Android Listview下拉刷新數據

Android listview仿新浪微博下拉刷新例子，其實所有此功能最早是國外實現的，現在網上能看到的都是基于這個例子，只是有些細節不同。算法上確實比較巧妙，直得學習一下。

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="cn.com.karl.list"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="4" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:label="@string/app_name"
            android:name=".MainActivity" >
            <intent-filter >
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

<?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" >

    <cn.com.karl.list.MyListView
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:id="@+id/listView"
    />    

</LinearLayout>

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

<!-- ListView的頭部 -->

<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:background="#ffffff"
 >

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

  <!-- 箭頭圖像、進度條 -->
  <FrameLayout
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:layout_alignParentLeft="true"
  android:layout_centerVertical="true"
  >

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

  <!-- 進度條 -->
  <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:textSize="15dp"
  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:textSize="12dp"
  />

  </LinearLayout>


  </RelativeLayout>


</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center_vertical"
    android:background="#ffffff"
    android:orientation="horizontal" >

    <ImageView
        android:id="@+id/imageView_item"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="10dp"
        android:src="@drawable/ic_launcher" />

    <TextView
        android:id="@+id/textView_item"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="10dp"
        android:text="TextView" />

</LinearLayout>

package cn.com.karl.list;


import java.util.LinkedList;

import cn.com.karl.list.MyListView.OnRefreshListener;

import android.app.Activity;
import android.content.res.Configuration;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.BaseAdapter;
import android.widget.TextView;

public class MainActivity extends Activity 
{

    private LinkedList<String> data;
    private BaseAdapter adapter;
    private MyListView listView;

    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // 取得屏幕尺寸大小
        displayScreenSize();

        data = new LinkedList<String>();
        for(int i=0;i<10;i++)
        {
            data.add(String.valueOf(i));
        }

        listView = (MyListView) findViewById(R.id.listView);

        adapter = new BaseAdapter() 
        {
            public View getView(int position, View convertView, ViewGroup parent) 
            {
                convertView = LayoutInflater.from(getApplicationContext()).inflate(R.layout.item, null);
                TextView textView = (TextView) convertView.findViewById(R.id.textView_item);
                textView.setText(data.get(position));
                return convertView;
            }

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

            public Object getItem(int position) 
            {
                return data.get(position);
            }

            public int getCount() 
            {
                return data.size();
            }
        };

        listView.setAdapter(adapter);

        listView.setOnRefreshListener(new OnRefreshListener() 
        {
            public void onRefresh() 
            {
                RefreshTask rTask = new RefreshTask();
                rTask.execute(1000);
            }
        });
    }

    // AsyncTask異步任務
    class RefreshTask extends AsyncTask<Integer, Integer, String>
    {    
        @Override
        protected String doInBackground(Integer... params) 
        {
            try 
            {
                Thread.sleep(params[0]);
            } 
            catch (Exception e) 
            {
                e.printStackTrace();
            }
            // 在data最前添加數據
            data.addFirst("刷新后的內容");
            return null;
        }   

        @Override
        protected void onPostExecute(String result) 
        {
            super.onPostExecute(result);
            adapter.notifyDataSetChanged();
            listView.onRefreshComplete();
        }       
    }

    // 取得屏幕尺寸大小
    public void displayScreenSize()
    {
        // 屏幕方面切換時獲得方向
        if (this.getResources().getConfiguration().orientation == Configuration.ORIENTATION_LANDSCAPE) 
        {       
            setTitle("landscape");
        }

        if (this.getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT) 
        {
            setTitle("portrait");
        }

        // 獲得屏幕大小1
        WindowManager manager = getWindowManager();
        int width = manager.getDefaultDisplay().getWidth();
        int height = manager.getDefaultDisplay().getHeight();

        Log.v("am10", "width: " + width + " height: " + height);

        // 獲得屏幕大小2
        DisplayMetrics dMetrics = new DisplayMetrics();
        getWindowManager().getDefaultDisplay().getMetrics(dMetrics);
        int screenWidth = dMetrics.widthPixels;
        int screenHeight = dMetrics.heightPixels;

        Log.v("am10", "screenWidth: " + screenWidth + " screenHeight: " + screenHeight);
    }
}

package cn.com.karl.list;

import java.text.SimpleDateFormat;
import java.util.Date;

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 = "am10";
    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;

    // 實際的padding的距離與界面上偏移距離的比例
    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;

    // 用于保證startY的值在一個完整的touch事件中只被記錄一次
    private boolean isRecored;

    private int startY;
    private int firstItemIndex;

    private int headContentWidth;
    private int headContentHeight;

    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);

        // 估算headView的寬和高
        measureView(headView);
        headContentHeight = headView.getMeasuredHeight();
        headContentWidth = headView.getMeasuredWidth();

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

        Log.v(TAG, "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;
        //Log.v(TAG, "firstItemIndex: "+firstItemIndex);
    }

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

    public boolean onTouchEvent(MotionEvent event) 
    {
        // Log.v(TAG, "isRefreshable: "+isRefreshable);
        if (isRefreshable) 
        {
            switch (event.getAction()) 
            {
            case MotionEvent.ACTION_DOWN:
                if (firstItemIndex == 0 && !isRecored) 
                {
                    isRecored = true;

                    // 觸摸屏幕的位置
                    startY = (int) event.getY();    
                    Log.v(TAG, "在down時候記錄當前位置" + " startY:"+startY);
                }
                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, "由下拉刷新狀態，到done狀態");
                    }

                    if (state == RELEASE_To_REFRESH) 
                    {
                        state = REFRESHING;
                        changeHeaderViewByState();
                        onRefresh();
                        Log.v(TAG, "由松開刷新狀態，到done狀態");
                    }
                }

                isRecored = false;
                isBack = false;
                break;

            case MotionEvent.ACTION_MOVE:
                int tempY = (int) event.getY();
                //Log.v(TAG, "tempY: " + tempY);

                /**                              
                 * 手指移動過程中tempY數據會不斷變化,當滑動到firstItemIndex,即到達頂部,
                 * 需要記錄手指所在屏幕的位置: startY = tempY ,后面作位置比較使用
                 * 
                 * 如果手指繼續向下推,tempY繼續變化,當tempY-startY>0,即是需要顯示header部分
                 * 
                 * 此時需要更改狀態：state = PULL_To_REFRESH
                 */
                if (!isRecored && firstItemIndex == 0) 
                {
                    isRecored = true;
                    startY = tempY;
                    Log.v(TAG, "在move時候記錄下位置" + " startY:"+startY);
                }

                if (state != REFRESHING && isRecored && state != LOADING) 
                {
                    /**
                     * 保證在設置padding的過程中，當前的位置一直是在head，
                     * 否則如果當列表超出屏幕的話，當在上推的時候，列表會同時進行滾動
                     */                 

                    // 可以松手去刷新了
                    if (state == RELEASE_To_REFRESH) 
                    {
                        setSelection(0);

                        // 往上推了，推到了屏幕足夠掩蓋head的程度，但是還沒有推到全部掩蓋的地步
                        if (((tempY - startY) / RATIO < headContentHeight) && (tempY - startY) > 0) 
                        {
                            state = PULL_To_REFRESH;
                            changeHeaderViewByState();
                            Log.v(TAG, "由松開刷新狀態轉變到下拉刷新狀態");
                        }

                        // 一下子推到頂了,沒有顯示header部分時,應該恢復DONE狀態,這里機率很小
                        else if (tempY - startY <= 0) 
                        {
                            state = DONE;
                            changeHeaderViewByState();
                            Log.v(TAG, "---由松開刷新狀態轉變到done狀態");
                        }                       
                        else 
                        {
                            // 往下拉了，或者還沒有上推到屏幕頂部掩蓋head的地步
                            // 不用進行特別的操作，只用更新paddingTop的值就行了
                        }
                    }

                    // 還沒有到達顯示松開刷新的時候,DONE或者是PULL_To_REFRESH狀態
                    if (state == PULL_To_REFRESH) 
                    {
                        setSelection(0);

                        /**
                         * 下拉到可以進入RELEASE_TO_REFRESH的狀態
                         * 
                         * 等于headContentHeight時,即是正好完全顯示header部分
                         * 大于headContentHeight時,即是超出header部分更多
                         * 
                         * 當header部分能夠完全顯示或者超出顯示,
                         * 需要更改狀態: state = RELEASE_To_REFRESH
                         */
                        if ((tempY - startY) / RATIO >= headContentHeight) 
                        {
                            state = RELEASE_To_REFRESH;
                            isBack = true;
                            changeHeaderViewByState();
                            Log.v(TAG, "由done或者下拉刷新狀態轉變到松開刷新");
                        }

                        // 上推到頂了,沒有顯示header部分時,應該恢復DONE狀態
                        else if (tempY - startY <= 0) 
                        {
                            state = DONE;
                            changeHeaderViewByState();
                            Log.v(TAG, "由done或者下拉刷新狀態轉變到done狀態");
                        }
                    }

                    // done狀態下
                    if (state == DONE) 
                    {
                        if (tempY - startY > 0) 
                        {
                            /**                              
                             * 手指移動過程中tempY數據會不斷變化,當滑動到firstItemIndex,即到達頂部,
                             * 需要記錄手指所在屏幕的位置: startY = tempY ,后面作位置比較使用
                             * 
                             * 如果手指繼續向下推,tempY繼續變化,當tempY-startY>0,即是需要顯示header部分
                             * 
                             * 此時需要更改狀態：state = PULL_To_REFRESH
                             */
                            //Log.v(TAG, "----------------PULL_To_REFRESH " + (tempY - startY));                            
                            state = PULL_To_REFRESH;
                            changeHeaderViewByState();
                        }
                    }

                    // 更新headView的paddingTop
                    if (state == PULL_To_REFRESH) 
                    {
                        //Log.v(TAG, "----------------PULL_To_REFRESH2 " + (tempY - startY));
                        headView.setPadding(0, -1 * headContentHeight + (tempY - startY) / RATIO, 0, 0);
                    }

                    // 繼續更新headView的paddingTop
                    if (state == RELEASE_To_REFRESH) 
                    {
                        headView.setPadding(0, (tempY - startY) / RATIO - headContentHeight, 0, 0);
                    }
                }
                break;
            }
        }
        return super.onTouchEvent(event);
    }

    // 當狀態改變時候，調用該方法，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("松開刷新");

                Log.v(TAG, "當前狀態，松開刷新");
                break;

            case PULL_To_REFRESH:
                //progressBar.setVisibility(View.GONE);
                tipsTextview.setVisibility(View.VISIBLE);
                lastUpdatedTextView.setVisibility(View.VISIBLE);
                arrowImageView.clearAnimation();
                arrowImageView.setVisibility(View.VISIBLE);

                /**
                 *  是否向下滑回，是由RELEASE_To_REFRESH狀態轉變來的
                 */
                if (isBack) 
                {                   
                    isBack = false;
                    arrowImageView.clearAnimation();
                    arrowImageView.startAnimation(reverseAnimation);    
                    tipsTextview.setText("下拉刷新");
                    //Log.v(TAG, "isBack: " + isBack);
                } 
                else 
                {                   
                    tipsTextview.setText("下拉刷新");
                    //Log.v(TAG, "isBack: " + isBack);
                }

                Log.v(TAG, "當前狀態，下拉刷新");
                break;

            case REFRESHING:
                Log.v(TAG, "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, "當前狀態,正在刷新...");
                break;

            case DONE:
                headView.setPadding(0, -1 * headContentHeight, 0, 0);

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

                Log.v(TAG, "當前狀態，done");
                break;
        }
    }

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

    public interface OnRefreshListener 
    {
        public void onRefresh();
    }

    public void onRefreshComplete() 
    {
        state = DONE;
        SimpleDateFormat format = new SimpleDateFormat("yyyy年MM月dd日  HH:mm");
        String date = format.format(new Date());
        lastUpdatedTextView.setText("最近更新:" + date);
        changeHeaderViewByState();
    }

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

    // 此方法直接照搬自網絡上的一個下拉刷新的demo，此處是“估計”headView的width以及height
    private void measureView(View child) 
    {
        ViewGroup.LayoutParams p = child.getLayoutParams();
        if (p == null) 
        {
            //Log.v(TAG, "LayoutParams is 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) 
    {
        SimpleDateFormat format=new SimpleDateFormat("yyyy年MM月dd日  HH:mm");
        String date=format.format(new Date());
        lastUpdatedTextView.setText("最近更新:" + date);
        super.setAdapter(adapter);
    }
}

這個例子忘記那里下載的，這里也尊重作者，注明并不是我本人寫的。如果誰知道原作者資料請告知，在此添加。

我修改了一下代碼，使用AsyncTask異步任務更新數據，還有添加和修改了一些注釋。