A simple view support delegate touch event to another view

DelegateTouchSpace

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;

/**
 * Created by zeyiwu on 1/10/15.
 */
public class DelegateTouchSpace extends View {
    private View mDelegateView;
    private Rect mBoundRect;
    private Rect mSlopBoundRect;
    private int mSlop;
    private boolean mDelegateTargeted;

    public DelegateTouchSpace(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mBoundRect = new Rect();
        mSlopBoundRect = new Rect();
        mSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
    }

    /**
     * {@inheritDoc}
     */
    public DelegateTouchSpace(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    /**
     * {@inheritDoc}
     */
    public DelegateTouchSpace(Context context) {
        //noinspection NullableProblems
        this(context, null);
    }

    /**
     * Draw nothing.
     *
     * @param canvas an unused parameter.
     */
    @Override
    public void draw(Canvas canvas) {
    }

    /**
     * Compare to: {@link View#getDefaultSize(int, int)}
     * If mode is AT_MOST, return the child size instead of the parent size
     * (unless it is too big).
     */
    private int getDefaultSize2(int size, int measureSpec) {
        int result = size;
        int specMode = View.MeasureSpec.getMode(measureSpec);
        int specSize = View.MeasureSpec.getSize(measureSpec);

        switch (specMode) {
            case View.MeasureSpec.UNSPECIFIED:
                result = size;
                break;
            case View.MeasureSpec.AT_MOST:
                result = Math.min(size, specSize);
                break;
            case View.MeasureSpec.EXACTLY:
                result = specSize;
                break;
        }
        return result;
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        setMeasuredDimension(
                getDefaultSize2(getSuggestedMinimumWidth(), widthMeasureSpec),
                getDefaultSize2(getSuggestedMinimumHeight(), heightMeasureSpec));
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int x = (int)event.getRawX();
        int y = (int)event.getRawY();
        boolean sendToTarget = false;
        boolean hit = true;
        //boolean handled = false;
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                calculateBounds();
                if (mBoundRect.contains(x, y)) {
                    mDelegateTargeted = true;
                    sendToTarget = true;
                }
                break;
            case MotionEvent.ACTION_CANCEL:
            case MotionEvent.ACTION_MOVE:
                sendToTarget = mDelegateTargeted;
                if (sendToTarget) {
                    if (!mSlopBoundRect.contains(x, y)) {
                        hit = false;
                    }
                }
                break;
            case MotionEvent.ACTION_UP:
                sendToTarget = mDelegateTargeted;
                mDelegateTargeted = false;
                break;
        }
        if (sendToTarget && hit) {
            return mDelegateView.onTouchEvent(event);
        } else {
            return super.onTouchEvent(event);
        }
    }

    /**
     * 设置delegate view，将touch事件重定向到该view
     * @param view delgate view
     */
    public void setDelegateView(View view) {
        if (mDelegateView != view) {
            mDelegateView = view;
        }
    }

    private boolean calculateBounds() {
        if (mDelegateView == null) {
            return false;
        }
        Rect mHitRect = new Rect();
        Rect mDelegateHitRect = new Rect();
        int[] mLocation = new int[2];
        int[] mDelegateLocation = new int[2];

        this.getLocationOnScreen(mLocation);
        mDelegateView.getLocationOnScreen(mDelegateLocation);

        this.getHitRect(mHitRect);
        mDelegateView.getHitRect(mDelegateHitRect);

        int width = mHitRect.width();
        int height = mHitRect.height();
        mHitRect.left = mLocation[0];
        mHitRect.right = mLocation[0] + width;
        mHitRect.top = mLocation[1];
        mHitRect.bottom = mLocation[1] + height;

        width = mDelegateHitRect.width();
        height = mDelegateHitRect.height();
        mDelegateHitRect.left = mDelegateLocation[0];
        mDelegateHitRect.right = mDelegateLocation[0] + width;
        mDelegateHitRect.top = mDelegateLocation[1];
        mDelegateHitRect.bottom = mDelegateLocation[1] + height;

        if (mHitRect.intersect(mDelegateHitRect)) {
            mBoundRect.left = mHitRect.left;
            mBoundRect.right = mHitRect.right;
            mBoundRect.top = mHitRect.top;
            mBoundRect.bottom = mHitRect.bottom;
            mSlopBoundRect.inset(-mSlop, -mSlop);
            return true;
        } else {
            mBoundRect.left = 0;
            mBoundRect.right = 0;
            mBoundRect.top = 0;
            mBoundRect.bottom = 0;
            mSlopBoundRect.left = 0;
            mSlopBoundRect.right = 0;
            mSlopBoundRect.top = 0;
            mSlopBoundRect.bottom = 0;
            return false;
        }
    }
}