转载请注明出处:http://blog.csdn.net/guolin_blog/article/details/8769904
首先题外话,今天早上起床的时候,手滑一下把我的手机甩了出去,结果陪伴我两年半的摩托罗拉里程碑一代就这么安息了,于是我今天决定怒更一记,纪念我死去的爱机。
如果你是网购达人,你的手机上一定少不了淘宝客户端。关注特效的人一定都会发现,淘宝不管是网站还是手机客户端,主页上都会有一个图片滚动播放器,上面展示一些它推荐的商品。这个几乎可以用淘宝来冠名的功能,看起来还是挺炫的,我们今天就来实现一下。
实现原理其实还是之前那篇文章Android滑动菜单特效实现,仿人人客户端侧滑效果,史上最简单的侧滑实现 ,算是以那个原理为基础的另外一个变种。正所谓一通百通,真正掌握一种方法之后,就可以使用这个方法变换出各种不通的效果。
今天仍然还是实现一个自定义控件,然后我们在任意Activity的布局文件中引用一下,即可实现图片滚动器的效果。
在Eclipse中新建一个Android项目,项目名就叫做SlidingViewSwitcher。
新建一个类,名叫SlidingSwitcherView,这个类是继承自RelativeLayout的,并且实现了OnTouchListener接口,具体代码如下:
- public class SlidingSwitcherView extends RelativeLayout implements OnTouchListener {
-
-
-
-
- public static final int SNAP_VELOCITY = 200;
-
-
-
-
- private int switcherViewWidth;
-
-
-
-
- private int currentItemIndex;
-
-
-
-
- private int itemsCount;
-
-
-
-
- private int[] borders;
-
-
-
-
-
- private int leftEdge = 0;
-
-
-
-
- private int rightEdge = 0;
-
-
-
-
- private float xDown;
-
-
-
-
- private float xMove;
-
-
-
-
- private float xUp;
-
-
-
-
- private LinearLayout itemsLayout;
-
-
-
-
- private LinearLayout dotsLayout;
-
-
-
-
- private View firstItem;
-
-
-
-
- private MarginLayoutParams firstItemParams;
-
-
-
-
- private VelocityTracker mVelocityTracker;
-
-
-
-
-
-
-
- public SlidingSwitcherView(Context context, AttributeSet attrs) {
- super(context, attrs);
- }
-
-
-
-
- public void scrollToNext() {
- new ScrollTask().execute(-20);
- }
-
-
-
-
- public void scrollToPrevious() {
- new ScrollTask().execute(20);
- }
-
-
-
-
- @Override
- protected void onLayout(boolean changed, int l, int t, int r, int b) {
- super.onLayout(changed, l, t, r, b);
- if (changed) {
- initializeItems();
- initializeDots();
- }
- }
-
-
-
-
- private void initializeItems() {
- switcherViewWidth = getWidth();
- itemsLayout = (LinearLayout) getChildAt(0);
- itemsCount = itemsLayout.getChildCount();
- borders = new int[itemsCount];
- for (int i = 0; i < itemsCount; i++) {
- borders[i] = -i * switcherViewWidth;
- View item = itemsLayout.getChildAt(i);
- MarginLayoutParams params = (MarginLayoutParams) item.getLayoutParams();
- params.width = switcherViewWidth;
- item.setLayoutParams(params);
- item.setOnTouchListener(this);
- }
- leftEdge = borders[itemsCount - 1];
- firstItem = itemsLayout.getChildAt(0);
- firstItemParams = (MarginLayoutParams) firstItem.getLayoutParams();
- }
-
-
-
-
- private void initializeDots() {
- dotsLayout = (LinearLayout) getChildAt(1);
- refreshDotsLayout();
- }
-
- @Override
- public boolean onTouch(View v, MotionEvent event) {
- createVelocityTracker(event);
- switch (event.getAction()) {
- case MotionEvent.ACTION_DOWN:
-
- xDown = event.getRawX();
- break;
- case MotionEvent.ACTION_MOVE:
-
- xMove = event.getRawX();
- int distanceX = (int) (xMove - xDown) - (currentItemIndex * switcherViewWidth);
- firstItemParams.leftMargin = distanceX;
- if (beAbleToScroll()) {
- firstItem.setLayoutParams(firstItemParams);
- }
- break;
- case MotionEvent.ACTION_UP:
-
- xUp = event.getRawX();
- if (beAbleToScroll()) {
- if (wantScrollToPrevious()) {
- if (shouldScrollToPrevious()) {
- currentItemIndex--;
- scrollToPrevious();
- refreshDotsLayout();
- } else {
- scrollToNext();
- }
- } else if (wantScrollToNext()) {
- if (shouldScrollToNext()) {
- currentItemIndex++;
- scrollToNext();
- refreshDotsLayout();
- } else {
- scrollToPrevious();
- }
- }
- }
- recycleVelocityTracker();
- break;
- }
- return false;
- }
-
-
-
-
-
-
- private boolean beAbleToScroll() {
- return firstItemParams.leftMargin < rightEdge && firstItemParams.leftMargin > leftEdge;
- }
-
-
-
-
-
-
- private boolean wantScrollToPrevious() {
- return xUp - xDown > 0;
- }
-
-
-
-
-
-
- private boolean wantScrollToNext() {
- return xUp - xDown < 0;
- }
-
-
-
-
-
-
-
- private boolean shouldScrollToNext() {
- return xDown - xUp > switcherViewWidth / 2 || getScrollVelocity() > SNAP_VELOCITY;
- }
-
-
-
-
-
-
-
- private boolean shouldScrollToPrevious() {
- return xUp - xDown > switcherViewWidth / 2 || getScrollVelocity() > SNAP_VELOCITY;
- }
-
-
-
-
- private void refreshDotsLayout() {
- dotsLayout.removeAllViews();
- for (int i = 0; i < itemsCount; i++) {
- LinearLayout.LayoutParams linearParams = new LinearLayout.LayoutParams(0,
- LayoutParams.FILL_PARENT);
- linearParams.weight = 1;
- RelativeLayout relativeLayout = new RelativeLayout(getContext());
- ImageView image = new ImageView(getContext());
- if (i == currentItemIndex) {
- image.setBackgroundResource(R.drawable.dot_selected);
- } else {
- image.setBackgroundResource(R.drawable.dot_unselected);
- }
- RelativeLayout.LayoutParams relativeParams = new RelativeLayout.LayoutParams(
- LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
- relativeParams.addRule(RelativeLayout.CENTER_IN_PARENT);
- relativeLayout.addView(image, relativeParams);
- dotsLayout.addView(relativeLayout, linearParams);
- }
- }
-
-
-
-
-
-
-
- private void createVelocityTracker(MotionEvent event) {
- if (mVelocityTracker == null) {
- mVelocityTracker = VelocityTracker.obtain();
- }
- mVelocityTracker.addMovement(event);
- }
-
-
-
-
-
-
- private int getScrollVelocity() {
- mVelocityTracker.computeCurrentVelocity(1000);
- int velocity = (int) mVelocityTracker.getXVelocity();
- return Math.abs(velocity);
- }
-
-
-
-
- private void recycleVelocityTracker() {
- mVelocityTracker.recycle();
- mVelocityTracker = null;
- }
-
-
-
-
-
-
-
-
-
-
- private boolean isCrossBorder(int leftMargin, int speed) {
- for (int border : borders) {
- if (speed > 0) {
- if (leftMargin >= border && leftMargin - speed < border) {
- return true;
- }
- } else {
- if (leftMargin <= border && leftMargin - speed > border) {
- return true;
- }
- }
- }
- return false;
- }
-
-
-
-
-
-
-
-
- private int findClosestBorder(int leftMargin) {
- int absLeftMargin = Math.abs(leftMargin);
- int closestBorder = borders[0];
- int closestMargin = Math.abs(Math.abs(closestBorder) - absLeftMargin);
- for (int border : borders) {
- int margin = Math.abs(Math.abs(border) - absLeftMargin);
- if (margin < closestMargin) {
- closestBorder = border;
- closestMargin = margin;
- }
- }
- return closestBorder;
- }
-
- class ScrollTask extends AsyncTask<Integer, Integer, Integer> {
-
- @Override
- protected Integer doInBackground(Integer... speed) {
- int leftMargin = firstItemParams.leftMargin;
-
- while (true) {
- leftMargin = leftMargin + speed[0];
- if (isCrossBorder(leftMargin, speed[0])) {
- leftMargin = findClosestBorder(leftMargin);
- break;
- }
- publishProgress(leftMargin);
-
- sleep(10);
- }
- return leftMargin;
- }
-
- @Override
- protected void onProgressUpdate(Integer... leftMargin) {
- firstItemParams.leftMargin = leftMargin[0];
- firstItem.setLayoutParams(firstItemParams);
- }
-
- @Override
- protected void onPostExecute(Integer leftMargin) {
- firstItemParams.leftMargin = leftMargin;
- firstItem.setLayoutParams(firstItemParams);
- }
- }
-
-
-
-
-
-
-
- private void sleep(long millis) {
- try {
- Thread.sleep(millis);
- } catch (InterruptedException e) {
- e.printStackTrace();
- }
- }
- }
细心的朋友可以看出来,我还是重用了很多之前的代码,这里有几个重要点我说一下。在onLayout方法里,重定义了各个包含图片的控件的大小,然后为每个包含图片的控件都注册了一个touch事件监听器。这样当我们滑动任何一样图片控件的时候,都会触发onTouch事件,然后通过改变第一个图片控件的leftMargin,去实现动画效果。之后在onLayout里又动态加入了页签View,有几个图片控件就会加入几个页签,然后根据currentItemIndex来决定高亮显示哪一个页签。其它也没什么要特别说明的了,更深的理解大家去看代码和注释吧。
然后看一下布局文件中如何使用我们自定义的这个控件,创建或打开activity_main.xml,里面加入如下代码:
- <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
- xmlns:tools="http://schemas.android.com/tools"
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:orientation="horizontal"
- tools:context=".MainActivity" >
-
- <com.example.viewswitcher.SlidingSwitcherView
- android:id="@+id/slidingLayout"
- android:layout_width="fill_parent"
- android:layout_height="100dip" >
-
- <LinearLayout
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:orientation="horizontal" >
-
- <Button
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:background="@drawable/image1" />
-
- <Button
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:background="@drawable/image2" />
-
- <Button
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:background="@drawable/image3" />
-
- <Button
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:background="@drawable/image4" />
- </LinearLayout>
-
- <LinearLayout
- android:layout_width="60dip"
- android:layout_height="20dip"
- android:layout_alignParentBottom="true"
- android:layout_alignParentRight="true"
- android:layout_margin="15dip"
- android:orientation="horizontal" >
- </LinearLayout>
- </com.example.viewswitcher.SlidingSwitcherView>
-
- </LinearLayout>
我们可以看到,com.example.viewswitcher.SlidingSwitcherView的根目录下放置了两个LinearLayout。第一个LinearLayout中要放入需要滚动显示的图片,这里我们加入了四个Button,每个Button都设置了一张背景图片。第二个LinearLayout中不需要加入任何东西,只要控制好大小和位置,标签会在运行的时候自动加入到这个layout中。
然后创建或打开MainActivity作为主界面,里面没有加入任何新增的代码:
- public class MainActivity extends Activity {
-
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.activity_main);
- }
-
- }
最后是给出AndroidManifest.xml的代码,也都是自动生成的内容:
- <?xml version="1.0" encoding="utf-8"?>
- <manifest xmlns:android="http://schemas.android.com/apk/res/android"
- package="com.example.viewswitcher"
- android:versionCode="1"
- android:versionName="1.0" >
-
- <uses-sdk
- android:minSdkVersion="8"
- android:targetSdkVersion="8" />
-
- <application
- android:allowBackup="true"
- android:icon="@drawable/ic_launcher"
- android:label="@string/app_name"
- android:theme="@android:style/Theme.NoTitleBar" >
- <activity
- android:name="com.example.viewswitcher.MainActivity"
- android:label="@string/app_name" >
- <intent-filter>
- <action android:name="android.intent.action.MAIN" />
-
- <category android:name="android.intent.category.LAUNCHER" />
- </intent-filter>
- </activity>
- </application>
-
- </manifest>
好了,现在我们来看下运行效果吧,由于手机坏了,只能在模拟器上运行了。
首先是程序打开的时候,界面显示如下:

然后手指在图片上滑动,我们可以看到图片滚动的效果:

不停的翻页,页签也会跟着一起改变,下图中我们可以看到高亮显示的点是变换的:

恩,对比一下淘宝客户端的效果,我觉得我们模仿的还是挺好的。咦,好像少了点什么。。。。。。原来图片并不会自动播放。。。。。
没关系,我在后面的一篇文章中补充了自动播放这个功能,而且不仅仅是自动播放功能喔,请参考 Android图片滚动,加入自动播放功能,使用自定义属性实现,霸气十足!
今天的文章就到这里了,有问题的朋友请在下面留言。
源码下载,请点击这里