如何限制只在android中沿y轴拖放？

我正在尝试将拖放动作限制为仅限Y轴,以便用户只能拍摄视图并向上或向下拖动 - 而不是向左或向右拖动.

我现在有两个视图(textView和dropZone的id).一个(textView)设置了一个触摸侦听器,另一个(dropZone)设置了一个拖动侦听器.

这是布局xml(activity_main.xml):

以下是活动代码:

package com.example.dragexperiment;

import android.app.Activity;
import android.content.ClipData;
import android.graphics.Color;
import android.os.Bundle;
import android.util.Log;
import android.view.DragEvent;
import android.view.Menu;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.DragShadowBuilder;
import android.view.View.OnDragListener;
import android.view.View.OnGenericMotionListener;
import android.view.View.OnTouchListener;
import android.widget.RelativeLayout;
import android.widget.TextView;

public class MainActivity extends Activity {
TextView tv, dz, sv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        tv = (TextView) findViewById(R.id.textView);
        dz = (TextView) findViewById(R.id.dropZone);
        tv.setOnTouchListener(new MyTouchListener());
        dz.setOnDragListener(new MyDragListener());
    }

    private final class MyTouchListener implements OnTouchListener {
        int viewX0, viewY0,
            cY0, cY1,
            deltaCursorY;

        @Override
        public boolean onTouch(final View v,final MotionEvent event) {
              switch(event.getAction()) {
                case MotionEvent.ACTION_DOWN:
                    viewX0 = (int) v.getX();
                    viewY0 = (int) v.getY();
                    cY0 = (int) event.getRawY();
                    ClipData data = ClipData.newPlainText("", "");
                    DragShadowBuilder shadow = new View.DragShadowBuilder(v);
                    v.startDrag(data, shadow, v, 0);
                    return true;
                case MotionEvent.ACTION_MOVE:
                //  cY1 = (int) event.getRawY();
                //  deltaCursorY = cY1 - cY0;
                //  v.setX(viewX0);
                //  v.setY(viewY0 + deltaCursorY);
                    return true;
              }
              return false;
        }
    }

    class MyDragListener implements OnDragListener {

        public boolean onDrag(View v, DragEvent event) {
            switch (event.getAction()) {
            case DragEvent.ACTION_DRAG_STARTED:
                break;
            case DragEvent.ACTION_DRAG_ENTERED:
                v.setBackgroundColor(Color.BLUE);
                break;
            case DragEvent.ACTION_DRAG_EXITED:
                break;
            case DragEvent.ACTION_DROP:
                v.setBackgroundColor(Color.BLUE);
                break;
            case DragEvent.ACTION_DRAG_ENDED:
                break;
            default:
                break;
            }
            return true;
        }
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

从上面的代码中可以看出,当用户在dropZone上拖动textView时,我尝试将dropZone视图背景颜色变为蓝色.如果我在ACTION_DOWN运动事件中使用创建DragShadowBuilder,这可以正常工作:

    ClipData data = ClipData.newPlainText("", "");
    DragShadowBuilder shadow = new View.DragShadowBuilder(v);
    v.startDrag(data, shadow, v, 0);

问题是我无法控制阴影,只能沿Y轴(垂直)轴移动.

如果我取出DragShadowBuilder代码(上面的三行),并添加代码以在ACTION_MOVE运动事件中移动拖动的视图(上面已注释掉):

    cY1 = (int) event.getRawY();
    deltaCursorY = cY1 - cY0;
    v.setX(viewX0);
    v.setY(viewY0 + deltaCursorY);

然后我可以控制textView只沿Y轴移动.不幸的是,如果没有DragShadowBuilder,我无法通过ACTION_DRAG_ENTERED DragEvent触发将dropZone视图变为蓝色.

如果我同时保留DragShadowBuilder代码和上面四行代码,则ACTION_MOVE运动事件仅在拖动时触发一次; 它不会继续跟随拖累.

谁有任何关于我能做什么的想法？我已经使用了一段时间,但没有运气.我甚至尝试过创建一个扩展Android View类的自定义视图,但是我无法覆盖startDrag方法,因为它被声明为final.我希望我能做得更好.:(