Android系統上拉刷新功能的實現

自定義ListView：

public class MyListView extends ListView implements OnScrollListener {


public final int RATIO = 5;// 手拖動時，手指拖動距離與header下移的倍數
private final int LOADING = 0;// 正在加載
private final int RELEASE_To_REFRESH = 2;// 正在下拉狀態，即將松手進行刷新
private final int DONE = 3;// 完成
private final int HIDE_To_REFRESH = 1;// 未下拉或已完成狀態，設置padding為負值把header擋住

private int refreshStatus;// 下拉刷新過程狀態變量

private LinearLayout hearderLayout;
private ImageView arrowImageView;
private ProgressBar progressBar;
private TextView tipsTextview;
private TextView lastUpdatedTime;
private int headContentHeight;
private int headContentWidth;
private RotateAnimation animation;
private RotateAnimation reverseAnimation;
private boolean isStartRefreshEvent = false;// 下拉刷新事件是否已經開始
private boolean isRefreshable = false;// 是否設置下拉刷新監聽
private int firstItemIndex;

private OnRefreshListener refreshListener;

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

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

private void init(Context context) {

    LayoutInflater inflater = LayoutInflater.from(context);
    hearderLayout = (LinearLayout) inflater.inflate(R.layout.list_view_header, null);
    // 下拉箭頭
    arrowImageView = (ImageView) hearderLayout.findViewById(R.id.head_arrowImageView);
    // 進度條
    progressBar = (ProgressBar) hearderLayout.findViewById(R.id.head_progressBar);
    // 下拉提示 刷新
    tipsTextview = (TextView) hearderLayout.findViewById(R.id.head_tipsTextView);
    // 最新一次刷新時間
    lastUpdatedTime = (TextView) hearderLayout.findViewById(R.id.head_lastUpdatedTextView);
    // 計算head的高寬
    this.measureView(hearderLayout);
    headContentHeight = hearderLayout.getMeasuredHeight();
    headContentWidth = hearderLayout.getMeasuredWidth();

    // 初始狀態是 隱藏掉head 布局
    hearderLayout.setPadding(0, -1 * headContentHeight, 0, 0);
    hearderLayout.invalidate();

    Log.e("sys", "width:" + headContentWidth + " height:" + headContentHeight);
    // list添加頭文件
    addHeaderView(hearderLayout, null, false);
    setOnScrollListener(this);// TODO
    // 下拉以及恢復動畫
    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);
    refreshStatus = DONE;
}

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

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

private int startY = 0;
@Override
public boolean onTouchEvent(MotionEvent event) {

    if (firstItemIndex == 0 && isRefreshable) {
        switch (event.getAction()) {
        // 在down時候記錄當前Y的位置
        case MotionEvent.ACTION_DOWN:
            if (!isStartRefreshEvent) {
                isStartRefreshEvent = true;
                startY = (int) event.getY();
            }
            break;

        case MotionEvent.ACTION_MOVE:

            int tempY = (int) event.getY();
            int scrollY = (tempY - startY) / RATIO;

            Log.i("sys", "拉開方向 " + scrollY);

            if (!isStartRefreshEvent) {
                isStartRefreshEvent = true;
                startY = tempY;
            } else if (isStartRefreshEvent && refreshStatus != LOADING) {
                // 可以松手去刷新了
                if (refreshStatus == RELEASE_To_REFRESH) {
                    setSelection(0);
                    // header被用戶拉下來后，又往上推了，推到了已經小于header高度時，則推回去，并取消刷新
                    if (scrollY < headContentHeight && scrollY > 0) {
                        refreshStatus = HIDE_To_REFRESH;
                        this.changeHeaderView();
                    }
                    // 一下子推到頂了
                    else if (scrollY <= 0) {
                        refreshStatus = DONE;
                        this.changeHeaderView();
                    }
                }
                // 還沒有到達顯示松開刷新的時候,DONE或者是HIDE_To_REFRESH狀態
                if (refreshStatus == HIDE_To_REFRESH) {
                    setSelection(0);
                    // 下拉至超過header本身高度后，可以進入RELEASE_TO_REFRESH的狀態
                    if (scrollY > headContentHeight) {
                        refreshStatus = RELEASE_To_REFRESH;
                        this.changeHeaderView();
                    }
                    // 上推到頂了
                    else if (scrollY <= 0) {
                        refreshStatus = DONE;
                        this.changeHeaderView();
                    }
                }
                // done狀態下
                if (refreshStatus == DONE) {
                    if (scrollY > 0) {
                        refreshStatus = HIDE_To_REFRESH;
                        this.changeHeaderView();
                    }
                }
                // 更新headView的size
                if (refreshStatus == HIDE_To_REFRESH) {
                    hearderLayout.setPadding(0, -1 * headContentHeight + scrollY, 0, 0);
                }
                // 更新headView的paddingTop
                if (refreshStatus == RELEASE_To_REFRESH) {
                    hearderLayout.setPadding(0, scrollY - headContentHeight, 0, 0);
                }
            }
            break;

        case MotionEvent.ACTION_UP:
            if (refreshStatus != LOADING) {
                if (refreshStatus == DONE) {
                    // 什么都不做
                }
                // 由下拉刷新狀態，到done狀態
                if (refreshStatus == HIDE_To_REFRESH) {
                    refreshStatus = DONE;
                    this.changeHeaderView();
                }

                if (refreshStatus == RELEASE_To_REFRESH) {
                    refreshStatus = LOADING;
                    this.changeHeaderView();
                    onRefresh();
                }
            }
            isStartRefreshEvent = false;
            break;

        }
    }
    return super.onTouchEvent(event);
}

private void changeHeaderView() {
    switch (refreshStatus) {
    // 松開刷新狀態
    case RELEASE_To_REFRESH:
        arrowImageView.setVisibility(View.VISIBLE);
        progressBar.setVisibility(View.GONE);
        tipsTextview.setVisibility(View.VISIBLE);
        lastUpdatedTime.setVisibility(View.VISIBLE);
        arrowImageView.clearAnimation();
        arrowImageView.startAnimation(animation);
        tipsTextview.setText("松開刷新");
        break;
    // 下拉刷新
    case HIDE_To_REFRESH:
        progressBar.setVisibility(View.GONE);
        tipsTextview.setVisibility(View.VISIBLE);
        lastUpdatedTime.setVisibility(View.VISIBLE);
        arrowImageView.setVisibility(View.VISIBLE);
        // 是由RELEASE_To_REFRESH狀態轉變來的
        arrowImageView.clearAnimation();
        arrowImageView.startAnimation(reverseAnimation);
        tipsTextview.setText("下拉刷新");
        break;
    // 刷新中 狀態
    case LOADING:
        hearderLayout.setPadding(0, 0, 0, 0);
        progressBar.setVisibility(View.VISIBLE);
        arrowImageView.clearAnimation();
        arrowImageView.setVisibility(View.GONE);
        tipsTextview.setText("正在刷新...");
        lastUpdatedTime.setVisibility(View.VISIBLE);
        break;
    // 刷新完畢
    case DONE:
        hearderLayout.setPadding(0, -1 * headContentHeight, 0, 0);
        progressBar.setVisibility(View.GONE);
        arrowImageView.clearAnimation();
        // arrowImageView.setImageResource(R.drawable.goicon);
        tipsTextview.setText("下拉刷新");
        lastUpdatedTime.setVisibility(View.VISIBLE);
        break;
    }
}

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

public interface OnRefreshListener {
    public void onRefresh();
}

public void onRefreshFinished() {
    refreshStatus = DONE;
    DateFormat format = new SimpleDateFormat("yyyy年MM月dd日  HH:mm");
    String date = format.format(new Date());
    lastUpdatedTime.setText("最近更新:" + date);
    changeHeaderView();
}

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

// 此方法計算高度
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) {
    DateFormat format = new SimpleDateFormat("yyyy年MM月dd日  HH:mm");
    String date = format.format(new Date());
    lastUpdatedTime.setText("最近更新:" + date);
    super.setAdapter(adapter);
}

}
  </pre> 

 layout:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android&quot;
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:background="#ffffff" >


<!-- 內容 -->

<RelativeLayout
    android:id="@+id/head_contentLayout"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:paddingLeft="30dip" >

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

        <!-- 進度條,style集合了一個anim -->
        <ProgressBar
            android:id="@+id/head_progressBar"
            style="@style/wait_anim"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            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:gravity="center_horizontal"
        android:orientation="vertical" >

        <!-- 提示 -->
        <TextView
            android:id="@+id/head_tipsTextView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="下拉刷新"
            android:textSize="15dp" />

        <!-- 最近更新 -->
        <TextView
            android:id="@+id/head_lastUpdatedTextView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="上次更新"
            android:textSize="12dp" />
    </LinearLayout>
</RelativeLayout>


</LinearLayout>
Activity中關鍵代碼：
mListView.setonRefreshListener(new OnRefreshListener() {
            public void onRefresh() {
                new AsyncTask<Void, Void, Void>() {
                    protected Void doInBackground(Void... params) {
                        try {
                            Thread.sleep(3000);
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
//                      dates.addFirst(new AttachmentModule(new Date(), WorkLogContentType.WORKLOG_ATTACHMENT, AttachmentType.Attachment_Nomal));
                        return null;
                    }

                @Override
                protected void onPostExecute(Void result) {
                    adapter.notifyDataSetChanged();
                    mListView.onRefreshFinished();
                }
            }.execute(null);
        }
    });</pre>