Android PullToZoomListView实现放大回弹效果

将相本无种，男儿当自强。这篇文章主要讲述Android PullToZoomListView实现放大回弹效果相关的知识，希望能为你提供帮助。
版本号：1.0 日期：2014.8.4版权：? 2014 kince 转载注明出处
之前看过一篇文章，链接是：能够下拉缩放HeaderView的ListView:PullToZoomInListView。
说的就是PullToZoomListView。只是这篇文章有个地方须要勘误，就是PullToZoomListView这个控件尽管是github上一个开源项目。只是最美应用并非使用这个开源项目，而是这个开源项目反编译了最美应用的代码。
可是，它这个代码是有问题的，当手指在屏幕上滑动的时候会引发onItemClick事件。
看了一下它的代码。发现是由于在onTouchEvent()方法中的MotionEvent.ACTION_MOVE中return true了，这样就会消费这个事件。所以导致了onItemClick事件。
之后我也反编译了一下最美应用，看了一下这个控件的实现，发现还有其它问题，比方少了一些变量，没有重写onInterceptTouchEvent()方法等。因此我又自己动手把这个控件丰富了一下。使其能够最大限度的接近原始代码。并且可正常使用。改动后代码例如以下：

package com.kince.android.pulltozoomlistview; import android.app.Activity; import android.content.Context; import android.os.SystemClock; import android.util.AttributeSet; import android.util.DisplayMetrics; import android.util.Log; import android.view.MotionEvent; import android.view.ViewGroup; import android.view.animation.Interpolator; import android.widget.AbsListView; import android.widget.FrameLayout; import android.widget.ImageView; import android.widget.ListView; public class PullToZoomListView extends ListView implements AbsListView.OnScrollListener { private static final int INVALID_VALUE = https://www.songbingjia.com/android/-1; private static final String TAG ="PullToZoomListView"; private static final Interpolator sInterpolator = new Interpolator() { public float getInterpolation(float paramAnonymousFloat) { float f = paramAnonymousFloat - 1.0F; return 1.0F + f * (f * (f * (f * f))); } }; int mActivePointerId = -1; private FrameLayout mHeaderContainer; private int mHeaderHeight; private ImageView mHeaderImage; float mLastMotionY = -1.0F; float mLastScale = -1.0F; float mMaxScale = -1.0F; private AbsListView.OnScrollListener mOnScrollListener; private ScalingRunnalable mScalingRunnalable; private int mScreenHeight; private ImageView mShadow; private boolean mScrollable = true; private boolean mShowHeaderImage = true; private boolean mZoomable = true; public PullToZoomListView(Context paramContext) { super(paramContext); init(paramContext); } public PullToZoomListView(Context paramContext, AttributeSet paramAttributeSet) { super(paramContext, paramAttributeSet); init(paramContext); } public PullToZoomListView(Context paramContext, AttributeSet paramAttributeSet, int paramInt) { super(paramContext, paramAttributeSet, paramInt); init(paramContext); } private void endScraling() { if (this.mHeaderContainer.getBottom() > = this.mHeaderHeight) Log.d("mmm", "endScraling"); this.mScalingRunnalable.startAnimation(200L); } private void init(Context paramContext) { DisplayMetrics localDisplayMetrics = new DisplayMetrics(); ((Activity) paramContext).getWindowManager().getDefaultDisplay() .getMetrics(localDisplayMetrics); this.mScreenHeight = localDisplayMetrics.heightPixels; this.mHeaderContainer = new FrameLayout(paramContext); this.mHeaderImage = new ImageView(paramContext); int i = localDisplayMetrics.widthPixels; setHeaderViewSize(i, (int) (9.0F * (i / 16.0F))); this.mShadow = new ImageView(paramContext); FrameLayout.LayoutParams localLayoutParams = new FrameLayout.LayoutParams( -1, -2); localLayoutParams.gravity = 80; this.mShadow.setLayoutParams(localLayoutParams); this.mHeaderContainer.addView(this.mHeaderImage); this.mHeaderContainer.addView(this.mShadow); addHeaderView(this.mHeaderContainer); this.mScalingRunnalable = new ScalingRunnalable(); super.setOnScrollListener(this); } private void onSecondaryPointerUp(MotionEvent paramMotionEvent) { int i = (paramMotionEvent.getAction()) > > 8; Log.d("onSecondaryPointerUp", i + ""); if (paramMotionEvent.getPointerId(i) == this.mActivePointerId) if (i != 0) { this.mLastMotionY = paramMotionEvent.getY(1); this.mActivePointerId = paramMotionEvent.getPointerId(0); return; } } private void reset() { this.mActivePointerId = -1; this.mLastMotionY = -1.0F; this.mMaxScale = -1.0F; this.mLastScale = -1.0F; } public ImageView getHeaderView() { return this.mHeaderImage; } public void hideHeaderImage() { this.mShowHeaderImage = false; this.mZoomable = false; this.mScrollable = false; removeHeaderView(this.mHeaderContainer); } public boolean isScrollable() { return this.mScrollable; } public boolean isZoomable() { return this.mZoomable; } public boolean onInterceptTouchEvent(MotionEvent paramMotionEvent) { if (!this.mZoomable) { return super.onInterceptTouchEvent(paramMotionEvent); } switch (paramMotionEvent.getAction() & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_DOWN:this.mActivePointerId = paramMotionEvent.getPointerId(0); this.mMaxScale = (this.mScreenHeight / this.mHeaderHeight); break; case MotionEvent.ACTION_UP: reset(); break; case MotionEvent.ACTION_POINTER_DOWN: this.mActivePointerId = paramMotionEvent .getPointerId(paramMotionEvent.getActionIndex()); break; case MotionEvent.ACTION_POINTER_UP: onSecondaryPointerUp(paramMotionEvent); break; } return super.onInterceptTouchEvent(paramMotionEvent); } protected void onLayout(boolean paramBoolean, int paramInt1, int paramInt2, int paramInt3, int paramInt4) { super.onLayout(paramBoolean, paramInt1, paramInt2, paramInt3, paramInt4); if (this.mHeaderHeight == 0) this.mHeaderHeight = this.mHeaderContainer.getHeight(); } @Override public void onScroll(AbsListView paramAbsListView, int paramInt1, int paramInt2, int paramInt3) { if (this.mScrollable) { Log.d(TAG, "onScroll"); float f = this.mHeaderHeight - this.mHeaderContainer.getBottom(); Log.d("onScroll", "f|" + f); if ((f > 0.0F) & & (f < this.mHeaderHeight)) { Log.d("onScroll", "1"); int i = (int) (0.65D * f); this.mHeaderImage.scrollTo(0, -i); } else if (this.mHeaderImage.getScrollY() != 0) { Log.d("onScroll", "2"); this.mHeaderImage.scrollTo(0, 0); } }if (this.mOnScrollListener != null) { this.mOnScrollListener.onScroll(paramAbsListView, paramInt1, paramInt2, paramInt3); } } public void onScrollStateChanged(AbsListView paramAbsListView, int paramInt) { if (this.mOnScrollListener != null) this.mOnScrollListener.onScrollStateChanged(paramAbsListView, paramInt); } public boolean onTouchEvent(MotionEvent ev) {Log.d(TAG, "" + (0xFF & ev.getAction())); if (!this.mZoomable) { Log.i("zoom", "zoom"); return super.onTouchEvent(ev); } switch (ev.getAction() & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_OUTSIDE: case MotionEvent.ACTION_DOWN: if (!this.mScalingRunnalable.mIsFinished) { this.mScalingRunnalable.abortAnimation(); } this.mLastMotionY = ev.getY(); this.mActivePointerId = ev.getPointerId(0); this.mMaxScale = (this.mScreenHeight / this.mHeaderHeight); this.mLastScale = (this.mHeaderContainer.getBottom() / this.mHeaderHeight); break; case MotionEvent.ACTION_MOVE: Log.d("onTouchEvent", "mActivePointerId" + mActivePointerId); int j = ev.findPointerIndex(this.mActivePointerId); if (j == -1) { Log.e("PullToZoomListView", "Invalid pointerId=" + this.mActivePointerId + " in onTouchEvent"); } else { if (this.mLastMotionY == -1.0F) this.mLastMotionY = ev.getY(j); if (this.mHeaderContainer.getBottom() > = this.mHeaderHeight) { ViewGroup.LayoutParams localLayoutParams = this.mHeaderContainer .getLayoutParams(); float f = ((ev.getY(j) - this.mLastMotionY + this.mHeaderContainer .getBottom()) / this.mHeaderHeight - this.mLastScale) / 2.0F + this.mLastScale; if ((this.mLastScale < = 1.0D) & & (f < this.mLastScale)) { localLayoutParams.height = this.mHeaderHeight; this.mHeaderContainer .setLayoutParams(localLayoutParams); } this.mLastScale = Math.min(Math.max(f, 1.0F), this.mMaxScale); localLayoutParams.height = ((int) (this.mHeaderHeight * this.mLastScale)); if (localLayoutParams.height < this.mScreenHeight) this.mHeaderContainer .setLayoutParams(localLayoutParams); this.mLastMotionY = ev.getY(j); } this.mLastMotionY = ev.getY(j); } break; case MotionEvent.ACTION_UP: reset(); endScraling(); break; case MotionEvent.ACTION_CANCEL:break; case MotionEvent.ACTION_POINTER_DOWN: int i = ev.getActionIndex(); this.mLastMotionY = ev.getY(i); this.mActivePointerId = ev.getPointerId(i); break; case MotionEvent.ACTION_POINTER_UP: onSecondaryPointerUp(ev); this.mLastMotionY = ev.getY(ev .findPointerIndex(this.mActivePointerId)); break; } return super.onTouchEvent(ev); } public void setHeaderViewSize(int paramInt1, int paramInt2) { if (!this.mShowHeaderImage) { return; } Object localObject = this.mHeaderContainer.getLayoutParams(); if (localObject == null) localObject = new AbsListView.LayoutParams(paramInt1, paramInt2); ((ViewGroup.LayoutParams) localObject).width = paramInt1; ((ViewGroup.LayoutParams) localObject).height = paramInt2; this.mHeaderContainer .setLayoutParams((ViewGroup.LayoutParams) localObject); this.mHeaderHeight = paramInt2; } public void setOnScrollListener( AbsListView.OnScrollListener paramOnScrollListener) { this.mOnScrollListener = paramOnScrollListener; } public void setScrollable(boolean paramBoolean) { if (!this.mShowHeaderImage) { return; } this.mScrollable = paramBoolean; } public void setShadow(int paramInt) { if (!this.mShowHeaderImage) { return; } this.mShadow.setBackgroundResource(paramInt); } public void setZoomable(boolean paramBoolean) { if (!this.mShowHeaderImage) { return; } this.mZoomable = paramBoolean; } class ScalingRunnalable implements Runnable { long mDuration; boolean mIsFinished = true; float mScale; long mStartTime; ScalingRunnalable() { }public void abortAnimation() { this.mIsFinished = true; }public boolean isFinished() { return this.mIsFinished; }public void run() { float f2; ViewGroup.LayoutParams localLayoutParams; if ((!this.mIsFinished) & & (this.mScale > 1.0D)) { float f1 = ((float) SystemClock.currentThreadTimeMillis() - (float) this.mStartTime) / (float) this.mDuration; f2 = this.mScale - (this.mScale - 1.0F) * PullToZoomListView.sInterpolator.getInterpolation(f1); localLayoutParams = PullToZoomListView.this.mHeaderContainer .getLayoutParams(); if (f2 > 1.0F) { Log.d("mmm", "f2> 1.0"); localLayoutParams.height = PullToZoomListView.this.mHeaderHeight; localLayoutParams.height = ((int) (f2 * PullToZoomListView.this.mHeaderHeight)); PullToZoomListView.this.mHeaderContainer .setLayoutParams(localLayoutParams); PullToZoomListView.this.post(this); return; } this.mIsFinished = true; } }public void startAnimation(long paramLong) { this.mStartTime = SystemClock.currentThreadTimeMillis(); this.mDuration = paramLong; this.mScale = ((float) (PullToZoomListView.this.mHeaderContainer .getBottom()) / PullToZoomListView.this.mHeaderHeight); this.mIsFinished = false; PullToZoomListView.this.post(this); } } }

关于这个控件的实现原理能够自行參考上面链接的文章，里面已经有较为仔细的解说，此处不再赘述。
【Android PullToZoomListView实现放大回弹效果】实现的效果就是以下这样：