问题
I have an int "flag" variable , which will have two possible int values , 0 & 1.
Main theme of the app here is : Ask user yes or no?
If user selects YES, assign int=1. else if Selects No, assign int=0;
I am achieving this using:
public static int flag;
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.flag0:
flag=0;
System.err.println("Flag : " + flag);
break;
case R.id.flag1:
flag=1;
System.err.println("Flag : " + flag);
break;
default:
break;
}
}
My problem is here: it is ok & saving the preference upto my Application is running either foreground or background.
and once if we close/kill the application, all the stored preferences are being cleared i.e., setting to the default value of Zero.
As I just started working on STORAGE Options, I just tried to implement SHARED PREFERENCES, which still having the same above problem . the method I used to store the int value using Shared preferences is ;
Edit: I just tried the below answers but in vain & here is my total code I am posting it , will be helpful for you to test(Maybe)
xml File:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<TextView
android:id="@+id/text"
android:textSize="30sp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world" />
<Button android:id="@+id/flag0"
android:layout_marginTop="10dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/text"
android:text="set to 0"/>
<Button android:id="@+id/flag1"
android:layout_marginTop="10dp"
android:layout_below="@+id/text"
android:layout_toRightOf="@+id/flag0"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="set to 1"/>
<Button android:id="@+id/test0"
android:layout_marginTop="10dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/flag1"
android:text="Test for 0"/>
MainActivity:
public class MainActivity extends Activity implements OnClickListener {
TextView textView;
Button bt1,bt2,testbt1;
public static int flag;
SharedPreferences pref;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textView = (TextView) findViewById(R.id.text);
bt1 = (Button) findViewById(R.id.flag0);
bt2 = (Button) findViewById(R.id.flag1);
testbt1 = (Button) findViewById(R.id.test0);
bt1.setOnClickListener(this);
bt2.setOnClickListener(this);
testbt1.setOnClickListener(this);
pref=getSharedPreferences("Sai", MODE_PRIVATE);
pref.getInt("lang_us", 0);
System.err.println("Flag Value in Main method : " + flag);
}
public void saveFlag(){
pref=getSharedPreferences("Sai",MODE_PRIVATE);
Editor editor = pref.edit();
editor.putInt("lang_us", flag);
editor.commit();
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.flag0:
flag=0;
saveFlag();
System.err.println("Flag : " + flag);
break;
case R.id.flag1:
flag=1;
saveFlag();
System.err.println("Flag : " + flag);
break;
case R.id.test0:
System.err.println("Flag : " + flag);
if (flag == 0) {
textView.setText("flag is zero");
} else {
textView.setText("flag is not zero");
}
break;
default:
break;
}
}
}
Where is it going wrong?
回答1:
Your way of doing it is wrong
1.> Use Mode_PRIVATE(Used when you want your shared preference file should be accessible only to your app) instead of MODE_WORLD_WRITABLE(Used when you want your shared preference file should be accessible only outside your app)
2.> Make a method to save the state of flag
public void saveFlag(){
pref=getSharedPreferences("Sai",Context.MODE_PRIVATE);
Editor editor = pref.edit();
editor.putInt("lang_us", flag);
editor.commit();
}
3.> Call this method whenever you change flag
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.flag0:
flag=0;
saveFlag();
System.err.println("Flag : " + flag);
break;
case R.id.flag1:
flag=1;
saveFlag();
System.err.println("Flag : " + flag);
break;
default:
break;
}
4.> Then in your onCreate() method you should retrieve this value.
pref=getSharedPreferences("Sai",Context.MODE_PRIVATE);
flag = prefs.getInt("lang_us", 0);
回答2:
Put this code in your onClick method:
pref=getSharedPreferences("Sai",Context.MODE_PRIVATE);
Editor editor = pref.edit();
editor.putInt("lang_us", flag);
editor.commit();
Then in your onCreate() method you should retrieve this value.
pref=getSharedPreferences("Sai",Context.MODE_PRIVATE);
flag =prefs.getInt("lang_us", 0);
flag should now have the value you saved.
回答3:
Try this:
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
SharedPreferences.Editor sharedEditor = preferences.edit();
sharedEditor.putInt("lang_us", flag);
sharedEditor.commit();
It works for me.
And dont forget to retrieve the values with sharedEditor.getInt(..);
回答4:
Why not you use Boolean SharedPreferences I think that is best in your case.
This is an example
SharedPreferences prefs = PreferenceManager
.getDefaultSharedPreferences(this);
if (!prefs.getBoolean("firstTime", false)) {
SharedPreferences.Editor editor = prefs.edit();
editor.putBoolean("firstTime", true);
editor.commit();
}
来源：https://stackoverflow.com/questions/18757299/storing-an-int-value-using-shared-preferences