This question is a kind of followup on this unanswered question with more and better details.
Basically, I have an android main activity showing some data which are taken from a database (via SQLiteDatabase
). Now I have a PreferenceActivity
which is shown when the user wants to change some preference, or delete the content of the database. In the latter case the content of the database is deleted - but how do I make the main activity to be updated? If I look at the main activity after I pressed the button to delete the content of the database, I expect to show the main activity zero entries!
Here is the relevant part of the main activity:
public class MainActivity extends AppCompatActivity {
SharedPreferences.OnSharedPreferenceChangeListener mPrefListener;
private SharedPreferences settings;
public interface MyCallBack
{
public void refreshMainActivity();
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Intent intent = new Intent(this, AlarmService.class);
startService(intent);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
mCallback = new MyCallBack() {
@Override
public void refreshMainActivity() {
Toast.makeText(MainActivity.this, "TOAST MAINACTIVITY", Toast.LENGTH_LONG).show();
MainActivity.this.recreate();
}
};
/*
settings = PreferenceManager.getDefaultSharedPreferences(this);
mPrefListener = new SharedPreferences.OnSharedPreferenceChangeListener() {
@Override
public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
Log.d("TEST", "testtest");
Toast.makeText(MainActivity.this, "TOAST MAINACTIVITY", Toast.LENGTH_LONG).show();
finish();
startActivity(getIntent());
}
};
*/
// Register the listener on the SharedPreferences
settings.registerOnSharedPreferenceChangeListener(mPrefListener);
Here is the content of UserSettingActivity.java
:
public class UserSettingActivity extends PreferenceActivity {
private Preference myPreference;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.preferences);
myPreference = findPreference("reset");
myPreference.setOnPreferenceClickListener(new Preference.OnPreferenceClickListener() {
public boolean onPreferenceClick(Preference arg0) {
AlertDialog.Builder alertDialog = new AlertDialog.Builder(UserSettingActivity.this);
alertDialog.setMessage("Are you sure to delete the database?");
alertDialog.setCancelable(true);
alertDialog.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
final DBAdapter db = new DBAdapter(UserSettingActivity.this);
db.open();
db.resetDatabase();
callBack = MainActivity.mCallback;
callBack.refreshMainActivity();
} });
alertDialog.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
} });
alertDialog.show();
return false;
}
});
}
}
And finally, the xml file describing the layout of the settings in xml/preferences.xml
:
<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
<EditTextPreference android:title="Your Name"
android:key="username"
android:summary="Please provide your username"></EditTextPreference>
<CheckBoxPreference android:title="Application Updates"
android:defaultValue="false"
android:summary="This option if selected will allow the application to check for latest versions."
android:key="applicationUpdates" />
<Preference
android:key="reset"
android:title="Reset database"
android:summary="This will remove every entry in the database"
/>
</PreferenceScreen>
When I click on the button reset
on the Settings screen and confirm this choice, the database is deleted resetDatabase
does a DROP
and a CREATE TABLE
of the two tables in the database). However, the Toast
'TOAST MAINACTIVITY' is never shown on the display!
What do I miss here to make this work as I expect it to work? How do I trigger a method/function/something in my main activity from the UserSettingActivity
?
The Solution could be a bit tricky with using callback but i hope this will work for you according to your conditions..
First of all create interface in your MainActivity.java like this
public interface MyCallBack
{
public void refreshMainActivity();
}
then implement this interface in your main activity like this
public class MainActivity extends AppCompatActivity {
public static MyCallBack mCallback;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mCallback = new MyCallBack() {
@Override
public void refreshMainActivity() {
MainActivity.this.recreate();
"OR"
finish();
startActivity(getIntent());
}
};
}
Now in your userSettingActivity.java use this interface like this and call its method when you want to update your MainActivity.java
public class UserSettingActivity extends AppCompatActivity{
MainActivity.MyCallBack callBack;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.settingsactivity);
callBack = MainActivity.mCallback;
//this is sample code ..call this function when you want to update mainactivity
callBack.refreshMainActivity();
}
}
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