我如何以其他方式使变量读取而不是使其变为全局变量

Question

为什么sum变量不能读入if语句，我认为是有效的。 我的问题是如何让它在if语句中可读。

private int r1, r2, num1, num2, num3, sum; /*I set it global but it cant
private int count = 0;                       /*read inside of onClickButton

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

}
private void giveNewRandom() {
    Random rand = new Random();
    r1 = rand.nextInt(100);
    r2 = rand.nextInt(100);

    TextView e1 = (TextView) findViewById(R.id.textView5);
    e1.setText(Integer.toString(r1));
    TextView e2 = (TextView) findViewById(R.id.textView6);
    e2.setText(Integer.toString(r2));
    num1 = Integer.parseInt(e1.getText().toString());
    num2 = Integer.parseInt(e2.getText().toString());
    sum = num1 + num2;
    EditText e3 = (EditText) findViewById(R.id.editText5);
    num3 = Integer.parseInt(e3.getText().toString());
}

public void onButtonClick(View v) {
    if (num3 == sum){                /*sum become red when I set it local
        count ++;}
     else{
        count --;}
        TextView t1 = (TextView) findViewById(R.id.textView4);
        t1.setText(""+ count);
        giveNewRandom();
}

帮助我们。提前谢谢^ _ ^