how to disable the radio group until checkbox is selected

Am a fresher in android..

am trying to design an app which contains a list of check boxes followed by radio group (contains 4 radio buttons each).

Concept is,until we select the particular checkbox its relevant radio group should be disabled.I tried all solutions provided at

How to disable a RadioGroup until checkbox is checked

Android: How do I enable/disable a Checkbox, depending on a Radio button being selected first

Android disable radio group in xml

http://ift.tt/1GMVdXa but none of them are working for me..the app is crashing out..am providing my code here:

public class Service extends Activity {    String op1=" ",op2=" ";    CheckBox ck1 = (CheckBox)findViewById(R.id.checkBox1);    CheckBox ck2 = (CheckBox)findViewById(R.id.checkBox2);    protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_service);    RadioGroup rg1 = (RadioGroup) findViewById(R.id.radioGroup1);    RadioGroup rg2 = (RadioGroup) findViewById(R.id.radioGroup2);    rg1.setOnCheckedChangeListener(new OnCheckedChangeListener()    {    public void onCheckedChanged(RadioGroup group, int checkedId) {    switch(checkedId){     case R.id.radio1:    op1="Yes";    break;    case R.id.radio2:    op1="No";    break;    }    }    });

rg2.setOnCheckedChangeListener(new OnCheckedChangeListener()    {    public void onCheckedChanged(RadioGroup group, int checkedId) {    switch(checkedId){    case R.id.radio3:    op1="Yes";    break;    case R.id.radio4:    op1="No";    break;    }    }    });    }

public void onCheckboxClicked(View view) {    ck1.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {    public void onCheckedChanged(CompoundButton checkBox, boolean isChecked) {    RadioGroup rg1 = (RadioGroup) findViewById(R.id.radioGroup4);    for(int i = 0; i < rg1.getChildCount(); i++){    ((RadioGroup)rg1.getChildAt(i)).setEnabled(isChecked);    }    }    });    for(int i = 0; i < rg1.getChildCount(); i++){    ((RadioGroup)rg1.getChildAt(i)).setEnabled(false);    }    }    ck2.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {    public void onCheckedChanged(CompoundButton checkBox, boolean isChecked) {    RadioGroup rg2 = (RadioGroup) findViewById(R.id.radioGroup5);    for(int i = 0; i < rg2.getChildCount(); i++){    ((RadioGroup)rg2.getChildAt(i)).setEnabled(isChecked);    }    }    });    for(int i = 0; i < rg2.getChildCount(); i++){    ((RadioGroup)rg2.getChildAt(i)).setEnabled(false);    }    }`