android: 分享一个带多行选择功能的RadioGroup

分享一个带多行选择功能的RadioGroup, Github上看到的。

android 的RadioGroup有两个缺陷：

1. 不支持多行选择
什么意思呢？比如要实现下图这样的效果：

上面的10组选项其实都只能单选，但是要用RadioGroup去做的话，最少要定义3个RadioGroup， 原生的RadioGroup只支持单向排列，要么是横向，要么是纵向, 且不能自动换行。

2. 没办法自动区分选中状态是由代码触发的还是用户触发的

这个问题其实也存在于SwitchButton、CheckBox等其它原生控件中。这点我觉得非常不好，因为这个需求其实很常见，比如我进入一个新界面，需要更新RadioGroup中RadioButton的选中状态，如果你直接使用RadioGroup#check()或RadioButton#setChecked()方法，这两个方法都会触发监听器的 onCheckedChanged() 回调，而我们一般是将选中后执行的动作写在这个回调方法里的，这样就会导致一个很奇葩的现象：比如选中按钮后需要下一个setter指令，我更新界面时调用了RadioButton#setChecked()方法，本来是来更新界面的，结果却莫名其妙下了一个setter指令。

另外，使用RadioGroup#check()方法还会触发多次 onCheckedChanged() 回调！这是最坑的，完全跟我们的预期效果不一样，你可以说是我们用法上的问题，但我觉得一个好的api设计最起码从名称上就让人一目了然，光看名字就知道能达到什么效果, 而不是用了发现跟预期不一致，睬了个坑，再回去翻源码，发现原来是这样设计的，关于这个问题可参考：Android-为什么 RadioGroup.onCheckedChanged() 会调用多次？

下面直接贴代码：

code 是基于 https://github.com/pheng/android_radiogroup_MutilRadioGroup/blob/master/MutilRadioGroup/src/com/pheng/mutilradiogroup/MyRadioGroup.java

我在上面加了一段code, 用于在代码选中时不会触发 onCheckedChanged()方法。 setCheckWithoutNotif 

/**
 * RadioGroup with multi-line function and Code selection function
 * <br/>
 */
public class MultiLineRadioGroup 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;

    /**
     * {@inheritDoc}
     */
    public MultiLineRadioGroup(Context context) {
        super(context);
        setOrientation(VERTICAL);
        init();
    }

    /**
     * {@inheritDoc}
     */
    public MultiLineRadioGroup(Context context, AttributeSet attrs) {
        super(context, attrs);
        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;
    }

    /**
     * set the default checked radio button, without notification the listeners
     */
    public void setCheckWithoutNotif(int id) {
        if (id != -1 && (id == mCheckedId)) {
            return;
        }

        mProtectFromCheckedChange = true;
        if (mCheckedId != -1) {
            setCheckedStateForView(mCheckedId, false);
        }

        if (id != -1) {
            setCheckedStateForView(id, true);
        }

        mCheckedId = id;
        mProtectFromCheckedChange = false;
    }

    @Override
    public void addView(View child, int index, ViewGroup.LayoutParams params) {
        List<RadioButton> btns = getAllRadioButton(child);
        if (btns != null && btns.size() > 0) {
            for (RadioButton button : btns) {
                if (button.isChecked()) {
                    mProtectFromCheckedChange = true;
                    if (mCheckedId != -1) {
                        setCheckedStateForView(mCheckedId, false);
                    }
                    mProtectFromCheckedChange = false;
                    setCheckedId(button.getId());
                }
            }
        }
        super.addView(child, index, params);
    }

    /**
     * get all radio buttons which are in the view
     *
     * @param child
     */
    private List<RadioButton> getAllRadioButton(View child) {
        List<RadioButton> btns = new ArrayList<RadioButton>();
        if (child instanceof RadioButton) {
            btns.add((RadioButton) child);
        } else if (child instanceof ViewGroup) {
            int counts = ((ViewGroup) child).getChildCount();
            for (int i = 0; i < counts; i++) {
                btns.addAll(getAllRadioButton(((ViewGroup) child).getChildAt(i)));
            }
        }
        return btns;
    }

    /**
     * Use program to check a radioButton, the {@link OnCheckedChangeListener#onCheckedChanged(MultiLineRadioGroup, int)}
     * method will not be triggered
     *
     * @param rationButtonId Selected radio button ID.
     * @param checked        Checked state.
     */
    public void setChecked(int rationButtonId, boolean checked) {
        RadioButton radioButton = findViewById(rationButtonId);
        if (radioButton != null) {
            OnCheckedChangeListener tmpListener = mOnCheckedChangeListener;
            setOnCheckedChangeListener(null);
            radioButton.setChecked(checked);
            setOnCheckedChangeListener(tmpListener);
        }
    }

    /**
     * <p>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()}.</p>
     *
     * @param id the unique id of the radio button to select in this group
     * @see #getCheckedRadioButtonId()
     * @see #clearCheck()
     */
    public void check(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(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);
        }
    }

    /**
     * <p>Returns the identifier of the selected radio button in this group.
     * Upon empty selection, the returned value is -1.</p>
     *
     * @return the unique id of the selected radio button in this group
     * @attr ref android.R.styleable#MyRadioGroup_checkedButton
     * @see #check(int)
     * @see #clearCheck()
     */
    public int getCheckedRadioButtonId() {
        return mCheckedId;
    }

    /**
     * <p>Clears the selection. When the selection is cleared, no radio button
     * in this group is selected and {@link #getCheckedRadioButtonId()} returns
     * null.</p>
     *
     * @see #check(int)
     * @see #getCheckedRadioButtonId()
     */
    public void clearCheck() {
        check(-1);
    }

    /**
     * <p>Register a callback to be invoked when the checked radio button
     * changes in this group.</p>
     *
     * @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 MultiLineRadioGroup.LayoutParams(getContext(), attrs);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
        return p instanceof MultiLineRadioGroup.LayoutParams;
    }

    @Override
    protected LinearLayout.LayoutParams generateDefaultLayoutParams() {
        return new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
    }

    @Override
    public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
        super.onInitializeAccessibilityEvent(event);
        event.setClassName(MultiLineRadioGroup.class.getName());
    }

    @Override
    public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {
        super.onInitializeAccessibilityNodeInfo(info);
        info.setClassName(MultiLineRadioGroup.class.getName());
    }

    /**
     * <p>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.</p>
     */
    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);
        }

        /**
         * <p>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.</p>
         *
         * @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;
            }
        }
    }

    /**
     * <p>Interface definition for a callback to be invoked when the checked
     * radio button changed in this group.</p>
     */
    public interface OnCheckedChangeListener {
        /**
         * <p>Called when the checked radio button has changed. When the
         * selection is cleared, checkedId is -1.</p>
         *
         * @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(MultiLineRadioGroup group, 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);
        }
    }

    /**
     * <p>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.</p>
     */
    private class PassThroughHierarchyChangeListener implements
            ViewGroup.OnHierarchyChangeListener {
        private ViewGroup.OnHierarchyChangeListener mOnHierarchyChangeListener;

        /**
         * {@inheritDoc}
         */
        @SuppressLint("NewApi")
        public void onChildViewAdded(View parent, View child) {
            if (parent == MultiLineRadioGroup.this) {
                List<RadioButton> btns = getAllRadioButton(child);
                if (btns != null && btns.size() > 0) {
                    for (RadioButton btn : btns) {
                        int id = btn.getId();
                        // generates an id if it's missing
                        if (id == View.NO_ID && Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
                            id = View.generateViewId();
                            btn.setId(id);
                        }
                        btn.setOnCheckedChangeListener(
                                mChildOnCheckedChangeListener);
                    }
                }
            }

            if (mOnHierarchyChangeListener != null) {
                mOnHierarchyChangeListener.onChildViewAdded(parent, child);
            }
        }

        /**
         * {@inheritDoc}
         */
        public void onChildViewRemoved(View parent, View child) {
            if (parent == MultiLineRadioGroup.this) {
                List<RadioButton> btns = getAllRadioButton(child);
                if (btns != null && btns.size() > 0) {
                    for (RadioButton btn : btns) {
                        btn.setOnCheckedChangeListener(null);
                    }
                }
            }

            if (mOnHierarchyChangeListener != null) {
                mOnHierarchyChangeListener.onChildViewRemoved(parent, child);
            }
        }
    }
}

使用这份code, 可以很轻易实现多行的RadioButton效果，另外如果想选中RadioButton时不触发  onCheckedChanged 回调，可以调用： public void setChecked(int rationButtonId, boolean checked) 方法，其实这个code的原始作者也加了这个功能，
 setCheckWithoutNotif , 但我最开始没看到，所以就自己实现了一份，也可以实现相同的效果。

参考链接：

1. Android-为什么 RadioGroup.onCheckedChanged() 会调用多次？

2. How can I distinguish whether Switch,Checkbox Value is changed by user or programmatically (including by retention)?