对话框打开时如何处理屏幕方向变化？

Question

I have an android app which is already handling changes for orientation, ie there is a android:configChanges="orientation" in the manifest and an onConfigurationChange() handler in the activity that switches to the appropriate layout and preps it. I have a landscape / portrait version of the layout.

The problem I face is that the activity has a dialog which could be open when the user rotates the device orientation. I also have a landscape / portrait version of the dialog.

Should I go about changing the layout of the dialog on the fly or perhaps locking the activity's rotation until the user dismisses the dialog.

The latter option of locking the app appeals to me since it saves having to do anything special in the dialog. I am supposing that I might disable the orientation when a dialog opens, such as

setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_NOSENSOR);

and then when it dismisses

setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR);

Would that be a sensible thing to do? If the screen orientation did change while it was locked, would it immediately sense the orientation change when it was unlocked?

Are there alternatives?

Answer 1

I would recommend not turning off the screen rotation, instead of this handle the configuration changes for the Dialog. You could use one of these two approach for this:

The first one is using a flag variable in onSaveInstanceState(outState) method, and restore the dialog onCreate(bundle) method:

in this example my flag variable is called 'isShowing Dialog', when the onCreate method is called by the android System for first time, the bundle argument will be null and nothing happens. However when the activity it's recreated by a configuration change (screen rotation), the bundle will have the boolean value isShowing Dialog, previously saved by the inSaveInstanceState(...) method, so if the variable gets true the dialog is created again, the trick here is set the flag in true when the dialog get showing, and false when it's not, is a little but simple trick.

Class MyClass extends Activity {
    Boolean isShowingDialog = false;
    AlertDialog myDialog;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        if(savedInstanceState!=null){
            isShowingDialog = savedInstanceState.getBoolean("IS_SHOWING_DIALOG", false);
            if(isShowingDialog){
                createDialog();
            }
        }

    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        outState.putBoolean("IS_SHOWING_DIALOG", isShowingDialog);
        super.onSaveInstanceState(outState);
    }

    @Override
    protected void onPause() {
        if(myDialog!=null && myDialog.isShowing()) {
            myDialog.dismiss();
        }
    }

    private void createDialog() {
        AlertDialog.Builder dialog_builder = new AlertDialog.Builder(this);
        dialog_builder.setTitle("Some Title"):
        ... more dialog settings ...

        myDialog = dialog_builder.create();
        myDialog.show();
        isShowingDialog = true;
    }

    private void hideDialog(){
        myDialog.dismiss();
        isShowingDialog = false;
    }
}

The second approach is to use the ability of the fragments components to retain its states, the main idea is create the dialog inside a fragment, there is the problem about detach and reattach the fragment during the configuration changes (because you need dismiss and show the dialog correctly), but the solution is very similar to the first approach. The advantage of this approach is that if you have an AlertDialog with a couple of configurations, when the fragment is recreated there is not needed to create and setting up the dialog again, only make it show() and the AlertDialog state is maintained by the fragment.

I hope this helps.

Answer 2

I suggest your Dialog should override onSaveInstanceState() and onRestoreInstanceState(Bundle) to save its state into a Bundle.

You then override those methods in your Activity, checking if the Dialog is shown and if so - calling the dialog's methods to save and restore it's state.

If you are displaying this dialog from a fragment, you will want to override OnActivityCreated(Bundle) instead of OnRestoreInstanceState .

For a source example see the built-in clock app provided with Android, where the SetAlarm Activity handles the TimePickerDialog this way.

Answer 3

If you are handling orientation changes yourself, then here is an approach.

I won't claim that this is an elegant solution, but it works:

You can keep track of whether the dialog has an active instance inside the dialog class itself, by using a static variable activeInstance, and overriding onStart() to set activeInstance = this and onCancel() to set activeInstance = null.

Provide a static method updateConfigurationForAnyCurrentInstance() that tests that activeInstance variable and, if non-null, invokes a method activeInstance.reInitializeDialog(), which is a method that you will write to contain the setContentView() call plus the code that wires the handlers for the dialog controls (button onClick handlers, etc. - this is code that would normally appear in onCreate()). Following that, you would restore any displayed data to those controls (from member variables in your dialog object). So, for example, if you had a list of items to be viewed, and the user were viewing item three of that list before the orientation change, you would re-display that same item three at the end of updateConfigurationForAnyCurrentInstance(), right after re-loading the controls from the dialog resource and re-wiring the control handlers.

You would then call that same reInitializeDialog() method from onCreate(), right after super.onCreate(), and place your onCreate()-specific initialization code (eg, setting up the list of items from which the user could choose, as described above) after that call.

This will cause the appropriate resource (portrait or landscape) for the dialog's new orientation to be loaded (provided that you have two resources defined having the same name, one in the layout folder and the other in the layout-land folder, as usual).

Here's some code that would be in a class called YourDialog:

ArrayList<String> listOfPossibleChoices = null;
int currentUserChoice = 0;

static private YourDialog activeInstance = null;

@Override
protected void onStart() {
  super.onStart();
  activeInstance = this;
}

@Override
public void cancel() {
  super.cancel();
  activeInstance = null;
}


static public void updateConfigurationForAnyCurrentInstance() {
    if(activeInstance != null) {
        activeInstance.reInitializeDialog();
        displayCurrentUserChoice();
    }
}

private void reInitializeDialog() {
  setContentView(R.layout.your_dialog);
  btnClose = (Button) findViewById(R.id.btnClose);
  btnClose.setOnClickListener(this);
  btnNextChoice = (Button) findViewById(R.id.btnNextChoice);
  btnNextChoice.setOnClickListener(this);
  btnPriorChoice = (Button) findViewById(R.id.btnPriorChoice);
  btnPriorChoice.setOnClickListener(this);
  tvCurrentChoice = (TextView) findViewById(R.id.tvCurrentChoice);
}

private void displayCurrentUserChoice() {
  tvCurrentChoice.setText(listOfPossibleChoices.get(currentUserChoice));
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    reInitializeDialog();
    listOfPossibleChoices = new ArrayList<String>();
    listOfPossibleChoices.add("One");
    listOfPossibleChoices.add("Two");
    listOfPossibleChoices.add("Three");
    currentUserChoice = 0;
    displayCurrentUserChoice();
}

@Override
public void onClick(View v) {
    int viewID = v.getId();

    if(viewID == R.id.btnNextChoice) {
      if(currentUserChoice < (listOfPossibleChoices.size() - 1))
        currentUserChoice++;
        displayCurrentUserChoice();
      }
    }
    else if(viewID == R.id.btnPriorChoice) {
      if(currentUserChoice > 0) {
        currentUserChoice--;
        displayCurrentUserChoice();
      }
    }
    Etc.

Then, in your main activity's onConfigurationChanged() method, you would just invoke YourDialog.updateConfigurationForAnyCurrentInstance() whenever onConfigurationChanged() is called by the OS.

Answer 4

Doesn't seem the title was ever resolved (Google Necro Direct).

Here is the solution, matching the request.

When your activity is created, log the screen orientation value. when onConfiguration change is called on your activity, compare the orientation values. if the values don't match, fire off all of your orientation change listeners, THEN record the new orientation value.

Here is some constructive code to put in your activity (or any object that can handle configuration change events)

int orientation; // TODO: record orientation here in your on create using Activity.this.getRequestedOrientation() to initialize!

public int getOrientation(){return orientation;}
public interface OrientationChangeListener {
    void onOrientationChange();
}
Stack<OrientationChangeListener> orientationChangeListeners = new Stack<>();
public void addOrientationChangeListener(OrientationChangeListener ocl){ ... }
public void removeOrientationChangeListener(OrientationChangeListener ocl){ ... }

That's the basic environment. Here's your executive:

public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    if (orientation != newConfig.orientation)
        for (OrientationChangeListener ocl:orientationChangeListeners) ocl.onOrientationChange();
    orientation = newConfig.orientation;
}

In YOUR code model, you may need to send the new configuration, with the event, or the two orientation values with the event. However, Activity.this.getOrientation().= Activity.this.getRequestedOrientation() during event handling (because we are in a logical state of change between two logical values).

In review of my post, i have determined that there could be some synchronization issues, with multiple events, This is not a fault of this code, but a fault of "Android Platform" for not having defacto orientation sense handlers on every window. thusly trashing the polymorphic benefits of using java in the first place..

Answer 5

See the answer from Viktor Valencia above. That will work perfectly with the slight adjustment that you move the createDialog() to onResume.

@Override
protected void onResume() {
    super.onResume();
    if(isShowingDialog){
        createDialog();
    }
}

Fetch the boolean isShowingDialog value at onCreate, as suggested, but wait for onResume to display the dialog.