如何等待 Android 对话框完成？

Question

我正在做一个逃脱游戏，我有一个 useObjectButton。 单击时，它会显示一个带有 ListView 的对话框，我希望它在玩家单击对话框的某个项目后更新信息。 但是，它会立即更新，我不知道如何修复它。

我的对话框如下所示：

public Inventory.ITEM selectItem() {

        if (game.inventory.isEmpty()) {

            Toast.makeText(this, "Inventory is empty", Toast.LENGTH_SHORT).show();
            return null;

        } else {

            AlertDialog inventoryDialog;
            AlertDialog.Builder inventoryDialogBuilder = new AlertDialog.Builder(ActivityGame.this);
            View inventoryPopup = getLayoutInflater().inflate(R.layout.inventory, null, false);

            inventoryDialogBuilder.setView(inventoryPopup);
            inventoryDialog = inventoryDialogBuilder.create();
            inventoryDialog.setCancelable(true);

            ListView lvInventory = inventoryPopup.findViewById(R.id.inventory_lv);

            if (!game.inventory.isEmpty()) {

                ArrayAdapter adapter = new ArrayAdapter(ActivityGame.this, android.R.layout.simple_list_item_1, game.inventory.getInventory());
                lvInventory.setAdapter(adapter);
                   
                lvInventory.setOnItemClickListener((parent, view, position, id) -> {
                    selectedItem = game.inventory.getItem(position);
                    inventoryDialog.dismiss();    
                });    

                inventoryDialog.show();

            }
        }
}

我在各种函数中调用它，例如：

btnUseObject.setOnClickListener(v -> {
            Inventory.ITEM item=selectItem();
            info.setText(game.nightStand.useObject(item));
            if(game.nightStand.isUnlocked()) {
                btnDrawer1.setEnabled(true);
                btnDrawer2.setEnabled(true);
            }
        });

Answer 1

首先，您必须了解这些指令的异步性质：

Inventory.ITEM item=selectItem();

和

lvInventory.setOnItemClickListener((parent, view, position, id) -> {
    selectedItem = game.inventory.getItem(position);
    inventoryDialog.dismiss();    
});

您不能让此方法返回 selectedItem 的值，因为它在执行时是未知的。 将单击侦听器绑定到按钮的时间与用户实际单击按钮的操作不同。 你应该做的是给一个 function 作为异步 function 的参数，当用户单击按钮时，它会被调用。 像这样的东西：

    public void selectItem(Consumer callbackFn) {
        if (game.inventory.isEmpty()) {
            Toast.makeText(this, "Inventory is empty", Toast.LENGTH_SHORT).show();
            return;
        }
        
        AlertDialog inventoryDialog;
        AlertDialog.Builder inventoryDialogBuilder = new AlertDialog.Builder(ActivityGame.this);
        View inventoryPopup = getLayoutInflater().inflate(R.layout.inventory, null, false);
    
        inventoryDialogBuilder.setView(inventoryPopup);
        inventoryDialog = inventoryDialogBuilder.create();
        inventoryDialog.setCancelable(true);
    
        ListView lvInventory = inventoryPopup.findViewById(R.id.inventory_lv);
        ArrayAdapter adapter = new ArrayAdapter(ActivityGame.this, android.R.layout.simple_list_item_1, game.inventory.getInventory());
        lvInventory.setAdapter(adapter);
            
        lvInventory.setOnItemClickListener((parent, view, position, id) -> {
            // The asynchronous function that gets called whenever an user clicks a button. 
            // You cannot return a value from it because it is not immediately known at execution time.
            callbackFn.accept(game.inventory.getItem(position));
            inventoryDialog.dismiss();    
        });
    
    inventoryDialog.show();
}

接着

btnUseObject.setOnClickListener(v -> {
    Consumer callbackFn = (Inventory.ITEM item) -> {
        info.setText(game.nightStand.useObject(item));
        if (game.nightStand.isUnlocked()) {
            btnDrawer1.setEnabled(true);
            btnDrawer2.setEnabled(true);
        }
    };

    selectItem(callbackFn); // When an user clicks the button, please execute my callback function
});