RadioGroup.OnCheckedChangeListener 被回调两次
今天又碰到了,貌似还没有被修复,顺便贴出来。
原android Issue地址:RadioGroup.OnCheckedChangeListener is called twice when the selection is cleared
具体表现 RadioGroup中包含有若干个RadioButton,当在代码中调用RadioGroup.check(id)方法动态设置被选中的RadioButton的时候,RadioGroup.OnCheckedChangeListener(RadioGroup group, int checkedId)会被调用多次。
示例 假设当前选择的是RadioButtonA,调用RadioGroup.check(RadioButtonBid)之后,RadioGroup.OnCheckedChangeListener(RadioGroup group, int checkedId)的调用情况如下:
第一次:checkedId 为 RadioButtonAId
第二次:checkedId 为 RadioButtonBId
第三次:checkedId 为 RadioButtonBId
测试代码 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 public class MainActivity extends Activity implements CompoundButton .OnCheckedChangeListener,RadioGroup.OnCheckedChangeListener{ RadioGroup mRadioGroup; RadioButton radio_0; RadioButton radio_1; RadioButton radio_2; @Override protected void onCreate (Bundle savedInstanceState) { super .onCreate(savedInstanceState); setContentView(R.layout.activity_main); mRadioGroup = (RadioGroup) findViewById(R.id.group); radio_0 = (RadioButton) findViewById(R.id.radio_0); radio_1 = (RadioButton) findViewById(R.id.radio_1); radio_2 = (RadioButton) findViewById(R.id.radio_2); mRadioGroup.setOnCheckedChangeListener(this ); radio_0.setOnCheckedChangeListener(this ); radio_1.setOnCheckedChangeListener(this ); radio_2.setOnCheckedChangeListener(this ); } public void doTestClick (View view) { switch (view.getId()) { case R.id.check_radio_0: mRadioGroup.check(R.id.radio_0); break ; case R.id.check_radio_1: mRadioGroup.check(R.id.radio_1); break ; case R.id.check_radio_2: mRadioGroup.check(R.id.radio_2); break ; default : break ; } } @Override public void onCheckedChanged (RadioGroup group, int checkedId) { Log.i("mRadioGroup onCheckedChanged" , "checkedId:" + checkedId); } @Override public void onCheckedChanged (CompoundButton buttonView, boolean isChecked) { switch (buttonView.getId()) { case R.id.radio_0: Log.i("radio_0 onCheckedChanged" , "isChecked:" + isChecked); break ; case R.id.radio_1: Log.i("radio_1 onCheckedChanged" , "isChecked:" + isChecked); break ; case R.id.radio_2: Log.i("radio_2 onCheckedChanged" , "isChecked:" + isChecked); break ; default : break ; } } }
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 <LinearLayout xmlns:android ="http://schemas.android.com/apk/res/android" xmlns:tools ="http://schemas.android.com/tools" android:layout_width ="match_parent" android:layout_height ="match_parent" android:orientation ="vertical" tools:context =".MainActivity" > <LinearLayout android:layout_width ="wrap_content" android:layout_height ="wrap_content" android:orientation ="vertical" > <Button android:id ="@+id/check_radio_0" android:layout_width ="wrap_content" android:layout_height ="wrap_content" android:onClick ="doTestClick" android:text ="check_radio_0" /> <Button android:id ="@+id/check_radio_1" android:layout_width ="wrap_content" android:layout_height ="wrap_content" android:onClick ="doTestClick" android:text ="check_radio_1" /> <Button android:id ="@+id/check_radio_2" android:layout_width ="wrap_content" android:layout_height ="wrap_content" android:onClick ="doTestClick" android:text ="check_radio_2" /> </LinearLayout > <RadioGroup android:id ="@+id/group" android:layout_width ="match_parent" android:layout_height ="wrap_content" android:orientation ="vertical" > <RadioButton android:id ="@+id/radio_0" android:layout_width ="match_parent" android:layout_height ="wrap_content" android:text ="0" /> <RadioButton android:id ="@+id/radio_1" android:layout_width ="match_parent" android:layout_height ="wrap_content" android:text ="1" /> <RadioButton android:id ="@+id/radio_2" android:layout_width ="match_parent" android:layout_height ="wrap_content" android:text ="2" /> </RadioGroup > </LinearLayout >
产生原因 RadioGroup check简化如下:
1 2 3 4 5 public void check (int newid) { setCheckedStateForView(mCheckedId, false ); setCheckedStateForView(newid, true ); setCheckedId(newid); }
RadioGroup setCheckedStateForView简化如下:
1 2 3 4 private void setCheckedStateForView (int viewId, boolean checked) { RadioButton childRadioButton = (RadioButton)findViewById(viewId); childRadioButton.setChecked(checked); }
RadioGroup setCheckedId简化如下:
1 2 3 4 private void setCheckedId (int id) { mCheckedId = id; mOnCheckedChangeListener.onCheckedChanged(this , mCheckedId); }
同时RadioGroup内部有一个check状态跟踪器,简化一下如下:
1 2 3 4 5 6 private class CheckedStateTracker implements CompoundButton .OnCheckedChangeListener { public void onCheckedChanged (CompoundButton childRadioButton, boolean isChecked) { int childRadioButtonId = childRadioButton.getId(); setCheckedId(id); } }
当每一个RadioButton被添加到RadioGroup的时候,就给每一个RadioButton设置一个checked状态监听
1 childRadioButton.mOnCheckedChangeWidgetListener = mCheckedStateTracker;
所以每当RadioButton的check状态发生变化,都会触发check状态跟踪器。
RadioButton的setChecked(boolean)简化如下:
1 2 3 4 public void setChecked (boolean checked) { mOnCheckedChangeListener.onCheckedChanged(this , mChecked); mOnCheckedChangeWidgetListener.onCheckedChanged(this , mChecked); }
说明 所以结合开头的例子,调用RadioGroup.check(RadioButtonBid)之后发生的情况如下:
1.RadioGroup.setCheckedStateForView(RadioButtonAid, false);
--> RaidoButton.mOnCheckedChangeWidgetListener.onCheckedChanged(RadioButtonA, false)
--> RadioGroup.setCheckedId(RadioButtonAId)
--> RadioGroup.mOnCheckedChangeListener.onCheckedChanged(RadioGroup, RadioButtonAId);
2.RadioGroup.setCheckedStateForView(RadioButtonBid, true);
--> RaidoButton.mOnCheckedChangeWidgetListener.onCheckedChanged(RadioButtonB, true)
--> RadioGroup.setCheckedId(RadioButtonBId)
--> RadioGroup.mOnCheckedChangeListener.onCheckedChanged(RadioGroup, RadioButtonBId);
3.RadioGroup.setCheckedId(RadioButtonBId)
--> RadioGroup.mOnCheckedChangeListener.onCheckedChanged(RadioGroup, RadioButtonBId);
按照Android官方文档的API说明:
public abstract void onCheckedChanged (RadioGroup group, int checkedId)
Parameters
group the group in which the checked radio button has changed
checkedId the unique identifier of the newly checked radio button
那个checkedId的参数在实现上是名不副实的。