Android圖片浏覽源碼解讀

Android手機操作系統的應用方式靈活，簡單，深受廣大編程愛好者的喜愛。尤其是它的開源代碼，使得我們能夠方便的得到自己想要的功能需求。今天我們就為大家帶來了有關Android圖片浏覽的相關方法。

首先是Android圖片浏覽中layout xml:

1. < ?xml version="1.0" encoding="utf-8"?>
2. < RelativeLayout xmlns:android="http://schemas.Android.com/apk/res/Android"
3. Android:layout_width="fill_parent"
4. Android:layout_height="fill_parent">
5. < ImageSwitcher Android: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. < Gallery Android: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裡面用到了前面所說的兩個控件，ImageSwitcher用啦顯示全圖，Gallery用來顯示縮略圖。著重看看ImageSwitcher,在ImageSwitcher1中需要實現ViewSwitcher.ViewFactory這個接口，這個接口裡有個方法makeView，這樣就產生了用來顯示圖片的view. ImageSwitcher調用過程是這樣的，首先要有一個Factory為它提供一個View，然後ImageSwitcher就可以初始化各種資源了。注意在使用一個ImageSwitcher之前，一定要調用setFactory方法，要不setImageResource這個方法會報空指針異常。

下面是Android圖片浏覽代碼：

1. package com.zx.imageswitcher;
2. import Android.app.Activity;
3. import Android.content.Context;
4. import Android.os.Bundle;
5. import Android.view.View;
6. import Android.view.ViewGroup;
7. import Android.view.animation.AnimationUtils;
8. import Android.widget.AdapterView;
9. import Android.widget.BaseAdapter;
10. import Android.widget.Gallery;
11. import Android.widget.ImageSwitcher;
12. import Android.widget.ImageView;
13. import Android.widget.ViewSwitcher;
14. import Android.widget.Gallery.LayoutParams;
15. public class ImageSwitcherTest extends Activity implements
16. AdapterView.OnItemSelectedListener, ViewSwitcher.ViewFactory{
17. private ImageSwitcher mSwitcher;
18. private Integer[] 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. private Integer[] 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. /** Called when the activity is first created. */
28. @Override
29. public void onCreate(Bundle savedInstanceState) {
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. Gallery g = (Gallery) findViewById(R.id.gallery);
39. g.setAdapter(new ImageAdapter(this));
40. g.setOnItemSelectedListener(this);
41. }
42. /*
43. * override for ViewSwitcher.ViewFactory#makeView()
44. */
45. public View makeView() {
46. ImageView i = new ImageView(this);
47. i.setBackgroundColor(0xFF000000);
48. i.setScaleType(ImageView.ScaleType.FIT_CENTER);
49. i.setLayoutParams(new ImageSwitcher.LayoutParams
    (LayoutParams.FILL_PARENT,
50. LayoutParams.FILL_PARENT));
51. return i;
52. }
53. /*
54. * override for
55. * AdapterView.OnItemSelectedListener#onItemSelected()
56. */
57. public void onItemSelected(AdapterView parent,
    View v, int position, long id) {
58. mSwitcher.setImageResource(mImageIds[position]);
59. }
60. /*
61. * override for AdapterView.OnItemSelectedListener
    #onNothingSelected()
62. */
63. public void onNothingSelected(AdapterView< ?> arg0) {
64. // TODO Auto-generated method stub
65. }
66. public class ImageAdapter extends BaseAdapter {
67. public ImageAdapter(Context c) {
68. mContext = c;
69. }
70. public int getCount() {
71. return mThumbIds.length;
72. }
73. public Object getItem(int position) {
74. return position;
75. }
76. public long getItemId(int position) {
77. return position;
78. }
79. public View getView(int position, View convertView,
    ViewGroup parent) {
80. ImageView i = new ImageView(mContext);
81. i.setImageResource(mThumbIds[position]);
82. i.setAdjustViewBounds(true);
83. i.setLayoutParams(new Gallery.LayoutParams(
84. LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
85. i.setBackgroundResource(R.drawable.picture_frame);
86. return i;
87. }
88. private Context mContext;
89. }
90. }

從Android圖片浏覽的代碼中看到還實現了AdapterView.OnItemSelectedListener，這樣就需要重寫onItemSelected()方法，然後在該方法中：mSwitcher.setImageResource(mImageIds[position]);這樣就實現了圖片在ImageSwitcher中的切換。