在实际的项目中，我们经常都是RadioButton和RadioGroup一起配合使用。RadioGroup是单选组合框，可以容纳多个RadioButton的容器。在没有RadioGroup的情况下，RadioButton可以全部都选中；当多个RadioButton被RadioGroup包含的情况下，RadioButton只可以选中一个。并用setOnCheckedChangeListener来对单选按钮进行监听。
RadioButton和RadioGroup的关系：
- RadioButton表示单个圆形单选框，而RadioGroup是可以容纳多个RadioButton的容器。
- 每个RadioGroup中的RadioButton同时只能有一个被选中。
- 不同的RadioGroup中的RadioButton互不相干，即如果组A中有一个选中了，组B中依然可以有一个被选中。
- 一般情况下，一个RadioGroup中至少有2个RadioButton。
- 一般情况下，一个RadioGroup中的RadioButton默认会有一个被选中，并建议您将它放在RadioGroup中的起始位置。
实际使用的问题：
众所周知，
RadioGroup只能够通过设置
radioGroup.setOrientation()实现纵向或者横向排列，并且只能是一列或者一行，并且
RadioGroup中还只能直接放
RadioButton，但在实际项目中我们大都是需要实现上面的效果，所以简单的封装了一个，取名为： XRadioGroup。
XRadioGroup的实现
RadioGroup源码分析
本着求知好学的心态，首先研究一下RadioGroup的实现代码，为什么不能实现上面的效果（源码中省略了部分代码）。
public class RadioGroup extends LinearLayout {
/**
* {@inheritDoc}
*/
public RadioGroup(Context context) {
super(context);
setOrientation(VERTICAL);
init();
}
@Override
public void addView(View child, int index, ViewGroup.LayoutParams params) {
if (child instanceof RadioButton) {
final RadioButton button = (RadioButton) child;
if (button.isChecked()) {
mProtectFromCheckedChange = true;
if (mCheckedId != -1) {
setCheckedStateForView(mCheckedId, false);
}
mProtectFromCheckedChange = false;
setCheckedId(button.getId());
}
}
super.addView(child, index, params);
}
/**
* Sets the selection to the radio button whose identifier is passed in
* parameter. Using -1 as the selection identifier clears the selection;
* such an operation is equivalent to invoking {@link #clearCheck()}.
*
* @param id the unique id of the radio button to select in this group
*
* @see #getCheckedRadioButtonId()
* @see #clearCheck()
*/
public void check(@IdRes int id) {
// don't even bother
if (id != -1 && (id == mCheckedId)) {
return;
}
if (mCheckedId != -1) {
setCheckedStateForView(mCheckedId, false);
}
if (id != -1) {
setCheckedStateForView(id, true);
}
setCheckedId(id);
}
private void setCheckedId(@IdRes int id) {
mCheckedId = id;
if (mOnCheckedChangeListener != null) {
mOnCheckedChangeListener.onCheckedChanged(this, mCheckedId);
}
}
private void setCheckedStateForView(int viewId, boolean checked) {
View checkedView = findViewById(viewId);
if (checkedView != null && checkedView instanceof RadioButton) {
((RadioButton) checkedView).setChecked(checked);
}
}
/**
* Clears the selection. When the selection is cleared, no radio button
* in this group is selected and {@link #getCheckedRadioButtonId()} returns
* null.
*
* @see #check(int)
* @see #getCheckedRadioButtonId()
*/
public void clearCheck() {
check(-1);
}
/**
* Register a callback to be invoked when the checked radio button
* changes in this group.
*
* @param listener the callback to call on checked state change
*/
public void setOnCheckedChangeListener(OnCheckedChangeListener listener) {
mOnCheckedChangeListener = listener;
}
/**
* This set of layout parameters defaults the width and the height of
* the children to {@link #WRAP_CONTENT} when they are not specified in the
* XML file. Otherwise, this class ussed the value read from the XML file.
*
* See
* {@link android.R.styleable#LinearLayout_Layout LinearLayout Attributes}
* for a list of all child view attributes that this class supports.
*
*/
public static class LayoutParams extends LinearLayout.LayoutParams {
/**
* {@inheritDoc}
*/
public LayoutParams(Context c, AttributeSet attrs) {
super(c, attrs);
}
/**
* Interface definition for a callback to be invoked when the checked
* radio button changed in this group.
*/
public interface OnCheckedChangeListener {
/**
* Called when the checked radio button has changed. When the
* selection is cleared, checkedId is -1.
*
* @param group the group in which the checked radio button has changed
* @param checkedId the unique identifier of the newly checked radio button
*/
public void onCheckedChanged(RadioGroup group, @IdRes int checkedId);
}
private class CheckedStateTracker implements CompoundButton.OnCheckedChangeListener {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
// prevents from infinite recursion
if (mProtectFromCheckedChange) {
return;
}
mProtectFromCheckedChange = true;
if (mCheckedId != -1) {
setCheckedStateForView(mCheckedId, false);
}
mProtectFromCheckedChange = false;
int id = buttonView.getId();
setCheckedId(id);
}
}
/**
* A pass-through listener acts upon the events and dispatches them
* to another listener. This allows the table layout to set its own internal
* hierarchy change listener without preventing the user to setup his.
*/
private class PassThroughHierarchyChangeListener implements
ViewGroup.OnHierarchyChangeListener {
private ViewGroup.OnHierarchyChangeListener mOnHierarchyChangeListener;
/**
* {@inheritDoc}
*/
public void onChildViewAdded(View parent, View child) {
if (parent == RadioGroup.this && child instanceof RadioButton) {
int id = child.getId();
// generates an id if it's missing
if (id == View.NO_ID) {
id = View.generateViewId();
child.setId(id);
}
((RadioButton) child).setOnCheckedChangeWidgetListener(
mChildOnCheckedChangeListener);
}
if (mOnHierarchyChangeListener != null) {
mOnHierarchyChangeListener.onChildViewAdded(parent, child);
}
}
/**
* {@inheritDoc}
*/
public void onChildViewRemoved(View parent, View child) {
if (parent == RadioGroup.this && child instanceof RadioButton) {
((RadioButton) child).setOnCheckedChangeWidgetListener(null);
}
if (mOnHierarchyChangeListener != null) {
mOnHierarchyChangeListener.onChildViewRemoved(parent, child);
}
}
}
}
源码中可以发现RadioGroup是继承至LinearLayout，因为LinearLayout的特性缘故，所以RadioGroup也就只能够使其子类实现纵向或横向排列。再看为什么只能够直接包裹RadioButton，在public void addView(View child, int index, ViewGroup.LayoutParams params)方法中可以发现只判断了直接子类，所以要是RadioGroup中包含了其他ViewGroup，即使ViewGroup中包含了RadioButton也不会处理。现在问题就清楚了，需要解决的就是让ViewGroup中的RadioButton也能够被同时处理。
XRadioGroup源码分析
public class XRadioGroup extends LinearLayout {
// holds the checked id; the selection is empty by default
private int mCheckedId = -1;
// tracks children radio buttons checked state
private CompoundButton.OnCheckedChangeListener mChildOnCheckedChangeListener;
// when true, mOnCheckedChangeListener discards events
private boolean mProtectFromCheckedChange = false;
private OnCheckedChangeListener mOnCheckedChangeListener;
private PassThroughHierarchyChangeListener mPassThroughListener;
public XRadioGroup(Context context) {
super(context);
init();
}
public XRadioGroup(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public XRadioGroup(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
public XRadioGroup(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
init();
}
private void init() {
mChildOnCheckedChangeListener = new CheckedStateTracker();
mPassThroughListener = new PassThroughHierarchyChangeListener();
super.setOnHierarchyChangeListener(mPassThroughListener);
}
/**
* {@inheritDoc}
*/
@Override
public void setOnHierarchyChangeListener(OnHierarchyChangeListener listener) {
// the user listener is delegated to our pass-through listener
mPassThroughListener.mOnHierarchyChangeListener = listener;
}
/**
* {@inheritDoc}
*/
@Override
protected void onFinishInflate() {
super.onFinishInflate();
// checks the appropriate radio button as requested in the XML file
if (mCheckedId != -1) {
mProtectFromCheckedChange = true;
setCheckedStateForView(mCheckedId, true);
mProtectFromCheckedChange = false;
setCheckedId(mCheckedId);
}
}
private void setViewState(View child) {
if (child instanceof RadioButton) {
final RadioButton button = (RadioButton) child;
if (button.isChecked()) {
mProtectFromCheckedChange = true;
if (mCheckedId != -1) {
setCheckedStateForView(mCheckedId, false);
}
mProtectFromCheckedChange = false;
setCheckedId(button.getId());
}
} else if (child instanceof ViewGroup) {
ViewGroup view = (ViewGroup) child;
for (int i = 0; i < view.getChildCount(); i++) {
setViewState(view.getChildAt(i));
}
}
}
@Override
public void addView(View child, int index, ViewGroup.LayoutParams params) {
setViewState(child);
super.addView(child, index, params);
}
/**
* Sets the selection to the radio button whose identifier is passed in
* parameter. Using -1 as the selection identifier clears the selection;
* such an operation is equivalent to invoking {@link #clearCheck()}.
*
* @param id the unique id of the radio button to select in this group
* @see #getCheckedRadioButtonId()
* @see #clearCheck()
*/
public void check(@IdRes int id) {
// don't even bother
if (id != -1 && (id == mCheckedId)) {
return;
}
if (mCheckedId != -1) {
setCheckedStateForView(mCheckedId, false);
}
if (id != -1) {
setCheckedStateForView(id, true);
}
setCheckedId(id);
}
private void setCheckedId(@IdRes int id) {
mCheckedId = id;
if (mOnCheckedChangeListener != null) {
mOnCheckedChangeListener.onCheckedChanged(this, mCheckedId);
}
}
private void setCheckedStateForView(int viewId, boolean checked) {
View checkedView = findViewById(viewId);
if (checkedView != null && checkedView instanceof RadioButton) {
((RadioButton) checkedView).setChecked(checked);
}
}
/**
* Returns the identifier of the selected radio button in this group.
* Upon empty selection, the returned value is -1.
*
* @return the unique id of the selected radio button in this group
* @attr ref android.R.styleable#RadioGroup_checkedButton
* @see #check(int)
* @see #clearCheck()
*/
@IdRes
public int getCheckedRadioButtonId() {
return mCheckedId;
}
/**
* Clears the selection. When the selection is cleared, no radio button
* in this group is selected and {@link #getCheckedRadioButtonId()} returns
* null.
*
* @see #check(int)
* @see #getCheckedRadioButtonId()
*/
public void clearCheck() {
check(-1);
}
/**
* Register a callback to be invoked when the checked radio button
* changes in this group.
*
* @param listener the callback to call on checked state change
*/
public void setOnCheckedChangeListener(OnCheckedChangeListener listener) {
mOnCheckedChangeListener = listener;
}
/**
* {@inheritDoc}
*/
@Override
public LayoutParams generateLayoutParams(AttributeSet attrs) {
return new XRadioGroup.LayoutParams(getContext(), attrs);
}
/**
* {@inheritDoc}
*/
@Override
protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
return p instanceof XRadioGroup.LayoutParams;
}
@Override
protected LinearLayout.LayoutParams generateDefaultLayoutParams() {
return new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
}
@Override
public CharSequence getAccessibilityClassName() {
return XRadioGroup.class.getName();
}
/**
* This set of layout parameters defaults the width and the height of
* the children to {@link #WRAP_CONTENT} when they are not specified in the
* XML file. Otherwise, this class ussed the value read from the XML file.
*
* See
* {@link LinearLayout Attributes}
* for a list of all child view attributes that this class supports.
*/
public static class LayoutParams extends LinearLayout.LayoutParams {
/**
* {@inheritDoc}
*/
public LayoutParams(Context c, AttributeSet attrs) {
super(c, attrs);
}
/**
* {@inheritDoc}
*/
public LayoutParams(int w, int h) {
super(w, h);
}
/**
* {@inheritDoc}
*/
public LayoutParams(int w, int h, float initWeight) {
super(w, h, initWeight);
}
/**
* {@inheritDoc}
*/
public LayoutParams(ViewGroup.LayoutParams p) {
super(p);
}
/**
* {@inheritDoc}
*/
public LayoutParams(MarginLayoutParams source) {
super(source);
}
/**
* Fixes the child's width to
* {@link android.view.ViewGroup.LayoutParams#WRAP_CONTENT} and the child's
* height to {@link android.view.ViewGroup.LayoutParams#WRAP_CONTENT}
* when not specified in the XML file.
*
* @param a the styled attributes set
* @param widthAttr the width attribute to fetch
* @param heightAttr the height attribute to fetch
*/
@Override
protected void setBaseAttributes(TypedArray a,
int widthAttr, int heightAttr) {
if (a.hasValue(widthAttr)) {
width = a.getLayoutDimension(widthAttr, "layout_width");
} else {
width = WRAP_CONTENT;
}
if (a.hasValue(heightAttr)) {
height = a.getLayoutDimension(heightAttr, "layout_height");
} else {
height = WRAP_CONTENT;
}
}
}
/**
* Interface definition for a callback to be invoked when the checked
* radio button changed in this group.
*/
public interface OnCheckedChangeListener {
/**
* Called when the checked radio button has changed. When the
* selection is cleared, checkedId is -1.
*
* @param group the group in which the checked radio button has changed
* @param checkedId the unique identifier of the newly checked radio button
*/
public void onCheckedChanged(XRadioGroup group, @IdRes int checkedId);
}
private class CheckedStateTracker implements CompoundButton.OnCheckedChangeListener {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
// prevents from infinite recursion
if (mProtectFromCheckedChange) {
return;
}
mProtectFromCheckedChange = true;
if (mCheckedId != -1) {
setCheckedStateForView(mCheckedId, false);
}
mProtectFromCheckedChange = false;
int id = buttonView.getId();
setCheckedId(id);
}
}
/**
* A pass-through listener acts upon the events and dispatches them
* to another listener. This allows the table layout to set its own internal
* hierarchy change listener without preventing the user to setup his.
*/
private class PassThroughHierarchyChangeListener implements
ViewGroup.OnHierarchyChangeListener {
private ViewGroup.OnHierarchyChangeListener mOnHierarchyChangeListener;
/**
* {@inheritDoc}
*/
public void onChildViewAdded(View parent, View child) {
setListener(child);
if (mOnHierarchyChangeListener != null) {
mOnHierarchyChangeListener.onChildViewAdded(parent, child);
}
}
/**
* {@inheritDoc}
*/
public void onChildViewRemoved(View parent, View child) {
removeListener(child);
if (mOnHierarchyChangeListener != null) {
mOnHierarchyChangeListener.onChildViewRemoved(parent, child);
}
}
}
/**
* 设置监听
*
* @param child
*/
private void setListener(View child) {
if (child instanceof RadioButton) {
int id = child.getId();
// generates an id if it's missing
if (id == View.NO_ID) {
id = child.hashCode();
child.setId(id);
}
((RadioButton) child).setOnCheckedChangeListener(
mChildOnCheckedChangeListener);
} else if (child instanceof ViewGroup) {
ViewGroup view = (ViewGroup) child;
for (int i = 0; i < view.getChildCount(); i++) {
setListener(view.getChildAt(i));
}
}
}
/**
* 移除监听
*
* @param child
*/
private void removeListener(View child) {
if (child instanceof RadioButton) {
((RadioButton) child).setOnCheckedChangeListener(null);
} else if (child instanceof ViewGroup) {
ViewGroup view = (ViewGroup) child;
for (int i = 0; i < view.getChildCount(); i++) {
removeListener(view.getChildAt(i));
}
}
}
}
在public void addView(View child, int index, ViewGroup.LayoutParams params)方法中调用的private void setViewState(View child)，setViewState通过递归来实现设置RadioButton的初始状态。在PassThroughHierarchyChangeListener中增加了private void setListener(View child)和private void removeListener(View child)分别用来处理设置监听和移除监听。
详细的代码可以查看Github：XRadioGroup。
如何使用
java代码中使用方式与android.widget.RadioGroup完全一致
XRadioGroup xRadioGroup = (XRadioGroup) findViewById(R.id.xRadioGroup);
xRadioGroup.setOnCheckedChangeListener(new XRadioGroup.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(XRadioGroup group, @IdRes int checkedId) {
Log.d("TAG", checkedId + "is checked");
}
});
在xml中你可以里面嵌套使用
详细的使用代码可以查看Github：XRadioGroup。
gradle快速集成
allprojects {
repositories {
...
maven { url 'https://www.jitpack.io' }
}
}
dependencies {
compile 'com.github.fodroid:XRadioGroup:v1.1'
}