Question

我想在onClick方法上放置ArrayList。但它告诉我，我应该将arraylist改为final（我会把东西放在那里，所以不能）。我该怎么把arraylist放进去呢？

  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    final TextView txt1;
    Button btn1;


     ArrayList <String> shop= new ArrayList <String>();
    impshop(shop);

    txt1 =(TextView)findViewById(R.id.tv1);
    btn1 =(Button)findViewById(R.id.button1);

    btn1.setOnClickListener(new OnClickListener(){

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            Random ran = new Random();
            int choose = ran.nextInt(shop.size());  
            txt1.setText(shop.get(choose));
        }});

}

我可以点击（查看v，ArrayList商店）吗？

Answer 1

除了将final添加到ArrayList之外，您还可以在onCreate方法之外定义它。这样做不需要您定义final修饰符。

虽然请确保不使用ArrayList来存储属于Activity的上下文的元素或可能链接到应用程序的其他上下文的元素，否则可能会导致在大内存泄漏。

Answer 2

在

之前添加final

ArrayList <String> shop= new ArrayList <String>();

所以它看起来像：

final ArrayList <String> shop= new ArrayList <String>();

Answer 3

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    final TextView txt1;
    Button btn1;

    final ArrayList <String> shop= new ArrayList <String>();
    impshop(shop);

    txt1 =(TextView)findViewById(R.id.tv1);
    btn1 =(Button)findViewById(R.id.button1);

    btn1.setOnClickListener(new OnClickListener(){

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        Random ran = new Random();
        int choose = ran.nextInt(shop.size());  
        txt1.setText(shop.get(choose));
    }});
}

或将ArrayList声明为字段

如何在按钮onclick方法上放置arraylist？

3 个答案: