Gallery自动循环滚动，手动滚动的平滑切换及存在问题

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来自：http://blog.csdn.net/lenghun00/article/details/7635374

 

 

@Gallery配合dot使用时，如果放在RelativeLayout中，则手动滑动有反弹现象，其他layout没问题，现在还没弄清原因。
首先继承Gallery重写OnFling函数，去除gallery的滚动惯性

public class MyGallery extends Gallery {

     public MyGallery(Context context, AttributeSet attrs) {
         super(context, attrs);
         // TODO Auto-generated constructor stub
    }

     private boolean isScrollingLeft(MotionEvent e1, MotionEvent e2) {

         return e2.getX() > e1.getX();

    }

     @Override
     public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
             float velocityY) {
         int keyCode;

         if (isScrollingLeft(e1, e2)) {

            keyCode = KeyEvent.KEYCODE_DPAD_LEFT;

         } else {

            keyCode = KeyEvent.KEYCODE_DPAD_RIGHT;

        }

         onKeyDown(keyCode, null);

         return true;
    }

}

public class MyGallery extends Gallery {

	public MyGallery(Context context, AttributeSet attrs) {
		super(context, attrs);
		// TODO Auto-generated constructor stub
	}

	private boolean isScrollingLeft(MotionEvent e1, MotionEvent e2) {

		return e2.getX() > e1.getX();

	}
	
	@Override
	public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
			float velocityY) {
		int keyCode;

		if (isScrollingLeft(e1, e2)) {

			keyCode = KeyEvent.KEYCODE_DPAD_LEFT;

		} else {

			keyCode = KeyEvent.KEYCODE_DPAD_RIGHT;

		}

		onKeyDown(keyCode, null);

		return true;
	}

}

 

@注OnFling直接返回false也能实现类似效果，但那样需要滑动很大距离，图片才会切换，用户体验不好

第二步，构造adapter

要想平滑的实现循环滚动，可以让getCount返回一个很大的值，这样gallery就认为是有多个item,item之间的切换动画是平滑的

public class GalleryAdapter extends BaseAdapter {

    private LayoutInflater mInflater;
    private Context mContext;
    private int width;
    private int count;
    private int[] mImageIds;

    public GalleryAdapter(Context context, int[] ids) {
         mContext = context;
         mImageIds = ids;
         mInflater = LayoutInflater.from(mContext);
         DisplayMetrics dm = mContext.getApplicationContext().getResources()
                .getDisplayMetrics();
         width = dm.widthPixels;
         count = mImageIds.length;
    }

    @Override
    public int getCount() {
        return Integer.MAX_VALUE;//用于循环滚动
    }

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

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
         position = position % count;
         if (convertView == null) {
             convertView = mInflater.inflate(R.layout.gallery_item, null);
        }
         ImageView v = (ImageView) convertView.findViewById(R.id.img);
        v.setLayoutParams(new Gallery.LayoutParams(width, 200));
        v.setScaleType(ImageView.ScaleType.FIT_XY);
        v.setBackgroundResource(mImageIds[position]);
        return v;
    }

}

public class GalleryAdapter extends BaseAdapter {

	private LayoutInflater mInflater;
	private Context mContext;
	private int width;
	private int count;
	private int[] mImageIds;

	public GalleryAdapter(Context context, int[] ids) {
		mContext = context;
		mImageIds = ids;
		mInflater = LayoutInflater.from(mContext);
		DisplayMetrics dm = mContext.getApplicationContext().getResources()
				.getDisplayMetrics();
		width = dm.widthPixels;
		count = mImageIds.length;
	}

	@Override
	public int getCount() {
		return Integer.MAX_VALUE;//用于循环滚动
	}

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

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

	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
		position = position % count;
		if (convertView == null) {
			convertView = mInflater.inflate(R.layout.gallery_item, null);
		}
		ImageView v = (ImageView) convertView.findViewById(R.id.img);
		v.setLayoutParams(new Gallery.LayoutParams(width, 200));
		v.setScaleType(ImageView.ScaleType.FIT_XY);
		v.setBackgroundResource(mImageIds[position]);
		return v;
	}

}

 

第三，实现自动滚动

由于我们还要手动滚动，所以自动滚动用单独一个进程来实现

private void startAutoScroll() {
        new Thread() {
            @Override
            public void run() {
                 int count = 0;
                while (mAutoScroll) {
                     count = 0;
                     while (count < 30) {
                        count++;
                        try {
                            Thread.sleep(100);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        if (mOnTouch) {// 用戶手动滑动时，停止自动滚动
                             count = 0;
                        }
                    }
                    mPosition++;
                     Message msg = mHandler.obtainMessage(SCROLL, mPosition, 0);
                    mHandler.sendMessage(msg);
                }
            }

        }.start();
    }

     private Handler mHandler = new Handler() {

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
            case SCROLL:
                mGallery.setSelection(msg.arg1);
                break;
            }
        }

    };

private void startAutoScroll() {
		new Thread() {
			@Override
			public void run() {
				int count = 0;
				while (mAutoScroll) {
					count = 0;
					while (count < 30) {
						count++;
						try {
							Thread.sleep(100);
						} catch (InterruptedException e) {
							e.printStackTrace();
						}
						if (mOnTouch) {// 用戶手动滑动时，停止自动滚动
							count = 0;
						}
					}
					mPosition++;
					Message msg = mHandler.obtainMessage(SCROLL, mPosition, 0);
					mHandler.sendMessage(msg);
				}
			}

		}.start();
	}

	private Handler mHandler = new Handler() {

		@Override
		public void handleMessage(Message msg) {
			switch (msg.what) {
			case SCROLL:
				mGallery.setSelection(msg.arg1);
				break;
			}
		}

	};

 

第四实现手动滚动

手动滚动时，要停止自动滚动，监听gallery的onTouch事件，DOWN时mOnTouch置为true,UP时mOnTouch置为false即可

mGallery.setOnTouchListener(new OnTouchListener() {

             @Override
             public boolean onTouch(View v, MotionEvent event) {
                 int action = event.getAction();
                 if (action == MotionEvent.ACTION_DOWN) {
                     mOnTouch = true;
                 } else if (action == MotionEvent.ACTION_UP) {
                     mOnTouch = false;
                }
                 return false;
            }

        });

mGallery.setOnTouchListener(new OnTouchListener() {

			@Override
			public boolean onTouch(View v, MotionEvent event) {
				int action = event.getAction();
				if (action == MotionEvent.ACTION_DOWN) {
					mOnTouch = true;
				} else if (action == MotionEvent.ACTION_UP) {
					mOnTouch = false;
				}
				return false;
			}

		});

到现在我们已经可以自动滚动，手动滚动时自动滚动也会停止。

我们也许还需要加上dot提示图片滚动的位置

LinearLayout layout = (LinearLayout) findViewById(R.id.dot);
         if (mDots == null) {
             mDots = new ImageView[ids.length];
             for (int i = 0; i < ids.length; i++) {
                 if (mDots[i] == null)
                     mDots[i] = new ImageView(this);

                mDots[i].setBackgroundResource(R.drawable.banner_tab_unselected);
                 layout.addView(mDots[i], new LinearLayout.LayoutParams(mWidth
                         / ids.length + 1, LayoutParams.WRAP_CONTENT));
            }
             mDots[0].setBackgroundResource(R.drawable.banner_tab_selected);
        }

LinearLayout layout = (LinearLayout) findViewById(R.id.dot);
		if (mDots == null) {
			mDots = new ImageView[ids.length];
			for (int i = 0; i < ids.length; i++) {
				if (mDots[i] == null)
					mDots[i] = new ImageView(this);

				mDots[i].setBackgroundResource(R.drawable.banner_tab_unselected);
				layout.addView(mDots[i], new LinearLayout.LayoutParams(mWidth
						/ ids.length + 1, LayoutParams.WRAP_CONTENT));
			}
			mDots[0].setBackgroundResource(R.drawable.banner_tab_selected);
		}

 

mGallery.setOnItemSelectedListener(new OnItemSelectedListener() {

             @Override
             public void onItemSelected(AdapterView arg0, View view,
                     int position, long arg3) {
                mDotPosition = position % ids.length;
                mDots[mDotPosition]
                        .setBackgroundResource(R.drawable.banner_tab_selected);
                 if (mDotPosition != mPreDotPosition)
                    mDots[mPreDotPosition]
                            .setBackgroundResource(R.drawable.banner_tab_unselected);
                mPreDotPosition = mDotPosition;
            }

             @Override
             public void onNothingSelected(AdapterView arg0) {

            }

        });