/**
 * 使用onSaveInstanceState，onRestoreInstanceState；
 * 在这里不考虑没有加载完毕，就旋转屏幕的情况。
 * @author 超超boy
 *
 */
public class SavedInstanceStateActivity extends ListActivity
{
 private static final String TAG = "MainActivity";
 private ListAdapter mAdapter;
 private ArrayList<String> mDatas;
 private DialogFragment mLoadingDialog;
 private LoadDataAsyncTask mLoadDataAsyncTask;
 @Override
 public void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 Log.e(TAG, "onCreate");
 initData(savedInstanceState);
 }

 /**
 * 初始化数据
 */
 private void initData(Bundle savedInstanceState)
 {
 if (savedInstanceState != null)
 mDatas = savedInstanceState.getStringArrayList("mDatas");
 if (mDatas == null)
 {
 mLoadingDialog = new LoadingDialog();
 mLoadingDialog.show(getFragmentManager(), "LoadingDialog");
 mLoadDataAsyncTask = new LoadDataAsyncTask();
 mLoadDataAsyncTask.execute();
 //mLoadDataAsyncTas
 } else
 {
 initAdapter();
 }
 }
 /**
 * 初始化适配器
 */
 private void initAdapter()
 {
 mAdapter = new ArrayAdapter<String>(
 SavedInstanceStateActivity.this,
 android.R.layout.simple_list_item_1, mDatas);
 setListAdapter(mAdapter);
 }
 @Override
 protected void onRestoreInstanceState(Bundle state)
 {
 super.onRestoreInstanceState(state);
 Log.e(TAG, "onRestoreInstanceState");
 }
 @Override
 //在这里保存数据，好用于返回
 protected void onSaveInstanceState(Bundle outState)
 {
 super.onSaveInstanceState(outState);
 Log.e(TAG, "onSaveInstanceState");
 outState.putSerializable("mDatas", mDatas);
 }
 /**
 * 模拟耗时操作
 *
 * @return
 */
 private ArrayList<String> generateTimeConsumingDatas()
 {
 try
 {
 Thread.sleep(3000);
 } catch (InterruptedException e)
 { e.printStackTrace();
 }
 return new ArrayList<String>(Arrays.asList("通过Fragment保存大量数据",
 "onSaveInstanceState保存数据",
 "getLastNonConfigurationInstance已经被弃用", "RabbitMQ", "Hadoop",
 "Spark"));
 }
 private class LoadDataAsyncTask extends AsyncTask<Void, Void, Void>
 {
 @Override
 protected Void doInBackground(Void... params)
 {
 mDatas = generateTimeConsumingDatas();
 return null;
 }
 @Override
 protected void onPostExecute(Void result)
 {
 mLoadingDialog.dismiss();
 initAdapter();
 }
 }
 @Override
 protected void onDestroy()
 {
 Log.e(TAG, "onDestroy");
 super.onDestroy();
 }
}

public class RetainedFragment extends Fragment {
 // data object we want to retain
 private MyDataObject data;
 // this method is only called once for this fragment
 @Override
 public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 // retain this fragment
 setRetainInstance(true);
 }
 public void setData(MyDataObject data) {
 this.data = data;
 }
 public MyDataObject getData() {
 return data;
 }
}

public class RetainedFragment extends Fragment
{
 // data object we want to retain
 private Bitmap data;
 // this method is only called once for this fragment
 @Override
 public void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 // retain this fragment
 setRetainInstance(true);
 }
 public void setData(Bitmap data)
 {
 this.data = data;
 }
 public Bitmap getData()
 {
 return data;
 }
}

public class FragmentRetainDataActivity extends Activity
{
 private static final String TAG = "FragmentRetainData";
 private RetainedFragment dataFragment;
 private DialogFragment mLoadingDialog;
 private ImageView mImageView;
 private Bitmap mBitmap;
 BitmapWorkerTask bitmapWorkerTask;
 @Override
 public void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 Log.e(TAG, "onCreate");
 // find the retained fragment on activity restarts
 FragmentManager fm = getFragmentManager();
 dataFragment = (RetainedFragment) fm.findFragmentByTag("data");
 // create the fragment and data the first time
 if (dataFragment == null)
 {
 // add the fragment
 dataFragment = new RetainedFragment();
 fm.beginTransaction().add(dataFragment, "data").commit();
 }
 // the data is available in dataFragment.getData()
 mBitmap = dataFragment.getData();
 initView();
 }
 /**
 * 初始化控件
 */
 private void initView()
 {
 mImageView = (ImageView) findViewById(R.id.id_imageView);
 if(mBitmap != null)
 mImageView.setImageBitmap(mBitmap);
 //图片为空时，加载图片;有时候即使dataFragment！=null时，图片也不一定就加载完了，比如在加载的过程中，旋转屏幕，此时图片就没有加载完
 else{
 mLoadingDialog = new LoadingDialog();
 mLoadingDialog.show(getFragmentManager(), "LOADING_DIALOG");
 bitmapWorkerTask = new BitmapWorkerTask(this);
 bitmapWorkerTask.execute("http://images2015.cnblogs.com/blog/747969/201612/747969-20161222164357995-1098775233.jpg");
 }
 }
 /**
 * 异步下载图片的任务。
 * 设置成静态内部类是为了防止内存泄漏
 * @author guolin
 */
 private static class BitmapWorkerTask extends AsyncTask<String, Void, Bitmap> {
 //图片的URL地址
 private String imageUrl;
 //保存外部activity的弱引用
 private WeakReference<Context> weakReference;
 public BitmapWorkerTask(Context context) {
 weakReference = new WeakReference<>(context);
 }
 @Override
 protected Bitmap doInBackground(String... params) {
 imageUrl = params[0];
 //为了演示加载过程，阻塞2秒
 try
 {Thread.sleep(2000);
 } catch (InterruptedException e)
 { e.printStackTrace();
 }
 return downloadUrlToStream(imageUrl);
 }
 @Override
 protected void onPostExecute(Bitmap bitmap) {
 super.onPostExecute(bitmap);
 if(bitmap !=null){
 FragmentRetainDataActivity retainDataActivity= (FragmentRetainDataActivity) weakReference.get();
 //调用回调方法
 retainDataActivity.onLoaded(bitmap);
 }
 }
 /**
 * 建立HTTP请求，并获取Bitmap对象。
 * 修改了下
 * @param urlString
 * 图片的URL地址
 * @return 解析后的Bitmap对象
 */
 private Bitmap downloadUrlToStream(String urlString) {
 HttpURLConnection urlConnection = null;
 Bitmap bitmap = null;
 try {
 final URL url = new URL(urlString);
 urlConnection = (HttpURLConnection) url.openConnection();
 if(urlConnection.getResponseCode()==HttpURLConnection.HTTP_OK){ //连接成功
  InputStream is = urlConnection.getInputStream();
  bitmap = BitmapFactory.decodeStream(is);
  is.close();
  return bitmap;
 }else{
  return null;
 }
 } catch (final IOException e) {
 e.printStackTrace();
 } finally {
 if (urlConnection != null) {
  urlConnection.disconnect();
 }
 }
 return null;
 }
 }
 //加载完毕的回掉
 public void onLoaded(Bitmap bitmap){
 mBitmap = bitmap;
 mLoadingDialog.dismiss();
 mImageView.setImageBitmap(mBitmap);
 // load the data from the web
 dataFragment.setData(mBitmap);
 Log.e(TAG, "onLoaded");
 }
 public void onPause(){
 super.onPause();
 Log.e(TAG, "onPause");
 if(getFragmentManager() != null && mLoadingDialog != null)
 mLoadingDialog.dismiss();
 }
 @Override
 public void onDestroy()
 {
 super.onDestroy();
 Log.e(TAG, "onDestroy");
 if(bitmapWorkerTask !=null)
 bitmapWorkerTask.cancel(true);
 // store the data in the fragment
 dataFragment.setData(mBitmap);
 }
}

<activity android:name=".MyActivity" android:configChanges="orientation|keyboardHidden"
 android:label="@string/app_name">

@Override
public void onConfigurationChanged(Configuration newConfig) {
 super.onConfigurationChanged(newConfig);
 
 // Checks the orientation of the screen
 if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
 Toast.makeText(this, "landscape", Toast.LENGTH_SHORT).show();
 } else if (newConfig.orientation == Configuration.ORIENTATION_PORTRAIT){
 Toast.makeText(this, "portrait", Toast.LENGTH_SHORT).show();
 }
}

public class ConfigChangesTestActivity extends ListActivity
{
 private static final String TAG = "MainActivity";
 private ListAdapter mAdapter;
 private ArrayList<String> mDatas;
 private DialogFragment mLoadingDialog;
 private LoadDataAsyncTask mLoadDataAsyncTask;
 @Override
 public void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 Log.e(TAG, "onCreate");
 initData(savedInstanceState);
 }
 /**
 * 初始化数据
 */
 private void initData(Bundle savedInstanceState)
 {
 mLoadingDialog = new LoadingDialog();
 mLoadingDialog.show(getFragmentManager(), "LoadingDialog");
 mLoadDataAsyncTask = new LoadDataAsyncTask();
 mLoadDataAsyncTask.execute();
 }
 /**
 * 初始化适配器
 */
 private void initAdapter()
 {
 mAdapter = new ArrayAdapter<String>(ConfigChangesTestActivity.this,
 android.R.layout.simple_list_item_1, mDatas);
 setListAdapter(mAdapter);
 }
 /**
 * 模拟耗时操作
 *
 * @return
 */
 private ArrayList<String> generateTimeConsumingDatas()
 {
 try
 {
 Thread.sleep(2000);
 } catch (InterruptedException e)
 {
 }
 return new ArrayList<String>(Arrays.asList("通过Fragment保存大量数据",
 "onSaveInstanceState保存数据",
 "getLastNonConfigurationInstance已经被弃用", "RabbitMQ", "Hadoop",
 "Spark"));
 }
 /**
 * 当配置发生变化时，不会重新启动Activity。但是会回调此方法，用户自行进行对屏幕旋转后进行处理
 */
 @Override
 public void onConfigurationChanged(Configuration newConfig)
 {
 super.onConfigurationChanged(newConfig);
 if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE)
 {
 Toast.makeText(this, "landscape", Toast.LENGTH_SHORT).show();
 } else if (newConfig.orientation == Configuration.ORIENTATION_PORTRAIT)
 {
 Toast.makeText(this, "portrait", Toast.LENGTH_SHORT).show();
 }
 }
 private class LoadDataAsyncTask extends AsyncTask<Void, Void, Void>
 {
 @Override
 protected Void doInBackground(Void... params)
 {
 mDatas = generateTimeConsumingDatas();
 return null;
 }
 @Override
 protected void onPostExecute(Void result)
 {
 mLoadingDialog.dismiss();
 initAdapter();
 }
 }
 @Override
 protected void onDestroy()
 {
 Log.e(TAG, "onDestroy");
 super.onDestroy();
 }
}

/**
 * 保存对象的Fragment
 * @author 超超boy
 *
 */
public class OtherRetainedFragment extends Fragment
{
 // data object we want to retain
 // 保存一个异步的任务
 private MyAsyncTask data;
 // this method is only called once for this fragment
 @Override
 public void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 // retain this fragment
 setRetainInstance(true);
 }
 public void setData(MyAsyncTask data)
 {
 this.data = data;
 }
 public MyAsyncTask getData()
 {
 return data;
 }

public class MyAsyncTask extends AsyncTask<Void, Void, Void>
{
 //保存外部activity的弱引用
 private WeakReference<Context> weakReference;
 public MyAsyncTask(Context context) {
 weakReference = new WeakReference<>(context);
 }
 private FixProblemsActivity activity;
 /**
 * 是否完成
 */
 private boolean isCompleted;
 /**
 * 进度框
 */
 private LoadingDialog mLoadingDialog;
 private List<String> items;
 /**
 * 开始时，显示加载框
 */
 @Override
 protected void onPreExecute()
 {
 mLoadingDialog = new LoadingDialog();
 activity = (FixProblemsActivity) weakReference.get();
 if(activity != null)
 mLoadingDialog.show(activity.getFragmentManager(), "LOADING");
 }
 /**
 * 加载数据
 */
 @Override
 protected Void doInBackground(Void... params)
 {
 items = loadingData();
 return null;
 }
 /**
 * 加载完成回调当前的Activity
 */
 @Override
 protected void onPostExecute(Void unused)
 {
 isCompleted = true;
 notifyActivityTaskCompleted();
 if (mLoadingDialog != null)
 mLoadingDialog.dismiss();
 }
 public List<String> getItems()
 {
 return items;
 }
 private List<String> loadingData()
 {
 try
 {
 Thread.sleep(5000);
 } catch (InterruptedException e)
 {
 }
 return new ArrayList<String>(Arrays.asList("通过Fragment保存大量数据",
 "onSaveInstanceState保存数据",
 "getLastNonConfigurationInstance已经被弃用", "RabbitMQ", "Hadoop",
 "Spark"));
 }
 /**
 * 设置Activity，因为Activity会一直变化
 *
 * @param activity
 */
 public void setActivity(Context activity)
 { weakReference = new WeakReference<>(activity);
 // 设置为当前的Activity
 this.activity = (FixProblemsActivity) activity;
 // 开启一个与当前Activity绑定的等待框
 if (activity != null && !isCompleted)
 {
 mLoadingDialog = new LoadingDialog();
 mLoadingDialog.show(this.activity.getFragmentManager(), "LOADING");
 }
 // 如果完成，通知Activity
 if (isCompleted)
 {
 notifyActivityTaskCompleted();
 }
 }
 /**
 * 在Activity不可见时，关闭dialog
 */
 public void dialogDismiss(){
 if(mLoadingDialog != null){
 mLoadingDialog.dismiss();
 }
 }
 private void notifyActivityTaskCompleted()
 {
 if (null != activity)
 {
 activity.onTaskCompleted();
 }
 }
}

public class FixProblemsActivity extends ListActivity
{
 private static final String TAG = "MainActivity";
 private ListAdapter mAdapter;
 private List<String> mDatas;
 private OtherRetainedFragment dataFragment;
 private MyAsyncTask mMyTask;
 @Override
 public void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 Log.e(TAG, "onCreate");
 // find the retained fragment on activity restarts
 FragmentManager fm = getFragmentManager();
 dataFragment = (OtherRetainedFragment) fm.findFragmentByTag("data");
 // create the fragment and data the first time
 if (dataFragment == null)
 {
 // add the fragment
 dataFragment = new OtherRetainedFragment();
 fm.beginTransaction().add(dataFragment, "data").commit();
 }
 mMyTask = dataFragment.getData();
 if (mMyTask != null)
 { //与新的Activity进行绑定
 mMyTask.setActivity(this);
 } else { //启动一个新的
 mMyTask = new MyAsyncTask(this);
 dataFragment.setData(mMyTask);
 mMyTask.execute();
 }
 // the data is available in dataFragment.getData()
 }
 @Override
 protected void onRestoreInstanceState(Bundle state)
 {
 super.onRestoreInstanceState(state);
 Log.e(TAG, "onRestoreInstanceState");
 }
 @Override
 protected void onDestroy()
 {
 Log.e(TAG, "onDestroy");
 super.onDestroy();
 }
 @Override
 //在这里关闭Dialog，否则容易造成内存泄漏
 protected void onPause() {
 super.onPause();
 mMyTask.dialogDismiss();
 }
 /**
 * 回调方法，更新UI
 * 这里如果在加载的过程中按下返回键返回主Activity时，会出现异常，setAdapter on a null object reference。因为activity被销毁，
 * 要解决这个问题，可以监听返回键事件做相应处理。
 */
 public void onTaskCompleted()
 {
 mDatas = mMyTask.getItems();
 mAdapter = new ArrayAdapter<String>(FixProblemsActivity.this,
 android.R.layout.simple_list_item_1, mDatas);
 setListAdapter(mAdapter);
 }
}