自己动手（二）──PullToRefresh之上拉翻页（3）

来源：互联网发布：内锥形螺纹编程实例编辑：程序博客网时间：2024/06/16 11:07

前言

其实，上拉作为一个手势可以和很多动作关联，不仅仅局限于翻页。我的实现里面很多东西写的比较死，比如其实bottom view其实可以由使用者创建，bottom view在上拉过程中状态的改变也可以定制，通过addView加入到PullToRefresh容器中，这样可以提供更多灵活性。即，可以定义一个AbsBottomView的虚基类，它会有一些诸如onFinish，onRelease， onPull之类的函数，供PullToRefresh容器调用。

改进

处理一个手势分两半，一半container处理、一半content处理的情况。即，处理权从content变到container，手动给content发个cancel event，处理权从container变到content，手动给conten发个down event。
让容器继承自FrameLayout
使得content view可以是任意类型的view，增强通用性
用Scroller工具类替代自定义Animation来实现平滑移动
给变量、函数起个好名字

完整demo

github任意门

相关源码

public class PTRFrameLayout extends FrameLayout {    private final static float SCROLL_RATIO = 0.35f;    private static final long ROTATE_ANIM_DURATION = 180;    enum STATE {GUIDE_USER_PULL, GUIDE_USER_RELEASE}    private STATE footerViewState = STATE.GUIDE_USER_PULL;    private View contentView;    private View footerView;    private float lastY = -1;    private int footerViewHeight;    private TextView footerTextView;    private Animation rotateUpAnim;    private Animation rotateDownAnim;    private ImageView arrowImageView;    private Scroller scroller;    public PTRFrameLayout(Context context) {        super(context);        init();    }    public PTRFrameLayout(Context context, AttributeSet attrs) {        super(context, attrs);        init();    }    public PTRFrameLayout(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        init();    }    private void init() {        scroller = new Scroller(getContext(), new DecelerateInterpolator(1.6F));        rotateUpAnim = new RotateAnimation(0.0f, -180.0f,                Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF,                0.5f);        rotateUpAnim.setDuration(ROTATE_ANIM_DURATION);        rotateUpAnim.setFillAfter(true);        rotateDownAnim = new RotateAnimation(-180.0f, 0.0f,                Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF,                0.5f);        rotateDownAnim.setDuration(ROTATE_ANIM_DURATION);        rotateDownAnim.setFillAfter(true);    }    @Override    protected void onFinishInflate() {        super.onFinishInflate();        contentView = getChildAt(0);        footerView = getChildAt(1);        arrowImageView = (ImageView) findViewById(R.id.iv_ptr_arrow);        footerTextView = (TextView) findViewById(R.id.tv_ptr_operation_hint);    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        super.onMeasure(widthMeasureSpec, heightMeasureSpec);        footerViewHeight = footerView.getMeasuredHeight();    }    @Override    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {        contentView.layout(left, top, right, bottom);        footerView.layout(left, bottom, right, bottom + footerView.getMeasuredHeight());    }    /**     * should get touch event from here, otherwise you can not scroll out the footerView closely after scroll the scrollview     *     * @param event     * @return     */    @Override    public boolean dispatchTouchEvent(MotionEvent event) {        if (lastY == -1) {            lastY = event.getY();        }        float dy = event.getY() - lastY;        lastY = event.getY();        if (getScrollY() != 0 || (dy < 0 && !contentCanScrollUp())) {            //content scroll end, ptr container scroll begin,            //send a cancel event to content view, for content view's sake            if (getScrollY() == 0) {                MotionEvent cancelEvent = MotionEvent.obtain(event);                cancelEvent.setAction(MotionEvent.ACTION_CANCEL | (event.getActionIndex() << MotionEvent.ACTION_POINTER_INDEX_SHIFT));                super.dispatchTouchEvent(cancelEvent);            }            switch (event.getAction()) {                case MotionEvent.ACTION_DOWN:                    break;                case MotionEvent.ACTION_MOVE:                    //make sure getScrollY() >= 0, aka never let top show blank area                    int calibratedScrollY = (int) (-dy * SCROLL_RATIO);                    if ((getScrollY() - dy * SCROLL_RATIO) < 0) {                        calibratedScrollY = -getScrollY();                    }                    scrollBy(0, calibratedScrollY);                    break;                case MotionEvent.ACTION_UP:                case MotionEvent.ACTION_CANCEL:                    if (getScrollY() >= footerViewHeight) {                        if (PTRListener != null) {                            PTRListener.onTrigger();                        }                    }                    release();                    break;            }            updateFooterViewState();            //ptr container scroll end, content  scroll begin,            //send a down event to content view, so it can recognize this second part of the gesture            if (getScrollY() == 0) {                MotionEvent downEvent = MotionEvent.obtain(event);                downEvent.setAction(MotionEvent.ACTION_DOWN | event.getActionIndex() << MotionEvent.ACTION_POINTER_INDEX_SHIFT);                downEvent.setLocation(event.getX(), event.getY());                super.dispatchTouchEvent(downEvent);            }        }        return super.dispatchTouchEvent(event);    }    private void updateFooterViewState() {        if (getScrollY() >= footerViewHeight && footerViewState != STATE.GUIDE_USER_RELEASE) {            footerTextView.setText("let it go ~ baby");            arrowImageView.startAnimation(rotateDownAnim);            footerViewState = STATE.GUIDE_USER_RELEASE;        } else if (getScrollY() < footerViewHeight && footerViewState != STATE.GUIDE_USER_PULL) {            footerTextView.setText("pull ~ baby");            arrowImageView.startAnimation(rotateUpAnim);            footerViewState = STATE.GUIDE_USER_PULL;        }    }    private void release() {        scroller.startScroll(0, getScrollY(), 0, -getScrollY());        invalidate();//this will make computeScroll() get called    }    @Override    public void computeScroll() {        if (scroller.computeScrollOffset()){            scrollTo(0, scroller.getCurrY());        }    }    private boolean contentCanScrollUp() {        if (contentView instanceof AdapterView<?>) {            AdapterView<?> adapterView = (AdapterView<?>) contentView;            if (adapterView.getLastVisiblePosition() == adapterView.getCount() - 1                    && adapterView.getChildAt(adapterView.getChildCount() - 1).getBottom() <= adapterView.getHeight()) {                Log.e("", "adapterView content can not scroll up anymore");                return false;            } else {                return true;            }        } else {            if (contentView.getScrollY() >= contentView.getMeasuredHeight() - contentView.getHeight()) {                return false;            } else {                return true;            }        }    }    private PTRListener PTRListener;    public void setPTRListener(PTRListener PTRListener) {        this.PTRListener = PTRListener;    }    public static interface PTRListener {        public void onTrigger();    }}

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