[Android开发札记]Android中使用系统桌面背景作为应用背景，支持拖动

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一、在Android应用开发中，使用系统桌面背景作为应用的背景，需要把应用的背景设置为透明背景，然后设置窗口的属性为FLAG_SHOW_WALLPAPER即可显示背景。

1>.修改AndroidManifest.xml文件里面activity属性：

???????<activity android:name=".WallPaperTest"

?????????????????android:label="@string/app_name"

?????????????????android:theme="@android:style/Theme.Translucent">

2>.然后在使用的时候，在onCreate里面添加一个窗口属性

getWindow().addFlags(WindowManager.LayoutParams.FLAG_SHOW_WALLPAPER);

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二、背景拖动主要是使用了WallpaperManager这个类的两个方法

public voidsetWallpaperOffsetSteps(float xStep, float yStep)

1>.修改ScrollLayout的类，让它支持显示系统背景，并且拖动的时候背景也跟着拖动.基本类文件ScrollLayout.java

[java]?view plain?copy

1. packagecom.yao_guet;

2. importandroid.app.WallpaperManager;

3. importandroid.content.Context;

4. importandroid.os.IBinder;

5. importandroid.util.AttributeSet;

6. importandroid.util.Log;

7. importandroid.view.MotionEvent;

8. importandroid.view.VelocityTracker;

9. importandroid.view.View;

10. importandroid.view.ViewConfiguration;

11. importandroid.view.ViewGroup;

12. importandroid.widget.Scroller;

13. /**

14. * 仿Launcher中的WorkSapce，可以左右滑动切换屏幕的类，支持显示系统背景和滑动

15. * @author Hekang

16. * blog: 6600s.diandian.com

17. * date: 2012-04-22

18. */

19. publicclassScrollLayoutextendsViewGroup {

20. privatestaticfinalString TAG ="ScrollLayout";

21. privateScroller mScroller;

22. privateVelocityTracker mVelocityTracker;

23. ?

24. privateintmCurScreen;

25. privateintmDefaultScreen =0;

26. ?

27. privatestaticfinalintTOUCH_STATE_REST =0;

28. privatestaticfinalintTOUCH_STATE_SCROLLING =1;

29. ?

30. privatestaticfinalintSNAP_VELOCITY =600;

31. ?

32. privateintmTouchState = TOUCH_STATE_REST;

33. privateintmTouchSlop;

34. privatefloatmLastMotionX;

35. privatefloatmLastMotionY;

36. ?

37. privateWallpaperManager mWallpaperManager;

38. privateintmScrollX;

39. publicScrollLayout(Context context, AttributeSet attrs) {

40. this(context, attrs,0);

41. // TODO Auto-generated constructor stub

42. }

43. publicScrollLayout(Context context, AttributeSet attrs,intdefStyle) {

44. super(context, attrs, defStyle);

45. // TODO Auto-generated constructor stub

46. ?

47. mWallpaperManager = WallpaperManager.getInstance(context);

48. mScroller =newScroller(context);

49. ?

50. mCurScreen = mDefaultScreen;

51. mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();

52. }

53. @Override

54. protectedvoidonLayout(booleanchanged,intl,intt,intr,intb) {

55. // TODO Auto-generated method stub

56. Log.e(TAG,"onLayout");

57. intchildLeft =0;

58. finalintchildCount = getChildCount();

59. ?

60. for(inti=0; i<childCount; i++) {

61. finalView childView = getChildAt(i);

62. if(childView.getVisibility() != View.GONE) {

63. finalintchildWidth = childView.getMeasuredWidth();

64. childView.layout(childLeft,0,

65. childLeft+childWidth, childView.getMeasuredHeight());

66. childLeft += childWidth;

67. }

68. }

69. updateWallpaperOffset();

70. }

71. ?

72. @Override

73. protectedvoidonMeasure(intwidthMeasureSpec,intheightMeasureSpec) {

74. Log.e(TAG,"onMeasure");

75. super.onMeasure(widthMeasureSpec, heightMeasureSpec);

76. ?

77. finalintwidth = MeasureSpec.getSize(widthMeasureSpec);

78. finalintwidthMode = MeasureSpec.getMode(widthMeasureSpec);

79. if(widthMode != MeasureSpec.EXACTLY) {

80. thrownewIllegalStateException("ScrollLayout only canmCurScreen run at EXACTLY mode!");

81. }

82. ?

83. finalintheightMode = MeasureSpec.getMode(heightMeasureSpec);

84. if(heightMode != MeasureSpec.EXACTLY) {

85. thrownewIllegalStateException("ScrollLayout only can run at EXACTLY mode!");

86. }

87. ?

88. // The children are given the same width and height as the scrollLayout

89. finalintcount = getChildCount();

90. for(inti =0; i < count; i++) {

91. getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);

92. }

93. // Log.e(TAG, "moving to screen "+mCurScreen);

94. scrollTo(mCurScreen * width,0);

95. }

96. ?

97. /**

98. * According to the position of current layout

99. * scroll to the destination page.

100. */

101. publicvoidsnapToDestination() {

102. finalintscreenWidth = getWidth();

103. finalintdestScreen = (getScrollX()+ screenWidth/2)/screenWidth;

104. snapToScreen(destScreen);

105. }

106. ?

107. publicvoidsnapToScreen(intwhichScreen) {

108. // get the valid layout page

109. whichScreen = Math.max(0, Math.min(whichScreen, getChildCount()-1));

110. if(getScrollX() != (whichScreen*getWidth())) {

111. ?

112. finalintdelta = whichScreen*getWidth()-getScrollX();

113. mScroller.startScroll(getScrollX(),0,

114. delta,0, Math.abs(delta)*2);

115. mCurScreen = whichScreen;

116. invalidate();// Redraw the layout

117. }

118. }

119. ?

120. publicvoidsetToScreen(intwhichScreen) {

121. whichScreen = Math.max(0, Math.min(whichScreen, getChildCount()-1));

122. mCurScreen = whichScreen;

123. scrollTo(whichScreen*getWidth(),0);

124. }

125. ?

126. publicintgetCurScreen() {

127. returnmCurScreen;

128. }

129. ?

130. @Override

131. publicvoidcomputeScroll() {

132. // TODO Auto-generated method stub

133. mScrollX = mScroller.getCurrX();

134. if(mScroller.computeScrollOffset()) {

135. scrollTo(mScroller.getCurrX(), mScroller.getCurrY());

136. updateWallpaperOffset();

137. ?

138. postInvalidate();

139. }

140. }

141. @Override

142. publicbooleanonTouchEvent(MotionEvent event) {

143. // TODO Auto-generated method stub

144. ?

145. if(mVelocityTracker ==null) {

146. mVelocityTracker = VelocityTracker.obtain();

147. }

148. mVelocityTracker.addMovement(event);

149. ?

150. finalintaction = event.getAction();

151. finalfloatx = event.getX();

152. finalfloaty = event.getY();

153. ?

154. switch(action) {

155. caseMotionEvent.ACTION_DOWN:

156. Log.e(TAG,"event down!");

157. if(!mScroller.isFinished()){

158. mScroller.abortAnimation();

159. }

160. mLastMotionX = x;

161. break;

162. ?

163. caseMotionEvent.ACTION_MOVE:

164. intdeltaX = (int)(mLastMotionX - x);

165. mLastMotionX = x;

166. scrollBy(deltaX,0);

167. updateWallpaperOffset();

168. break;

169. ?

170. caseMotionEvent.ACTION_UP:

171. Log.e(TAG,"event : up");

172. // if (mTouchState == TOUCH_STATE_SCROLLING) {

173. finalVelocityTracker velocityTracker = mVelocityTracker;

174. velocityTracker.computeCurrentVelocity(1000);

175. intvelocityX = (int) velocityTracker.getXVelocity();

176. Log.e(TAG,"velocityX:"+velocityX);

177. ?

178. if(velocityX > SNAP_VELOCITY && mCurScreen >0) {

179. // Fling enough to move left

180. Log.e(TAG,"snap left");

181. snapToScreen(mCurScreen -1);

182. }elseif(velocityX < -SNAP_VELOCITY

183. && mCurScreen < getChildCount() -1) {

184. // Fling enough to move right

185. Log.e(TAG,"snap right");

186. snapToScreen(mCurScreen +1);

187. }else{

188. snapToDestination();

189. }

190. if(mVelocityTracker !=null) {

191. mVelocityTracker.recycle();

192. mVelocityTracker =null;

193. }

194. // }

195. mTouchState = TOUCH_STATE_REST;

196. break;

197. caseMotionEvent.ACTION_CANCEL:

198. mTouchState = TOUCH_STATE_REST;

199. break;

200. }

201. ?

202. returntrue;

203. }

204. @Override

205. publicbooleanonInterceptTouchEvent(MotionEvent ev) {

206. // TODO Auto-generated method stub

207. Log.e(TAG,"onInterceptTouchEvent-slop:"+mTouchSlop);

208. ?

209. finalintaction = ev.getAction();

210. if((action == MotionEvent.ACTION_MOVE) &&

211. (mTouchState != TOUCH_STATE_REST)) {

212. returntrue;

213. }

214. ?

215. finalfloatx = ev.getX();

216. finalfloaty = ev.getY();

217. ?

218. switch(action) {

219. caseMotionEvent.ACTION_MOVE:

220. finalintxDiff = (int)Math.abs(mLastMotionX-x);

221. if(xDiff>mTouchSlop) {

222. mTouchState = TOUCH_STATE_SCROLLING;

223. ?

224. }

225. break;

226. ?

227. caseMotionEvent.ACTION_DOWN:

228. mLastMotionX = x;

229. mLastMotionY = y;

230. mTouchState = mScroller.isFinished()? TOUCH_STATE_REST : TOUCH_STATE_SCROLLING;

231. break;

232. ?

233. caseMotionEvent.ACTION_CANCEL:

234. caseMotionEvent.ACTION_UP:

235. mTouchState = TOUCH_STATE_REST;

236. break;

237. }

238. ?

239. returnmTouchState != TOUCH_STATE_REST;

240. }

241. ?

242. ?

243. privatevoidupdateWallpaperOffset() {

244. intscrollRange = getChildAt(getChildCount() -1).getRight() - getWidth();

245. IBinder token = getWindowToken();

246. if(token !=null) {

247. mWallpaperManager.setWallpaperOffsetSteps(1.0f / (getChildCount() -1),0);

248. mWallpaperManager.setWallpaperOffsets(getWindowToken(),

249. Math.max(0.f, Math.min(getScrollX()/(float)scrollRange,1.f)),0);

250. }

251. }

252. }

2>.测试代码WallPaperTest.java：

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[java]?view plain?copy

1. packagecom.yao_guet;

2. importandroid.app.Activity;

3. importandroid.app.WallpaperManager;

4. importandroid.content.Context;

5. importandroid.os.Bundle;

6. importandroid.view.KeyEvent;

7. importandroid.view.Window;

8. importandroid.view.WindowManager;

9. publicclassWallPaperTestextendsActivity {

10. @Override

11. protectedvoidonCreate(Bundle savedInstanceState) {

12. // TODO Auto-generated method stub

13. super.onCreate(savedInstanceState);

14. this.requestWindowFeature(Window.FEATURE_NO_TITLE);

15. setContentView(R.layout.wallpaper_test);

16. getWindow().addFlags(WindowManager.LayoutParams.FLAG_SHOW_WALLPAPER);

17. }

18. @Override

19. protectedvoidonDestroy() {

20. // TODO Auto-generated method stub

21. super.onDestroy();

22. }

23. @Override

24. publicbooleanonKeyDown(intkeyCode, KeyEvent event) {

25. // TODO Auto-generated method stub

26. returnsuper.onKeyDown(keyCode, event);

27. }

28. }

3>.layout布局文件wallpaper_test.xml：

[html]?view plain?copy

1. <?xmlversion="1.0"encoding="utf-8"?>

2. <com.sf.test.ScrollLayout

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

4. android:id="@+id/WallPaperTest"

5. android:layout_width="fill_parent"

6. android:layout_height="fill_parent">

7. <LinearLayout

8. android:layout_width="fill_parent"

9. android:layout_height="fill_parent">

10. <TextView

11. android:layout_width="fill_parent"

12. android:layout_height="wrap_content"

13. android:text="This is page 1"/>

14. </LinearLayout>

15. ?

16. <LinearLayout

17. android:layout_width="fill_parent"

18. android:layout_height="fill_parent">

19. <TextView

20. android:layout_width="fill_parent"

21. android:layout_height="wrap_content"

22. android:text="This is page 2"/>

23. </LinearLayout>

24. ?

25. <LinearLayout

26. android:layout_width="fill_parent"

27. android:layout_height="fill_parent">

28. <TextView

29. android:layout_width="fill_parent"

30. android:layout_height="wrap_content"

31. android:text="This is page 3"/>

32. </LinearLayout>

33. ?

34. <LinearLayout

35. android:layout_width="fill_parent"

36. android:layout_height="fill_parent">

37. <TextView

38. android:layout_width="fill_parent"

39. android:layout_height="wrap_content"

40. android:text="This is page 4"/>

41. </LinearLayout>

42. <LinearLayout

43. android:layout_width="fill_parent"

44. android:layout_height="fill_parent">

45. <TextView

46. android:layout_width="fill_parent"

47. android:layout_height="wrap_content"

48. android:text="This is page 5"/>

49. </LinearLayout>

50. <LinearLayout

51. android:layout_width="fill_parent"

52. android:layout_height="fill_parent">

53. <TextView

54. android:layout_width="fill_parent"

55. android:layout_height="wrap_content"

56. android:text="This is page 6"/>

57. </LinearLayout>

58. ?

59. <LinearLayout

60. android:layout_width="fill_parent"

61. android:layout_height="fill_parent">

62. <TextView

63. android:layout_width="fill_parent"

64. android:layout_height="wrap_content"

65. android:text="This is page 7"/>

66. </LinearLayout>

67. </com.sf.test.ScrollLayout>

4>.最后记得修改AndroidManifest.xml文件

???????<activity android:name=".WallPaperTest"

?????????????????android:label="@string/app_name"

?????????????????android:theme="@android:style/Theme.Translucent">

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