Android 图像滚动时查看视差
我在滚动或listview视差时看到了许多演示视差背景的示例,但我找不到一个清晰的示例,说明如何在活动中滚动时在图像上实现视差效果 示例实现可在Airbnb应用程序中找到。当你向下滚动时,你可以看到更多的图像底部,当你向上滚动时,你可以看到更多的图像顶部 关于如何创造这样的效果有什么提示和提示吗Android 图像滚动时查看视差,android,Android,我在滚动或listview视差时看到了许多演示视差背景的示例,但我找不到一个清晰的示例,说明如何在活动中滚动时在图像上实现视差效果 示例实现可在Airbnb应用程序中找到。当你向下滚动时,你可以看到更多的图像底部,当你向上滚动时,你可以看到更多的图像顶部 关于如何创造这样的效果有什么提示和提示吗 有几个库可以产生视差效果,这取决于您的应用程序是否对您的特定情况有用,例如: 谷歌是你的好友;)如果这些都不适合您的需要,那么您必须创建一个自定义的滚动视图,但这是一个较长的故事,请首先尝试一
有几个库可以产生视差效果,这取决于您的应用程序是否对您的特定情况有用,例如:
滚动视图
,但这是一个较长的故事,请首先尝试一下并发布您的结果
编辑
如果这些都不符合您的要求,则您必须这样做:
首先,创建一个自定义的滚动视图
,以便您可以收听滚动更改
public class ObservableScrollView extends ScrollView {
public interface OnScrollChangedListener {
public void onScrollChanged(int deltaX, int deltaY);
}
private OnScrollChangedListener mOnScrollChangedListener;
public ObservableScrollView(Context context) {
super(context);
}
public ObservableScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public ObservableScrollView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
@Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
super.onScrollChanged(l, t, oldl, oldt);
if(mOnScrollChangedListener != null) {
mOnScrollChangedListener.onScrollChanged(l - oldl, t - oldt);
}
}
public void setOnScrollChangedListener(OnScrollChangedListener listener) {
mOnScrollChangedListener = listener;
}
}
显然,您需要在布局中使用此选项,而不是默认的ScrollView
:
<your.app.package.ObservableScrollView
android:id="@+id/scroll_view"
android:layout_width="match_parent"
android:layout_height="match_parent">
根据需要的视差大小,可以修改0.5值
编辑
如果您的ImageView位于“活动”的顶部,则上述答案适用。我在下面发布了一些代码,以添加功能,使ImageView在我成功制作的活动布局中的任何位置都可以使用。这些都是一般性的计算(可能会有一些错误),只要稍加调整,您就可以将其用于您自己的情况
对于本例,我为图像容器200dp和图像240dp设置了固定高度。主要目的是当图像容器在屏幕中部没有视差效果时,当用户向上或向下滚动时,应用效果。因此,当图像容器靠近屏幕顶部或屏幕底部时,将应用更多的视差效果。通过阅读下面的计算结果有点难理解,所以试着在纸上用实数做一个例子
public class MyActivity extends Activity implements ObservableScrollView.OnScrollChangedListener {
private ObservableScrollView mScrollView;
private View imgContainer;
private ImageView mImageView;
@Override
public void onCreate(Bundle savedInstanceState) {
// Init your layout and set your listener
mScrollView = (ObservableScrollView)findViewById(R.id.scroll_view);
mScrollView.setOnScrollChangedListener(this);
// Store the reference of your image container
imgContainer = findViewById(R.id.img_container);
// Store the reference of your image
mImageView = findViewById(R.id.img);
}
@Override
public void onScrollChanged(int deltaX, int deltaY) {
// Get scroll view screen bound
Rect scrollBounds = new Rect();
mScrollView.getHitRect(scrollBounds);
// Check if image container is visible in the screen
// so to apply the translation only when the container is visible to the user
if (imgContainer.getLocalVisibleRect(scrollBounds)) {
Display display = getWindowManager().getDefaultDisplay();
DisplayMetrics outMetrics = new DisplayMetrics ();
display.getMetrics(outMetrics);
// Get screen density
float density = getResources().getDisplayMetrics().density;
// Get screen height in pixels
float dpHeight = outMetrics.heightPixels / density;
int screen_height_pixels = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dpHeight, getResources().getDisplayMetrics());
int half_screen_height = screen_height_pixels/2;
// Get image container height in pixels
int container_height_pixels = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 200, getResources().getDisplayMetrics());
// Get the location that consider a vertical center for the image (where the translation should be zero)
int center = half_screen_height - (container_height_pixels/2);
// get the location (x,y) of the image container in pixels
int[] loc_screen = {0,0};
imgContainer.getLocationOnScreen(loc_screen);
// trying to transform the current image container location into percentage
// so when the image container is exaclty in the middle of the screen percentage should be zero
// and as the image container getting closer to the edges of the screen should increase to 100%
int final_loc = ((loc_screen[1]-center)*100)/half_screen_height;
// translate the inner image taking consideration also the density of the screen
mImageView.setTranslationY(-final_loc * 0.4f * density);
}
}
}
我希望它能帮助那些正在寻找类似功能的人。scrollView.getViewTreeObserver().addOnScrollChangedListener(新的ViewTreeObserver.OnScrollChangedListener(){
scrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
@Override
public void onScrollChanged() {
int top = scrollView.getScrollY(); // Increases when scrolling up ^
if(top != 0) {
int newTop = (int) (top * .5f);
imageFrame.setTop(newTop < 0 ? 0 : newTop);
}
}
});
@凌驾
public void onScrollChanged(){
int top=scrollView.getScrollY();//向上滚动时增加^
如果(顶部!=0){
int newTop=(int)(顶部*.5f);
imageFrame.setTop(newTop<0?0:newTop);
}
}
});
似乎提供了很多。谢谢你的回答。我已经看到了它们,但是因为我看不清楚我正在寻找的功能,我决定问一下,以防我错过了一个库!但是你说得对,我必须花时间先试试。@xinaris,它有用吗?如果有,请接受我的帖子作为回答:)谢谢你的努力帮助我!实际上,我有一个类似的代码,用于为活动顶部的图像创建视差效果,效果很好。我的问题实际上是对scrollview中任何位置的imageview产生视差效果。您的代码不适用于此,但您的指导原则很好。该解决方案与您的代码类似,但需要进行一些数学计算,以计算imageview在scrollview中的当前位置。我在@peguerosdc anwser中添加了一些代码,以获得我要求的功能。谢谢你花时间在这上面。@xinaris我已经接受了你的编辑。我很高兴看到我的代码很有用。这使得快速移动时ImageView
顶部出现间隙。移除top!=0
检查将修复快速滚动时顶部显示的间隙。删除顶部!=0,但在快速移动时仍会在ImageView顶部留下间隙。还有其他解决办法吗?
public class MyActivity extends Activity implements ObservableScrollView.OnScrollChangedListener {
private ObservableScrollView mScrollView;
private View imgContainer;
private ImageView mImageView;
@Override
public void onCreate(Bundle savedInstanceState) {
// Init your layout and set your listener
mScrollView = (ObservableScrollView)findViewById(R.id.scroll_view);
mScrollView.setOnScrollChangedListener(this);
// Store the reference of your image container
imgContainer = findViewById(R.id.img_container);
// Store the reference of your image
mImageView = findViewById(R.id.img);
}
@Override
public void onScrollChanged(int deltaX, int deltaY) {
// Get scroll view screen bound
Rect scrollBounds = new Rect();
mScrollView.getHitRect(scrollBounds);
// Check if image container is visible in the screen
// so to apply the translation only when the container is visible to the user
if (imgContainer.getLocalVisibleRect(scrollBounds)) {
Display display = getWindowManager().getDefaultDisplay();
DisplayMetrics outMetrics = new DisplayMetrics ();
display.getMetrics(outMetrics);
// Get screen density
float density = getResources().getDisplayMetrics().density;
// Get screen height in pixels
float dpHeight = outMetrics.heightPixels / density;
int screen_height_pixels = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dpHeight, getResources().getDisplayMetrics());
int half_screen_height = screen_height_pixels/2;
// Get image container height in pixels
int container_height_pixels = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 200, getResources().getDisplayMetrics());
// Get the location that consider a vertical center for the image (where the translation should be zero)
int center = half_screen_height - (container_height_pixels/2);
// get the location (x,y) of the image container in pixels
int[] loc_screen = {0,0};
imgContainer.getLocationOnScreen(loc_screen);
// trying to transform the current image container location into percentage
// so when the image container is exaclty in the middle of the screen percentage should be zero
// and as the image container getting closer to the edges of the screen should increase to 100%
int final_loc = ((loc_screen[1]-center)*100)/half_screen_height;
// translate the inner image taking consideration also the density of the screen
mImageView.setTranslationY(-final_loc * 0.4f * density);
}
}
}
scrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
@Override
public void onScrollChanged() {
int top = scrollView.getScrollY(); // Increases when scrolling up ^
if(top != 0) {
int newTop = (int) (top * .5f);
imageFrame.setTop(newTop < 0 ? 0 : newTop);
}
}
});