我使用延迟加载来下载图像，从而填充到水平列表视图中。但是滚动并不顺畅，特别是从右到左滚动时。这些是我的代码：
主页pg.xml
<ScrollView
android:id="@+id/scrollView1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:scrollbars="none" >
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<RelativeLayout
android:id="@+id/Horizlistlatestnews"
android:layout_width="match_parent"
android:layout_height="105dp"
android:orientation="horizontal"
android:layout_below="@+id/Titlelatestnews"
>
<com.xxx.xxx.HorizontalView
android:id="@+id/horizontallistln"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="2dp"
android:scrollbars="none"
>
</com.xxx.xxx.HorizontalView>
</RelativeLayout>
</RelativeLayout>
<RelativeLayout
android:id="@+id/Boxoffice"
android:layout_width="match_parent"
android:layout_height="145dp"
android:background="@drawable/bggray" >
<RelativeLayout
android:id="@+id/Titleboxofc"
android:layout_width="match_parent"
android:layout_height="30dp"
>
<TextView
android:id="@+id/textViewboxofc"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="BOX OFFICE"
android:textColor="#FFFFFF"
android:textStyle="bold"
android:layout_alignParentLeft="true"
android:layout_marginLeft="5dp"
android:layout_centerVertical="true" />
<ProgressBar
android:id="@+id/progressBarboxofc"
android:layout_width="15dp"
android:layout_height="15dp"
android:visibility="gone"
android:layout_alignParentRight="true"
android:layout_marginRight="10dp"
android:layout_centerVertical="true"
/>
</RelativeLayout>
<RelativeLayout
android:id="@+id/Horizlistboxofc"
android:layout_width="match_parent"
android:layout_height="105dp"
android:orientation="horizontal"
android:layout_below="@+id/Titleboxofc"
>
<com.xxx.xxx.HorizontalView
android:id="@+id/horizontallistbo"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="2dp"
android:scrollbars="none"
>
</com.xxx.xxx.HorizontalView>
</RelativeLayout>
</LinearLayout>
</ScrollView>
水平视图.java
package com.xxx.xxx;
import java.util.LinkedList;
import java.util.Queue;
import android.content.Context;
import android.database.DataSetObserver;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.GestureDetector.OnGestureListener;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Adapter;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.Scroller;
public class HorizontalView extends AdapterView<Adapter> {
public boolean mAlwaysOverrideTouch = true;
protected ListAdapter mAdapter;
private int mLeftViewIndex = -1;
private int mRightViewIndex = 0;
protected int mCurrentX;
protected int mNextX;
private int mMaxX = Integer.MAX_VALUE;
private int mDisplayOffset = 0;
protected Scroller mScroller;
private GestureDetector mGesture;
private Queue mRemovedViewQueue = new LinkedList();
private OnItemSelectedListener mOnItemSelected;
private OnItemClickListener mOnItemClicked;
private OnItemLongClickListener mOnItemLongClicked;
private boolean mDataChanged = false;
public HorizontalView(Context context, AttributeSet attrs) {
super(context, attrs);
initView();
}
private synchronized void initView() {
mLeftViewIndex = -1;
mRightViewIndex = 0;
mDisplayOffset = 0;
mCurrentX = 0;
mNextX = 0;
mMaxX = Integer.MAX_VALUE;
mScroller = new Scroller(getContext());
mGesture = new GestureDetector(getContext(), mOnGesture);
}
@Override
public void setOnItemSelectedListener(
AdapterView.OnItemSelectedListener listener) {
mOnItemSelected = listener;
}
@Override
public void setOnItemClickListener(AdapterView.OnItemClickListener listener) {
mOnItemClicked = listener;
}
@Override
public void setOnItemLongClickListener(
AdapterView.OnItemLongClickListener listener) {
mOnItemLongClicked = listener;
}
private DataSetObserver mDataObserver = new DataSetObserver() {
@Override
public void onChanged() {
synchronized (HorizontalView.this) {
mDataChanged = true;
}
invalidate();
requestLayout();
}
@Override
public void onInvalidated() {
reset();
invalidate();
requestLayout();
}
};
@Override
public Adapter getAdapter() {
return mAdapter;
}
@Override
public View getSelectedView() {
return null;
}
@Override
public void setAdapter(Adapter adapter) {
if (mAdapter != null) {
mAdapter.unregisterDataSetObserver(mDataObserver);
}
mAdapter = (ListAdapter) adapter;
mAdapter.registerDataSetObserver(mDataObserver);
reset();
}
private synchronized void reset() {
initView();
removeAllViewsInLayout();
requestLayout();
}
@Override
public void setSelection(int position) {
}
private void addAndMeasureChild(final View child, int viewPos) {
LayoutParams params = child.getLayoutParams();
if (params == null) {
params = new LayoutParams(LayoutParams.FILL_PARENT,
LayoutParams.FILL_PARENT);
}
addViewInLayout(child, viewPos, params, true);
child.measure(
MeasureSpec.makeMeasureSpec(getWidth(), MeasureSpec.AT_MOST),
MeasureSpec.makeMeasureSpec(getHeight(), MeasureSpec.AT_MOST));
}
@Override
protected synchronized void onLayout(boolean changed, int left, int top,
int right, int bottom) {
super.onLayout(changed, left, top, right, bottom);
if (mAdapter == null) {
return;
}
if (mDataChanged) {
int oldCurrentX = mCurrentX;
initView();
removeAllViewsInLayout();
mNextX = oldCurrentX;
mDataChanged = false;
}
if (mScroller.computeScrollOffset()) {
int scrollx = mScroller.getCurrX();
mNextX = scrollx;
}
if (mNextX <= 0) {
mNextX = 0;
mScroller.forceFinished(true);
}
if (mNextX >= mMaxX) {
mNextX = mMaxX;
mScroller.forceFinished(true);
}
int dx = mCurrentX - mNextX;
// removeNonVisibleItems(dx);
fillList(dx);
positionItems(dx);
mCurrentX = mNextX;
if (!mScroller.isFinished()) {
post(new Runnable() {
@Override
public void run() {
requestLayout();
}
});
}
}
private void fillList(final int dx) {
int edge = 0;
View child = getChildAt(getChildCount() - 1);
if (child != null) {
edge = child.getRight();
}
fillListRight(edge, dx);
edge = 0;
child = getChildAt(0);
if (child != null) {
edge = child.getLeft();
}
fillListLeft(edge, dx);
}
private void fillListRight(int rightEdge, final int dx) {
while (rightEdge + dx < getWidth()
&& mRightViewIndex < mAdapter.getCount()) {
View child = mAdapter.getView(mRightViewIndex,
(View) mRemovedViewQueue.poll(), this);
addAndMeasureChild(child, -1);
rightEdge += child.getMeasuredWidth();
if (mRightViewIndex == mAdapter.getCount() - 1) {
mMaxX = mCurrentX + rightEdge - getWidth();
}
if (mMaxX < 0) {
mMaxX = 0;
}
mRightViewIndex++;
}
}
private void fillListLeft(int leftEdge, final int dx) {
while (leftEdge + dx > 0 && mLeftViewIndex >= 0) {
View child = mAdapter.getView(mLeftViewIndex,
(View) mRemovedViewQueue.poll(), this);
addAndMeasureChild(child, 0);
leftEdge -= child.getMeasuredWidth();
mLeftViewIndex--;
mDisplayOffset -= child.getMeasuredWidth();
}
}
private void positionItems(final int dx) {
if (getChildCount() > 0) {
mDisplayOffset += dx;
int left = mDisplayOffset;
for (int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
int childWidth = child.getMeasuredWidth();
child.layout(left, 0, left + childWidth,
child.getMeasuredHeight());
left += childWidth;
}
}
}
public synchronized void scrollTo(int x) {
mScroller.startScroll(mNextX, 0, x - mNextX, 0);
requestLayout();
}
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
boolean handled = super.dispatchTouchEvent(ev);
handled |= mGesture.onTouchEvent(ev);
return handled;
}
protected boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
float velocityY) {
synchronized (HorizontalView.this) {
mScroller.fling(mNextX, 0, (int) -velocityX, 0, 0, mMaxX, 0, 0);
}
requestLayout();
return true;
}
protected boolean onDown(MotionEvent e) {
mScroller.forceFinished(true);
return true;
}
private OnGestureListener mOnGesture = new GestureDetector.SimpleOnGestureListener() {
public boolean onDown(MotionEvent e) {
return HorizontalView.this.onDown(e);
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
float velocityY) {
return HorizontalView.this.onFling(e1, e2, velocityX, velocityY);
}
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2,
float distanceX, float distanceY) {
synchronized (HorizontalView.this) {
mNextX += (int) distanceX;
}
requestLayout();
return true;
}
@Override
public boolean onSingleTapConfirmed(MotionEvent e) {
for (int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
if (isEventWithinView(e, child)) {
if (mOnItemClicked != null) {
mOnItemClicked.onItemClick(HorizontalView.this, child,
mLeftViewIndex + 1 + i,
mAdapter.getItemId(mLeftViewIndex + 1 + i));
}
if (mOnItemSelected != null) {
mOnItemSelected.onItemSelected(HorizontalView.this,
child, mLeftViewIndex + 1 + i,
mAdapter.getItemId(mLeftViewIndex + 1 + i));
}
break;
}
}
return true;
}
@Override
public void onLongPress(MotionEvent e) {
int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
View child = getChildAt(i);
if (isEventWithinView(e, child)) {
if (mOnItemLongClicked != null) {
mOnItemLongClicked.onItemLongClick(HorizontalView.this,
child, mLeftViewIndex + 1 + i,
mAdapter.getItemId(mLeftViewIndex + 1 + i));
}
break;
}
}
}
private boolean isEventWithinView(MotionEvent e, View child) {
Rect viewRect = new Rect();
int[] childPosition = new int[2];
child.getLocationOnScreen(childPosition);
int left = childPosition[0];
int right = left + child.getWidth();
int top = childPosition[1];
int bottom = top + child.getHeight();
viewRect.set(left, top, right, bottom);
return viewRect.contains((int) e.getRawX(), (int) e.getRawY());
}
};
}
HorizontalImageAdapter.java
package com.xxx.xxx;
import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.content.Context;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.ImageView.ScaleType;
public class HorizontalImageAdapter extends ArrayAdapter<RSSItem> {
//private Context context;
private List<RSSItem> objectsln = new ArrayList<RSSItem>();
int ResourceId;
private Activity activity;
public ImageManager imageManager1;
private static ViewHolder holder;
public HorizontalImageAdapter(Activity a, int textViewResourceId, List<RSSItem> objectsln) {
super(a, textViewResourceId, objectsln);
System.out.println("LISTVIEW Constructor Called");
activity = a;
this.objectsln = objectsln;
this.ResourceId = textViewResourceId;
imageManager1 = new ImageManager(activity.getApplicationContext());
}
@Override
public int getCount() {
return this.objectsln.size();
}
@Override
public RSSItem getItem(int position) {
return this.objectsln.get(position);
}
@Override
public long getItemId(int position) {
System.out.println("LISTVIEW POSITION Called: "+position);
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
holder = new ViewHolder();
LayoutInflater infleter = (LayoutInflater) this.getContext().getSystemService(Context.
LAYOUT_INFLATER_SERVICE);
convertView = infleter.inflate(ResourceId, parent, false);
holder = new ViewHolder();
holder.imageViewln = (ImageView) convertView.findViewById(R.id.imageViewhlist);
holder.textviewln=(TextView)convertView.findViewById(R.id.textViewhlist);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
RSSItem dataln = null ;
//get the item
if(objectsln.size() !=0){
dataln = getItem(position);
}else{
Log.i("test TAG", "Size zero found");
}
if (dataln != null) {
holder.textviewln.setText(dataln.title); // For taking the title from
// Web Services and set into text view
System.out.println("TITLE LATEST NEWS - "+position+": "+dataln.title);
holder.imageViewln.setScaleType(ScaleType.FIT_XY);
holder.imageViewln.setTag(dataln.imageurl);
imageManager1.displayImage(dataln.imageurl, activity,
holder.imageViewln);
}
return convertView;
}
private static class ViewHolder {
ImageView imageViewln;
TextView textviewln;
}
}