问题
I have used lazy loading to download the images and thus populate in horizontal list view. But scrolling is not smooth, specially when scrolling from right to left end. These are my codes:
homepg.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>
HorizontalView.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;
}
}
来源：https://stackoverflow.com/questions/17119991/horizontal-list-view-scrolling-is-not-smooth-in-android