1. 程式人生 > >Android 自定義ScrollView阻尼效果

Android 自定義ScrollView阻尼效果

廢話不多說,直接程式碼

package voc.cn.cnvoccoin.util;

import android.animation.ObjectAnimator;
import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.TranslateAnimation;
import android.widget.ScrollView;

public class MyScrollView extends ScrollView {
    //----頭部收縮屬性--------
    // 記錄首次按下位置
    private float mFirstPosition = 0;
    // 頭部圖片是否正在放大
    private Boolean mScaling = false;
    private View dropZoomView;//需要被放大的view
    private int dropZoomViewWidth;
    private int dropZoomViewHeight;
    //----頭部收縮屬性end--------
    //------尾部收縮屬性--------
    private View inner;// 子View
    private float y;// 點選時y座標
    private Rect normal = new Rect();// 矩形(這裡只是個形式,只是用於判斷是否需要動畫.)
    private boolean isCount = false;// 是否開始計算
    //最後的座標
    private float lastX = 0;
    private float lastY = 0;
    //當前座標
    private float currentX = 0;
    private float currentY = 0;
    //移動的座標量
    private float distanceX = 0;
    private float distanceY = 0;
    private boolean upDownSlide = false; //判斷上下滑動的flag
    //------尾部收縮屬性end--------
    public MyScrollView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    //初始化
    private void init() {
        setOverScrollMode(OVER_SCROLL_NEVER);
        if (getChildAt(0) != null) {
            inner = getChildAt(0);//這個是底部收縮的view
            //頭部收縮的
            ViewGroup vg = (ViewGroup) getChildAt(0);
            if (vg.getChildAt(0) != null) {
                dropZoomView = vg.getChildAt(0);
            }
        }
    }
    /***
     * 生成檢視工作完成.該函式在生成檢視的最後呼叫,在所有子檢視新增完之後. 即使子類覆蓋了 onFinishInflate
     * 方法,也應該呼叫父類的方法,使該方法得以執行.
     */
    @Override
    protected void onFinishInflate() {
        //初始化
        init();
        super.onFinishInflate();
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        //這裡只是計算尾部座標
        currentX = ev.getX();
        currentY = ev.getY();
        switch (ev.getAction()) {
            case MotionEvent.ACTION_MOVE:
                distanceX = currentX - lastX;
                distanceY = currentY - lastY;
                if (Math.abs(distanceX) < Math.abs(distanceY) && Math.abs(distanceY) > 12) {
                    upDownSlide = true;
                }
                break;
        }
        lastX = currentX;
        lastY = currentY;
        if (upDownSlide && inner != null) commOnTouchEvent(ev);
        return super.dispatchTouchEvent(ev);
    }
    /***
     * 觸控事件
     *
     * @param ev
     */
    public void commOnTouchEvent(MotionEvent ev) {
        //頭部縮放計算
        if (dropZoomViewWidth <= 0 || dropZoomViewHeight <= 0) {
            dropZoomViewWidth = dropZoomView.getMeasuredWidth();
            dropZoomViewHeight = dropZoomView.getMeasuredHeight();
        }

        switch (ev.getAction()) {
            case MotionEvent.ACTION_UP:
                //手指離開後頭部恢復圖片
                mScaling = false;
                replyImage();

                // 手指鬆開尾部恢復
                if (isNeedAnimation()) {
                    animation();
                    isCount = false;
                }
                clear0();
                break;
            //這裡頭尾分開處理,互不干擾
            case MotionEvent.ACTION_MOVE:
                //尾部處理
                final float preY = y;// 按下時的y座標
                float nowY = ev.getY();// 時時y座標
                int deltaY = (int) (preY - nowY);// 滑動距離
                if (!isCount) {
                    deltaY = 0; // 在這裡要歸0.
                }
                y = nowY;
//                 當滾動到最上或者最下時就不會再滾動,這時移動佈局
                if (isNeedMove()) {
                    // 初始化頭部矩形
                    if (normal.isEmpty()) {
                        // 儲存正常的佈局位置
                        normal.set(inner.getLeft(), inner.getTop(),
                                inner.getRight(), inner.getBottom());
                    }
                    // 移動佈局
                    inner.layout(inner.getLeft(), inner.getTop() - deltaY / 2,
                            inner.getRight(), inner.getBottom() - deltaY / 2);
                }
                isCount = true;
                //尾部處理end
                //頭部處理
                if (!mScaling) {
                    if (getScrollY() == 0) {
                        mFirstPosition = ev.getY();// 滾動到頂部時記錄位置,否則正常返回
                    } else {
                        break;
                    }
                }
                int distance = (int) ((ev.getY() - mFirstPosition) * 0.5); // 滾動距離乘以一個係數
                if (distance < 0) { // 當前位置比記錄位置要小,正常返回
                    break;
                }
                // 處理放大
                mScaling = true;
                setZoom(distance);
                //頭部處理end
                break;
        }
    }

    /***
     * 回縮動畫,尾部往下縮動畫
     */
    public void animation() {
        // 開啟移動動畫
        TranslateAnimation ta = new TranslateAnimation(0, 0, inner.getTop(),
                normal.top);
        ta.setDuration(300);
        inner.startAnimation(ta);
        // 設定回到正常的佈局位置
        inner.layout(normal.left, normal.top, normal.right, normal.bottom);
        normal.setEmpty();
    }

    // 是否需要開啟動畫
    public boolean isNeedAnimation() {
        return !normal.isEmpty();
    }
    // 回彈動畫,header往上縮動畫 (使用了屬性動畫)
    public void replyImage() {
        //final float distance = dropZoomView.getMeasuredWidth() - dropZoomViewWidth;
        final float distance = dropZoomView.getMeasuredHeight() - dropZoomViewHeight;
        // 設定動畫
        ValueAnimator anim = ObjectAnimator.ofFloat(distance, 0F).setDuration((long) (distance * 0.5f));

        anim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                setZoom((Float) animation.getAnimatedValue());
            }
        });
        anim.start();
    }

    //頭部縮放
    public void setZoom(float zoom) {
        if (dropZoomViewHeight <= 0 || dropZoomViewWidth <= 0) {
            return;
        }
        ViewGroup.LayoutParams lp = dropZoomView.getLayoutParams();
        lp.width = (int) (dropZoomViewWidth + zoom);
        lp.height = (int) (dropZoomViewHeight * ((dropZoomViewWidth + zoom) / dropZoomViewWidth));
        ((MarginLayoutParams) lp).setMargins(-(lp.width - dropZoomViewWidth) / 2, 0, 0, 0);
        dropZoomView.setLayoutParams(lp);
    }

    /***
     * 是否需要移動佈局 inner.getMeasuredHeight():獲取的是控制元件的總高度
     *
     * getHeight():獲取的是螢幕的高度
     *
     * @return
     */
    public boolean isNeedMove() {
        int offset = inner.getMeasuredHeight() - getHeight();
        int scrollY = getScrollY();
        // 0是頂部,後面那個是底部
        if (scrollY == 0 || scrollY == offset) {
            return true;
        }
        return false;
    }

    //清理尾部屬性值
    private void clear0() {
        lastX = 0;
        lastY = 0;
        distanceX = 0;
        distanceY = 0;
        upDownSlide = false;
    }
}