Android控件拖动的实现

              这个也是从网上得到的代码，例子比较简单，但是如果有需要此功能的，这个例子可以提供很多提示，首先，给个截图

这个是拖动以后的效果，一个imageview和一个button控件，提供两份代码下载吧，一份是只有一个Button的，另一份就是像上图，就是多了一个imagview！先看下代码吧，比较简单：

public class DraftTest extends Activity implements OnTouchListener{/** Called when the activity is first created. */int screenWidth;int screenHeight;int lastX;int lastY;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);DisplayMetrics dm = getResources().getDisplayMetrics();screenWidth = dm.widthPixels;screenHeight = dm.heightPixels - 50;Button button=(Button)findViewById(R.id.btn);ImageView imageView=(ImageView)findViewById(R.id.btn2);imageView.setOnTouchListener(this);button.setOnTouchListener(this);}@Overridepublic boolean onTouch(View v, MotionEvent event) {// TODO Auto-generated method stubint action=event.getAction();Log.i("@@@@@@", "Touch:"+action);//Toast.makeText(DraftTest.this, "λ�ã�"+x+","+y, Toast.LENGTH_SHORT).show();switch(action){case MotionEvent.ACTION_DOWN:lastX = (int) event.getRawX();lastY = (int) event.getRawY();break;/** * layout(l,t,r,b) * l  Left position, relative to parent             t  Top position, relative to parent             r  Right position, relative to parent             b  Bottom position, relative to parent   * */case MotionEvent.ACTION_MOVE:int dx =(int)event.getRawX() - lastX;int dy =(int)event.getRawY() - lastY;int left = v.getLeft() + dx;int top = v.getTop() + dy;int right = v.getRight() + dx;int bottom = v.getBottom() + dy;if(left < 0){left = 0;right = left + v.getWidth();}if(right > screenWidth){right = screenWidth;left = right - v.getWidth();}if(top < 0){top = 0;bottom = top + v.getHeight();}if(bottom > screenHeight){bottom = screenHeight;top = bottom - v.getHeight();}v.layout(left, top, right, bottom);Log.i("@@@@@@", "position��" + left +", " + top + ", " + right + ", " + bottom);   lastX = (int) event.getRawX();lastY = (int) event.getRawY();break;case MotionEvent.ACTION_UP:break;        }return false;}}

高度减去50是减去状态栏和标题栏的高度。

case MotionEvent.ACTION_DOWN:lastX = (int) event.getRawX();lastY = (int) event.getRawY();break;

然后获取控件一开始的位置，然后在ACTION_MOVIE中：

int dx =(int)event.getRawX() - lastX;int dy =(int)event.getRawY() - lastY;int left = v.getLeft() + dx;int top = v.getTop() + dy;int right = v.getRight() + dx;int bottom = v.getBottom() + dy;if(left < 0){left = 0;right = left + v.getWidth();}if(right > screenWidth){right = screenWidth;left = right - v.getWidth();}if(top < 0){top = 0;bottom = top + v.getHeight();}if(bottom > screenHeight){bottom = screenHeight;top = bottom - v.getHeight();}v.layout(left, top, right, bottom);Log.i("@@@@@@", "position��" + left +", " + top + ", " + right + ", " + bottom);   lastX = (int) event.getRawX();lastY = (int) event.getRawY();

getLeft()方法得到的是控件坐标距离父控件原点(左上角，坐标（0，0）)的x轴距离，getReght()是控件右边距离父控件原点的x轴距离，同理，getTop和getButtom是距离的y轴距离。

if(left < 0){left = 0;right = left + v.getWidth();}if(right > screenWidth){right = screenWidth;left = right - v.getWidth();}if(top < 0){top = 0;bottom = top + v.getHeight();}if(bottom > screenHeight){bottom = screenHeight;top = bottom - v.getHeight();}

这里的判断是为了是控件不超出屏幕以外，即：到达边界以后，不能再移动。

v.layout(left, top, right, bottom);

设置View的位置。

有一点忘记说了，就是像ImageView和TextView这些控件，要想实现拖动，要在xml文件中设置它的clickable为true。

android:clickable="true"

就这样，这些就是这个demo的全部内容。

最后，是代码的下载地址：

http://download.csdn.net/detail/aomandeshangxiao/4187376，

http://download.csdn.net/detail/aomandeshangxiao/4189910