Android图片浏览源码解读

首先是Android图片浏览中layoutxml:

1. <?xmlversion="1.0"encoding="utf-8"?>
2. <RelativeLayoutxmlns:android="http://schemas.Android.com/apk/res/Android"
3. Android:layout_width="fill_parent"
4. Android:layout_height="fill_parent">
5. <ImageSwitcherAndroid:id="@+id/switcher"
6. Android:layout_width="fill_parent"
7. Android:layout_height="fill_parent"
8. Android:layout_alignParentTop="true"
9. Android:layout_alignParentLeft="true"
10. />
11. <GalleryAndroid:id="@+id/gallery"
12. Android:background="#55000000"
13. Android:layout_width="fill_parent"
14. Android:layout_height="60dp"
15. Android:layout_alignParentBottom="true"
16. Android:layout_alignParentLeft="true"
17. Android:gravity="center_vertical"
18. Android:spacing="16dp"
19. />
20. </RelativeLayout>

layout里面用到了前面所说的两个控件，ImageSwitcher用啦显示全图，Gallery用来显示缩略图。着重看看ImageSwitcher,在ImageSwitcher1中需要实现ViewSwitcher.ViewFactory这个接口，这个接口里有个方法makeView，这样就产生了用来显示图片的view.ImageSwitcher调用过程是这样的，首先要有一个Factory为它提供一个View，然后ImageSwitcher就可以初始化各种资源了。注意在使用一个ImageSwitcher之前，一定要调用setFactory方法，要不setImageResource这个方法会报空指针异常。

下面是Android图片浏览代码：

1. packagecom.zx.imageswitcher;
2. importAndroid.app.Activity;
3. importAndroid.content.Context;
4. importAndroid.os.Bundle;
5. importAndroid.view.View;
6. importAndroid.view.ViewGroup;
7. importAndroid.view.animation.AnimationUtils;
8. importAndroid.widget.AdapterView;
9. importAndroid.widget.BaseAdapter;
10. importAndroid.widget.Gallery;
11. importAndroid.widget.ImageSwitcher;
12. importAndroid.widget.ImageView;
13. importAndroid.widget.ViewSwitcher;
14. importAndroid.widget.Gallery.LayoutParams;
15. publicclassImageSwitcherTestextendsActivityimplements
16. AdapterView.OnItemSelectedListener,ViewSwitcher.ViewFactory{
17. privateImageSwitchermSwitcher;
18. privateInteger[]mThumbIds={
19. R.drawable.sample_thumb_0,R.drawable.sample_thumb_1,
20. R.drawable.sample_thumb_2,R.drawable.sample_thumb_3,
21. R.drawable.sample_thumb_4,R.drawable.sample_thumb_5,
22. R.drawable.sample_thumb_6,R.drawable.sample_thumb_7};
23. privateInteger[]mImageIds={
24. R.drawable.sample_0,R.drawable.sample_1,R.drawable.sample_2,
25. R.drawable.sample_3,R.drawable.sample_4,R.drawable.sample_5,
26. R.drawable.sample_6,R.drawable.sample_7};
27. /**Calledwhentheactivityisfirstcreated.*/
28. @Override
29. publicvoidonCreate(BundlesavedInstanceState){
30. super.onCreate(savedInstanceState);
31. setContentView(R.layout.main);
32. mSwitcher=(ImageSwitcher)findViewById(R.id.switcher);
33. mSwitcher.setFactory(this);
34. mSwitcher.setInAnimation(AnimationUtils.loadAnimation(this,
35. Android.R.anim.fade_in));
36. mSwitcher.setOutAnimation(AnimationUtils.loadAnimation(this,
37. Android.R.anim.fade_out));
38. Galleryg=(Gallery)findViewById(R.id.gallery);
39. g.setAdapter(newImageAdapter(this));
40. g.setOnItemSelectedListener(this);
41. }
42. /*
43. *overrideforViewSwitcher.ViewFactory#makeView()
44. */
45. publicViewmakeView(){
46. ImageViewi=newImageView(this);
47. i.setBackgroundColor(0xFF000000);
48. i.setScaleType(ImageView.ScaleType.FIT_CENTER);
49. i.setLayoutParams(newImageSwitcher.LayoutParams
    (LayoutParams.FILL_PARENT,
50. LayoutParams.FILL_PARENT));
51. returni;
52. }
53. /*
54. *overridefor
55. *AdapterView.OnItemSelectedListener#onItemSelected()
56. */
57. publicvoidonItemSelected(AdapterViewparent,
    Viewv,intposition,longid){
58. mSwitcher.setImageResource(mImageIds[position]);
59. }
60. /*
61. *overrideforAdapterView.OnItemSelectedListener
    #onNothingSelected()
62. */
63. publicvoidonNothingSelected(AdapterView<?>arg0){
64. //TODOAuto-generatedmethodstub
65. }
66. publicclassImageAdapterextendsBaseAdapter{
67. publicImageAdapter(Contextc){
68. mContext=c;
69. }
70. publicintgetCount(){
71. returnmThumbIds.length;
72. }
73. publicObjectgetItem(intposition){
74. returnposition;
75. }
76. publiclonggetItemId(intposition){
77. returnposition;
78. }
79. publicViewgetView(intposition,ViewconvertView,
    ViewGroupparent){
80. ImageViewi=newImageView(mContext);
81. i.setImageResource(mThumbIds[position]);
82. i.setAdjustViewBounds(true);
83. i.setLayoutParams(newGallery.LayoutParams(
84. LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT));
85. i.setBackgroundResource(R.drawable.picture_frame);
86. returni;
87. }
88. privateContextmContext;
89. }
90. }

从Android图片浏览的代码中看到还实现了AdapterView.OnItemSelectedListener，这样就需要重写onItemSelected()方法，然后在该方法中：mSwitcher.setImageResource(mImageIds[position]);这样就实现了图片在ImageSwitcher中的切换。