每当拖动时，可拖动按钮就会脱离相对布局

Question

我正在开发一个使用Drag and Drop 功能的应用程序。 我正在生成按钮OnClick。代码工作正常，但是当我drag button 到relativelayout 的角落时，按钮脱离layout。我希望它留在layout 内。

拖动按钮之前

拖动按钮后（在本例中为上角）

正如您所看到的，每当我将drag 移向layout 的末端/角落时，button 就会脱离layout，我希望它保持在layout 中完好无损，显示完整的button。我该怎么做？

提前致谢！

MainActivity.java

public class MainActivity extends Activity implements OnTouchListener {
    Button btnAddButton;
    RelativeLayout rl1;
    int i = 1;
    private int _xDelta;
    private int _yDelta;
    ViewGroup _root;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btnAddButton = (Button) findViewById(R.id.btnAdd);

        rl1 = (RelativeLayout) findViewById(R.id.relative_layout);
        _root = (ViewGroup)findViewById(R.id.relative_layout);
        btnAddButton.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                add(v);

            }
        });
    }
    public void add(View v) {
        Button btn = new Button(MainActivity.this);
        //btn.setId(i);
        RelativeLayout.LayoutParams layoutParam = new RelativeLayout.LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);

        int a=(int) (Math.random()*100);
       // Toast.makeText(MainActivity.this, String.valueOf(Math.random()*100), 1).show();//double a=Math.random();
        layoutParam.leftMargin = 30+a;

        if (i > 1) {

            layoutParam.addRule(RelativeLayout.BELOW, (i - 1));
        }

        btn.setText("Button" + i);
        rl1.addView(btn, layoutParam);
        btn.setOnTouchListener(this);
        i++;
    } 
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
    @Override
    public boolean onTouch(View v, MotionEvent event) {
         final int X = (int) event.getRawX();
            final int Y = (int) event.getRawY();
            switch (event.getAction() & MotionEvent.ACTION_MASK) {
                case MotionEvent.ACTION_DOWN:
                    RelativeLayout.LayoutParams lParams = (RelativeLayout.LayoutParams) v.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) v.getLayoutParams();
                    layoutParams.leftMargin = X - _xDelta;
                    layoutParams.topMargin = Y - _yDelta;
                    layoutParams.rightMargin = -250;
                    layoutParams.bottomMargin = -250;
                    v.setLayoutParams(layoutParams);
                    break;
            }
            _root.invalidate();
        return true;
    }
}

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/linear_layout"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <Button
        android:id="@+id/btnAdd"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="AddButton"
        android:text="Button" />

    <RelativeLayout
        android:id="@+id/relative_layout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:layout_toRightOf="@+id/btnAdd" >
    </RelativeLayout>

</RelativeLayout>

Answer 1

我能够通过使用这些条件来解决这个问题：

        if ((v.getY() < lay.getY())) {

            v.setX(xVal);
            v.setY(yVal);
        } else if (v.getX() < lay.getX()) {

            v.setX(xVal);
            v.setY(yVal);
        } else if (v.getX() + v.getWidth() > lay.getX() + lay.getWidth()) {

            v.setX(xVal);
            v.setY(yVal);
        } else if (v.getY() + v.getHeight() > lay.getY() + lay.getHeight()) {

            v.setX(xVal);
            v.setY(yVal);
        } else {
            for (int i = 0; i <= viewIdList.size() - 1; i++) {
                if (v.getId() != viewIdList.get(i).getId()) {

                    View v3 = viewIdList.get(i);
                    Rect rect1 = new Rect(v.getLeft(), v.getTop(),
                            v.getRight(), v.getBottom());
                    v.getHitRect(rect1);
                    Rect rect2 = new Rect(v3.getLeft(), v3.getTop(),
                            v3.getRight(), v3.getBottom());
                    v3.getHitRect(rect2);
                    if (Rect.intersects(rect1, rect2)) {

                        System.out.println("overlap");
                        v.setX(xVal);
                        v.setY(yVal);
                    }

其中 v 是视图（在我的例子中是 ImageView），这段代码是用 onTouchListener 的 MotionEvent.ACTION_UP 编写的。