <TextView
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="下拉刷新"
  android:textColor="@color/white"
  android:textSize="20sp"
  android:id="@+id/head_tipsTextView"
  />

  <!-- 最近更新 -->
  <TextView
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:id="@+id/head_lastUpdatedTextView"
  android:text="上次更新"
  android:textColor="@color/gold"
  android:textSize="10sp"
  />

  </LinearLayout>


  </RelativeLayout>


</LinearLayout>

2.然后写一个class： 

package com.laohuai.appdemo.customui.ui;

import java.util.Date;

import com.laohuai.appdemo.customui.R;

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.LinearInterpolator;
import android.view.animation.RotateAnimation;
import android.widget.AbsListView;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ProgressBar;
import android.widget.TextView;

public class MyListView extends ListView implements OnScrollListener {

    private static final String TAG = "listview";

    private final static int RELEASE_To_REFRESH = 0;
    private final static int PULL_To_REFRESH = 1;
    private final static int REFRESHING = 2;
    private final static int DONE = 3;
    private final static int LOADING = 4;

    // 实际的padding的距离与界面上偏移距离的比例
    private final static int RATIO = 3;

    private LayoutInflater inflater;

    private LinearLayout headView;

    private TextView tipsTextview;
    private TextView lastUpdatedTextView;
    private ImageView arrowImageView;
    private ProgressBar progressBar;


    private RotateAnimation animation;
    private RotateAnimation reverseAnimation;

    // 用于保证startY的值在一个完整的touch事件中只被记录一次
    private boolean isRecored;

    private int headContentWidth;
    private int headContentHeight;

    private int startY;
    private int firstItemIndex;

    private int state;

    private boolean isBack;

    private OnRefreshListener refreshListener;

    private boolean isRefreshable;

    public MyListView(Context context) {
        super(context);
        init(context);
    }

    public MyListView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context);
    }

    private void init(Context context) {
        setCacheColorHint(context.getResources().getColor(R.color.transparent));
        inflater = LayoutInflater.from(context);

        headView = (LinearLayout) inflater.inflate(R.layout.head, null);

        arrowImageView = (ImageView) headView
                .findViewById(R.id.head_arrowImageView);
        arrowImageView.setMinimumWidth(70);
        arrowImageView.setMinimumHeight(50);
        progressBar = (ProgressBar) headView
                .findViewById(R.id.head_progressBar);
        tipsTextview = (TextView) headView.findViewById(R.id.head_tipsTextView);
        lastUpdatedTextView = (TextView) headView
                .findViewById(R.id.head_lastUpdatedTextView);

        measureView(headView);
        headContentHeight = headView.getMeasuredHeight();
        headContentWidth = headView.getMeasuredWidth();

        headView.setPadding(0, -1 * headContentHeight, 0, 0);
        headView.invalidate();

        Log.v("size", "width:" + headContentWidth + " height:"
                + headContentHeight);

        addHeaderView(headView, null, false);
        setOnScrollListener(this);

        animation = new RotateAnimation(0, -180,
                RotateAnimation.RELATIVE_TO_SELF, 0.5f,
                RotateAnimation.RELATIVE_TO_SELF, 0.5f);
        animation.setInterpolator(new LinearInterpolator());
        animation.setDuration(250);
        animation.setFillAfter(true);

        reverseAnimation = new RotateAnimation(-180, 0,
                RotateAnimation.RELATIVE_TO_SELF, 0.5f,
                RotateAnimation.RELATIVE_TO_SELF, 0.5f);
        reverseAnimation.setInterpolator(new LinearInterpolator());
        reverseAnimation.setDuration(200);
        reverseAnimation.setFillAfter(true);

        state = DONE;
        isRefreshable = false;
    }

    public void onScroll(AbsListView arg0, int firstVisiableItem, int arg2,
            int arg3) {
        firstItemIndex = firstVisiableItem;
    }

    public void onScrollStateChanged(AbsListView arg0, int arg1) {
    }

    public boolean onTouchEvent(MotionEvent event) {

        if (isRefreshable) {
            switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                if (firstItemIndex == 0 && !isRecored) {
                    isRecored = true;
                    startY = (int) event.getY();
                    Log.v(TAG, "在down时候记录当前位置‘");
                }
                break;

            case MotionEvent.ACTION_UP:

                if (state != REFRESHING && state != LOADING) {
                    if (state == DONE) {
                        // 什么都不做
                    }
                    if (state == PULL_To_REFRESH) {
                        state = DONE;
                        changeHeaderViewByState();

                        Log.v(TAG, "由下拉刷新状态，到done状态");
                    }
                    if (state == RELEASE_To_REFRESH) {
                        state = REFRESHING;
                        changeHeaderViewByState();
                        onRefresh();

                        Log.v(TAG, "由松开刷新状态，到done状态");
                    }
                }

                isRecored = false;
                isBack = false;

                break;

            case MotionEvent.ACTION_MOVE:
                int tempY = (int) event.getY();

                if (!isRecored && firstItemIndex == 0) {
                    Log.v(TAG, "在move时候记录下位置");
                    isRecored = true;
                    startY = tempY;
                }

                if (state != REFRESHING && isRecored && state != LOADING) {

                    // 保证在设置padding的过程中，当前的位置一直是在head，否则如果当列表超出屏幕的话，当在上推的时候，列表会同时进行滚动

                    // 可以松手去刷新了
                    if (state == RELEASE_To_REFRESH) {

                        setSelection(0);

                        // 往上推了，推到了屏幕足够掩盖head的程度，但是还没有推到全部掩盖的地步
                        if (((tempY - startY) / RATIO < headContentHeight)
                                && (tempY - startY) > 0) {
                            state = PULL_To_REFRESH;
                            changeHeaderViewByState();

                            Log.v(TAG, "由松开刷新状态转变到下拉刷新状态");
                        }
                        // 一下子推到顶了
                        else if (tempY - startY <= 0) {
                            state = DONE;
                            changeHeaderViewByState();

                            Log.v(TAG, "由松开刷新状态转变到done状态");
                        }
                        // 往下拉了，或者还没有上推到屏幕顶部掩盖head的地步
                        else {
                            // 不用进行特别的操作，只用更新paddingTop的值就行了
                        }
                    }
                    // 还没有到达显示松开刷新的时候,DONE或者是PULL_To_REFRESH状态
                    if (state == PULL_To_REFRESH) {

                        setSelection(0);

                        // 下拉到可以进入RELEASE_TO_REFRESH的状态
                        if ((tempY - startY) / RATIO >= headContentHeight) {
                            state = RELEASE_To_REFRESH;
                            isBack = true;
                            changeHeaderViewByState();

                            Log.v(TAG, "由done或者下拉刷新状态转变到松开刷新");
                        }
                        // 上推到顶了
                        else if (tempY - startY <= 0) {
                            state = DONE;
                            changeHeaderViewByState();

                            Log.v(TAG, "由DOne或者下拉刷新状态转变到done状态");
                        }
                    }

                    // done状态下
                    if (state == DONE) {
                        if (tempY - startY > 0) {
                            state = PULL_To_REFRESH;
                            changeHeaderViewByState();
                        }
                    }

                    // 更新headView的size
                    if (state == PULL_To_REFRESH) {
                        headView.setPadding(0, -1 * headContentHeight
                                + (tempY - startY) / RATIO, 0, 0);

                    }

                    // 更新headView的paddingTop
                    if (state == RELEASE_To_REFRESH) {
                        headView.setPadding(0, (tempY - startY) / RATIO
                                - headContentHeight, 0, 0);
                    }

                }

                break;
            }
        }

        return super.onTouchEvent(event);
    }

    // 当状态改变时候，调用该方法，以更新界面
    private void changeHeaderViewByState() {
        switch (state) {
        case RELEASE_To_REFRESH:
            arrowImageView.setVisibility(View.VISIBLE);
            progressBar.setVisibility(View.GONE);
            tipsTextview.setVisibility(View.VISIBLE);
            lastUpdatedTextView.setVisibility(View.VISIBLE);

            arrowImageView.clearAnimation();
            arrowImageView.startAnimation(animation);

            tipsTextview.setText("松开刷新");

            Log.v(TAG, "当前状态，松开刷新");
            break;
        case PULL_To_REFRESH:
            progressBar.setVisibility(View.GONE);
            tipsTextview.setVisibility(View.VISIBLE);
            lastUpdatedTextView.setVisibility(View.VISIBLE);
            arrowImageView.clearAnimation();
            arrowImageView.setVisibility(View.VISIBLE);
            // 是由RELEASE_To_REFRESH状态转变来的
            if (isBack) {
                isBack = false;
                arrowImageView.clearAnimation();
                arrowImageView.startAnimation(reverseAnimation);

                tipsTextview.setText("下拉刷新");
            } else {
                tipsTextview.setText("下拉刷新");
            }
            Log.v(TAG, "当前状态，下拉刷新");
            break;

        case REFRESHING:

            headView.setPadding(0, 0, 0, 0);

            progressBar.setVisibility(View.VISIBLE);
            arrowImageView.clearAnimation();
            arrowImageView.setVisibility(View.GONE);
            tipsTextview.setText("正在刷新...");
            lastUpdatedTextView.setVisibility(View.VISIBLE);

            Log.v(TAG, "当前状态,正在刷新...");
            break;
        case DONE:
            headView.setPadding(0, -1 * headContentHeight, 0, 0);

            progressBar.setVisibility(View.GONE);
            arrowImageView.clearAnimation();
            arrowImageView.setImageResource(R.drawable.pull_down_arrow);
            tipsTextview.setText("下拉刷新");
            lastUpdatedTextView.setVisibility(View.VISIBLE);

            Log.v(TAG, "当前状态，done");
            break;
        }
    }

    public void setonRefreshListener(OnRefreshListener refreshListener) {
        this.refreshListener = refreshListener;
        isRefreshable = true;
    }

    public interface OnRefreshListener {
        public void onRefresh();
    }

    public void onRefreshComplete() {
        state = DONE;
        lastUpdatedTextView.setText("最近更新:" + new Date().toLocaleString());
        changeHeaderViewByState();
    }

    private void onRefresh() {
        if (refreshListener != null) {
            refreshListener.onRefresh();
        }
    }

    // 此方法直接照搬自网络上的一个下拉刷新的demo，此处是“估计”headView的width以及height
    private void measureView(View child) {
        ViewGroup.LayoutParams p = child.getLayoutParams();
        if (p == null) {
            p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT,
                    ViewGroup.LayoutParams.WRAP_CONTENT);
        }
        int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0 + 0, p.width);
        int lpHeight = p.height;
        int childHeightSpec;
        if (lpHeight > 0) {
            childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight,
                    MeasureSpec.EXACTLY);
        } else {
            childHeightSpec = MeasureSpec.makeMeasureSpec(0,
                    MeasureSpec.UNSPECIFIED);
        }
        child.measure(childWidthSpec, childHeightSpec);
    }

    public void setAdapter(BaseAdapter adapter) {
        lastUpdatedTextView.setText("最近更新:" + new Date().toLocaleString());
        super.setAdapter(adapter);
    }

}

3.在main.xml 中调用上面的这个class： 

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    android:background="#FFFFFF">

    <com.laohuai.appdemo.customui.ui.MyListView
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:id="@+id/listView"
    android:listSelector="@android:color/transparent"
    />

</LinearLayout>

4.实现Activity： 

package com.laohuai.appdemo.customui;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import com.laohuai.appdemo.customui.ui.MyListView;
import com.laohuai.appdemo.customui.ui.MyListView.OnRefreshListener;

import android.app.Activity;
import android.content.Context;
import android.content.res.Resources;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;

public class MainActivity extends Activity {
    HashMap<String, Object> maps;
    MyListView listView;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        listView = (MyListView) findViewById(R.id.listView);
        getData();
    }

    private void getData() {
        List<HashMap<String, Object>> lists = new ArrayList<HashMap<String, Object>>();

        for (int i = 0; i < 40; i++) {

            maps = new HashMap<String, Object>();
            maps.put("test", "搞定了没有啊");

            lists.add(maps);
        }
        final ListAdapter adapter = new ListAdapter(MainActivity.this, lists);
        listView.setAdapter(adapter);

        listView.setonRefreshListener(new OnRefreshListener() {
            public void onRefresh() {
                new AsyncTask<Void, Void, Void>() {
                    protected Void doInBackground(Void... params) {
                        try {
                            Thread.sleep(1000);
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                        maps.get("刷新后添加的内容");
                        return null;
                    }

                    protected void onPostExecute(Void result) {
                        adapter.notifyDataSetChanged();
                        listView.onRefreshComplete();
                    }

                }.execute(null);
            }
        });
    }

    class ListAdapter extends BaseAdapter {

        private Context mContext;
        private List<HashMap<String, Object>> data;

        public ListAdapter(Context mContext, List<HashMap<String, Object>> data) {
            super();
            this.mContext = mContext;
            this.data = data;
        }

        public int getCount() {
            // TODO Auto-generated method stub
            return data.size();
        }

        public Object getItem(int position) {
            // TODO Auto-generated method stub
            return position;
        }

        public long getItemId(int position) {
            // TODO Auto-generated method stub
            return position;
        }

        public View getView(int position, View convertView, ViewGroup parent) {
            TextView tv = new TextView(getApplicationContext());
            tv.setText((String)data.get(position).get("test"));
            Resources rs = getResources();
            tv.setTextColor(rs.getColor(R.color.white));
            return tv;
        }

    }
}