A RadioGroup with Relative Layout capabilities

RelativeRadioGroup.java

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.emoodji.view;

import android.content.Context;
import android.os.Build;
import android.support.annotation.IdRes;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.widget.CompoundButton;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.RelativeLayout;


/**
 * @author João Pedro Evangelista
 */
public class RelativeRadioGroup extends RelativeLayout {

    // 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 RelativeRadioGroup(Context context) {
        super(context);
        init();
    }

    public RelativeRadioGroup(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;
    }

    /**
     * {@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);
        }
    }

    @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);
    }

    /**
     * <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(@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);
        }
    }

    /**
     * <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
     *
     * @see #check(int)
     * @see #clearCheck()
     *
     * @attr ref android.R.styleable#RadioGroup_checkedButton
     */
    @IdRes
    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 RelativeRadioGroup.LayoutParams(getContext(), attrs);
    }

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

    @Override
    protected RelativeLayout.LayoutParams generateDefaultLayoutParams() {
        return new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
    }

    @Override
    public CharSequence getAccessibilityClassName() {
        return RadioGroup.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 RelativeLayout.LayoutParams {
        */
/**
         * {@inheritDoc}
         *//*

        public LayoutParams(Context c, AttributeSet attrs) {
            super(c, attrs);
        }

        */
/**
         * {@inheritDoc}
         *//*

        public LayoutParams(int w, int h) {
            super(w, h);
        }

        */
/**
         * {@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(RelativeRadioGroup 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);
        }
    }

    /**
     * <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}
         */
        public void onChildViewAdded(View parent, View child) {
            if (parent == RelativeRadioGroup.this && child instanceof RadioButton) {
                int id = child.getId();
                // generates an id if it's missing
                if (id == View.NO_ID) {
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
                        id = View.generateViewId();
                    }
                    child.setId(id);
                }
                ((RadioButton) child).setOnCheckedChangeListener(
                        mChildOnCheckedChangeListener);
            }

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

        /**
         * {@inheritDoc}
         */
        public void onChildViewRemoved(View parent, View child) {
            if (parent == RelativeRadioGroup.this && child instanceof RadioButton) {
                ((RadioButton) child).setOnCheckedChangeListener(null);
            }

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