Android控制項拖動的實現

              這個也是從網上得到的代碼，例子比較簡單，但是如果有需要此功能的，這個例子可以提供很多提示，首先，給個

這個是拖動以後的效果，一個imageview和一個button控制項，提供兩份代碼下載吧，一份是只有一個Button的，另一份就是像，就是多了一個imagview！先看下代碼吧，比較簡單：

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;}}

高度減去50是減去狀態列和標題列的高度。

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

然後擷取控制項一開始的位置，然後在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()方法得到的是控制項座標距離父控制項原點(左上方，座標（0，0）)的x軸距離，getReght()是控制項右邊距離父控制項原點的x軸距離，同理，getTop和getButtom是距離的y軸距離。

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();}

這裡的判斷是為了是控制項不超出螢幕以外，即：到達邊界以後，不能再移動。

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

設定View的位置。

有一點忘記說了，就是像ImageView和TextView這些控制項，要想實現拖動，要在xml檔案中設定它的clickable為true。

android:clickable="true"

就這樣，這些就是這個demo的全部內容。

最後，是代碼的：

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

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