android - SharedPreferences behaviour on Update/Uninstall

Question

I am using shared preferences to store the number of times my application has been launched. Only on the first launch i display an Welcome message telling the user about the new features and changes in that version.

But as i absorbed on reinstalling the app or upgrading the application i am not able to remove the previous shared preferences. i would like to get the dialog when i reinstall the software or upgrade it too.

AppLauncher

public class AppLauncher {
    static long launch_count = 0;
    private static boolean isLaunch = false;

    public static void app_launched(Context mContext) {
        System.out.println("I m in AppLauncher");
        SharedPreferences prefs = mContext.getSharedPreferences("apprater", 0);
        if (prefs.getBoolean("dontshowagain", false)) {
            return;
        }

        SharedPreferences.Editor editor = prefs.edit();

        // Increment launch counter

        launch_count = prefs.getLong("launch_count", 0);
        editor.putLong("launch_count", launch_count);

        System.out.println("launch_count=" + launch_count);
        if (launch_count == 0 || launch_count == 1) {
            // showLaunchDialog(mContext);
            isLaunch = true;
        }
        if (isLaunch == true) {
            showLaunchDialog(mContext);
            isLaunch = false;
        }
        editor.commit();
    }

    public static void showLaunchDialog(Context mcontext) {
        final Dialog dialog = new Dialog(mcontext);
        dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
        dialog.setContentView(R.layout.whatsnew);

        Button dismisButton = (Button) dialog.findViewById(R.id.dismisButtom);
        System.out.println("inside dialog_started");
        dismisButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View arg0) {
                dialog.dismiss();
            }
        });
        dialog.show();
    }
}

Answer 1

There is no hook that you can use to erase the shared preferences in the case of an update.

Nikolay is right you can save the version number of your app. And compare it with the current version number.

To obtain the current version number call:

this.getPackageManager().getPackageInfo(this.getPackageName(), 0).versionCode

For more info on what information is available in the package info read the Documentation on the PackageInfo and the PackageManager.