Android实现扩大View点击区域的三种方式

<TextView
        android:id="@+id/tv_view_delegate2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@color/gray_holo_light"
        android:padding="20dp"
        android:text="TouchDelegate2" />

/**
 * 扩展方法，扩大点击区域
 * NOTE: 需要保证目标targetView有父View，否则无法扩大点击区域
 *
 * @param expandSize 扩大的大小，单位px
 */
fun View.expandTouchView(expandSize: Int = 10.dp2px()) {
    val parentView = (parent as? View)
    parentView?.post {
        val rect = Rect()
        getHitRect(rect) //getHitRect(rect)将视图在父容器中所占据的区域存储到rect中。
        log("rect = $rect")
        rect.left -= expandSize
        rect.top -= expandSize
        rect.right += expandSize
        rect.bottom += expandSize
        log("expandRect = $rect")
        parentView.touchDelegate = TouchDelegate(rect, this)
    }
}

private val tvExpandTouch: TextView by id(R.id.tv_view_delegate)

tvExpandTouch.run {
    expandTouchView(50.dp2px()) //扩大点击区域
    setOnClickListener { showToast("通过TouchDelegate扩大点击区域") }
}

public class TouchDelegate {
    private View mDelegateView; //需要接收触摸事件的 View，即代理 View。
    private Rect mBounds;//本地坐标中的代理 View 的边界，用于初始命中测试。
    private Rect mSlopBounds;//增加一定范围的 mBounds，用于追踪触摸事件是否应被视为在代理 View 内。
    @UnsupportedAppUsage
    private boolean mDelegateTargeted;
    private TouchDelegateInfo mTouchDelegateInfo;

    public TouchDelegate(Rect bounds, View delegateView) {
        mBounds = bounds;
        mSlop = ViewConfiguration.get(delegateView.getContext()).getScaledTouchSlop();
        mSlopBounds = new Rect(bounds);
        mSlopBounds.inset(-mSlop, -mSlop);
        mDelegateView = delegateView;
    }

    //接收并处理触摸事件。若事件在 mBounds 内，则会将其转发到 mDelegateView。
    public boolean onTouchEvent(@NonNull MotionEvent event) {
        int x = (int)event.getX();
        int y = (int)event.getY();
        boolean sendToDelegate = false;
        boolean hit = true;
        boolean handled = false;

        switch (event.getActionMasked()) {
            case MotionEvent.ACTION_DOWN:
                mDelegateTargeted = mBounds.contains(x, y);
                sendToDelegate = mDelegateTargeted;
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
            case MotionEvent.ACTION_POINTER_UP:
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_MOVE:
                sendToDelegate = mDelegateTargeted;
                if (sendToDelegate) {
                    Rect slopBounds = mSlopBounds;
                    if (!slopBounds.contains(x, y)) {
                        hit = false;
                    }
                }
                break;
            case MotionEvent.ACTION_CANCEL:
                sendToDelegate = mDelegateTargeted;
                mDelegateTargeted = false;
                break;
        }
        if (sendToDelegate) {
            if (hit) {
                // Offset event coordinates to be inside the target view
                event.setLocation(mDelegateView.getWidth() / 2, mDelegateView.getHeight() / 2);
            } else {
                // Offset event coordinates to be outside the target view (in case it does
                // something like tracking pressed state)
                int slop = mSlop;
                event.setLocation(-(slop * 2), -(slop * 2));
            }
            //NOTE:重点看这里，最终是调用的代理View去处理事件了。
            handled = mDelegateView.dispatchTouchEvent(event);
        }
        return handled;
    }
}

   private TouchDelegate mTouchDelegate = null;
    
   public void setTouchDelegate(TouchDelegate delegate) {
       mTouchDelegate = delegate;
   }

   public TouchDelegate getTouchDelegate() {
       return mTouchDelegate;
   }

   public boolean onTouchEvent(MotionEvent event) {
      //......
      if (mTouchDelegate != null) {
          if (mTouchDelegate.onTouchEvent(event)) {
              return true;
          }
      }
      switch (action) {
          case MotionEvent.ACTION_DOWN:
          //...省略...
          case MotionEvent.ACTION_CANCEL:
          case MotionEvent.ACTION_UP:
      }
    }     

class ParentInnerTouchView @JvmOverloads constructor(
    context: Context,
    attrs: AttributeSet? = null,
    defStyleAttr: Int = 0
) : ConstraintLayout(context, attrs, defStyleAttr) {

    private val tvChildView: TextView

    init {
        inflate(context, R.layout.expand_touch_view, this)
        tvChildView = findViewById(R.id.tv_expand_view)
        tvChildView.setOnClickListener { showToast("扩大了点击事件") }
    }

    @SuppressLint("ClickableViewAccessibility")
    override fun onTouchEvent(event: MotionEvent?): Boolean {
        event?.let { ev ->
            if (ev.action == MotionEvent.ACTION_DOWN) {
                val isChildHit = isHitExpandChildView(tvChildView, Pair(ev.rawX, ev.rawY))
                if (isChildHit) {
                    //将事件传递给子控件
                    tvChildView.performClick()
                }
            }
        }
        return super.onTouchEvent(event)
    }

    /**
     * 判断是否点击到了子 View 的扩大区域
     * @param childView 子 View
     * @param touchPair 点击的位置 (x, y)
     * @param expandSize 扩大区域的大小
     * @return 是否命中
     */
    private fun isHitExpandChildView(
        childView: View,
        touchPair: Pair<Float, Float>,
        expandSize: Int = 50.dp2px()
    ): Boolean {

        // 获取子 View 在屏幕上的位置
        val location = IntArray(2)
        childView.getLocationOnScreen(location)

        val childX = location[0].toFloat()
        val childY = location[1].toFloat()
        val touchX = touchPair.first
        val touchY = touchPair.second

        // 扩大点击区域
        val rect = RectF()
        rect.set(
            childX - expandSize,
            childY - expandSize,
            childX + childView.width + expandSize,
            childY + childView.height + expandSize
        )
        // 判断点击是否在扩大的子 View 区域内
        return rect.contains(touchX, touchY)
    }
}