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Android之Shared Preferences

Eric Song — Mon, 07 Jun 2010 09:18:00 GMT

懒得再翻译，�q�段应该很好理解�Q�直接将Dev Guide中复制过来�?br />

The SharedPreferences class provides a general framework that allows you to save and retrieve persistent key-value pairs of primitive data types. You can use SharedPreferences to save any primitive data: booleans, floats, ints, longs, and strings. This data will persist across user sessions (even if your application is killed).

To get a SharedPreferences object for your application, use one of two methods:

getSharedPreferences() - Use this if you need multiple preferences files identified by name, which you specify with the first parameter.
getPreferences() - Use this if you need only one preferences file for your Activity. Because this will be the only preferences file for your Activity, you don't supply a name.

To write values:

Call edit() to get a SharedPreferences.Editor.
Add values with methods such as putBoolean() and putString().
Commit the new values with commit()

To read values, use SharedPreferences methods such as getBoolean() and getString().

Here is an example that saves a preference for silent keypress mode in a calculator:

1public class Calc extends Activity {
2    public static final String PREFS_NAME = "MyPrefsFile";
3
4    @Override
5    protected void onCreate(Bundle state){
6       super.onCreate(state);
7       . . .
8
9       // Restore preferences
10       SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
11       boolean silent = settings.getBoolean("silentMode", false);
12       setSilent(silent);
13    }
14
15    @Override
16    protected void onStop(){
17       super.onStop();
18
19      // We need an Editor object to make preference changes.
20      // All objects are from android.context.Context
21      SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
22      SharedPreferences.Editor editor = settings.edit();
23      editor.putBoolean("silentMode", mSilentMode);
24
25      // Commit the edits!
26      editor.commit();
27    }
28}

Eric Song 2010-06-07 17:18 发表评论

Eric Song — Mon, 07 Jun 2010 08:28:00 GMT

首先内部存储路径�?data/data/youPackageName/�Q�下面讲解的各�\径都是基于你自己的应用的内部存储路径下。所有内部存储中保存的文件在用户卸蝲应用的时候会(x��)被删除�?br />
一�?nbsp;files
1. Context.getFilesDir()�Q�该�Ҏ(gu��)��q�回/data/data/youPackageName/files的File对象�?br /> 2. Context.openFileInput()与Context.openFileOutput()�Q�只能读取和写入files下的文�g�Q�返回的是FileInputStream和FileOutputStream对象�?br /> 3. Context.fileList()�Q�返回files下所有的文�g名，�q�回的是String[]对象�?br /> 4. Context.deleteFile(String)�Q�删除files下指定名�U�的文�g�?br />
二、cache
1. Context.getCacheDir()�Q�该�Ҏ(gu��)��q�回/data/data/youPackageName/cache的File对象�?br />
三、custom dir

getDir(String name, int mode)�Q�返�?data/data/youPackageName/下的指定名称的文件夹File对象�Q�如果该文�g夹不存在则用指定名称创徏一个新的文件夹�?/span>

Eric Song 2010-06-07 16:28 发表评论

Eric Song — Wed, 19 May 2010 11:20:00 GMT

�l�过不断的测试最�l�得�?个结果：(x��)

1.适用于模拟器和OPhone

1Intent sendIntent = new Intent(Intent.ACTION_SEND);
2sendIntent.putExtra(Intent.EXTRA_STREAM, Uri.parse("file:///sdcard/map.jpg"));
3sendIntent.setType("image/jpeg");
4startActivity(sendIntent);

2.适用于Hero�Q�未��试是否支持其他HTC手机�Q?/span>

1Intent sendIntent = new Intent("android.intent.action.SEND_MSG");
2sendIntent.putExtra(Intent.EXTRA_STREAM, Uri.parse("file:///sdcard/map.jpg"));
3sendIntent.setType("image/jpeg");
4startActivity(sendIntent);

3.目前为止在多数手��Z��工作正常的代�?/span>

1Intent intent = new Intent(Intent.ACTION_SEND);
2intent.setClassName("com.android.mms", "com.android.mms.ui.ComposeMessageActivity");
3intent.putExtra(Intent.EXTRA_STREAM, Uri.parse("file:///sdcard/map.jpg")); // imageUri set previously
4intent.setType("image/jpeg");
5startActivity(intent);

需要注意的一个问题是之前一直用Uri指向自己开发应用的data文�g夹下的文�Ӟ��始终无法成功�Q�最�l�换成sdcard��O(ji��n)K了，看来�q�是权限的问题�?/span>

Eric Song 2010-05-19 19:20 发表评论

Eric Song — Mon, 14 Dec 2009 05:36:00 GMT

�?a >参�?http://hi.baidu.com/54nop/blog/item/08e7fad33db6bc32960a16ce.html

Eric Song 2009-12-14 13:36 发表评论

Eric Song — Wed, 09 Dec 2009 13:49:00 GMT

在MYSQL中如果在��的时候没有指定Timestamp字段是否为NULL�Q�则�pȝ��自动��d��默认��|��使用DEFAULT NULL也不好用�Q�其实是可以使用NULL直接指定的，如下�Q?br />
`CREATE_DATE` TIMESTAMP NULL

Eric Song 2009-12-09 21:49 发表评论

Java偏向锁实现原理讲�?Biased Locking)

Eric Song — Wed, 18 Nov 2009 05:10:00 GMT

引用�Q�Java偏向锁实现原理讲�?Biased Locking)(版权归原作者所�?

Eric Song 2009-11-18 13:10 发表评论

Eric Song — Sun, 18 Oct 2009 14:59:00 GMT

style和currentStyle都能用来取得当前样式表中的信息，但是style只能取得在HTML中用style声明的样式表信息�Q�无法取得通过class声明的样式表信息�Q�而currentStyle两种声明方式都可以取得�?

Eric Song 2009-10-18 22:59 发表评论