Java 移动不适合手指的视图

我正在做一个项目，用户可以用手指触摸移动视图。它可以工作，但不能精确到手指的位置。我不是问你有什么好的代码，而是想知道为什么我的代码使视图不适合你的手指。这就像视图有更多关于20dp的边距。代码如下：

活动\u main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/lyRoot"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.zihadrizkyef.dragviewwithfinger.MainActivity">

    <TextView
        android:id="@+id/tvText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="0dp"
        android:text="Hello World!"/>
</LinearLayout>

---

您应该使用拖动距离，而不是屏幕上的坐标

layoutParams.leftMargin = layoutParams.leftMargin + deltaX;
layoutParams.topMargin = layoutParams.leftMargin + deltaY;

您可以从Android开发者网站获得完整的解决方案
你必须使它适应你的需要。我把它改了一点

// The ‘active pointer’ is the one currently moving our object.
private int mActivePointerId = INVALID_POINTER_ID;

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

    final int action = MotionEventCompat.getActionMasked(ev);

    switch (action) {
        case MotionEvent.ACTION_DOWN: {
            final int pointerIndex = MotionEventCompat.getActionIndex(ev);
            final float x = MotionEventCompat.getX(ev, pointerIndex);
            final float y = MotionEventCompat.getY(ev, pointerIndex);

            // Remember where we started (for dragging)
            mLastTouchX = x;
            mLastTouchY = y;
            // Save the ID of this pointer (for dragging)
            mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
            break;
        }
        case MotionEvent.ACTION_MOVE: {
            // Find the index of the active pointer and fetch its position
            final int pointerIndex =
                    MotionEventCompat.findPointerIndex(ev, mActivePointerId);

            final float x = MotionEventCompat.getX(ev, pointerIndex);
            final float y = MotionEventCompat.getY(ev, pointerIndex);

            // Calculate the distance moved
            final float dx = x - mLastTouchX;
            final float dy = y - mLastTouchY;

            layoutParams.leftMargin += dx;
            layoutParams.topMargin += dy;
            tvText.setLayoutParams(layoutParams);
            lyRoot.invalidate();

            // Remember this touch position for the next move event
            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 = MotionEventCompat.getActionIndex(ev);
            final int pointerId = MotionEventCompat.getPointerId(ev, 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 = MotionEventCompat.getX(ev, newPointerIndex);
                mLastTouchY = MotionEventCompat.getY(ev, newPointerIndex);
                mActivePointerId = MotionEventCompat.getPointerId(ev, newPointerIndex);
            }
            break;
        }
    }
    return true;
}

---

谢谢你的链接。但这并不意味着使用屏幕坐标是错误的，不是吗？我只是喜欢用屏幕坐标。那么你能告诉我代码的错误吗？不，我给你展示的例子也使用了屏幕坐标，但它们会被调整。我的意思是你总是会有额外的边距（20dp或更多），因为

event.getRawX（）

是你在屏幕上点击的位置。相反，您需要拖动距离来设置精确的leftMarginTry，以适应我发布的代码的需要。它确实有效，因为我在我的一个项目中使用了它。否则，您将始终具有随机边距。

// The ‘active pointer’ is the one currently moving our object.
private int mActivePointerId = INVALID_POINTER_ID;

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

    final int action = MotionEventCompat.getActionMasked(ev);

    switch (action) {
        case MotionEvent.ACTION_DOWN: {
            final int pointerIndex = MotionEventCompat.getActionIndex(ev);
            final float x = MotionEventCompat.getX(ev, pointerIndex);
            final float y = MotionEventCompat.getY(ev, pointerIndex);

            // Remember where we started (for dragging)
            mLastTouchX = x;
            mLastTouchY = y;
            // Save the ID of this pointer (for dragging)
            mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
            break;
        }
        case MotionEvent.ACTION_MOVE: {
            // Find the index of the active pointer and fetch its position
            final int pointerIndex =
                    MotionEventCompat.findPointerIndex(ev, mActivePointerId);

            final float x = MotionEventCompat.getX(ev, pointerIndex);
            final float y = MotionEventCompat.getY(ev, pointerIndex);

            // Calculate the distance moved
            final float dx = x - mLastTouchX;
            final float dy = y - mLastTouchY;

            layoutParams.leftMargin += dx;
            layoutParams.topMargin += dy;
            tvText.setLayoutParams(layoutParams);
            lyRoot.invalidate();

            // Remember this touch position for the next move event
            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 = MotionEventCompat.getActionIndex(ev);
            final int pointerId = MotionEventCompat.getPointerId(ev, 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 = MotionEventCompat.getX(ev, newPointerIndex);
                mLastTouchY = MotionEventCompat.getY(ev, newPointerIndex);
                mActivePointerId = MotionEventCompat.getPointerId(ev, newPointerIndex);
            }
            break;
        }
    }
    return true;
}