Android下图片或按钮等可拖动到任意位置的效果实现源码

from： http://www.2cto.com/kf/201207/140218.html
Android下图片可拖动到任意位置的效果

下面为Activity的代码：

01

public class DraftTest extends Activity {

02

/** Called when the activity is first created. */

03

@Override

04

public void onCreate(Bundle savedInstanceState) {

05

super.onCreate(savedInstanceState);

06

setContentView(R.layout.sign);

07

DisplayMetrics dm = getResources().getDisplayMetrics();

08

final int screenWidth = dm.widthPixels;

09

final int screenHeight = dm.heightPixels - 50;

10

//拖动的按钮

11

final Button b=(Button)findViewById(R.id.startBtn);

12

13

//添加触摸事件

14

15

b.setOnTouchListener(new OnTouchListener(){

16

int lastX, lastY; //记录移动的最后的位置

17

public boolean onTouch(View v, MotionEvent event) {

18

//获取Action

19

20

int ea=event.getAction();

21

22

Log.i("TAG", "Touch:"+ea);

23

switch(ea){

24

case MotionEvent.ACTION_DOWN: //按下

25

lastX = (int) event.getRawX();

26

lastY = (int) event.getRawY();

27

break;

28

/**

29

* layout(l,t,r,b)

30

* l Left position, relative to parent

31

t Top position, relative to parent

32

r Right position, relative to parent

33

b Bottom position, relative to parent

34

* */

35

case MotionEvent.ACTION_MOVE: //移动

36

//移动中动态设置位置

37

int dx =(int)event.getRawX() - lastX;

38

int dy =(int)event.getRawY() - lastY;

39

int left = v.getLeft() + dx;

40

int top = v.getTop() + dy;

41

int right = v.getRight() + dx;

42

int bottom = v.getBottom() + dy;

43

if(left < 0){

44

left = 0;

45

right = left + v.getWidth();

46

}

47

if(right > screenWidth){

48

right = screenWidth;

49

left = right - v.getWidth();

50

}

51

if(top < 0){

52

top = 0;

53

bottom = top + v.getHeight();

54

}

55

if(bottom > screenHeight){

56

bottom = screenHeight;

57

top = bottom - v.getHeight();

58

}

59

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

60

Log.i("", "position：" + left +", " + top + ", " + right + ", " + bottom);

61

//将当前的位置再次设置

62

lastX = (int) event.getRawX();

63

lastY = (int) event.getRawY();

64

break;

65

case MotionEvent.ACTION_UP: //脱离

66

break;

67

}

68

return false;

69

}});

70 www.2cto.com

}

71

}

XML配置文件Sign.xml的代码:

01

<?xml version="1.0" encoding="utf-8"?>

02

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

03

android:id="@+id/layoutRacingNeedForSpeed" android:padding="0px"

04

android:layout_width="fill_parent" android:layout_height="fill_parent">

05

<Button

06

android:id="@+id/startBtn"

07

android:text="tuodongdeanniu"

08

android:layout_centerInParent="true"

09

android:layout_width="wrap_content" android:layout_height="wrap_content"/>

10

</RelativeLayout>