如何將多個edittext值傳遞到Arraylist中，然后將其發送到另一個活動？

Question

我試圖將5個edittext值傳遞到Arraylist ，然后將其發送到另一個活動。 我使用Intent將其發送到下一個活動，但是它一直崩潰。 我收到此錯誤：

java.lang.NullPointerException：嘗試從空數組讀取

我認為我將值添加到arraylist的方式是錯誤的，或者在意圖中發送arraylist出現了問題。

活動1：

EditText p1, p2, p3, p4, p5;
ArrayList<String> playerList = new ArrayList<>();
BootstrapButton btnStart;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    btnStart = (BootstrapButton) findViewById(R.id.start);
    p1 = (EditText) findViewById(R.id.player1);
    p2 = (EditText) findViewById(R.id.player2);
    p3 = (EditText) findViewById(R.id.player3);
    p4 = (EditText) findViewById(R.id.player4);
    p5 = (EditText) findViewById(R.id.player5);

    playerList.add(p1.getText().toString());
    playerList.add(p2.getText().toString());
    playerList.add(p3.getText().toString());
    playerList.add(p4.getText().toString());
    playerList.add(p5.getText().toString());

    btnStart.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            Intent myIntent = new Intent(MainActivity.this, GameActivity.class);
            myIntent.putStringArrayListExtra("player_list", playerList);
            MainActivity.this.startActivity(myIntent);
        }

    });
  }

活動2：

TextView playerName;
ArrayList<String> playerList = new ArrayList<>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_game);
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);

    playerName = (TextView) findViewById(R.id.playerName);

    Intent myIntent = getIntent();
    if(myIntent != null){
        playerList = myIntent.getStringArrayListExtra("player_list");
        playerName.setText(playerList.get(0));
    }
  }

當我將其與硬編碼數組值一起使用時，它不會崩潰，並且該值將在下一個活動中正確打印出來。

活動1：

String[] array1={"asd","fgh","dcf","dg","ere","dsf"};
Intent myIntent = new Intent(MainActivity.this, GameActivity.class);
myIntent.putExtra("player_list", array1);
MainActivity.this.startActivity(myIntent);

活動2：

    Intent myIntent = getIntent();
    if(myIntent != null){
        String[] players = myIntent.getStringArrayExtra("player_list");
        playerName.setText(players[2]);
    }else{
        System.out.println("Error!");
    }

我想要做的是擁有一個像這樣的Arraylist ["p1","p2","p3","p4","p5"] ，然后在下一個活動中檢索該arraylist並從該數組中打印出一個隨機名稱。

Answer 1

使用getStringArrayListExtra而不是getStringArrayExtra

if(myIntent != null){
        String[] players = myIntent.getStringArrayListExtra("player_list");
        playerName.setText(players[2]);
    }

Answer 2

在活動1中使用intent.putStringArrayListExtra發送並在活動2中使用getStringArrayListExtra()檢索字符串ArrayList。

這是這樣做的代碼：

活動1：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    btnStart = (BootstrapButton) findViewById(R.id.start);
    p1 = (EditText) findViewById(R.id.player1);
    p2 = (EditText) findViewById(R.id.player2);
    p3 = (EditText) findViewById(R.id.player3);
    p4 = (EditText) findViewById(R.id.player4);
    p5 = (EditText) findViewById(R.id.player5);

    playerList.add(p1.getText().toString());
    playerList.add(p2.getText().toString());
    playerList.add(p3.getText().toString());
    playerList.add(p4.getText().toString());
    playerList.add(p5.getText().toString());

    btnStart.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            Intent myIntent = new Intent(MainActivity.this, GameActivity.class);
            myIntent.putStringArrayListExtra("player_list", playerList);
            MainActivity.this.startActivity(myIntent);
        }

    });
  }

活動2：

    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_game);
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);

    playerName = (TextView) findViewById(R.id.playerName);

    Intent myIntent = getIntent();
    if(myIntent != null){
            ArrayList<String> players = myIntent.getStringArrayListExtra("player_list");
            playerName.setText(players.get(0));
        }else{
            System.out.println("Error!");
        }
      }

還要確保playerList被聲明和初始化。 您的代碼沒有顯示它已被聲明或初始化。