1、SharedPreferences
What is it?
A method of data persistence to
share configuration data
Where is it used?
Save some simple data, key-value
only needs to log in once, and log in automatically next time
Where does it exist?
data/data/package name/shared_prefs
This is internal storage
2. How to use
Constant definition:
Key public static final String LIST_VIEW_DATA_COUNTS = "list_view_data_counts";
文件名称 public static final String PREFERENCE_NAME = "preference_name";
默认值 public static final int DEFAULT_VALUE = 10;
2-1 Save
The system will automatically create an xml file for us, the name is: preference_name, address: data/data/com.jsc4.aboutactivity
private void saveData2Preference() {
SharedPreferences sharedPreferences = ListViewDemoActivity.this.getSharedPreferences(PREFERENCE_NAME, Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.putInt(LIST_VIEW_DATA_COUNTS, mDataCounts);
editor.apply(); 注意与commit的区别
}
The generated preference_name.xml content:
<?xml version='1.0' encoding='utf-8' standalone='yes' ?>
<map>
<int name="list_view_data_counts" value="16" />
</map>
2-2 Read
If you can read the value corresponding to the key LIST_VIEW_DATA_COUNTS, use the read value; if you can't read it, use the default value DEFAULT_VALUE
SharedPreferences sharedPreferences = getSharedPreferences(PREFERENCE_NAME, Context.MODE_PRIVATE);
mDataCounts = sharedPreferences.getInt(LIST_VIEW_DATA_COUNTS, DEFAULT_VALUE);
2-3 Modification
editor.putInt("list_view_data_counts", mDataCounts); 这里mDataCounts就是要存起来的数字
传入不同的值，就是修改：
editor.putInt("list_view_data_counts", mDataCounts + 1); 这里mDataCounts就是要存起来的数字
editor.apply(); 提交修改
When the content changes, the listener will tell us which key has changed:
sharedPreferences.registerOnSharedPreferenceChangeListener(new SharedPreferences.OnSharedPreferenceChangeListener() {
@Override
public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
}
});
2-4 delete
editor.remove(LIST_VIEW_DATA_COUNTS);
editor.apply(); 提交修改
3. Other points of attention
3-1 difference between apply and commit
For network-related and IO-related, separate threads must be opened to complete, asynchronously.
apply Write in the background, and open another thread to write; return void.
commit writes immediately and writes with UI thread; returns bool value
3-2 Clear data
Install ADB IDEA plug-in first, file——"Settings——"Plugin——"search and install, restart AS after installation
Use adb command to clear data