ViewPager实现图片轮转
ViewPager实现图片轮转
viewpager的生命周期：
1：获取滑动的控件的个数。。。。getCount
2：当要缓存的图片可以进行的时候，会调用者方法进行图片的初始化，我们将要显示的View放入到ViewGroup中。然后作为返回值返回即可instantiateItem
3：PageAdapter只显示三张需要哦缓存的图片。如果滑动的图片超过了缓存的范围。就会调用者方法，将图片摧毁destroyItem
4：isViewFromObject来判断显示的是否是同一张图片
具体的可以参考：
http://www.it165.net/pro/html/201403/11289.html
先从不可轮转的ViewPager说起
本例采用图片的数据源是三张的图片源。
1.具体的代码块：
public class MyAdapter extends PagerAdapter {
public MyAdapter(List<ImageView> list) {
super();
m_List = list;
}
/** * 获取滑动的控件的个数。。。。 * @return */
@Override
public int getCount()
{
//Log.i("TAG","数量 "+m_List.size());
return m_List.size();
}
/** *当要缓存的图片可以进行的时候，会调用者方法进行图片的初始化，我们将要显示的View放入到ViewGroup中。 * 然后作为返回值返回即可 * @param container * @param position * @return */
@Override
public Object instantiateItem(ViewGroup container, int position) {
container.addView(m_List.get(position % m_List.size()),0);
Log.i("TAG","初始化 "+position);
return m_List.get(position % m_List.size());
}
/** * PageAdapter只显示三张需要哦缓存的图片。如果滑动的图片超过了缓存的范围。就会调用者方法，将图片摧毁 * @param container * @param position * @param object */
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView(m_List.get(position %
Log.i("TAG","摧毁某一项目 "+position);
//super.destroyItem(container, position, object);
}
@Override
public int getItemPosition(Object object) {
//Log.i("TAG","getItemPosition ");
return super.getItemPosition(object);
}
/** * 来判断显示的是否是同一张图片 * @param view * @param object * @return */
@Override
public boolean isViewFromObject(View view, Object object) {
//Log.i("TAG","判断是否是同一张图片 "+view.toString() +" "+object.toString());
return view == object;
}
}2.日志的输出和分析：
left–to–right ：在刚启动程序的 时候，只会加载两张图片资源（ViewPager的最大的缓存数量时3张）在从左向右的滑动过程中，会先执行destroyItem方法，然后在执行instantiateItem方法。第一次滑动的时候，会执行instantiateItem方法，缓存第三张图片。当第二次滑动的时候，会先摧毁poistion为0的然后在缓存position为3的位置的资源。
right–to–left :这个时候会先执行instantiateItem方法，然后在执行destroyItem方法。上图可以清楚的看出两种方法的执行顺序。
3.遇到的问题以及解决方案：
java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child’s parent first.
at android.view.ViewGroup.addViewInner(ViewGroup.java:3378)
at android.view.ViewGroup.addView(ViewGroup.java:3249)
at android.support.v4.view.ViewPager.addView(ViewPager.java:1341)
at android.view.ViewGroup.addView(ViewGroup.java:3194)
at
在你instantiateItem方法中判断该ImageVIew是否存在父类。如果存在则remove。（以上的问题会出现在ImageViews的数量时2或者3的时候）
@Override
public Object instantiateItem(ViewGroup container, int position) {
if(m_List.size() != 2 && m_List.size() != 3)
{
if(container.getChildCount() == m_List.size());
{
container.removeView(m_List.get(position % m_List.size()));
}
}
if(m_List.size() == 2 || m_List.size() == 3)
{
if(m_List.get(position % m_List.size()).getParent()!= null)
{
container.removeView(m_List.get(position % m_List.size()));
}
}
container.addView(m_List.get(position % m_List.size()),0);
Log.i("TAG","初始化 "+position);
return m_List.get(position % m_List.size());
}2.真正的轮转的实现：
使用到的定时器：Timber.http://www.cnblogs.com/xzf158/archive/2009/09/04/1560042.html（参考文档）
1.自定义的PageAdapter：
public class MyViewPager extends ViewPager{
private Timer timer;
private Activity activity;
private List<ImageView> mList;
public MyViewPager(Context context) {
super(context);
}
public MyViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
public void startFlow(Activity context,List<ImageView> list,int duration)
{
mList = list;
activity = context;
startTime();
this.setOnTouchListener(new OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
if(event.getAction() == MotionEvent.ACTION_UP)
{
startTime();
}
else
{
stopTime();
}
return false;
}
});
}
public void setDotLinear(final LinearLayout parentLinear,int selected,int unselected)
{
for(int i=0;i<mList.size();i++)
{
ImageView imageView = new ImageView(activity);
imageView.setBackgroundResource(R.drawable.dot_selector);
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
params.width = 10;
params.height = 10;
params.leftMargin = 9;
imageView.setLayoutParams(params);
parentLinear.addView(imageView);
}
this.setOnPageChangeListener(new OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
for(int i=0;i<mList.size();i++)
{
if((position % mList.size()) == i)
{
parentLinear.getChildAt(i).setSelected(true);
}
else
{
parentLinear.getChildAt(i).setSelected(false);
}
}
}
@Override
public void onPageSelected(int position) {
}
@Override
public void onPageScrollStateChanged(int state) {
}
});
}
public void startTime()
{
timer = new Timer();
// new Fix
timer.schedule(new TimerTask() {
@Override
public void run() {
activity.runOnUiThread(new Runnable() {
@Override
public void run() {
MyViewPager.this.setCurrentItem(MyViewPager.this.getCurrentItem() + 1);
}
});
}
},50000,5000);
}
public void stopTime()
{
if(timer != null)
{
timer.cancel();
}
}
}
2.Activity的代码块：
public class PageAdapterActivity extends Activity {
private MyViewPager viewPager;
private List<ImageView> m_List ;
private LinearLayout dot_linear;
private int images[] = new int[]{R.drawable.image1,
R.drawable.image2,R.drawable.image3,R.drawable.image4,R.drawable.image5};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_pageadapter);
viewPager = (MyViewPager)this.findViewById(R.id.view);
dot_linear = (LinearLayout)this.findViewById(R.id.dot_linear);
m_List = new ArrayList<>();
for(int i=0;i<3;i++)
{
ImageView imageView = new ImageView(PageAdapterActivity.this);
ViewPager.LayoutParams params = new ViewPager.LayoutParams();
params.width = ViewPager.LayoutParams.FILL_PARENT;
imageView.setScaleType(ImageView.ScaleType.FIT_XY);
imageView.setLayoutParams(params);
imageView.setImageResource(images[i]);
m_List.add(imageView);
initPoint();
}
MyAdapter adapter = new MyAdapter(m_List);
viewPager.setAdapter(adapter);
viewPager.startFlow(PageAdapterActivity.this,m_List,500);
viewPager.setDotLinear(dot_linear,R.drawable.carousel_dot,R.drawable.carousel_un_dot);
MyScrolller scrolller = new MyScrolller(this);
scrolller.setDuration(viewPager,5000);
// viewPager.setCurrentItem((m_List.size()) * 100);
}
private void initPoint()
{
}
public class MyAdapter extends PagerAdapter {
public MyAdapter(List<ImageView> list) {
super();
m_List = list;
}
/** * 获取滑动的控件的个数。。。。 * @return */
@Override
public int getCount()
{
//Log.i("TAG","数量 "+m_List.size());
if(m_List.size() == 1)
{
return 1;
}
else
{
return Integer.MAX_VALUE;
}
}
/** *当要缓存的图片可以进行的时候，会调用者方法进行图片的初始化，我们将要显示的View放入到ViewGroup中。 * 然后作为返回值返回即可 * @param container * @param position * @return */
@Override
public Object instantiateItem(ViewGroup container, int position) {
if(m_List.size() != 2 && m_List.size() != 3)
{
if(container.getChildCount() == m_List.size());
{
container.removeView(m_List.get(position % m_List.size()));
}
}
if(m_List.size() == 2 || m_List.size() == 3)
{
if(m_List.get(position % m_List.size()).getParent()!= null)
{
container.removeView(m_List.get(position % m_List.size()));
}
}
container.addView(m_List.get(position % m_List.size()),0);
Log.i("TAG","初始化 "+position);
return m_List.get(position % m_List.size());
}
/** * PageAdapter只显示三张需要哦缓存的图片。如果滑动的图片超过了缓存的范围。就会调用者方法，将图片摧毁 * @param container * @param position * @param object */
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
if(m_List.size() != 2 && m_List.size() != 3)
{
container.removeView(m_List.get(position % m_List.size()));
}
Log.i("TAG","摧毁某一项目 "+position);
//super.destroyItem(container, position, object);
}
@Override
public int getItemPosition(Object object) {
//Log.i("TAG","getItemPosition ");
return super.getItemPosition(object);
}
/** * 来判断显示的是否是同一张图片 * @param view * @param object * @return */
@Override
public boolean isViewFromObject(View view, Object object) {
//Log.i("TAG","判断是否是同一张图片 "+view.toString() +" "+object.toString());
return view == object;
}
}
public class MyScrolller extends Scroller {
private Context context;
private int mDuration;
public MyScrolller(Context context) {
super(context);
this.context = context;
}
public MyScrolller(Context context, Interpolator interpolator, boolean flywheel) {
super(context, interpolator, flywheel);
this.context = context;
}
public MyScrolller(Context context, Interpolator interpolator)
{
super(context, interpolator);
this.context = context;
}
@Override
public void startScroll(int startX, int startY, int dx, int dy) {
super.startScroll(startX, startY, dx, dy);
}
@Override
public void startScroll(int startX, int startY, int dx, int dy, int duration) {
super.startScroll(startX, startY, dx, dy, duration);
}
public void setDuration(ViewPager pager,int duration)
{
try {
Field field = ViewPager.class.getDeclaredField("mScroller");
field.setAccessible(true);
this.setmDuration(duration);
field.set(pager,duration);
}catch (Exception e)
{
e.printStackTrace();
}
}
public int getmDuration() {
return mDuration;
}
public void setmDuration(int mDuration) {
this.mDuration = mDuration;
}
}
}