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 = -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。实现的效果就是以下这样：
