Android：对话强制在创建时关闭

Question

Goal is to make a dialog that appears on menu_key pressed, but it keeps force closing. I consulted the official FAQ on Dialogs , but no luck. Everything was done as explained there, but it still fails as soon as the button is pressed. Here is the creation of the dialog:

static final int Choice_ID = 0;

    protected Dialog onCreateDialog(int id) {
        Dialog dialog = null;
        switch(id) {
        case Choice_ID:
            // do the work to define the pause Dialog
            AlertDialog.Builder builder = new AlertDialog.Builder(this);
            builder.setMessage("TEST DIALOG")
                   .setCancelable(true);

            AlertDialog alert = builder.create();
            break;

        //default:
            //dialog = null;
        }
        return dialog;
    }

And the part about showing looks like this:

public boolean onKeyDown(int keyCode, KeyEvent event) {

        if (keyCode == KeyEvent.KEYCODE_MENU) {
            showDialog(Choice_ID);

        };
};

Answer 1

This should not cause a force close, but you can see the menu if you try setting the value of dialog :

dialog = builder.create();

As in:

protected Dialog onCreateDialog(int id) {
    Dialog dialog = null;
    switch(id) {
    case Choice_ID:
        // do the work to define the pause Dialog
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setMessage("TEST DIALOG")
               .setCancelable(true);

        dialog = builder.create();
        break;

    //default:
        //dialog = null;
    }
    return dialog;
}