Android实现滑动选择控件实例代码

前言

最近做了个滑动选择的小控件，拿出来给大家分享一下，先上图

运行效果

实现步骤

这里分解为3个动作:Down、Move、Up来进行分析，博主文采不好，大家直接看流程图吧！！

代码分析

前置知识

1、这个地方使用的是RecyclerView的代码，使用RecyclerView只能使用LinearLayoutManager,ListView的运行效果稍微要比RecyclerView差一些

//这里使用dispatchTouchEvent，因为onTouchEvent容易被OnTouchListener截取
  @Override
  public boolean dispatchTouchEvent(MotionEvent ev) {
    LayoutManager manager = getLayoutManager();
    //获取第一个和最后一个显示的Item对应的相对Position
    if (manager instanceof LinearLayoutManager) {
      mFirstVisiblePosition = ((LinearLayoutManager) manager).findFirstVisibleItemPosition();
      mLastVisiblePosition = ((LinearLayoutManager) manager).findLastVisibleItemPosition();
    }
    switch (ev.getAction()) {
      case MotionEvent.ACTION_DOWN:
        //获取按下时的位置,x,y
        int startX = (int) ev.getX();
        int startY = (int) ev.getY();
        int preX = startX;
        mPreY = startY;
        mPreFirstVisiblePosition = mFirstVisiblePosition;
        mPrePosition = mStartPosition = pointToPosition(startX, startY);
        if (mStartPosition > -1) {
          //获取当前Item的View
          View child = getChildAt(mStartPosition);
          if (null != child) {
            //获取响应域，一般响应域里面就是一个CheckBox
            View tmpCheckBoxContainer = child.findViewWithTag("checkbox_layout");
            if (null != tmpCheckBoxContainer && tmpCheckBoxContainer.getVisibility() == VISIBLE) {
              mCheckBoxWidth = tmpCheckBoxContainer.getWidth();
              //获取响应域的范围，一定要用这种获取绝对位置的方式，不然会受到padding或者是margin的影响
              int[] location = new int[2];
              tmpCheckBoxContainer.getLocationOnScreen(location);
              mCheckBoxX = location[0];
              //判断按下的位置是否是在响应域内
              if (startX >= mCheckBoxX && startX <= (mCheckBoxX + mCheckBoxWidth)) {
                Log.d(LOG_TAG, "dispatchTouchEvent() DOWN mStartPosition: " + mStartPosition);
                //设置截取事件的标志位
                mIsNeedScrollCheck = true;
                //设置为第一次滑动，这是用作判断折返的
                mIsFirstMove = true;
                setStartCheckBoxState();
                //截获Checkbox的点击事件，防止两次选中
                return true;
              } else {
                mIsNeedScrollCheck = false;
              }
            } else {
              mIsNeedScrollCheck = false;
              Log.e(LOG_TAG, "dispatchTouchEvent() ", new Throwable("Cannot get CheckBoxContainer!"));
            }
          } else {
            Log.e(LOG_TAG, "dispatchTouchEvent() ", new Throwable("Cannot get item view!"));
          }
        }
        break;
      case MotionEvent.ACTION_MOVE:
        //获取当前位置
        int currentX = (int) ev.getX();
        int currentY = (int) ev.getY();
        //获取当前的item
        int currentPosition = pointToPosition(currentX, currentY);
        //判断是否允许滑动选中
        if (mIsNeedScrollCheck && -1 != mFirstVisiblePosition && -1 != mLastVisiblePosition && -1 != currentPosition) {
          //判断是否在下一个Item的像英语
          if ((currentPosition + mFirstVisiblePosition) != (mPrePosition + mPreFirstVisiblePosition) &&
              currentX >= mCheckBoxX && currentX <= (mCheckBoxX + mCheckBoxWidth)) {
            Log.i(LOG_TAG, "********************************** dispatchTouchEvent() ********************************");
            Log.d(LOG_TAG, "dispatchTouchEvent() MOVE mCurrentPosition: " + currentPosition);
            Log.d(LOG_TAG, "dispatchTouchEvent() MOVE mFirstVisiblePosition: " + mFirstVisiblePosition);
            Log.d(LOG_TAG, "dispatchTouchEvent() MOVE mPrePosition: " + mPrePosition);
            Log.d(LOG_TAG, "dispatchTouchEvent() MOVE mPreFirstVisiblePosition: " + mPreFirstVisiblePosition);
            Log.i(LOG_TAG, "********************************** dispatchTouchEvent() ********************************");
            //折返回来时要改变前一个的Checkbox的状态
            if (mIsFirstMove) {
              mIsFirstMove = false;
              if (currentY >= mPreY) {
                mUpOrDown = false;
              } else {
                mUpOrDown = true;
              }
            } else {
              if ((currentPosition + mFirstVisiblePosition) > (mPrePosition + mPreFirstVisiblePosition) && mUpOrDown) {
                changeCheckBoxState(mPrePosition);
                mUpOrDown = false;
              } else if ((currentPosition + mFirstVisiblePosition) < (mPrePosition + mPreFirstVisiblePosition) && !mUpOrDown) {
                changeCheckBoxState(mPrePosition);
                mUpOrDown = true;
              }
            }
            changeCheckBoxState(currentPosition);
          }
          //判断是否是在最后一个item上滑动，如果是则进行自动向下滑动，如果是在第一个上下滑动，则自动向上滑动
          //Log.d(LOG_TAG, "dispatchTouchEvent() MOVE: " + (mLastVisiblePosition - mCurrentPosition - mFirstVisiblePosition));
          if ((mLastVisiblePosition - mFirstVisiblePosition - currentPosition) < 1 && currentY > mPreY) {
            //自动向下滑
            Log.d(LOG_TAG, "dispatchTouchEvent() MOVE mCount: " + mCount);
            View child = getChildAt(currentPosition);
            if (null != child && 0 == mCount % 5) {
              scrollToPosition(mLastVisiblePosition + 1);
            }
            mCount++;
          } else if (currentPosition < 2 && currentY < mPreY) {
            //自动向上滑
            View child = getChildAt(currentPosition);
            Log.d(LOG_TAG, "dispatchTouchEvent() MOVE mCount: " + mCount);
            //mCount用于降低滑动的频率，频率太快容易滑动的看不清楚
            if (null != child && 0 == mCount % 5) {
              scrollToPosition(mFirstVisiblePosition - 1);
            }
            mCount++;
          }
          mPreY = currentY;
          mPrePosition = currentPosition;
          mPreFirstVisiblePosition = mFirstVisiblePosition;
          return true;
        }
        break;
      case MotionEvent.ACTION_UP:
        if (mIsNeedScrollCheck) {
          mCount = 0;
          return false;
        }
        break;
    }
    return super.dispatchTouchEvent(ev);
  }

其他的代码片段

//改变开始的CheckBox状态
  private void setStartCheckBoxState() {
    View child = getChildAt(mStartPosition);
    if (null != child) {
      ViewGroup checkBoxContainer = (ViewGroup) child.findViewWithTag("checkbox_layout");
      if (null != checkBoxContainer) {
        CheckBox checkBox = (CheckBox) checkBoxContainer.getChildAt(0);
        if (null != checkBox && checkBox.getVisibility() == VISIBLE) {
          checkBox.toggle();
        }
      }
    }
  }

//判断当前Item的Position，相对位置
  private int pointToPosition(int x, int y) {
    Rect frame = mTouchFrame;
    if (frame == null) {
      mTouchFrame = new Rect();
      frame = mTouchFrame;
    }
    final int count = getChildCount();
    for (int i = count - 1; i >= 0; i--) {
      final View child = getChildAt(i);
      if (child.getVisibility() == View.VISIBLE) {
        child.getHitRect(frame);
        if (frame.contains(x, y)) {
          return i;
        }
      }
    }
    return -1;
  }

//改变Position的选中状态
  public void changeCheckBoxState(int position) {
    if (position < 0 || position >= getChildCount()) {
      return;
    }
    View child = getChildAt(position);
    if (null != child) {
      ViewGroup checkBoxLayout = (ViewGroup) child.findViewWithTag("checkbox_layout");
      if (null != checkBoxLayout && checkBoxLayout.getVisibility() == VISIBLE) {
        CheckBox checkBox = (CheckBox) checkBoxLayout.getChildAt(0);
        if (null != checkBox) {
          Log.d(LOG_TAG, "changeCheckBoxState() selectCheckBox: " + position);
          //checkBox.perfORMClick();
          checkBox.toggle();
          //checkBox.setClickable(false);
          //checkBox.callOnClick();
        }
      }
    }
  }

项目源码：ScrollCheckBox_jb51.rar

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