DragEvent - 预期的表达式

Question

尝试学习android / java，所以我正在为我女儿做一个简单的游戏。但我无法弄清楚我的参数中需要什么表达式？

我找到了一个可以通过＆＃39; onCreate＆＃39;传递的答案，但我想单独传递它，因为我觉得这是学习参数的好习惯。

爪哇

public class DragDropActivity extends MainActivity {
private ImageView dragPeppa = (ImageView) findViewById(R.id.drag_peppa);

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.drag_drop_layout);
    addTouchListener();
    onDrag(DragDropActivity.this, /** [DON'T KNOW WHAT TO PUT HERE] **/ );
}

public void addTouchListener() {
    dragPeppa.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View view, MotionEvent motionEvent) {
            if (motionEvent.getAction() == MotionEvent.ACTION_DOWN) {
                View.DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(view);
                view.startDrag(null, shadowBuilder, view, 0);
                view.setVisibility(View.INVISIBLE);
                return true;
            } else {
                return false;
            }
        }
    });
}
public boolean onDrag(View layoutview, DragEvent dragevent) {
    int action = dragevent.getAction();
    switch (action) {
        case DragEvent.ACTION_DRAG_STARTED:
            Log.d("DragDropActivity", "Drag event started");
            break;
        case DragEvent.ACTION_DRAG_ENTERED:
            Log.d("DragDropActivity", "Drag event entered into " + layoutview.toString());
            break;
        case DragEvent.ACTION_DRAG_EXITED:
            Log.d("DragDropActivity", "Drag event exited from " + layoutview.toString());
            break;
        case DragEvent.ACTION_DROP:
            Log.d("DragDropActivity", "Dropped");
            View view = (View) dragevent.getLocalState();
            ViewGroup owner = (ViewGroup) view.getParent();
            owner.removeView(view);
            LinearLayout container = (LinearLayout) layoutview;
            container.addView(view);
            view.setVisibility(View.VISIBLE);
            break;
        case DragEvent.ACTION_DRAG_ENDED:
            Log.d("DragDropActivity", "Drag ended");
            break;
        default:
            break;
    }
    return true;
}
}