Android PullToZoomListView实现放大回弹效果

另外一个相同项目的地址https://github.com/Frank-Zhu/PullZoomView

转自http://blog.csdn.net/wangjinyu501/article/details/38367669

之前看过一篇文章，链接是：可以下拉缩放HeaderView的ListView:PullToZoomInListView。说的就是PullToZoomListView，不过这篇文章有个地方需要勘误，就是PullToZoomListView这个控件虽然是github上一个开源项目。不过最美应用并不是使用这个开源项目，而是这个开源项目反编译了最美应用的代码。
但是，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，发现是因为在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，发现还有其他问题，比如少了一些变量，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，而且可正常使用。修改后代码如下：

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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 = -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可以自行参考上面链接的文章，里面已经有较为细致的讲解，此处不再赘述。实现的效果就是下面这样：



github链接：https://github.com/wangjinyu501/PullToZoomListView/，如果您发现了任何问题，可以在文章下面留言，我会第一时间处理，欢迎交流。