【慢慢学Android】:2.SharedPreferences对数据的存储
2012-05-25 16:19 ATP_ 阅读(1783) 评论(0) 编辑 收藏 举报SharedPreferences简介:
SharedPreferences是Android平台上一个轻量级的存储类,它的本质是基于XML文件存储key-value键值对数据,通常用来存储一些简单的配置信息,比如窗口状态,一些小型自定义数据等。其存储位置在/data/data/<包名>/shared_prefs目录下,可以通过DDMS--FileExplorer下查看(选中文件点击DDMS右上角的导出文件)。
数据的存储:
1.构造函数:
如示例,一般常用的构造函数为2个参数
第一个为sp的名称,第二个一般为权限比如Activity.MODE_PRIVATE, MODE_APPEND, MODE_WORLD_READABLE, MODE_WORLD_WRITEABLE
public class Calc extends Activity { public static final String PREFS_NAME = "MyPrefsFile"; @Override protected void onCreate(Bundle state){ super.onCreate(state); . . . // Restore preferences SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0); boolean silent = settings.getBoolean("silentMode", false); setSilent(silent); }
2.数据的存储以及修改:
使用SharedPreferences.Editor类来构造一个编辑器进行存储数据
add.setOnClickListener(new OnClickListener(){ @Override public void onClick(View v) { // TODO Auto-generated method stub String str_name = (String) name.getText(); String str_path = (String) text.getText(); SharedPreferences Addresses = getSharedPreferences(PREFS_NAME,Activity.M ); SharedPreferences.Editor editor = Addresses.edit();//通过SharedPreferences.edit()来对Editor进行初始化
editor.putString(str_name,str_path);//添加数据
editor.commit(); //数据添加后必须提交才会修改xml文件
Toast.makeText(getApplicationContext(), "Successed", Toast.LENGTH_LONG).show();
}
});
删除数据
public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) { SharedPreferences Addresses = getSharedPreferences(PREFS_NAME, Activity.MODE_PRIVATE); SharedPreferences.Editor editor = Addresses.edit(); //通过SharedPreferences.edit()来对Editor进行初始化 editor.remove((String) listview.getSelectedItem()); //删除相应的数据 editor.commit(); //同样需要提交 } });
3.一些常用的方法:
void apply()
Commit your preferences changes back from this Editor to the
SharedPreferences object it is editing. |
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SharedPreferences.Editor clear()
Mark in the editor to remove all values from the preferences.
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boolean commit()
Commit your preferences changes back from this Editor to the
SharedPreferences object it is editing. |
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SharedPreferences.Editorput Boolean(String key, boolean value)
Set a boolean value in the preferences editor, to be written back once
commit() or apply() are called. |
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SharedPreferences.Editor putInt(String key, int value)
Set an int value in the preferences editor, to be written back once
commit() or apply() are called. |
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SharedPreferences.Editor putString(String key, String value)
Set a String value in the preferences editor, to be written back once
commit() or apply() are called. |
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SharedPreferences.Editor putStringSet(String key, Set<String> values)
Set a set of String values in the preferences editor, to be written back once
commit() is called. |
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SharedPreferences.Editor remove(String key)
Mark in the editor that a preference value should be removed, which will be done in the actual preferences once
commit() is called. |
数据的读取:
SharedPreferences.Editor edit()
Create a new Editor for these preferences, through which you can make modifications to the data in the preferences and atomically commit those changes back to the SharedPreferences object.
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Map<String, ?> getAll()
Retrieve all values from the preferences.
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boolean getBoolean(String key, boolean defValue)
Retrieve a boolean value from the preferences.
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String getString(String key, String defValue)
Retrieve a String value from the preferences.
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Set<String> getStringSet(String key, Set<String> defValues)
Retrieve a set of String values from the preferences.
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void registerOnSharedPreferenceChangeListener(SharedPreferences.OnSharedPreferenceChangeListener listener)
Registers a callback to be invoked when a change happens to a preference.
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void unregisterOnSharedPreferenceChangeListener(SharedPreferences.OnSharedPreferenceChangeListener listener)
Unregisters a previous callback.
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使用getAll()读取所有数据存储在一个HashMap中:
listview = (ListView) findViewById(R.id.lv); SharedPreferences Addresses = getSharedPreferences(PREFS_NAME, 0); listItems = (HashMap<String, Object>) Addresses.getAll();
还是挺好用的哈~~