【移动应用开发技术】Android中怎么利用 ListView实现下拉顶部图片变大效果

【移动应用开发技术】Android中怎么利用ListView实现下拉顶部图片变大效果

Android中怎么利用ListView实现下拉顶部图片变大效果，针对这个问题，这篇文章详细介绍了相对应的分析和解答，希望可以帮助更多想解决这个问题的小伙伴找到更简单易行的方法。变量说明这里变量包含了：自定义返回动画加速度、自定义动画线程、头部图片view，最后的y坐标，做好的比例，做大的比例等。private

static

final

String

TAG

=

"PullToZoomListView";

private

static

final

int

INVALID_VALUE

=

-1;//重置值

//自定义加速度动画

private

static

final

Interpolator

sInterpolator

=

new

Interpolator()

{

public

float

getInterpolation(float

interpolator)

{

float

f

=

interpolator

-

1.0F;

return

1.0F

+

f

*

(f

*

(f

*

(f

*

f)));

}

};

private

int

mActivePointerId

=

INVALID_VALUE;//当前手指的Id

private

FrameLayout

mHeaderContainer;//头部

private

int

mHeaderHeight;//头部图片的高度

private

ImageView

mHeaderImage;//头部图片

float

mLastMotionY

=

INVALID_VALUE;//最后y坐标

float

mLastScale

=

INVALID_VALUE;//最后的比例

float

mMaxScale

=

INVALID_VALUE;//最大的比例

private

OnScrollListener

mOnScrollListener;//滑动监听

private

ScalingRunnalable

mScalingRunnalable;//动画线程

private

int

mScreenHeight;//屏幕高度

private

ImageView

mShadow;//阴影遮罩自定义View初始化：设置了头部的头部和遮罩并且设置了监听。/**

*

初始化

*

@param

paramContext

*/

private

void

init(Context

paramContext)

{

DisplayMetrics

metrics

=

new

DisplayMetrics();

((Activity)

paramContext).getWindowManager().getDefaultDisplay().getMetrics(metrics);

this.mScreenHeight

=

metrics.heightPixels;//屏幕高度赋值

this.mHeaderContainer

=

new

FrameLayout(paramContext);//头部

this.mHeaderImage

=

new

ImageView(paramContext);//头部图片

int

screenWidth

=

metrics.widthPixels;//屏幕宽度

//设置头部View的样式

设置屏幕宽度，最大样式高度为屏幕高度的9/16

setHeaderViewSize(screenWidth,

(int)

(9.0F

*

(screenWidth

/

16.0F)));

this.mShadow

=

new

ImageView(paramContext);//遮罩

FrameLayout.LayoutParams

layoutParams

=

new

FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,

ViewGroup.LayoutParams.MATCH_PARENT);

layoutParams.gravity

=

Gravity.CENTER;

this.mShadow.setLayoutParams(layoutParams);//设置遮罩样式

//头部添加View

this.mHeaderContainer.addView(this.mHeaderImage);

this.mHeaderContainer.addView(this.mShadow);

//添加头部

addHeaderView(this.mHeaderContainer);

//初始化返回动画

this.mScalingRunnalable

=

new

ScalingRunnalable();

//设置监听

super.setOnScrollListener(this);

}开启动画：判断当前的头部布局底部的位置–是否大于图片的初始化高度。/**

*

开启动画

*/

private

void

endScraling()

{

if

(this.mHeaderContainer.getBottom()

>=

this.mHeaderHeight)

{

Log.d(TAG,

"this.mScalingRunnalable.startAnimation(200L)");

this.mScalingRunnalable.startAnimation(200L);

}

}多指触碰时将第0个手指赋值。/**

*

多点触碰的时候按下,当第0个有手指抬起，再次有手指按下后，将按下的事件的手指指针作为当前手指指针

*

*

@param

motionEvent

*/

private

void

onSecondaryPointerUp(MotionEvent

motionEvent)

{

Log.d(TAG,

"onSecondaryPointerUp

motionEvent.getPointerId(0)

=

"

+

motionEvent.getPointerId(0));

Log.d(TAG,

"onSecondaryPointerUp

this.mActivePointerId

=

"

+

this.mActivePointerId);

if

(motionEvent.getPointerId(0)

==

this.mActivePointerId)

{

this.mLastMotionY

=

motionEvent.getY(0);

this.mActivePointerId

=

motionEvent.getPointerId(0);

}

Log.d(TAG,

"onSecondaryPointerUp

mLastMotionY

=

"

+

mLastMotionY);

Log.d(TAG,

"onSecondaryPointerUp

mActivePointerId

=

"

+

mActivePointerId);

}重置所有的数据/**

*

重置所有数据

*/

private

void

reset()

{

this.mActivePointerId

=

INVALID_VALUE;

this.mLastMotionY

=

INVALID_VALUE;

this.mMaxScale

=

INVALID_VALUE;

this.mLastScale

=

INVALID_VALUE;

}向上滚动时修改布局样式@Override

public

void

onScroll(AbsListView

view,

int

firstVisibleItem,

int

visibleItemCount,

int

totalItemCount)

{

Log.d(TAG,

"onScroll");

float

bottomSpacing

=

this.mHeaderHeight

-

this.mHeaderContainer.getBottom();

Log.d(TAG,

"onScroll

bottomSpacing

=

"

+

bottomSpacing);

if

((bottomSpacing

>

0.0F)

&&

(bottomSpacing

<

this.mHeaderHeight))

{//如果是向上滑动

int

toUpScroll

=

(int)

(0.65D

*

bottomSpacing);

this.mHeaderImage.scrollTo(0,

-toUpScroll);

Log.d(TAG,

"onScroll

向上滑动

toUpScroll

=

"

+

toUpScroll);

}

else

if

(this.mHeaderImage.getScrollY()

!=

0)

{

Log.d(TAG,

"onScroll

this.mHeaderImage.getScrollY()

=

"

+

this.mHeaderImage.getScrollY());

this.mHeaderImage.scrollTo(0,

0);

}

if

(this.mOnScrollListener

!=

null)

{

this.mOnScrollListener.onScroll(view,

firstVisibleItem,

visibleItemCount,

totalItemCount);

}

}不同事件处理，修改布局样式@Override

public

boolean

onTouchEvent(MotionEvent

motionEvent)

{

switch

(motionEvent.getAction()

&

MotionEvent.ACTION_MASK)

{

case

MotionEvent.ACTION_OUTSIDE:

case

MotionEvent.ACTION_DOWN:

if

(!this.mScalingRunnalable.mIsFinished)

{

this.mScalingRunnalable.abortAnimation();

}

this.mLastMotionY

=

motionEvent.getY();

//获取第一个手指指针的ID

this.mActivePointerId

=

motionEvent.getPointerId(0);

this.mMaxScale

=

(this.mScreenHeight

/

this.mHeaderHeight);

this.mLastScale

=

(this.mHeaderContainer.getBottom()

/

this.mHeaderHeight);

Log.d(TAG,

"onTouchEvent

ACTION_DOWN

mLastMotionY

=

"

+

mLastMotionY);

Log.d(TAG,

"onTouchEvent

ACTION_DOWN

mActivePointerId

=

"

+

mActivePointerId);

Log.d(TAG,

"onTouchEvent

ACTION_DOWN

mMaxScale

=

"

+

mMaxScale);

Log.d(TAG,

"onTouchEvent

ACTION_DOWN

mLastScale

=

"

+

mLastScale);

break;

case

MotionEvent.ACTION_MOVE:

Log.d(TAG,

"onTouchEvent

ACTION_MOVE

mActivePointerId"

+

mActivePointerId);

//获取当前id的手机指针

int

pointer

=

motionEvent.findPointerIndex(this.mActivePointerId);

//判断指针不为空

if

(pointer

==

INVALID_VALUE)

{

Log.e(TAG,

"Invalid

pointerId="

+

this.mActivePointerId

+

"

in

onTouchEvent");

}

else

{

//如果开始没有赋值，则需要赋值

if

(this.mLastMotionY

==

INVALID_VALUE)

{

this.mLastMotionY

=

motionEvent.getY(pointer);

}

if

(this.mHeaderContainer.getBottom()

>=

this.mHeaderHeight)

{

//获取头部样式

ViewGroup.LayoutParams

headerParams

=

this.mHeaderContainer.getLayoutParams();

float

currentScale

=

((motionEvent.getY(pointer)

-

this.mLastMotionY

+

this.mHeaderContainer.getBottom())

/

this.mHeaderHeight

-

this.mLastScale)

/

2.0F

+

this.mLastScale;

if

((this.mLastScale

<=

1.0D)

&&

(currentScale

<

this.mLastScale))

{

//最后比例小于默认并且当前的比例要小于上次的比例，则修改头部的高度

headerParams.height

=

this.mHeaderHeight;

this.mHeaderContainer.setLayoutParams(headerParams);

return

super.onTouchEvent(motionEvent);

}

else

{

//否则，将当前的比例赋值为最后一次的比例

this.mLastScale

=

Math.min(Math.max(currentScale,

1.0F),

this.mMaxScale);

headerParams.height

=

((int)

(this.mHeaderHeight

*

this.mLastScale));

//判断修改后的高度小于屏幕的高度

if

(headerParams.height

<

this.mScreenHeight)

{

this.mHeaderContainer.setLayoutParams(headerParams);

}

//记录最后的y坐标

this.mLastMotionY

=

motionEvent.getY(pointer);

return

true;

}

}

this.mLastMotionY

=

motionEvent.getY(pointer);

}

break;

case

MotionEvent.ACTION_UP:

Log.d(TAG,

"onTouchEvent

ACTION_UP

重置");

//重置

reset();

//当手指起来的时候，结算拉伸，判断是否开启动画

endScraling();

break;

case

MotionEvent.ACTION_CANCEL:

int

actionIndex

=

motionEvent.getActionIndex();//获取当前最上层的指针

this.mLastMotionY

=

motionEvent.getY(actionIndex);//获取最后的y坐标

this.mActivePointerId

=

motionEvent.getPointerId(actionIndex);//获取最上层指针的手指

Log.d(TAG,

"onTouchEvent

ACTION_CANCEL

actionIndex

=

"

+

actionIndex

+

"

mLastMotionY

=

"

+

mLastMotionY

+

"

mActivePointerId

=

"

+

mActivePointerId);

break;

case

MotionEvent.ACTION_POINTER_DOWN:

//当第二个手指按下或者放开触发这个事件

onSecondaryPointerUp(motionEvent);

this.mLastMotionY

=

motionEvent.getY(motionEvent.findPointerIndex(this.mActivePointerId));

Log.d(TAG,

"onTouchEvent_Po

ACTION_POINTER_DOWN

mLastMotionY

=

"

+

mLastMotionY);

break;

case

MotionEvent.ACTION_POINTER_UP:

//当第二个手指按下或者放开

Log.d(TAG,

"onTouchEvent_Po

ACTION_POINTER_UP

");

break;

}

return

super.onTouchEvent(motionEvent);

}向上返回时的动画/**

*

向上返回的动画

*/

class

ScalingRunnalable

implements

Runnable

{

long

mDuration;//持续时间

boolean

mIsFinished

=

true;//是否结束

float

mScale;//比例

long

mStartTime;//开始时间

ScalingRunnalable()

{

}

/**

*

中止动画

*/

public

void

abortAnimation()

{

this.mIsFinished

=

true;

}

/**

*

是否中止

*

*

@return

*/

public

boolean

isFinished()

{

return

this.mIsFinished;

}

public

void

run()

{

Log.d(TAG,

"ScalingRunnalable

mIsFinished

=

"

+

this.mIsFinished

+

"

this.mScale

=

"

+

this.mScale);

float

currentScale;

ViewGroup.LayoutParams

mHeaderContainerParams;//头部样式

//判断是否中止和已经滑动超过的默认大小

if

((!this.mIsFinished)

&&

(this.mScale

>

1.0D))

{

float

currentTime

=

((float)

SystemClock.currentThreadTimeMillis()

-

(float)

this.mStartTime)

/

(float)

this.mDuration;

currentScale

=

this.mScale

-

(this.mScale

-

1.0F)

*

PullToZoomListView.sInterpolator.getInterpolation(currentTime);

Log.d(TAG,

"ScalingRunnalable

currentTime

=

"

+

currentTime

+

"

currentScale

=

"

+

currentScale);

mHeaderContainerParams

=

PullToZoomListView.this.mHeaderContainer.getLayoutParams();

if

(currentScale

>

1.0F)

{

Log.d(TAG,

"ScalingRunnalable

currentScale

>

1.0

--

修改头部高度");

mHeaderContainerParams.height

=

PullToZoomListView.this.mHeaderHeight;

mHeaderContai