重新安装应用程序后，为什么数据没有被删除。 在模拟器上？

Question

I wrote some test code to learn how to use SharedPreferences. The app saves data fine, but when I ran the application again by pressing "run" on eclipse, the console window said it was uploading, installing, and starting the application. Since it said installing again, I was expecting the data stored with SharedPreferences to be deleted. However, the old data was still displayed when i went into the activity.

My program runs like this:

1. splash screen
2. list menu activity with 3 activity options
3. the target activity where i implemented the saving function

Here is my code for that specific activity:

public class StartingPoint extends Activity {
/** Called when the activity is first created. */

int counter;
Button add;
Button sub;
TextView display;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.main);

    counter=0;

    add= (Button) findViewById(R.id.bAdd);
    sub= (Button) findViewById(R.id.bSub);
    display= (TextView) findViewById(R.id.tvDisplay);

    add.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            counter++;
            display.setText(""+counter);
            display.setTextSize(counter);
        }
    });
    sub.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            counter--;
            display.setText(""+counter);
            display.setTextSize(counter);
        }
    });

}

@Override
protected void onStart() {
    // TODO Auto-generated method stub
    super.onStart();

    SharedPreferences prefs = getPreferences(0); 
    int getfromfile = prefs.getInt("counter_store", 1);
    counter=getfromfile;
    display.setText(""+getfromfile);
    display.setTextSize(getfromfile);
}

@Override
protected void onStop() {
    // TODO Auto-generated method stub
    super.onStop();

     SharedPreferences.Editor editor = getPreferences(0).edit();
     editor.putInt("counter_store", counter);
     editor.commit();
}
}

Answer 1

Since it said installing again, I was expecting the data stored with SharedPreferences to be deleted

Re-running the application from Eclipse is akin to doing an upgrade on the app in production. All data associated with the app is left intact.

You can clear out the old data in the emulator by the same means as you would use on a phone, via the Settings application and its Applications screen.

Answer 2

That's just how it works. It installs over the previous install. If you want to remove all that data, you can uninstall first, or you can clear data from Manage Applications.

Answer 3

I guess because testing some functionality in an app that uses shared prefs would be impossible if it was wiped every time you made a minor change to the code and re-ran the app. See CommonsWare answer if you want to clear the data.

Answer 4

The easiest/clean soln to wipe your app data is to uninstall it using adb . You will find adb in your sdk. -e option is for emulator. Use -d for device.

Command you can run is:

>adb -e uninstall <app_package_name>