I am new to Android and programming as a whole and I need a little help with callbacks. I understand the gist of callbacks but I am unsure of how to go about implementing.
Context: I am writing a simple notetaking app that allows the user to write text and saving it to the app. The user can then request to read the file with a button. The text is then displayed on a textview in the main activity. There is an option to wipe this file and this is done with a confirmation pop up, which is another activity. This pop up contains 2 buttons, one to cancel and one to wipe. If the file is not empty it will wipe and does nothing if empty. I am not sure if this is the best way to implement it but I want to use the wipe button to callback to the main activity to clear the textview. The way I was thinking of was by using the callback to send a boolean value back. The main activity will check if the boolean is true and clear the textview if it is. I am unsure of how to implement the callback in my popup display to send this boolean value back to the main activity.
Code for main activity
public class MainActivity extends AppCompatActivity implements Popout.ClearTextView {
Button bnRead,bnWrite,bnClear;
TextView tvFileOP;
EditText etInput;
// private static final String INPUT_CONTENT = "inputContent";
public static final String TV_CONTENT = "textViewContent";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bnRead = (Button) findViewById(R.id.bnRead);
bnWrite = (Button) findViewById(R.id.bnWrite);
bnClear = (Button) findViewById(R.id.bnClear);
tvFileOP = (TextView) findViewById(R.id.tvFileOP);
etInput = (EditText) findViewById(R.id.etInput);
tvFileOP.setMovementMethod(new ScrollingMovementMethod());
final String fileName = "test_file";
String data;
bnRead.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
try {
FileInputStream fIn = openFileInput(fileName);
int c;
String temp = "";
while ( (c=fIn.read()) != -1){
temp = temp + Character.toString((char) c);
}
tvFileOP.setText(temp);
Toast.makeText(getBaseContext(),"file successfully read", Toast.LENGTH_LONG).show();
} catch (Exception e) {
e.printStackTrace();
}
}
});
bnWrite.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String data = etInput.getText().toString();
try {
FileOutputStream fOut = openFileOutput(fileName,MODE_APPEND);
fOut.write(data.getBytes());
fOut.close();
etInput.setText("");
Toast.makeText(getBaseContext(),"file successfully written", Toast.LENGTH_LONG).show();
} catch (Exception e) {
e.printStackTrace();
}
}
});
bnClear.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this,Popout.class));
}
});
}
#Override
protected void onSaveInstanceState(#NonNull Bundle outState) {
outState.putString(TV_CONTENT,tvFileOP.getText().toString());
super.onSaveInstanceState(outState);
}
#Override
protected void onRestoreInstanceState(#NonNull Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
tvFileOP.setText(savedInstanceState.getString(TV_CONTENT));
}
#Override
public void clearTextView(Boolean clear) {
if (clear){
tvFileOP.setText("");
}
}
}
Code for popup confirmation menu
public class Popout extends AppCompatActivity {
Button bnClosepopup,bnWipe;
TextView tvConfirmation;
String fileName = "test_file";
TextView tvFileOP;
public interface ClearTextView {
public void clearTextView(Boolean clear);
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.popupwindow);
bnClosepopup = (Button) findViewById(R.id.bnClosepopup);
bnWipe = (Button) findViewById(R.id.bnWipe);
tvConfirmation = (TextView) findViewById(R.id.tvConfirmation);
//HIDING THE TOOL BAR AT THE TOP OF THE SCREEN
this.getSupportActionBar().hide();
//GETTING THE SIZE OF THE SCREEN
DisplayMetrics displayMetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
int height = displayMetrics.heightPixels;
int width = displayMetrics.widthPixels;
getWindow().setLayout((int) (width*0.8) , (int) (0.8*height));
bnClosepopup.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
finish();
}
});
bnWipe.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
try {
File dir = getFilesDir();
File file = new File(dir, fileName);
boolean deleted = file.delete();
Toast.makeText(getBaseContext(),"file has been deleted",Toast.LENGTH_SHORT).show();
} catch (Exception e) {
Toast.makeText(getBaseContext(), e.getMessage(), Toast.LENGTH_LONG).show();
}
finish();
}
});
}
}
I am very new to android development and any tips on how to improve my code would be greatly appreciated :)
In this case there is no way to pass the interface to the other activity, because this is an activity to activity communication.
You have to use some other method, there is multiple ways to approach, the best way I can think of is to use startActivityForResult() to start the activity and then wait for a response to come back, and then query this response in the MainActivity by overriding the onActivityResult() method:
Example
In the MainActivity:
//on click of this button
bnClear.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this,Popout.class);
int requestCode = 12; //it could be whatever you want
startActivityForResult(intent , requestCode);
}
});
//override this method
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
//this is triggered when you finish the Popout Activity
if(requestCode == 12 && resultCode == Activity.RESULT_OK){
// get the boolean data returned from the Popout Activity
boolean deleted = data.getBooleanExtra("deleted_state" , false); //false is default if no value exists
}
}
In the Popout activity:
bnWipe.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
try {
File dir = getFilesDir();
File file = new File(dir, fileName);
boolean deleted = file.delete();
//send the result to onActivtyResult() in MainActivity
Intent result = new Intent();
result.putExtra("deleted_state", deleted );
setResult(Activity.RESULT_OK, result);
Toast.makeText(getBaseContext(),"file has been deleted",Toast.LENGTH_SHORT).show();
} catch (Exception e) {
Toast.makeText(getBaseContext(), e.getMessage(), Toast.LENGTH_LONG).show();
}
finish();
}
});
UPDATE:
It will be like this:
// get the boolean data returned from the Popout Activity
boolean deleted = data.getBooleanExtra("deleted_state" , false);
if (deleted){
tvFileOP.setText("");
}
..........
As far as what if Understood your problem correctly: You want to control your 'Wipe' button click event from your activity. Here is the solution which may help you.
1: Make an overridden constructor of your dialog class.
2: Create one abstract method in the dialog class. (say - onWipeButtonClick)
You need to make your dialog class abstract as well.
3: Inside on Click Listener of 'Wipe' button, call onWipeButtonClick abstract method.
4: Create the instance of dialog in the main activity where ever you want. The compiler will give you an error because you haven't implemented the call back method.
do implement your onWipeButtonClick method and do needful for wipe data inside the method.
public abstract class WipeDialog extends Dialog{
private Context context;
public WipeDialog(Context context){
this.context = context;
}
public abstract void onWipeButtonClick(boolean isTextEmpty);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.<XML_FILE>);
<initialization>
btnWipe.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
onWipeButtonClick(<YOUR_BOOLEAN_CHECK>);
}
});
}
}
And now in Activity:
WipeDialog dialog = new WipeDialog(MainActivity.this) {
#Override
public void onWipeButtonClick(boolean isTextEmpty) {
//Do Need full with respected to your requirement on click of button 'WIPE'
}
};
Hope this will help.
Thanks!
Related
I'm developing a feed app, where people can make posts and these posts will populate a RecyclerView.
I have a FAB button that leads to a post activity, but when I post and then comeback to the MainActivity the list is not updated. But when I use the logout button and log back in, the list gets updated, or when I launch the activity it works.
I think this happens because my Async function gets called to work on onCreate, but I can't work like these, I need the AsyncTask to automatically fetch, otherwise people won't get the list updated in real time.
Could you please show me a light in the dark? Here are the codes for MainActivity, PostActivity and logout function from another class.
Main Activity:
public class MainActivity extends AppCompatActivity {
private AppCompatActivity activity = MainActivity.this;
private RecyclerView recyclerViewNews;
private List<Noticia> listNoticias;
private NewsRecyclerAdapter newsRecyclerAdapter;
private DBNoticias databaseHelper;
private Button btnLogout;
private LinearLayoutManager mLayoutManager;
UserSession userSession;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
userSession = new UserSession(getApplicationContext());
recyclerViewNews = findViewById(R.id.recyclerViewNews);
btnLogout = findViewById(R.id.btlogout);
TextView usuario = findViewById(R.id.textView5);
/**
* Olá mundo by Alciomar
*/
SharedPreferences sharedPreferences = getSharedPreferences("Reg", Context.MODE_PRIVATE);
String uName = sharedPreferences.getString("Name", "");
usuario.setText(uName.toUpperCase());
try {
btnLogout.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
userSession.logoutUser();
}
});
} catch (Exception e) {
e.printStackTrace();
}
initStuff();
getDataFromPostgres();
FloatingActionButton fab = findViewById(R.id.fabNews);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(MainActivity.this, PostNews.class);
startActivity(intent);
}
});
}
/**
* This method is to initialize objects to be used
*/
private void initStuff() {
try {
listNoticias = new ArrayList<>();
newsRecyclerAdapter = new NewsRecyclerAdapter(listNoticias);
mLayoutManager = new LinearLayoutManager(getApplicationContext());
mLayoutManager.setReverseLayout(true);
mLayoutManager.setStackFromEnd(true);
recyclerViewNews.setLayoutManager(mLayoutManager);
recyclerViewNews.setItemAnimator(new DefaultItemAnimator());
recyclerViewNews.setHasFixedSize(true);
recyclerViewNews.setAdapter(newsRecyclerAdapter);
databaseHelper = new DBNoticias(activity);
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* This method is to fetch all user records from SQLite
*/
private void getDataFromPostgres() {
// AsyncTask is used that SQLite operation not blocks the UI Thread.
new AsyncTask<Void, Void, Void>() {
#Override
protected Void doInBackground(Void... params) {
listNoticias.clear();
for (DBNoticias dbNoticias : databaseHelper.getNewsList()) {
Noticia noticia = new Noticia();
noticia.setUser_id(dbNoticias.getId());
noticia.setNewsTitle(dbNoticias.getNewsTitle());
noticia.setNewsMessage(dbNoticias.getNewsPost());
listNoticias.add(noticia);
}
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
newsRecyclerAdapter.notifyDataSetChanged();
}
}.execute();
}
Post News Activity:
public class PostNews extends AppCompatActivity {
private DBNoticias dbNoticias;
private Button btnpostar;
private EditText editTextCDNewsTitle;
private EditText editTextCDNewsPost;
private Noticia noticia;
private SharedPreferences sharedPreferences;
public void alert(String titulo, String txt){
AlertDialog alertDialog = new AlertDialog.Builder(PostNews.this).create();
alertDialog.setTitle(titulo);
alertDialog.setMessage(txt);
alertDialog.setButton(AlertDialog.BUTTON_NEUTRAL, "OK",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
alertDialog.show();
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_post_news);
btnpostar = findViewById(R.id.btn_postar);
dbNoticias = new DBNoticias();
editTextCDNewsTitle = findViewById(R.id.EditTextNewsTitle);
editTextCDNewsPost = findViewById(R.id.EditTextNewsPost);
}
public void salvarNoticia(View view) {
try {
{
String newsTitle = editTextCDNewsTitle.getText().toString();
String newsPost = editTextCDNewsPost.getText().toString();
if (!(editTextCDNewsTitle.getText().toString().equals("") || editTextCDNewsTitle.getText() == null ||
editTextCDNewsPost.getText().toString().equals("") || editTextCDNewsPost.getText() == null
)) {
sharedPreferences = getSharedPreferences("Reg", Context.MODE_PRIVATE);
String uName = sharedPreferences.getString("Name", "");
String uEmail = sharedPreferences.getString("Email", "");
int uIdUser = sharedPreferences.getInt("IdUser", 0);
dbNoticias.setNewsTitle(newsTitle);
dbNoticias.setNewsPost(newsPost);
dbNoticias.setIdUser(uIdUser);
dbNoticias.salvar();
noticia = new Noticia();
Toast.makeText(getApplicationContext(), "Notícia postada com sucesso",
Toast.LENGTH_LONG).show();
editTextCDNewsTitle.setText("");
editTextCDNewsPost.setText("");
}
}
}
catch (Exception e){
alert("Erro", e.getMessage());
}
}
Thank you in advance if you read and try to help!
There are multiple ways to do this:
Method 1 – Use onResume()
If you call your getDataFromPostgres() method in onResume instead of onCreate, it'll fetch data and refresh list every time the activity wakes from a pause (for example coming back from another activity)
// existing code
#Override
public void onResume(){
super.onResume();
getDataFromPostgres()
}
(This would be the simplest solution)
Method 2 – Poll the DB continuously
If there are other services that might be updating the database and you need to always show the latest state in the activity, another way (although really inefficient) would be to keep refreshing the list after a defined time period (let's say 10 seconds as an example).
How to run an async task for every x mins in android?
Method 3 – Use onActivityResult
If you want to update the list only when a new entry has been created in the second activity, you can use onActivityResult to notify the first activity on action and then refresh your list there.
How to manage `startActivityForResult` on Android?
Please use this, it's working for me
newsRecyclerAdapter.notifyItemInserted(position);
newsRecyclerAdapter.notifyDataSetChanged();
I have three Activities. MainActivity,ActivityB and ActivityC. In activity A and B there are two buttons source and destination in both activities. in Activity C there is a list of data. when button is clicked (either Source or destination) from activity A and B. both Activities are calling Activity C
code for Activity A is following
public class MainActivity extends Activity {
TextView source,destination;
Button sendSource,sendDestination,btnTob;
String src,des,activity,checksrc,checkdes;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
source=(TextView)findViewById(R.id.tv_rcvDataA);
destination=(TextView)findViewById(R.id.tv_rcvDataAa);
sendSource=(Button)findViewById(R.id.btn_sendA);
sendDestination=(Button)findViewById(R.id.btn_sendAa);
btnTob=(Button)findViewById(R.id.btn_toB);
sendSource.setText("source");
sendDestination.setText("destination");
src=sendSource.getText().toString();
des=sendDestination.getText().toString();
activity=getClass().getSimpleName();
sendSource.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent send= new Intent(MainActivity.this,ActivityC.class);
send.putExtra("source",src);
send.putExtra("Activity",activity);
startActivity(send);
}
});
sendDestination.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent senda= new Intent(MainActivity.this,ActivityC.class);
senda.putExtra("destination",des);
senda.putExtra("Activity",activity);
startActivity(senda);
}
});
btnTob.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent movetoB= new Intent(MainActivity.this,ActivityB.class);
startActivity(movetoB);
finish();
}
}); }}
and code for Activity B is
public class ActivityB extends Activity {
TextView sourceB,destinationB;
Button sendSourceB,sendDestinationB;
String src,des,activity,checksrc,checkdes;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_b);
sourceB=(TextView)findViewById(R.id.tv_rcvDataB);
destinationB=(TextView)findViewById(R.id.tv_rcvDataBa);
sendSourceB=(Button)findViewById(R.id.btn_sendB);
sendDestinationB=(Button)findViewById(R.id.btn_sendDataBa);
activity=getClass().getSimpleName();
sendDestinationB.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent senda= new Intent(ActivityB.this,ActivityC.class);
senda.putExtra("destination",src);
senda.putExtra("Activity",activity);
startActivity(senda);
}
});
sendSourceB.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent send= new Intent(ActivityB.this,ActivityC.class);
send.putExtra("source",src);
send.putExtra("Activity",activity);
startActivity(send);
}
});}}
now how to check in activityC which activity is calling this activity and which buttonclicklistener is calling the intent
You need to send the value for determine what value and what activity via Intent.putExtra(). Please be remember that you need to set the key as the first parameter for Intent.putExtra(), like
intent.putExtra(THIS_IS_THE_KEY, THIS_IS_YOUR_VALUE);
You need to create something like this:
// This is the key for your putExtra
// you need to create this as global variable.
public static final String FROM_KEY = "FROM";
public static final String ACTIVITY_KEY = "ACTIVITY";
public static final boolean IS_FROM_SOURCE = true;
// This is a sample to send data to Activity C
// where the activity caller is B and from source
Intent senda= new Intent(ActivityB.this,ActivityC.class);
senda.putExtra(FROM_KEY, IS_FROM_SOURCE);
senda.putExtra(ACTIVITY_KEY,"activity_a");
Then in your Activity C, you need to receive the Intent Extra.
You can get the value in Activity onCreate(), something like this:
Bundle extras = getIntent().getExtras();
boolean from = extras.getBoolean(FROM_KEY);
String act = extras.getString(ACTIVITY_KEY);
// do something here if from activity a
if(act.equals("activity_a")) {
if(IS_FROM_SOURCE) {
// do something if from source
} else {
// do something if from destination.
}
} else { // if from activity a
if(IS_FROM_SOURCE) {
// do something if from source
} else {
// do something if from destination.
}
}
In onCreate or anytime after that method is called in Activity-C, you should do the following:
Intent intent = getIntent();
if (intent != null) {
String activity = intent.getStringExtra("Activity");
String src = intent.getStringExtra("source");
// Do something with those values
}
I have this onClickListener method on my login activity in my android app:
btnLogin.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View arg0) {
InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(txtEmail.getWindowToken(), 0);
imm.hideSoftInputFromWindow(txtPassword.getWindowToken(), 0);
String password = txtPassword.getText().toString();
String email = txtEmail.getText().toString();
if ((txtEmail.length() == 0) || (txtPassword.length() == 0)) {
Toast.makeText(LoginMember.this, "You need to provide values for Email and Password", Toast.LENGTH_SHORT).show();
return;
}
//Go ahead and perform the transaction
String[] params = {email,password};
new EndpointsAsyncTaskInsert(LoginMember.this).execute(params);
}
});
It sends data to Google App Engine without any problems, already my EndpointsAsyncTask class defined, etc etc
Now, my problem is, I need to also go to another activity after this, I'm not realyl sure, but If I remember well I could do this automatically when logged in by using SQLite, don't know how to accomplish it here.
Already have the activities I need declared on manifest.
It should be something like this:
#Override
public void onClick(View v){
Intent intent = new Intent(LoginMember.this, WelcomeScreen.class);
startActivity(intent);
}
My problem is that I don't know how to "add" or "append" this activity transaction into this logic, I'm fairly new to android and google app engine, Any ideas???
Thanks in advance!
EDIT
This is my EndpointsAsyncTaskInsert code:
package com.kkoci.shairlook;
import android.content.Context;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.Toast;
import com.appspot.shairlook1.userEndpoint.UserEndpoint;
import com.appspot.shairlook1.userEndpoint.model.User;
import com.google.api.client.extensions.android.http.AndroidHttp;
import com.google.api.client.extensions.android.json.AndroidJsonFactory;
import com.google.api.client.googleapis.services.AbstractGoogleClientRequest;
import com.google.api.client.googleapis.services.GoogleClientRequestInitializer;
import java.io.IOException;
import java.util.Collections;
import java.util.List;
/**
* Created by kristian on 04/07/2015.
*/
public class EndpointsAsyncTaskInsert extends AsyncTask<String, Void, User> implements GoogleClientRequestInitializer {
private static UserEndpoint myApiService = null;
private Context context;
EndpointsAsyncTaskInsert(Context context) {
this.context = context;
}
#Override
public void initialize(AbstractGoogleClientRequest<?> abstractGoogleClientRequest) throws IOException {
// put it here no in MyClass
abstractGoogleClientRequest.setDisableGZipContent(true);
}
// class MyClass{} // you don't need it
#Override
protected User doInBackground(String... params) {
User response = null;
if (myApiService == null) { // Only do this once
UserEndpoint.Builder builder = new UserEndpoint.Builder(AndroidHttp.newCompatibleTransport(),
new AndroidJsonFactory(), null)
// options for running against local devappserver
// - 10.0.2.2 is localhost's IP address in Android emulator
// - turn off compression when running against local devappserver
.setRootUrl("https://shairlook1.appspot.com/_ah/api/")
.setGoogleClientRequestInitializer(this);
// end options for devappserver
myApiService = builder.build();
}
try {
User users = new User();
users.setEmail(params[0]);
users.setPassword(params[1]);
users.setName(params[2]);
response = myApiService.insertUser(users).execute();
} catch (Exception e) {
Log.d("Could not Add User", e.getMessage(), e);
}
return response;
}
}
SECOND EDIT
This is how it looks right now, it's giving me 'java.lang.NoClassDefFoundError' on this line: new EndpointsAsyncTaskInsert(LoginMember.this) {
:
public class LoginMember extends Activity {
private static
//DbAdapter dbAdapter = null;
//EditText txtUserName;
EditText txtPassword;
EditText txtEmail;
Button btnLogin;
TextView Forgot_text;
Button twitter;
Button facebook;
//Button btnRegister;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
txtPassword = (EditText) findViewById(R.id.et_pw);
txtEmail = (EditText) findViewById(R.id.et_email);
btnLogin = (Button) findViewById(R.id.btn_login);
twitter = (Button) findViewById(R.id.twitter);
facebook = (Button) findViewById(R.id.facebook);
Forgot_text = (TextView) findViewById(R.id.Forgot_text);
btnLogin.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View arg0) {
InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(txtEmail.getWindowToken(), 0);
imm.hideSoftInputFromWindow(txtPassword.getWindowToken(), 0);
String password = txtPassword.getText().toString();
String email = txtEmail.getText().toString();
if ((txtEmail.length() == 0) || (txtPassword.length() == 0)) {
Toast.makeText(LoginMember.this, "You need to provide values for Email and Password", Toast.LENGTH_SHORT).show();
return;
}
//Go ahead and perform the transaction
String[] params = {email,password};
//new EndpointsAsyncTaskInsert(LoginMember.this).execute(params);
/**try{ Intent k = new Intent(LoginMember.this, WelcomeScreen.class);
startActivity(k);
}catch(Exception e){
}**/
new EndpointsAsyncTaskInsert(LoginMember.this) {
protected void onPostExecute(User result) {
super.onPostExecute(result);
// Do something with result
Intent intent = new Intent(LoginMember.this, WelcomeScreen.class);
startActivity(intent);
}
}.execute(params);
}
});
}
public void getUser(View v) {
new EndpointsAsyncTask(this).execute();
}
public void insertUser(View v) {
new EndpointsAsyncTaskInsert(this).execute();
}
}
ok, i see, maybe you should do this, i haven't tryied this yet, but could help you:
Before onCreate method, declare a var of this way:
Activity currentActivity;
then inside onCreate method do this:
currentActivity=this;
so then, when you make you Asyctask, make this:
new EndpointsAsyncTaskInsert(currentActivity.getApplicationContext()).execute(params);
Hope that helps, let's me know if was helpFull, if not i try to help you in another way.
Regards.
In EndpointsAsyncTask class there should be method named onPostExecute() which is executed when your async task is completed. This is the place where you should notify your activity to go to another activity.
There are numerous way to do that.
You can create an Interface class for instance
public interface OnTaskFinishListener{
void onFinish();
}
and then implement this interface in your caller class:
public class YourActivity extends Activity implements OnTaskFinishListener {
void onFinish(){
Intent intent = new Intent(LoginMember.this, WelcomeScreen.class);
startActivity(intent);
}
}
When you create asynctask you should pass this reference as a parameter in its constructor and keep it in task fields and when the task is done call the onFinish method.
public EndpointsAsyncTaskInsert extends AsyncTask...{
private OnTaskFinishListener listener;
public EndpointsAsyncTaskInsert(OnTaskFinishListener listener){
this.listener = listener;
}
protected void onPostExecute(..){
//notify the listener
listener.onFinish();
}
}
Second and more loosely coupled way is to use an event bus library, for example, greenrobots EventBus https://github.com/greenrobot/EventBus, then you can post an event when your task is finished, and then you can receive that event in your activity without setting up any listeners.
You can make an anonymous version of your AsyncTask class and override the onPostExecute to start the new activity after it is done.
new EndpointsAsyncTaskInsert(LoginMember.this) {
protected void onPostExecute(User result) {
super.onPostExecute(result);
// Do something with result
Intent intent = new Intent(LoginMember.this, WelcomeScreen.class);
startActivity(intent);
}
}.execute(params);
Maybe this might work
if ((txtEmail.length() == 0) || (txtPassword.length() == 0)) {
Toast.makeText(LoginMember.this, "You need to provide values for Email and Password", Toast.LENGTH_SHORT).show();
return;
}
else{
String[] params = {email,password};
new EndpointsAsyncTaskInsert(LoginMember.this).execute(params);
}
In the class which extends the Asynctask override the onpostexecute method and add the following code
Intent in=new Intent(Login.this,Welcome.class);
in.putExtra("email",email);
in.putExtra("password",password);
startActivity(in);
You can use bundle to send data from one activity to another and retrieve from the bundle in the Welcome activity
Intent in=getIntent();
String email=in.getStringExtra("email");
I have problem with my App ,, and want to solve it but i could not access to solution please help me ,,,
// Main_Activity Class
public class MainActivity extends Activity {
Button Open_play_list;
AccessPlayList accessPL;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Open_play_list = (Button)findViewById(R.id.btnShA);
accessPL = new AccessPlayList();
Open_play_list.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// Calling method tht contain code for open playlist
try {
accessPL.openPlaylist();
}`enter code here`
catch (Exception ex) {
Toast.makeText(getBaseContext(), ex.getMessage().toString(), Toast.LENGTH_LONG).show();
}
}
});
}
// AccessPlayList Class
public class AccessPlayList extends Activity {
Intent intentPL;
int REQUEST_CODE = 1;
int PLAYLIST_ID = 2;
public void openPlaylist()
{
intentPL = new Intent(Intent.ACTION_PICK);
intentPL.setComponent(new ComponentName("com.android.music","com.android.music.PlaylistBrowserActivity"));
intentPL.setType("MediaStore.Audio.Playlist.CONTENT_TYPE");
intentPL.setFlags(0x10000000);
intentPL.putExtra("oneShot",false);
intentPL.putExtra("PlayList",PLAYLIST_ID);
startActivityForResult(intentPL,REQUEST_CODE);
}
}
Since you did not post which line of your code is where the error is occurring, the only thing I can tell you is that you need to check if the object causing the problem is null.
Try some validation like this:
if(object != null){
//do something
}
I have an Activity SaveData.class with a public method addEvent() use to add some information in a DataBase table as follows:
public class SaveData extends Activity implements OnClickListener {
public SoftCopyDatabase dB ;
public static String FILE_NAME;
String _subject, _topic,_lecturenumber,_date;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.save);
View add = findViewById(R.id.saveSave);
add.setOnClickListener(this);
View home = findViewById(R.id.saveBack);
home.setOnClickListener(this);
}public void onStart() {
super.onStart();
dB = new SoftCopyDatabase(this);
}
public void onStop() {
super.onStop();
if (dB.getReadableDatabase().isOpen()) {
//dB.close();
}
}
public void onDestroy() {
super.onDestroy();
if (dB.getReadableDatabase().isOpen()) {
dB.close();
}
}
public void onClick(View v) {
switch (v.getId()) {
case R.id.saveBack:
Intent i = new Intent(this, OpenScreen.class);
startActivity(i);
break;
case R.id.saveSave:
EditText subject = (EditText) findViewById(R.id.subjectid);
EditText topic = (EditText) findViewById(R.id.topicid);
EditText lecturenumber = (EditText) findViewById(R.id.lecturenumberid);
EditText date = (EditText) findViewById(R.id.dateid);
_subject = ((TextView) subject).getText().toString();
_topic = ((TextView) topic).getText().toString();
_lecturenumber = ((TextView) lecturenumber).getText()
.toString();
_date = ((TextView) date).getText().toString();
FILE_NAME = _subject + _topic + _lecturenumber;
//addEvent();
Intent j = new Intent(this, LectureNoting.class);
startActivity(j);
break;
}
}
public void addEvent() {
ContentValues values = new ContentValues();
values.put(SUBJECT, _subject);
values.put(TOPIC, _topic);
values.put(LECTURENUMBER, _lecturenumber);
values.put(DATE, _date);
values.put(_DATA, FILE_NAME + ".png");
dB.getWritableDatabase().insertOrThrow(TABLE_NAME, null, values);
}
}
Another activity LectureNoting.class is used to save Drawings on the disk and updates the entry in Database Table as follows:
public class LectureNoting extends Activity implements View.OnTouchListener{
private SaveData sD=new SaveData();
private File directory = new File("/sdcard/SoftCopy");
//...remaining code
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.drawing_activity);
}
//...remaining code
public void onClick(View view){
switch (view.getId()){
case R.id.saveBtn:
addEvent();
final Activity currentActivity = this;
Handler saveHandler = new Handler(){
#Override
public void handleMessage(Message msg) {
Toast.makeText(currentActivity, "Lecture Saved", Toast.LENGTH_SHORT).show();
}
} ;
new ExportBitmapToFile(this,saveHandler, softCopyInterface.getBitmap()).execute();
break;
//...remaining code
}
private class ExportBitmapToFile extends AsyncTask<Intent,Void,Boolean> {
private Context mContext;
private Handler mHandler;
private Bitmap nBitmap;
public ExportBitmapToFile(Context context,Handler handler,Bitmap bitmap) {
mContext = context;
nBitmap = bitmap;
mHandler = handler;
}
#Override
protected Boolean doInBackground(Intent... arg0) {
try {
if (!directory.exists()) {
directory.mkdirs();
}
final FileOutputStream out = new FileOutputStream(new File(directory + "/"+SaveData.FILE_NAME+".png"));
nBitmap.compress(Bitmap.CompressFormat.PNG, 90, out);
out.flush();
out.close();
return true;
}
catch (FileNotFoundException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}
return false;
}
#Override
protected void onPostExecute(Boolean bool) {
super.onPostExecute(bool);
if ( bool ){
mHandler.sendEmptyMessage(1);
}
}
}
}
And I am receiving following error:
Unable to start activity componentInfo(com.ned.LectureNoting):NullPointerException
At the addEvent(), used in the onClick method of LectureNoting.
Kindly tell me where I am going wrong. One point I would like to mention is if addEvent() is called from the same activity in which it was defined, this error does not appear.
Couple of things:
Logcat should be giving more information about the error. You may have to scroll down a bit to see the source of the problem in your code, but there should be more info.
you shouldnt be defining public methods inside of classes that extend Activity to be used by other classes. If you want to expose some database method to multiple activities, then create a separate class for that and then call that method inside of your activity. You said LectureNoting extends Activity. You sure about this? You must have it extending SaveData if you are just calling addEvent() like that.
Either way, DON'T CALL METHODS FROM ONE ACTIVITY INSIDE OF ANOTHER. If you want to expose a method to multiple activities, create it in it's own class with a sensible name related to the group of functions that you expose.