在Java中传递引用

Question

我有这个纸牌游戏,我将所有玩家存储在一个List.为了找出我想与谁一起行动的玩家,每个玩家都有一个Card(我可以得到卡片名称),a name(我可以得到玩家的名字),但每个玩家都有一个独特的ID.

现在,在我的onCreate()方法开始时,我找到并将列表的播放器分配给播放器Player clairvoyant:

public void initializeCharacters() {
    for (Player player : players) {
        if (player.getCardName().equals("Clairvoyant")) {
            clairvoyant = player;
        }
}

---

游戏在夜晚和白天之间切换.透视力的转折是在夜间,我用一个开关来确定何时轮到谁.

现在,在开始千里眼之前,我会检查他是否还活着,在否定的情况下,我只是跳过他的回合:

case 2:
                    clairvoyant(); // Clairvoyant's turn
                    Toast.makeText(Game.this, String.valueOf(clairvoyant.getLifeStatus()), Toast.LENGTH_SHORT).show();
                    if(clairvoyant.getLifeStatus()) {
                    /* --- Let him choose ---*/
                        Intent intent = new Intent(this, ListPlayersClairvoyant.class);
                        Bundle bundle = new Bundle();
                        bundle.putSerializable("PLAYERS", (Serializable) players);
                        intent.putExtras(bundle);
                        startActivityForResult(intent, REQUEST_CLAIRVOYANT);
                    /* --------------------- */
                    }
                    nightInsideCounter++;
                    if(medium == null) {
                        nightInsideCounter++;
                    }
                    if(guard == null) {
                        nightInsideCounter++;
                    }
                    break;

然而,我添加了Toasts,看看当我还活着的时候我会杀死玩家,但即使在列表中搜索到的玩家被杀死,先前创建的Clairvoyant玩家也不会.
所以基本上,带有透视牌的名单中的玩家已经死了 ; 但是,在开始轮到他之前初次确定的透视球员仍然活着!

我不明白为什么.有什么我想念的吗？那是我做过参考吗？在这种情况下,我应该如何创建它的引用？

---

编辑:

现在一切正常,我已经在Player Class和Card上实现了Parcelable接口.问题是当我从ListPlayersVote Activity到第一个游戏(主要的一个)的意图时,应用程序崩溃并且我收到此错误:

java.lang.NullPointerException:尝试在android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:401)上的空对象引用上调用虚方法'java.lang.String java.lang.Object.toString()'

[...] //许多其他链接,跳过

这是一个简单的NullPointer异常,但我没有链接到我的错误代码,而是我得到了其他脚本的所有其他链接(可能已经制作,而不是我)这让我卡住了,我怎么想修复如果我没有得到任何链接到我的代码？

---

资源

投票活动

球员类

我如何检索传递的ArrayLists,并检查它们的值(这是一个StartActivityForResult()):

    /* ------------------------------------------ */
    /* ---------- If they want to VOTE ---------- */
    /* ------------------------------------------ */
    if(requestCode == REQUEST_VOTE) {

        if(resultCode == Activity.RESULT_OK) {
            // Get the Player clicked
            ArrayList<Player> highestList = data.getParcelableArrayListExtra("HIGHEST");
            ArrayList<Player> highestList1 = data.getParcelableArrayListExtra("HIGHEST1");
            System.out.println("[5] The players of the first list are " + highestList.size() + ".");
            System.out.println("[6] The players of the second list are " + highestList1.size() + ".");

            // Add the most voted players to a signle List, highest
                highest.addAll(highestList);
                highestList.clear();

                highest.addAll(highestList1);
                highestList1.clear();

            // Write the names in chat
            write("Il villaggio ha i propri sospettati:");
            for (Player player : highest){
                write(player.getName());
            }
            System.out.println("[7] The players chosen are " + highest.size() + ".");
            highest.clear();

        } else if (resultCode == Activity.RESULT_CANCELED) {
            // Some stuff that will happen if there's no result
        }

    }

Answer 1

问题是，当我从 ListPlayersVote Activity 到达游戏（主要活动）的意图时，应用程序崩溃并收到此错误：

正如我在评论中所说，ArrayAdapter当适配器与其中包含空值的数据列表一起使用时，会发生与该类相关的异常。查看您的代码，罪魁祸首似乎是一个 Player 对象，该对象没有在ListPlayersVote类中初始化其字段。在该类中，您当前的代码几乎总是会引入未初始化的 Player 对象引用。在ListPlayersVote的onCreate()回调中，您首先将两个 Player 对象添加到持有者列表中，我假设将其作为进一步计算的基础：

// remove the lines below , there's no need for them
// also simply doing new Player() will result in a Player which doesn't have    
// its fields initialized(and you don't update them later either)
highestList.add(new Player()); // is there a reason for adding this empty players?
highestList1.add(new Player());

然后在 onEntryClick() 回调中更新您的代码以正确处理玩家投票的计数：

for (Player player1 : players){ // For each player
  // first of all you need to move the initialization for highest and highest1 INSIDE the
  // for loop to use the proper highest values at each iteration
  // With your current code the lists highestlist and highestlis1 each have
  // ONE Player object which is empty (because in the default constructor 
  // of Player you do nothing), you then use the empty initial Player in each list to
  // compare the vote count, this will mostly result in the first if  
  // clause(playerCount > highest) being triggered,
  // which will add the initial empty Player object to highestlist1
  int highest = highestList.size() == 0 ? -1 : highestList.get(0).getCount();// if the list is empty initialize it with -1 to signal the first player handled
  int highest1 = highestList1.size() == 0 ? -1 : highestList1.get(0).getCount();

  int playerCount = player1.getCount(); // Get his votes

    // you need to check for -1 to handle the case when you're dealing 
    // with the first player( which of course will have the highest 
    // count as there's no either player to compare it yet)
    if(playerCount > highest || highest == -1){ // If they're the highest so far, add it to the 1st list
        highestList1.addAll(highestList);
        highestList.clear();
        highestList.add(player1);
        // the same for highest1
    } else if (playerCount > highest1 || highest1 == -1){ // If they're the 2nd highest so far, add it to the 2nd list
        highestList1.clear();
        highestList1.add(player1);
    }else if(playerCount == highest){ // If they're equal to the current highest one, add it to the 1st list as well
        highestList1.add(player1);
    } else if (playerCount == highest1){ // If they're equal to the current 2nd highest one, add it to the 2nd list as well
        highestList1.add(player1);
    }