Android 判断ListView滑动方向
代码很简单，给mListView监听onScrollListener事件，然后在onScroll进行判断
//listView中第一项的索引
private int mListViewFirstItem = 0;
//listView中第一项的在屏幕中的位置
private int mScreenY = 0;
//是否向上滚动
private boolean mIsScrollToUp = false;
@Override
public void onScroll(AbsListView absListView, int firstVisibleItem,int visibleItemCount, int totalItemCount) {
if(mListView.getChildCount()>0)
{
boolean isScrollToUp = false;
View childAt = mListView.getChildAt(firstVisibleItem);
int[] location = new int[2];
childAt.getLocationOnScreen(location);
Log.d("onScroll", "firstVisibleItem= "+firstVisibleItem+" , y="+location[1]);
if(firstVisibleItem!=mListViewFirstItem)
{
if(firstVisibleItem>mListViewFirstItem)
{
Log.e("--->", "向上滑动");
isScrollToUp = true;
}else{
Log.e("--->", "向下滑动");
isScrollToUp = false;
}
mListViewFirstItem = firstVisibleItem;
mScreenY = location[1];
}else{
if(mScreenY>location[1])
{
Log.i("--->", "->向上滑动");
isScrollToUp = true;
}
else if(mScreenY<location[1])
{
Log.i("--->", "->向下滑动");
isScrollToUp = false;
}
mScreenY = location[1];
}
if(mIsScrollToUp!=isScrollToUp)
{
onScrollDirectionChanged(mIsScrollToUp);
}
}
}
private void onScrollDirectionChanged(boolean isScrollToUp)
{
}
-------使用ListView构建垂直滚动的View-------------
import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AbsListView.LayoutParams;
import android.widget.AbsListView.OnScrollListener;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ImageView.ScaleType;
import android.widget.ListView;
public class CardListActivity extends ActionBarActivity implements OnScrollListener {
private ListView mListView = null;
private Activity activity = null;
private DisplayMetrics screenMetrics = null;
private CardListAdapter mCardListAdapter = null;
//listView中第一项的索引
private int mListViewFirstItem = -1;
//listView中第一项的在屏幕中的位置
private int mScreenY = 0;
private int screenHeight = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.simple_listview);
activity = this;
mListView = (ListView) findViewById(R.id.app_listView);
screenMetrics = getResources().getDisplayMetrics();
screenHeight = screenMetrics.heightPixels-getStatusBarHeight();
initDataAndView();
}
private void initDataAndView()
{
mCardListAdapter = new CardListAdapter();
List<View> viewItems = mCardListAdapter.getViewItems();
for (int i = 0; i <= 3; i++)
{
int resId = activity.getResources().getIdentifier("slide_img_"+i, "drawable", getPackageName());
viewItems.add(createImageView(resId));
}
mListView.setAdapter(mCardListAdapter);
mCardListAdapter.notifyDataSetChanged();
mListView.setOnScrollListener(this);
}
public class CardListAdapter extends BaseAdapter{
private final List<View> viewItems = new ArrayList<View>();
public List<View> getViewItems()
{
return viewItems;
}
@Override
public int getCount() {
return viewItems.size();
}
@Override
public Object getItem(int position) {
return viewItems.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent)
{
return viewItems.get(position);
}
}
/**
* 图片二次采样
* @param resId
* @return
*/
private Bitmap sampleSizeBitmap(int resId)
{
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inJustDecodeBounds = true;
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), resId, opts);
opts.inSampleSize = calculateInSampleSize(opts, screenMetrics.widthPixels, screenMetrics.heightPixels);
opts.inJustDecodeBounds = false;
if(bitmap!=null)
{
bitmap.recycle();
}
return BitmapFactory.decodeResource(getResources(), resId, opts);
}
public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight)
{
final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 1;
if (height > reqHeight || width > reqWidth) {
final int heightRatio = Math.round((float) height / (float) reqHeight);
final int widthRatio = Math.round((float) width / (float) reqWidth);
inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
}
return inSampleSize;
}
/**
* 创建图片视图
* @param resId
* @return
*/
private ImageView createImageView(int resId)
{
ImageView iv = new ImageView(this);
LayoutParams lp = (LayoutParams) iv.getLayoutParams();
if(lp==null)
{
lp = new LayoutParams(LayoutParams.MATCH_PARENT,screenHeight);
}else{
lp.width = LayoutParams.MATCH_PARENT;
lp.height = screenHeight;
}
iv.setLayoutParams(lp);
iv.setScaleType(ScaleType.CENTER);
iv.setImageBitmap(sampleSizeBitmap(resId));
return iv;
}
private int getStatusBarHeight()
{
int result = 0;
int resourceId = getResources().getIdentifier("status_bar_height", "dimen", "android");
if (resourceId > 0) {
result = getResources().getDimensionPixelSize(resourceId);
}
return result;
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState)
{
if(mListViewFirstItem==-1)
{
return;
}
if (SCROLL_STATE_IDLE==scrollState || SCROLL_STATE_FLING==scrollState)
{
if(Math.abs(mScreenY)-(screenHeight*3)/5>0)
{
mListView.smoothScrollToPosition(mListViewFirstItem+1);
}else{
mListView.smoothScrollToPosition(mListViewFirstItem);
}
}
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem,int visibleItemCount, int totalItemCount)
{
if(mListView.getAdapter()==null || mListView.getChildCount()==0)
{
return;
}
View visibleFirstChild = (View) mListView.getAdapter().getItem(firstVisibleItem);
if(visibleFirstChild==null)
{
return;
}
int[] location = new int[2];
visibleFirstChild.getLocationOnScreen(location);
Log.d("onScroll", "first="+firstVisibleItem+" , screenY="+location[1]+",deltY="+(Math.abs(mScreenY)-(screenHeight*3)/5));
if(firstVisibleItem!=mListViewFirstItem)
{
if(firstVisibleItem>mListViewFirstItem)
{
Log.i("=======>", "向上滑动");
}else{
Log.e("--->", "向下滑动");
}
}else{
if(mScreenY>location[1])
{
Log.i("=======>", "->向上滑动");
}
else if(mScreenY<location[1])
{
Log.e("--->", "->向下滑动");
}
}
mListViewFirstItem = firstVisibleItem;
mScreenY = location[1];
}
}