RadioGroup中RadioButton的SharedPreferences.Editor

Question

如何使用廣播組中單選按鈕的共享首選項。我有兩個按鈕（下一個和上一個）。

我想檢查用戶選擇的選項，當用戶轉到下一個，並再次來到上一次。

我試過這樣會引發錯誤。在做什麼錯誤？

非常感謝。

 ImageView nextBtn = (ImageView) findViewById(R.id.nxt_btn); 
     nextBtn.setOnClickListener(new Button.OnClickListener(){ 
     public void onClick(View v){ 
     btn_practice1.setChecked(false); 
     btn_practice2.setChecked(false); 
     btn_practice3.setChecked(false); 
     btn_practice4.setChecked(false); 
    btn_practicerg.setOnCheckedChangeListener(new OnCheckedChangeListener() { 
    @Override 
     public void onCheckedChanged(RadioGroup group, int checkedId) { 
     RadioButton radioButton = (RadioButton)group. findViewById(checkedId);      
     int checkedIndex = group.indexOfChild(radioButton); 
     getSharedPreferences(KEY_SAVED_RADIO_BUTTON_INDEX, checkedIndex);            
     SharedPreferences sharedPreferences = getSharedPreferences("MY_SHARED_PREF", MODE_PRIVATE); 
     SharedPreferences.Editor editor = sharedPreferences.edit(); 
     editor.putInt("check", checkedIndex); 
     editor.commit(); 
    }); 
}); 
    ImageView previousbtn1 = (ImageView) findViewById(R.id.prv_btn); 
     previousbtn1.setOnClickListener(new Button.OnClickListener(){ 
     public void onClick(View v){ 
     SharedPreferences sharedPreferences = getSharedPreferences("MY_SHARED_PREF", MODE_PRIVATE); 
     int savedRadioIndex = sharedPreferences.getInt(KEY_SAVED_RADIO_BUTTON_INDEX, 0); 
     RadioButton savedCheckedRadioButton = (RadioButton)group.getChildAt(savedRadioIndex); // line number 570       
     savedCheckedRadioButton.setChecked(true); 
    }); 

logcat的

 E/AndroidRuntime(362): FATAL EXCEPTION: main 
     E/AndroidRuntime(362): java.lang.NullPointerException 
     E/AndroidRuntime(362): at 
     com.example.TEENEINSTIEN.Question$LoadQuestions$4.onClick(Question.java:570) 
     E/AndroidRuntime(362): at android.view.View.performClick(View.java:2485) 
     E/AndroidRuntime(362): at 
     android.view.View$PerformClick.run(View.java:9080) 
     E/AndroidRuntime(362): at 
     android.os.Handler.handleCallback(Handler.java:587) 
     E/AndroidRuntime(362): at 
     android.os.Handler.dispatchMessage(Handler.java:92) 
     E/AndroidRuntime(362): at android.os.Looper.loop(Looper.java:123) 
     E/AndroidRuntime(362): at 
     android.app.ActivityThread.main(ActivityThread.java:3683) 
     E/AndroidRuntime(362): at java.lang.reflect.Method.invokeNative(Native 
     Method) 
     E/AndroidRuntime(362): at java.lang.reflect.Method.invoke(Method.java:507) 
     E/AndroidRuntime(362): at 
     com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
     E/AndroidRuntime(362): at 
     com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
     E/AndroidRuntime(362): at dalvik.system.NativeStart.main(Native Method) 

Answer 1

也許group是invissible或沒有在previousbtn1.setOnClickListener()正確分配。嘗試在您的previousbtn1.setOnClickListener()中使用RadioGroup myradioGroup = (RadioGroup) findViewById(R.id.radioGroup1);。

btn_practicerg.setOnCheckedChangeListener(new OnCheckedChangeListener() { 
    @Override 
     public void onCheckedChanged(RadioGroup group, int checkedId) { 
     RadioButton radioButton = (RadioButton)group. findViewById(checkedId);      
     int checkedIndex = group.indexOfChild(radioButton); 
    // getSharedPreferences(KEY_SAVED_RADIO_BUTTON_INDEX, checkedIndex);            
     SharedPreferences sharedPreferences = getSharedPreferences("MY_SHARED_PREF", MODE_PRIVATE); 
     SharedPreferences.Editor editor = sharedPreferences.edit(); 
     editor.putInt("check", checkedIndex); 
     editor.commit(); 
    }); 
}); 
    ImageView previousbtn1 = (ImageView) findViewById(R.id.prv_btn); 
     previousbtn1.setOnClickListener(new Button.OnClickListener(){ 
     public void onClick(View v){ 
     SharedPreferences sharedPreferences = getSharedPreferences("MY_SHARED_PREF", MODE_PRIVATE); 
     int savedRadioIndex = sharedPreferences.getInt("check", 0); 
     System.out.println("savedRadioIndex is "+savedRadioIndex); 
     RadioGroup myradioGroup = (RadioGroup) findViewById(R.id.radioGroup1); 
     RadioButton savedCheckedRadioButton = (RadioButton)myradioGroup.getChildAt(savedRadioIndex); 
          // throws error line number 570 
     savedCheckedRadioButton.setChecked(true); 
    }); 

試試這種方法。我希望這能幫到您。