SharedPreferences

SharedPreferences:

Interface for accessing and modifying preference data returned by getSharedPreferences(String, int). For any particular set of preferences, there is a single instance of this class that all clients share. Modifications to the preferences must go through an SharedPreferences.Editor object to ensure the preference values remain in a consistent state and control when they are committed to storage.

可以用来在共享数据。

 

在SharedPreferences中保存数据，当Acitivity再次被launch，调用onResume()时，读取之前保存的数据。

注意：

1） SharedPreferences.Editor 用于编辑共享的数据

2）EditText 中的getSelectionStart()和getSelectionEnd()

代码如下：

PresistentState.java

public class PersistentState extends Activity { private EditText mSaved; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mSaved = (EditText)findViewById(R.id.saveField); } @Override protected void onPause() { // TODO Auto-generated method stub super.onPause(); SharedPreferences.Editor editor = getPreferences(0).edit(); editor.putString("text", mSaved.getText().toString()); editor.putInt("start", mSaved.getSelectionStart()); editor.putInt("end", mSaved.getSelectionEnd()); editor.commit(); } @Override protected void onResume() { // TODO Auto-generated method stub super.onResume(); SharedPreferences pre = getPreferences(0); String textString = pre.getString("text", null); if(textString != null){ mSaved.setText(textString, TextView.BufferType.EDITABLE); int start = pre.getInt("start", -1); int end = pre.getInt("end", -1); if(start != -1 && end != -1) mSaved.setSelection(start, end); } } } 

 

main.xml

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/hello" /> <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/save" /> <EditText android:id="@+id/saveField" android:layout_width="fill_parent" android:layout_height="wrap_content" android:background="@drawable/green" /> <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/notsave" /> <EditText android:id="@+id/notSaveField" android:layout_width="fill_parent" android:layout_height="wrap_content" android:background="@drawable/blue" /> </LinearLayout>