android - 如何在现有视图上使用拖放功能？

Question

我正在尝试在我的 Android 应用程序中为用户创建拖放任务，我希望在用户能够完成任务时更改活动。我用ChoiceTouchListener来检测用户的拖放。它应该使用户能够将纯白色按钮拖到虚线圆圈中。但发生的事情是，因为我将一些align_Parent参数设置为 true，它并没有离开屏幕的边界。因此Layout Parameters，一旦用户触摸屏幕，我就使用并将这些值设为 false。但发生的事情是我无法拖动它：

这是屏幕在触摸之前的样子。触摸按钮后，它会根据align_Parent参数被约束到一个角落。

布局代码：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="#03B0F5"
    android:id="@+id/bottom_right_layout">

    <TextView
        android:id="@+id/drag_drop_bottomRight"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:background="#FFFFFF"

        android:text="@string/drag_and_drop"
        android:textSize="50sp"
        android:textColor="#03B0F5"
        tools:ignore="MissingConstraints" />

    <ImageView
        android:id="@+id/circle_bottomRight"
        android:layout_width="150dp"
        android:layout_height="150dp"
        android:layout_alignParentRight="true"
        android:layout_alignParentBottom="true"
        app:srcCompat="@drawable/circle"
        tools:ignore="MissingConstraints,VectorDrawableCompat" />

    <ImageView
        android:id="@+id/circle_outline_bottomRight"
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:layout_centerInParent="true"
        app:srcCompat="@drawable/circle_outline"
        tools:ignore="MissingConstraints,VectorDrawableCompat"
        />
</RelativeLayout>

活动代码：

public class DragAndDrop extends AppCompatActivity {
    private ImageView img;
    private ImageView img_outline;
    private ViewGroup rootLayout;
    private int _xDelta;
    private int _yDelta;
    private RelativeLayout.LayoutParams params = null ;

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        List<Integer> givenList = Arrays.asList(0, 1, 2, 3);
        Random rand = new Random();
        int randomElement = givenList.get(rand.nextInt(givenList.size()));

        switch (randomElement){

            case 0:
                setContentView(R.layout.bottom_left);
                rootLayout = (ViewGroup) findViewById(R.id.bottom_left_layout);
                img = (ImageView) rootLayout.findViewById(R.id.circle_bottomLeft);
                img_outline = findViewById(R.id.circle_outline_bottomLeft);

                break;
            case 1:
                setContentView(R.layout.bottom_right);
                rootLayout = (ViewGroup) findViewById(R.id.bottom_right_layout);
                img = (ImageView) rootLayout.findViewById(R.id.circle_bottomRight);
                img_outline = findViewById(R.id.circle_outline_bottomRight);

                break;
            case 2:
                setContentView(R.layout.top_left);
                rootLayout = (ViewGroup) findViewById(R.id.top_left_layout);
                img = (ImageView) rootLayout.findViewById(R.id.circle_topleft);
                img_outline = findViewById(R.id.circle_outline_topleft);

                break;
            case 3:
                setContentView(R.layout.top_right);
                rootLayout = (ViewGroup) findViewById(R.id.top_right_layout);
                img = (ImageView) rootLayout.findViewById(R.id.circle_topRight);
                img_outline = findViewById(R.id.circle_outline_topRight);
                break;
        }

        img.setOnTouchListener(new ChoiceTouchListener());


    }

     public void check_success(){
        int[] location_circle = new int[2];
        int[] location_outline = new int[2];
        img.getLocationOnScreen(location_circle);
        img_outline.getLocationOnScreen(location_outline);

        if(((location_circle[0] >= location_outline[0]-75) &&(location_circle[0] <= location_outline[0]+75))
                && ((location_circle[1] >= location_outline[1]-75) &&(location_circle[1] <= location_outline[1]+75)) ){
            Intent i = new Intent(DragAndDrop.this, IntermediateActivity.class);
            startActivity(i);
        }
    }



    private final class ChoiceTouchListener implements View.OnTouchListener {
        public boolean onTouch(View view, MotionEvent event) {
            params = new RelativeLayout.LayoutParams(200, 200);
            params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM, 0);
            params.addRule(RelativeLayout.ALIGN_PARENT_RIGHT, 0);
            params.addRule(RelativeLayout.ALIGN_PARENT_LEFT, 0);
            params.addRule(RelativeLayout.ALIGN_PARENT_START, 0);
            params.addRule(RelativeLayout.ALIGN_PARENT_TOP, 0);


            img.setLayoutParams(params);

            final int X = (int) event.getRawX();
            final int Y = (int) event.getRawY();
            check_success();
            switch (event.getAction() & MotionEvent.ACTION_MASK) {
                case MotionEvent.ACTION_DOWN:
                    RelativeLayout.LayoutParams lParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
                    _xDelta = X - lParams.leftMargin;
                    _yDelta = Y - lParams.topMargin;
                    break;
                case MotionEvent.ACTION_UP:
                    break;
                case MotionEvent.ACTION_POINTER_DOWN:
                    break;
                case MotionEvent.ACTION_POINTER_UP:
                    break;
                case MotionEvent.ACTION_MOVE:
                    RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) view
                            .getLayoutParams();
                    layoutParams.leftMargin = X - _xDelta;
                    layoutParams.topMargin = Y - _yDelta;
                    layoutParams.rightMargin = -250;
                    layoutParams.bottomMargin = -250;
                    view.setLayoutParams(layoutParams);
                    check_success();
                    break;
            }
            rootLayout.invalidate();
            return true;

        }

    }
}

我如何确保实心圆从角落位置开始并且用户可以拖动它？

标签： androidandroid-layoutdrag-and-dropandroid-relativelayout