Android RetainFragment状态保存的方法

android:configChanges="locale|layoutDirection"

android:configChanges="orientation|keyboard|screenSize"

public class NetWorkTask extends Thread {
  private volatile ProgressUpdateLinster progressUpdateLinster;
  private Handler handler = new Handler(Looper.getMainLooper());

  public NetWorkTask(ProgressUpdateLinster progressUpdateLinster) {
    this.progressUpdateLinster = progressUpdateLinster;
  }

  private int progress = 0;
  @Override
  public void run() {
    while (progress <= 100) {
      if(progressUpdateLinster != null) {
        handler.post(new Runnable() {
         @Override
          public void run() {
            progressUpdateLinster.updateProgress(progress);
          }
        });
      }
      try {
        Thread.sleep(200);
      } catch (InterruptedException e) {
        return;
      }
      progress += 2;
    }
  }

  public interface ProgressUpdateLinster {
    void updateProgress(int progress);
  }

  public void cacel() {
    interrupt();
  }
  public void setProgressUpdateLinster(ProgressUpdateLinster progressUpdateLinster) {  
    this.progressUpdateLinster = progressUpdateLinster;
  }
}

private ProgressBar progressBar;
private TextView textView;
private static final String TAG = "MainActivity";

NetWorkTask netWorkTask = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  progressBar = (ProgressBar) findViewById(R.id.progressbar);
  textView = (TextView) findViewById(R.id.tv_progroess);

  if(getLastCustomNonConfigurationInstance() != null
      && getLastCustomNonConfigurationInstance() instanceof NetWorkTask) {

    this.netWorkTask = (NetWorkTask) getLastCustomNonConfigurationInstance(); //获取保存的任务
    this.netWorkTask.setProgressUpdateLinster(linster);
  }else {
    this.netWorkTask = new NetWorkTask();
    netWorkTask.setProgressUpdateLinster(linster);
    netWorkTask.start();
  }

}

private NetWorkTask.ProgressUpdateLinster linster = new NetWorkTask.ProgressUpdateLinster() {
  @Override
  public void updateProgress(int progress) {
    progressBar.setProgress(progress);
    textView.setText(progress+"%");
    Log.d(TAG,MainActivity.this.toString());
  }
};

/**
* 保存任务
*/
@Override
public Object onRetainCustomNonConfigurationInstance() {
  return netWorkTask;
}

public class WorkFragment extends Fragment {

NetWorkTask netWorkTask = null;

/**
 * 重建之后这里的Context会自动替换成新的Activity
 * @param context
 */
@Override
public void onAttach(Context context) {
  super.onAttach(context);
  //第一次启动的时候，这里network还没有初始化
  //Activity重建之后，更新回调
  if(netWorkTask != null) {
    netWorkTask.setProgressUpdateLinster((NetWorkTask.ProgressUpdateLinster) context);
  }
}

@Override
public void onDetach() {
  super.onDetach();
  netWorkTask.setProgressUpdateLinster(null);
}

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
  super.onCreate(savedInstanceState); //重建之后不再会调用此方法
  //设置为retain instance Fragment
  setRetainInstance(true);
  netWorkTask = new NetWorkTask();
  netWorkTask.setProgressUpdateLinster((NetWorkTask.ProgressUpdateLinster) getActivity());
  netWorkTask.start();
}
}

public class MainActivity extends AppCompatActivity implements NetWorkTask.ProgressUpdateLinster {

private ProgressBar progressBar;
private TextView textView;
private static final String TAG = "MainActivity";
private static final String TAG_TASK_FRAGMENT = "work";

@Override
protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  progressBar = (ProgressBar) findViewById(R.id.progressbar);
  textView = (TextView) findViewById(R.id.tv_progroess);
  
  //如果已经有了work fragment，那就不需要再新建了
  if(getSupportFragmentManager().findFragmentByTag(TAG_TASK_FRAGMENT) == null) {
    getSupportFragmentManager().beginTransaction().add(new WorkFragment(),TAG_TASK_FRAGMENT).commit();
  }
}

@Override
public void updateProgress(int progress) {
  progressBar.setProgress(progress);
  textView.setText(progress+"%");
}
}