Android實現背景圖下拉回彈效果

增加設置不橫向拉伸時增加回彈效果

增加切換橫屏時可滑動效果

效果

實現

public class HeadZoomScrollView extends NestedScrollView {public HeadZoomScrollView(Context context) {super(context);}public HeadZoomScrollView(Context context, AttributeSet attrs) {super(context, attrs);}public HeadZoomScrollView(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);}//用于記錄下拉位置private float y = 0f;//zoomView原本的寬高private int zoomViewWidth = 0;private int zoomViewHeight = 0;//是否正在放大private boolean mScaling = false;//放大的view，默認為第一個子viewprivate View zoomView;public void setZoomView(View zoomView) {this.zoomView = zoomView;}//滑動放大系數，系數越大，滑動時放大程度越大private float mScaleRatio = 0.4f;public void setmScaleRatio(float mScaleRatio) {this.mScaleRatio = mScaleRatio;}//最大的放大倍數private float mScaleTimes = 2f;public void setmScaleTimes(int mScaleTimes) {this.mScaleTimes = mScaleTimes;}//回彈時間系數，系數越小，回彈越快private float mReplyRatio = 0.5f;public void setmReplyRatio(float mReplyRatio) {this.mReplyRatio = mReplyRatio;}//滾動觸發子view橫向放大的方法private float moveDistance = 300.0f;public void setMoveDistance(float moveDistance) {this.moveDistance = moveDistance;}//是否橫向拉伸，默認為trueprivate boolean isTransverse = true;public void setTransverse(boolean isTransverse) {this.isTransverse = isTransverse;}@Overrideprotected void onFinishInflate() {super.onFinishInflate();//不可過度滾動，否則上移后下拉會出現部分空白的情況setOverScrollMode(OVER_SCROLL_NEVER);//獲得默認第一個viewif (getChildAt(0) != null && getChildAt(0) instanceof ViewGroup && zoomView == null) {ViewGroup vg = (ViewGroup) getChildAt(0);if (vg.getChildCount() > 0) {zoomView = vg.getChildAt(0);}}}@Overridepublic boolean onTouchEvent(MotionEvent ev) {if (zoomViewWidth <= 0 || zoomViewHeight <= 0) {zoomViewWidth = zoomView.getMeasuredWidth();zoomViewHeight = zoomView.getMeasuredHeight();}switch (ev.getAction()) {case MotionEvent.ACTION_UP://手指離開后恢復圖片mScaling = false;replyImage();break;case MotionEvent.ACTION_MOVE:if (!mScaling) {if (getScrollY() == 0) {y = 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() - y) * mScaleRatio); // 滾動距離乘以一個系數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);return true; // 返回true表示已經完成觸摸事件，不再處理}return super.onTouchEvent(ev);}//拉伸效果public void setZoom(float zoom) {if (zoomViewWidth <= 0 || zoomViewHeight <= 0) {return;}ViewGroup.LayoutParams lp = zoomView.getLayoutParams();if (isTransverse) {if (zoom <= moveDistance) {lp.width = (int) (zoomViewWidth);} else {lp.width = (int) (zoomViewWidth + zoom);if (onZoomListener != null) {onZoomListener.onZoom(zoom);}}} else {lp.width = (int) (zoomViewWidth);}lp.height = (int) (zoomViewHeight * ((zoomViewWidth + zoom) / zoomViewWidth));((MarginLayoutParams) lp).setMargins(-(lp.width - zoomViewWidth) / 2, 0, 0, 0);zoomView.setLayoutParams(lp);}private OnZoomListener onZoomListener;public interface OnZoomListener {void onZoom(float zoom);}public void setOnZoomListener(OnZoomListener onZoomListener){this.onZoomListener = onZoomListener;}//回彈動畫private void replyImage() {float distance = 0f;if(isTransverse){distance = zoomView.getMeasuredWidth() - zoomViewWidth;}else{distance = zoomView.getMeasuredHeight() - zoomViewHeight;}ValueAnimator valueAnimator = ValueAnimator.ofFloat(distance, 0f).setDuration((long) (distance * mReplyRatio));valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {@Overridepublic void onAnimationUpdate(ValueAnimator animation) {setZoom((Float) animation.getAnimatedValue());}});valueAnimator.start();}} <com.lwj.test.common.view.HeadZoomScrollViewandroid:id="@+id/scroll_view"android:layout_width="match_parent"android:layout_height="match_parent"><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><ImageViewandroid:id="@+id/iv_show"android:layout_width="match_parent"android:layout_height="200dp"android:layout_weight="1"android:src="@drawable/ic_my_background"/><TextViewandroid:layout_width="match_parent"android:layout_height="60dp"android:text="數據1"/><TextViewandroid:layout_width="match_parent"android:layout_height="60dp"android:text="數據2"/><TextViewandroid:layout_width="match_parent"android:layout_height="60dp"android:text="數據3"/><TextViewandroid:layout_width="match_parent"android:layout_height="60dp"android:text="數據4"/><TextViewandroid:layout_width="match_parent"android:layout_height="60dp"android:text="數據5"/><TextViewandroid:layout_width="match_parent"android:layout_height="60dp"android:text="數據6"/></LinearLayout> </com.lwj.test.common.view.HeadZoomScrollView> setZoomView(View view); // 設置要放大的view，默認為第一個子view setmScaleRatio(float mScaleRatio); // 設置滑動放大系數，系數越大，滑動時，放大程度越大 setmScaleTimes(int mScaleTimes); // 設置最大的放大倍數 setmReplyRatio(float mReplyRatio); //回彈時間系數，系數越小，回彈越快 setMoveDistance(float moveDistance); // 設置放大時移動的距離 setTransverse(boolean isTransverse); // 設置是否進行橫向拉伸 setOnZoomListener(OnZoomListener onZoomListener);// 設置滑動距離監聽

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