无法为对象解析此符号

Question

在 OnCreate() 中创建对象 RadioGroup 时，稍后在另一个函数中调用此对象时，会显示错误“无法解析此符号”

这里是java代码 MainActivity.java

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        RadioGroup group1 = (RadioGroup)findViewById(R.id.que1_rG);
        RadioGroup group2 = (RadioGroup)findViewById(R.id.que2rG);
        RadioGroup group3 = (RadioGroup)findViewById(R.id.que3rG);
        RadioGroup group4 = (RadioGroup)findViewById(R.id.que4rG);
        RadioGroup group5 = (RadioGroup)findViewById(R.id.que5rG);
        RadioGroup group6 = (RadioGroup)findViewById(R.id.que6rG);
        RadioGroup group7 = (RadioGroup)findViewById(R.id.que7rG);
        RadioGroup group8 = (RadioGroup)findViewById(R.id.que8rG);
        RadioGroup group9 = (RadioGroup)findViewById(R.id.que9rG);
        RadioGroup group10 = (RadioGroup)findViewById(R.id.que10rG);
    }

    public void submitButton(View view)
    {
        int checkedRadio1= group1.getCheckedRadioButtonId();
        Toast.makeText(this,"Score is : " + score,Toast.LENGTH_SHORT);
        Log.v("MainActivity","Score is  " + score);
        score = 0;
    }

Answer 1

你得到无法解析符号的原因是你没有在班级级别声明你的RadioGroup group1。由于您已在onCreate 中声明和分配，因此其范围仅限于onCreate()。要在其他方法中访问，请将其作为类成员。

如下声明RadioGroup group1为类成员：

public class MainAcivity extends Activity{
    private RadioGroup group1;
    //Declare other RadioGroup group2,group3...group 10. if you intend
    //to access them outside of onCreate()
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        group1 = (RadioGroup)findViewById(R.id.que1_rG);
        ...
    }
      public void submitButton(View view) {
        int checkedRadio1= group1.getCheckedRadioButtonId();
        Toast.makeText(this,"Score is : " + score,Toast.LENGTH_SHORT).show();
        Log.v("MainActivity","Score is  " + score);
        score = 0;
    }
}

注意： 同样的事情也适用于您想在onCreate() 之外访问的任何其他RadioGroup。

在尝试显示 Toast 时，您还缺少对 show() 方法的调用。如果不调用show()，则不会显示 Toast 消息。

代替

Toast.makeText(this,"Score is : " + score,Toast.LENGTH_SHORT)

使用

Toast.makeText(this,"Score is : " + score,Toast.LENGTH_SHORT).show()

Answer 2

在类级别声明单选组按钮。您在函数级别使用 veriable，因此您不能在函数之外使用该变量。

   private RadioGroup group1, group2, group3, group4, group5, group6, group7,group8,group9,group10;     

    @Override
            protected void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.activity_main);
                 group1 = (RadioGroup)findViewById(R.id.que1_rG);
                 group2 = (RadioGroup)findViewById(R.id.que2rG);
                 group3 = (RadioGroup)findViewById(R.id.que3rG);
                 group4 = (RadioGroup)findViewById(R.id.que4rG);
                 group5 = (RadioGroup)findViewById(R.id.que5rG);
                 group6 = (RadioGroup)findViewById(R.id.que6rG);
                 group7 = (RadioGroup)findViewById(R.id.que7rG);
                 group8 = (RadioGroup)findViewById(R.id.que8rG);
                 group9 = (RadioGroup)findViewById(R.id.que9rG);
                 group10 = (RadioGroup)findViewById(R.id.que10rG);
            }

            public void submitButton(View view)
            {
                int checkedRadio1= group1.getCheckedRadioButtonId();
                Toast.makeText(this,"Score is : " + score,Toast.LENGTH_SHORT);
                Log.v("MainActivity","Score is  " + score);
                score = 0;
            }