对话框：在后台切换活动

Question

Can I start an activity in the background of a dialog?

What I would like: Activity starts dialog, dialog swaps activity shown in the background. The dialog is not dismissed.

I think this can only be done when Dialog is also an Activity.

What I thought was a solution:

1. I send a localbroadcast from DialogActivity to Act 1
2. Act 1 starts Act 2 and destroys itself.

Problem: Act 2 will be shown in front of DialogActivity. I want it to switch at the back.

Is this possible?

Answer 1

Follow these couple of points to have a working solution:

1. To make the dialog's window appear on top of all the application windows, set its window type as system window.
2. Use the application context to create the dialog. If you use the activity context to create the dialog, the moment activity is finished, the dialog will also be terminated, as it is considered as window leakage by the system.

Here is the sample code which demonstrates the working solution.

// This is a button click handler.
public void launchDialog(final View v) {
    // Create the dialog with application context
    AlertDialog dialog = new AlertDialog.Builder(getApplicationContext())
            .setTitle("Title")
            .setMessage("This is dialog")
            .create();
    // Set the window type as system window
    dialog.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);
    dialog.show();

    // Demonstrates the activity change behind the dialog.
    v.postDelayed(new Runnable() {
        @Override
        public void run() {
            Intent intent = new Intent(v.getContext(), MyActivity2.class);
            startActivity(intent);

            finish();
        }
    }, 3000);
}

Remember to set the permissions in manifest to use system windows:

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />