擴展ViewFlow避免和ViewPager滑動沖突，同時支持無限循環，並完美和CircleFlowIndicator結合

本文轉載自查看原文 2014-09-29 03:07 6243 viewflow/ Android

首先，為了避免滑動沖突，我們要繼承ViewFlow，重寫onInterceptTouchEvent

 1 public class MyViewFlow extends ViewFlow {
 2     private ViewPager mPager;
 3 
 4     public MyViewFlow(Context context, AttributeSet attrs) {
 5         super(context, attrs);
 6     }
 7 
 8 
 9     public void setViewPager(ViewPager viewPager) {
10         mPager = viewPager;
11     }
12 
13     @Override
14     public boolean onInterceptTouchEvent(MotionEvent ev) {
15         if (mPager != null)
16             switch (ev.getAction()) {
17                 case MotionEvent.ACTION_DOWN:
18                     mPager.requestDisallowInterceptTouchEvent(true);
19                     break;
20                 case MotionEvent.ACTION_UP:
21                     mPager.requestDisallowInterceptTouchEvent(false);
22                     break;
23                 case MotionEvent.ACTION_CANCEL:
24                     mPager.requestDisallowInterceptTouchEvent(false);
25                     break;
26                 case MotionEvent.ACTION_MOVE:
27                     mPager.requestDisallowInterceptTouchEvent(true);
28                     break;
29             }
30         return super.onInterceptTouchEvent(ev);
31     }
32 }

調用setViewPager指定viewPager后，滑動便不再沖突

接下來，我們實現無限循環滾動

 1 public class AdapterBanner extends BaseAdapter {
 2 
 3     private LayoutInflater mInflater;
 4     private static final int[] ids = { R.drawable.banner, R.drawable.banner, R.drawable.banner, R.drawable.banner};
 5 
 6     public AdapterBanner(Context context) {
 7         mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
 8     }
 9 
10     @Override
11     public int getCount() {
12         //return ids.length;
13         return Integer.MAX_VALUE;//返回很大的值使得getView中的position不斷增大來實現循環
14     }
15 
16     @Override
17     public Object getItem(int position) {
18         return position;
19     }
20 
21     @Override
22     public long getItemId(int position) {
23         return position;
24     }
25 
26     @Override
27     public View getView(int position, View convertView, ViewGroup parent) {
28         if (convertView == null) {
29             convertView = mInflater.inflate(R.layout.item_fr_acmain_nearby_banner, null);
30         }
31         convertView.findViewById(R.id.imgView).setBackgroundResource(ids[position%ids.length]);
32         return convertView;
33     }
34 
35 }

關鍵代碼在第13行和31行的紅色部分。不過這樣實現之后，和CircleFlowIndicator結合使用，會發現程序ANR（無響應），原因是CircleFlowIndicator會調用ViewFlow.getViewCount()來繪制圓點，顯然這個數是Integer.MAX_VALUE,圓點數太多了導致ANR，我們需要繼續擴展MyViewFlow的getViewCount()。如下。

1     private int mCount;
2     public void setCount(int count){
3         mCount=count;
4     }
5     @Override
6     public int getViewsCount() {
7         return mCount;
8     }

需要調用MyViewFlow.setCount(int count)指定真實的數目，這樣做了之后，發現程序不會ANR了。CircleFlowIndicator繪制的圓點數目也正常。但是會發現，無論怎么滑動，圓點狀態都不變化，分析ViewFlow的源碼，發現要重寫一下onScrollChanged，我們繼續擴展MyViewFlow,代碼如下。

 1     private int mLastIndex;
 2     @Override
 3     public void setAdapter(Adapter adapter, int initialPosition){
 4         super.setAdapter(adapter,initialPosition);
 5         mLastIndex = initialPosition;
 6     }
 7 
 8     @Override
 9     protected void onScrollChanged(int h, int v, int oldh, int oldv) {
10         //super.onScrollChanged(h, v, oldh, oldv);
11         if (mIndicator != null) {
12             /*
13              * The actual horizontal scroll origin does typically not match the
14              * perceived one. Therefore, we need to calculate the perceived
15              * horizontal scroll origin here, since we use a view buffer.
16              */
17             int hPerceived = h + (mCurrentAdapterIndex%mCount - mCurrentBufferIndex)
18                     * getChildWidth();
19 
20             if(mLastIndex%mCount==mCount-1 && mCurrentAdapterIndex>mLastIndex) {
21                 oldh=0;
22                 hPerceived = 0;
23             }
24             if(mLastIndex%mCount==0&&mCurrentAdapterIndex<mLastIndex)
25                 hPerceived=h+(mCount-1-mCurrentBufferIndex)*getChildWidth();
26 
27             LogUtil.e(Config.MYTAG,"mCurrentAdapterIndex="+mCurrentAdapterIndex);
28             LogUtil.e(Config.MYTAG,"mLastIndex="+mLastIndex);
29             LogUtil.e(Config.MYTAG, "hPerceived=" + hPerceived);
30 
31             mIndicator.onScrolled(hPerceived, v, oldh, oldv);
32 
33             mLastIndex=mCurrentAdapterIndex;
34         }
35     }

當然，有幾個變量mIndicator,mCurrentAdapterIndex，mCurrentBufferIndex是沿用父類ViewFlow的，如果找不到，需要將父類ViewFlow中這些變量改為public即可（雖然從oop角度，這種做法很臟，但很省事，大半夜碼文字很累，我很懶）。

至此，大功告成！

整體MyViewFlow代碼如下：

package common.control.viewflow;

import android.content.Context;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.widget.Adapter;

import com.xxx.android.main.Config;

import common.util.LogUtil;


public class MyViewFlow extends ViewFlow {
    private ViewPager mPager;

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


    public void setViewPager(ViewPager viewPager) {
        mPager = viewPager;
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        if (mPager != null)
            switch (ev.getAction()) {
                case MotionEvent.ACTION_DOWN:
                    mPager.requestDisallowInterceptTouchEvent(true);
                    break;
                case MotionEvent.ACTION_UP:
                    mPager.requestDisallowInterceptTouchEvent(false);
                    break;
                case MotionEvent.ACTION_CANCEL:
                    mPager.requestDisallowInterceptTouchEvent(false);
                    break;
                case MotionEvent.ACTION_MOVE:
                    mPager.requestDisallowInterceptTouchEvent(true);
                    break;
            }
        return super.onInterceptTouchEvent(ev);
    }
    private int mCount;
    public void setCount(int count){
        mCount=count;
    }
    @Override
    public int getViewsCount() {
        return mCount;
    }
    private int mLastIndex;
    @Override
    public void setAdapter(Adapter adapter, int initialPosition){
        super.setAdapter(adapter,initialPosition);
        mLastIndex = initialPosition;
    }

    @Override
    protected void onScrollChanged(int h, int v, int oldh, int oldv) {
        //super.onScrollChanged(h, v, oldh, oldv);
        if (mIndicator != null) {
            /*
             * The actual horizontal scroll origin does typically not match the
             * perceived one. Therefore, we need to calculate the perceived
             * horizontal scroll origin here, since we use a view buffer.
             */
            int hPerceived = h + (mCurrentAdapterIndex%mCount - mCurrentBufferIndex)
                    * getChildWidth();

            if(mLastIndex%mCount==mCount-1 && mCurrentAdapterIndex>mLastIndex) {
                oldh=0;
                hPerceived = 0;
            }
            if(mLastIndex%mCount==0&&mCurrentAdapterIndex<mLastIndex)
                hPerceived=h+(mCount-1-mCurrentBufferIndex)*getChildWidth();

            LogUtil.e(Config.MYTAG,"mCurrentAdapterIndex="+mCurrentAdapterIndex);
            LogUtil.e(Config.MYTAG,"mLastIndex="+mLastIndex);
            LogUtil.e(Config.MYTAG, "hPerceived=" + hPerceived);

            mIndicator.onScrolled(hPerceived, v, oldh, oldv);

            mLastIndex=mCurrentAdapterIndex;
        }
    }
}

自動播放就不用講了，網上很多。同學們如果有收獲，記得回贊。

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