轉自:http://jameszhao84.iteye.com/blog/1344584
想開發像人人網相冊打開單張圖片時候能左右滑動切換圖片的效果,開始通過FlipperView實現,不能跟手拖動,效果不好,而且需要自己寫很多代碼來控制FlipperView中的View。後來發現Android 3.0之後的SDK中提供了android-support-v4包用以實現版本兼容,讓老版本系統下的應用通過加入jar包實現擴展,得到新版的各種技術優勢,例如Fragment等。
ViewPager是android-support-v4.jar包中的一個系統控件,繼承自ViewGroup,專門用以實現左右滑動切換View的效果,使用時需要首先在Project->properties->Java Build Path->Libraries->Add External Jars中加入sdk目錄下的extras/android/support/v4/android-support-v4.jar(如果找不到,則需要用sdk manager下載android support package)。加入這個jar包之後就可以使用ViewPager類了。
ViewPager的使用類似於ListView,需要有對應的Adapter進行數據綁定,實現圖片切換僅需要繼承PaperAdapter就可以了。繼承後需要重寫如下四個方法。
instantiateItem(ViewGroup, int)
destroyItem(ViewGroup, int, Object)
getCount()
isViewFromObject(View, Object)
- import java.io.FileNotFoundException;
- import java.util.List;
- import android.content.Context;
- import android.graphics.Bitmap;
- import android.net.Uri;
- import android.support.v4.view.PagerAdapter;
- import android.support.v4.view.ViewPager;
- import android.view.View;
- import android.view.ViewGroup;
- import android.widget.ImageView;
- public class TestAdapter extends PagerAdapter {
- private List<String> mPaths;
- private Context mContext;
- public TestAdapter(Context cx) {
- mContext = cx.getApplicationContext();
- }
- public void change(List<String> paths) {
- mPaths = paths;
- }
- @Override
- public int getCount() {
- // TODO Auto-generated method stub
- return mPaths.size();
- }
- @Override
- public boolean isViewFromObject(View view, Object obj) {
- // TODO Auto-generated method stub
- return view == (View) obj;
- }
- @Override
- public Object instantiateItem (ViewGroup container, int position) {
- ImageView iv = new ImageView(mContext);
- try {
- Bitmap bm = BitmapFactory.decodeFile(mPaths.get(position));//載入bitmap
- iv.setImageBitmap(bm);
- } catch (FileNotFoundException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- } catch (OutOfMemoryError e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
- ((ViewPager)container).addView(iv, 0);
- return iv;
- }
- @Override
- public void destroyItem (ViewGroup container, int position, Object object) {
- container.removeView((View)object);
- }
- }
- <android.support.v4.view.ViewPager
- android:id="@+id/pager"
- android:layout_width="fill_parent"
- android:layout_height="fill_parent" />
- @Override
- public void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- mViewPager = (ViewPager)findViewById(R.id.pager);
- mAdapter = new TestAdapter(this);
- mViewPager.setAdapter(mAdapter);
- mAdapter.change(getList());
- }
- private List<String> getList() {
- List<String> list = new ArrayList<String>();
- list.add("file:///sdcard/Sunset.jpg");
- list.add("file:///sdcard/Winter.jpg");
- list.add("file:///sdcard/Water lilies.jpg");
- list.add("file:///sdcard/Blue hills.jpg");
- return list;
- }