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Horizontal List View in Android

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Horizontal ListView

Here is the exmaple of Horizontal List View .Horizonatal list view is the list to show items in horizontal form.these are the classes to implement horizontal list view:

HorizontalListView.java

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.AdapterView;
import android.widget.ListAdapter;
import android.widget.Scroller;

public class HorizontalListView extends AdapterView<ListAdapter> {

    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<View> mRemovedViewQueue = new LinkedList<View>();
    private OnItemSelectedListener mOnItemSelected;
    private OnItemClickListener mOnItemClicked;
    private OnItemLongClickListener mOnItemLongClicked;
    private boolean mDataChanged = false;
   

    public HorizontalListView(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(HorizontalListView.this){
                mDataChanged = true;
            }
            setEmptyView(getEmptyView());
            invalidate();
            requestLayout();
        }

        @Override
        public void onInvalidated() {
            reset();
            invalidate();
            requestLayout();
        }
       
    };

    @Override
    public ListAdapter getAdapter() {
        return mAdapter;
    }

    @Override
    public View getSelectedView() {
        //TODO: implement
        return null;
    }

    @Override
    public void setAdapter(ListAdapter adapter) {
        if(mAdapter != null) {
            mAdapter.unregisterDataSetObserver(mDataObserver);
        }
        mAdapter = adapter;
        mAdapter.registerDataSetObserver(mDataObserver);
        reset();
    }
   
    private synchronized void reset(){
        initView();
        removeAllViewsInLayout();
        requestLayout();
    }

    @Override
    public void setSelection(int position) {
        //TODO: implement
    }
   
    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, 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, mRemovedViewQueue.poll(), this);
            addAndMeasureChild(child, 0);
            leftEdge -= child.getMeasuredWidth();
            mLeftViewIndex--;
            mDisplayOffset -= child.getMeasuredWidth();
        }
    }
   
    private void removeNonVisibleItems(final int dx) {
        View child = getChildAt(0);
        while(child != null && child.getRight() + dx <= 0) {
            mDisplayOffset += child.getMeasuredWidth();
            mRemovedViewQueue.offer(child);
            removeViewInLayout(child);
            mLeftViewIndex++;
            child = getChildAt(0);
           
        }
       
        child = getChildAt(getChildCount()-1);
        while(child != null && child.getLeft() + dx >= getWidth()) {
            mRemovedViewQueue.offer(child);
            removeViewInLayout(child);
            mRightViewIndex--;
            child = getChildAt(getChildCount()-1);
        }
    }
   
    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 = mGesture.onTouchEvent(ev);
        return handled;
    }
   
    protected boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
                float velocityY) {
        synchronized(HorizontalListView.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() {

        @Override
        public boolean onDown(MotionEvent e) {
            return HorizontalListView.this.onDown(e);
        }

        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
                float velocityY) {
            return HorizontalListView.this.onFling(e1, e2, velocityX, velocityY);
        }

        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2,
                float distanceX, float distanceY) {
           
            getParent().requestDisallowInterceptTouchEvent(true);

            synchronized(HorizontalListView.this){
                mNextX += (int)distanceX;
            }
            requestLayout();
           
            return true;
        }

        @Override
        public boolean onSingleTapConfirmed(MotionEvent e) {
            Rect viewRect = new Rect();
            for(int i=0;i<getChildCount();i++){
                View child = getChildAt(i);
                int left = child.getLeft();
                int right = child.getRight();
                int top = child.getTop();
                int bottom = child.getBottom();
                viewRect.set(left, top, right, bottom);
                if(viewRect.contains((int)e.getX(), (int)e.getY())){
                    if(mOnItemClicked != null){
                        mOnItemClicked.onItemClick(HorizontalListView.this, child, mLeftViewIndex + 1 + i, mAdapter.getItemId( mLeftViewIndex + 1 + i ));
                    }
                    if(mOnItemSelected != null){
                        mOnItemSelected.onItemSelected(HorizontalListView.this, child, mLeftViewIndex + 1 + i, mAdapter.getItemId( mLeftViewIndex + 1 + i ));
                    }
                    break;
                }
               
            }
            return true;
        }
       
        @Override
        public void onLongPress(MotionEvent e) {
            Rect viewRect = new Rect();
            int childCount = getChildCount();
            for (int i = 0; i < childCount; i++) {
                View child = getChildAt(i);
                int left = child.getLeft();
                int right = child.getRight();
                int top = child.getTop();
                int bottom = child.getBottom();
                viewRect.set(left, top, right, bottom);
                if (viewRect.contains((int) e.getX(), (int) e.getY())) {
                    if (mOnItemLongClicked != null) {
                        mOnItemLongClicked.onItemLongClick(HorizontalListView.this, child, mLeftViewIndex + 1 + i, mAdapter.getItemId(mLeftViewIndex + 1 + i));
                    }
                    break;
                }

            }
        }

    };

   

}




HorizontalListViewActivity.java

import android.app.Activity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;



public class HorizontalListViewActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
       
        setContentView(R.layout.main);
       
        HorizontalListView listview = (HorizontalListView) findViewById(R.id.listview);
        listview.setAdapter(mAdapter);
       
    }
   
    private static String[] dataObjects = new String[]{ "Text #1",
        "Text #2",
        "Text #3" };
   
    private BaseAdapter mAdapter = new BaseAdapter() {

        @Override
        public int getCount() {
            return dataObjects.length;
        }

        @Override
        public Object getItem(int position) {
            return null;
        }

        @Override
        public long getItemId(int position) {
            return 0;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            View retval = LayoutInflater.from(parent.getContext()).inflate(R.layout.viewitem, null);
            TextView title = (TextView) retval.findViewById(R.id.title);
            title.setText(dataObjects[position]);
           
            return retval;
        }
       
    };

}


viewitem.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:background="#fff"
  >
 
  <ImageView
      android:id="@+id/image"
      android:layout_width="150dip"
      android:layout_height="150dip"
      android:scaleType="centerCrop"
      android:src="@drawable/ic_launcher"
      />
     
      <TextView
      android:id="@+id/title"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:textColor="#000"
      android:gravity="center_horizontal"
      />
 
</LinearLayout>


main.xml

<?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:background="#fff"
    android:orientation="vertical" >
   
     <!-- here you have to put packagename where HorizontalListView.java exist.otherwise it will give not found exception -->
<horizomtal.listview.com.HorizontalListView
        android:id="@+id/listview"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="#ddd" />

</LinearLayout>

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