Android development: ViewPager for automatically scrolling labels of images,

Android development: ViewPager for automatically scrolling labels of images,

In Android, Image Auto-scrolling is very common. We can use our own animations to implement the function. But in Android provides a ViewPager class, to achieve the rolling effect, in the Android extras directory under the android-support-vx.jar, x represents version 4, 7 and so on. During use, we need the ViewPager tag of android. support. v4.view. viewPager.

Blog Source: Http://blog.csdn.net/fengshizty

The code is very simple and does not need to be explained:

The xml layout file is as follows:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context="com.andy.viewpagedemo.MainActivity" >    <android.support.v4.view.ViewPager        android:id="@+id/viewPager"        android:layout_width="wrap_content"        android:layout_height="200dip" />    <LinearLayout        android:layout_alignBottom="@id/viewPager"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:background="#33000000"        android:orientation="vertical" >        <TextView            android:id="@+id/image_desc"            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:gravity="center"            android:text="@string/app_name"            android:textColor="@android:color/white"            android:textSize="18sp" />        <LinearLayout            android:id="@+id/point_group"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:layout_gravity="center"            android:orientation="horizontal"             >        </LinearLayout>    </LinearLayout></RelativeLayout>

The Activity code is as follows:

Package com. andy. viewpagedemo; import java. util. arrayList; import android. app. activity; import android. OS. bundle; import android. OS. handler; import android. support. v4.view. pagerAdapter; import android. support. v4.view. viewPager; import android. support. v4.view. viewPager. onPageChangeListener; import android. view. view; import android. view. viewGroup; import android. widget. imageView; import android. widget. linearLay Out; import android. widget. textView; public class MainActivity extends Activity {private ViewPager viewPager; private LinearLayout point_group; private TextView image_desc; // image resource idprivate final int [] images = {R. drawable. a, R. drawable. b, R. drawable. c, R. drawable. d, R. drawable. e}; // image title set private final String [] imageDescriptions = {" Li is not vulgar, so I can't be vulgar", "It's coming back! Sing a classic old song to attract a chorus of thousands of people, "reveal how Beijing movies are upgraded", "letv TV edition big delivery", "hot-blooded anti-Kill"}; private ArrayList <ImageView> imageList; // The Position of the previous page protected int lastPosition = 0; // determine whether to automatically scroll viewPagerprivate boolean isRunning = true; private Handler handler = new Handler () {public void handleMessage (android. OS. message msg) {// run the slide to the next page viewPager. setCurrentItem (viewPager. getCurrentItem () + 1); if (isRunning) {// send a handler delay handler. sendEmptyMessageDelayed (0, 2000) ;}};@ Overrideprotected void onCreate (Bundle savedInstanceState) {super. onCreate (savedInstanceState); setContentView (R. layout. activity_main); viewPager = (ViewPager) findViewById (R. id. viewPager); point_group = (LinearLayout) findViewById (R. id. point_group); image_desc = (TextView) findViewById (R. id. image_desc); image_desc.setText (imageDescriptions [0]); // initialize the image resource imageList = new ArrayList <ImageView> (); for (int I: images) {// initialize the image resource ImageView imageView = new ImageView (this); imageView. setBackgroundResource (I); imageList. add (imageView); // you can specify ImageView point = new ImageView (this); LinearLayout. layoutParams params = new LinearLayout. layoutParams (5, 5); params. rightMargin = 20; point. setLayoutParams (params); point. setBackgroundResource (R. drawable. point_bg); if (I = R. drawable. a) {point. setEnabled (true);} else {point. setEnabled (false);} point_group.addView (point);} viewPager. setAdapter (new MyPageAdapter (); // you can specify the position of the current viewPager. setCurrentItem (Integer. MAX_VALUE/2-(Integer. MAX_VALUE/2% imageList. size (); viewPager. setOnPageChangeListener (new OnPageChangeListener () {@ Overridepublic void onPageSelected (int position) {// called after page switching, position is the new page position // implement unrestricted loop playback position % = imageList. size (); image_desc.setText (imageDescriptions [position]); // set the current vertex to true and set the previous vertex to falsepoint_group.getChildAt (position ). setEnabled (true); point_group.getChildAt (lastPosition ). setEnabled (false); lastPosition = position ;}@ Overridepublic void onPageScrolled (int position, float positionOffset, int positionOffsetPixels) {// sliding time callback} @ Overridepublic void onPageScrollStateChanged (int state) {// callback when the pageView status changes});/*** Automatic loop: 1. timer: Timer 2. enable sub-thread: while true loop 3. clockManger * 4. use Handler to send delayed messages to achieve loop, which is the simplest and most convenient **/handler. sendEmptyMessageDelayed (0, 2000) ;}@ Overrideprotected void onDestroy () {// stop rolling isRunning = false; super. onDestroy ();} private class MyPageAdapter extends PagerAdapter {// you need to implement the following four methods @ Overridepublic int getCount () {// get the total number of pages return Integer. MAX_VALUE ;}@ Overridepublic boolean isViewFromObject (View view, Object object) {// determine whether the view and Object are correlated. if (view = object) {return true ;} else {return false ;}@ Overridepublic Object instantiateItem (ViewGroup container, int position) {// obtain the view at the corresponding position; the container of the container view is actually the viewpage itself, // position: position on viewpager // Add content container to the container. addView (imageList. get (position % imageList. size (); return imageList. get (position % imageList. size () ;}@ Overridepublic void destroyItem (ViewGroup container, int position, Object object) {// destroy the Object at the corresponding position // super. destroyItem (container, position, object); container. removeView (View) object); object = null ;}}}

The effect is as follows: