无法解析 setText 方法

Question

这是程序。最后一行显示错误，如无法解析setText和toString 。

 public void onButtonClick(View v){}
 EditText e1=(EditText)findViewById(R.id.editText);
 EditText e2=(EditText)findViewById(R.id.editText2);
 TextView t1=(TextView)findViewById(R.id.textView);
 int num1 = Integer.parseInt(e1.getText().toString());
 int num2 = Integer.parseInt(e2.getText().toString());
 int sum = num1 + num2;
 t1.setText(Integer.toString(sum));

Answer 1

以下应该工作：

   public void onButtonClick(View v){
        EditText e1=(EditText)findViewById(R.id.editText);
        EditText e2=(EditText)findViewById(R.id.editText2);
        TextView t1=(TextView)findViewById(R.id.textView);
        int num1 = Integer.parseInt(e1.getText().toString());
        int num2 = Integer.parseInt(e2.getText().toString());
        int sum = num1 + num2;
        t1.setText(Integer.toString(sum));
    }

Answer 2

这工作改变数据类型

public void onButtonClick(View v){
        EditText e1=(EditText)findViewById(R.id.editText);
        EditText e2=(EditText)findViewById(R.id.editText2);
        TextView t1=(TextView)findViewById(R.id.textView);
        Integer num1 = Integer.parseInt(e1.getText().toString());
        Integer num2 = Integer.parseInt(e2.getText().toString());
        Integer sum = num1 + num2;
        t1.setText(Integer.toString(sum));
    }