android - 如何只为 View 设置触摸事件

Question

我正在使用来自 android 开发人员博客的 android touch 示例，但触摸适用于屏幕上的任何位置，而不仅仅是具有触摸的 View :使用代码是:

package pit.opensource.touch;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;

public class TouchExampleView extends View {
    private static final int INVALID_POINTER_ID = -1;

    private Drawable mIcon;
    private float mPosX;
    private float mPosY;

    private float mLastTouchX;
    private float mLastTouchY;
    private int mActivePointerId = INVALID_POINTER_ID;

    View currentView;

    private ScaleGestureDetector mScaleDetector;
    private float mScaleFactor = 1.f;

    public TouchExampleView(Context context) {
        this(context, null, 0);

        currentView = this;

    }

    public TouchExampleView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public TouchExampleView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        mIcon = context.getResources().getDrawable(R.drawable.ic_launcher);
        mIcon.setBounds(0, 0, mIcon.getIntrinsicWidth(), mIcon.getIntrinsicHeight());

        mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        // Let the ScaleGestureDetector inspect all events.
        mScaleDetector.onTouchEvent(ev);

        final int action = ev.getAction();
        switch (action & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN: {
            final float x = ev.getX();
            final float y = ev.getY();



            int viewTop = currentView.getPaddingTop();
            int viewLeft = currentView.getPaddingLeft();

            int viewWidth = currentView.getWidth();
            int viewHeight = currentView.getHeight();

            Log.d("Top",viewTop+"");
            Log.d("Left",viewLeft+"");
            Log.d("Width",viewWidth+"");
            Log.d("Height",viewHeight+"");

            if(x>(viewLeft + viewWidth) || y>(viewTop+viewHeight)) 
            {
                return false; 
            }else{
                mLastTouchX = x;
                mLastTouchY = y;
                mActivePointerId = ev.getPointerId(0);
            }


            break;
        }

        case MotionEvent.ACTION_MOVE: {
            final int pointerIndex = ev.findPointerIndex(mActivePointerId);
            final float x = ev.getX(pointerIndex);
            final float y = ev.getY(pointerIndex);

            // Only move if the ScaleGestureDetector isn't processing a gesture.
            if (!mScaleDetector.isInProgress()) {
                final float dx = x - mLastTouchX;
                final float dy = y - mLastTouchY;

                mPosX += dx;
                mPosY += dy;

                invalidate();
            }

            mLastTouchX = x;
            mLastTouchY = y;

            break;
        }

        case MotionEvent.ACTION_UP: {
            mActivePointerId = INVALID_POINTER_ID;
            break;
        }

        case MotionEvent.ACTION_CANCEL: {
            mActivePointerId = INVALID_POINTER_ID;
            break;
        }

        case MotionEvent.ACTION_POINTER_UP: {
            final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) 
                    >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
                    final int pointerId = ev.getPointerId(pointerIndex);
                    if (pointerId == mActivePointerId) {
                        // This was our active pointer going up. Choose a new
                        // active pointer and adjust accordingly.
                        final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
                        mLastTouchX = ev.getX(newPointerIndex);
                        mLastTouchY = ev.getY(newPointerIndex);
                        mActivePointerId = ev.getPointerId(newPointerIndex);
                    }
                    break;
        }
        }

        return true;
    }

    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        canvas.save();
        canvas.translate(mPosX, mPosY);
        canvas.scale(mScaleFactor, mScaleFactor);
        mIcon.draw(canvas);
        canvas.restore();
    }

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            mScaleFactor *= detector.getScaleFactor();

            // Don't let the object get too small or too large.
            mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 5.0f));

            invalidate();
            return true;
        }
    }
}

Answer 1

为要处理触摸事件的 View 实现 View.OnTouchListener。

否则，调用 getDrawingRect(Rect outRect) 获取 View 边界。然后使用 outRect.contains(touchX, touchY) 检查此 View 边界是否包含触摸点坐标。