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Android Studio - The (Very) Basics - startActivty doesn't work

im trying to move the info of a user from one activity to the other, but everytime i run the app it crashes at the "startActivity(i)" Line (i checked everything else, it only crashes at that line).
that's the MainActivity Code
package com.example.hw1511;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import com.example.hw1511.Model.User;
import org.w3c.dom.Text;
import java.io.Serializable;
import java.util.LinkedList;
import java.util.List;
public class MainActivity extends AppCompatActivity implements Serializable {
private EditText Name;
private EditText Age;
private EditText Birth;
private Button AddUser;
private Button Send;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Name = findViewById(R.id.Name);
Age = findViewById(R.id.Age);
Birth = findViewById(R.id.Birth);
AddUser = findViewById(R.id.AddUser);
Send = findViewById(R.id.Send);
Intent i = new Intent(MainActivity.this, SecondActivity.class);
List<User> list1 = new LinkedList<>();
AddUser.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (Name.getText().toString().trim().length() > 0 && Age.getText().toString().trim().length() > 0 && Birth.getText().toString().trim().length() > 0) {
User u = new User(Name.getText().toString(), Integer.parseInt(Age.getText().toString()), Birth.getText().toString());
list1.add(u);
Name.setText("");
Age.setText("");
Birth.setText("");
}
else {
Toast.makeText(MainActivity.this, "Fill All", Toast.LENGTH_SHORT).show();
}
}
});
Send.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
i.putExtra("Users", (Serializable) list1);
startActivity(i);
}
});
}
}
and that's the SecondActivty Code (it's preety much empty)
package com.example.hw1511;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import com.example.hw1511.Model.User;
import java.io.Serializable;
import java.util.LinkedList;
import java.util.List;
import java.util.jar.Attributes;
public class SecondActivity extends AppCompatActivity{
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
}
}
please if anyone help me understand what is making my app crash everytime i press the send button! it would really help me a lot.

Your User objects need to implement Serializable as well.
Also, since LinkedLists are Serializable you can use putSerializable(String key, Serializable value) instead of putExtra

Android app fails to connect with MySQL database

I have a .sql database which I edit using PHPmyadmin and a android app that retrieves the login credentials from the database and tries to login to the app according to the user's credentials. But it keeps showing "Unable to login" error in the app even though I use the correct credentials from the database, which in this case is phoneno and password. The Login_Activity.JAVA is as below. Why is the app not logging in properly?
Login_Activity.java
package com.example.ankit.mrestro.Controller;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
import com.baidu.android.pushservice.PushConstants;
import com.baidu.android.pushservice.PushManager;
import com.squareup.otto.Subscribe;
import com.example.ankit.mrestro.Bus.BusProvider;
import com.example.ankit.mrestro.Bus.LoginEvent;
import com.example.ankit.mrestro.Bus.LoginSuccessEvent;
import com.example.ankit.mrestro.Bus.PushRegisterEvent;
import com.example.ankit.mrestro.R;
import com.example.ankit.mrestro.model.LoginResult;
import com.example.ankit.mrestro.services.DataService;
import com.example.ankit.mrestro.services.RESTrepository;
public class LoginActivity extends Activity {
public static final String PREF_ACCOUNT_ID = "cust_id";
public static final String PREF_TOKEN = "accessToken";
public static final String SHARED_PREF_DB_NAME = "loginResult";
private ProgressDialog progressDialog;
public static Intent createIntent(Context c) {
return new Intent(c, LoginActivity.class);
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
DataService.init();
progressDialog = new ProgressDialog(this);
/**
* Check either we are already logged in
*/
SharedPreferences sharedPreferences = getSharedPreferences(SHARED_PREF_DB_NAME, 0);
if (sharedPreferences.getString(PREF_TOKEN, "").length() != 0) {
RESTrepository.setToken(sharedPreferences.getString(PREF_TOKEN, ""));
RESTrepository.setUser_id(sharedPreferences.getInt(PREF_ACCOUNT_ID, 0));
goToMainActivity();
}
setContentView(R.layout.activity_login);
PushManager.startWork(getApplicationContext(), PushConstants.LOGIN_TYPE_API_KEY,
"hwfeocSIPlgKTasIuARPREnS");
//SharedPreferences preferences=getSharedPreferences("pushService",0);
//String userId=preferences.getString("user_id","no data");
//Toast.makeText(this,"user id is:"+userId,Toast.LENGTH_SHORT).show();
Button loginButton=(Button)findViewById(R.id.email_sign_in_button);
loginButton.setOnClickListener(new OnClickListener(){
#Override
public void onClick(View v){
String phoneno=((TextView)findViewById(R.id.email)).getText().toString();
String password=((TextView)findViewById(R.id.password)).getText().toString();
// Toast.makeText(getBaseContext(),"login..."+phoneno+"..."+password,Toast.LENGTH_SHORT).show();
progressDialog.show();
BusProvider.get().post(new LoginEvent(phoneno,password));
}
});
}
#Override
protected void onResume(){
super.onResume();
BusProvider.get().register(this);
}
#Override
protected void onPause(){
super.onPause();
BusProvider.get().unregister(this);
}
#Subscribe
public void onLoginSuccessEvent(LoginSuccessEvent loginSuccessEvent){
progressDialog.hide();
LoginResult result=loginSuccessEvent.getResult();
if (result != null) {
// Toast.makeText(this,result.getCust_id()+result.getCust_name()+result.getCust_access_token(),Toast.LENGTH_SHORT).show();
//Toast.makeText(this,"Login Success",Toast.LENGTH_SHORT).show();
SharedPreferences preferences = this.getSharedPreferences(SHARED_PREF_DB_NAME, MODE_PRIVATE);
preferences.edit().putString(PREF_TOKEN,result.getCust_access_token()).commit();
preferences.edit().putInt(PREF_ACCOUNT_ID,result.getCust_id()).commit();
SharedPreferences pushPreferences=this.getSharedPreferences("pushService",0);
BusProvider.get().post(new PushRegisterEvent
(result.getCust_id(),result.getCust_access_token(),pushPreferences.getString("user_id","")));
goToMainActivity();
} else {
Toast.makeText(this, "Unable to login, please retry", Toast.LENGTH_SHORT).show();
}
}
private void goToMainActivity() {
Intent intent = new Intent(this, MainActivity.class);
startActivity(intent);
finish();
}
}

Android Sharing data between apps in 2 ways

I have app one and app two. In app one I'm sending a string to app two. I want also to return a value from app two to app one. This is my code :
App One:
package ed.letslearn.com.appone;
import android.app.Activity;
import android.content.ComponentName;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class MainActivity extends AppCompatActivity {
private static final int SOME_CONSTANT = 0;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button b=(Button)findViewById(R.id.button);
b.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Bundle b=new Bundle();
String a="Test";
b.putString("test",a);
Intent launchIntent = getPackageManager().getLaunchIntentForPackage("ed.letslearn.com.apptwo");
launchIntent.putExtras(b);
startActivityForResult(launchIntent, SOME_CONSTANT);
}
});
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
switch(requestCode) {
case (SOME_CONSTANT) : {
if (resultCode == Activity.RESULT_OK) {
String thedata = data.getStringExtra("result");
Log.d("The data",thedata);
}
break;
}
}
}
}
App Two:
package ed.letslearn.com.apptwo;
import android.app.Activity;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
EditText thesentvalue=(EditText)findViewById(R.id.editText2);
Button b=(Button)findViewById(R.id.button);
Bundle bundle=getIntent().getExtras();
String text=bundle.getString("test");
thesentvalue.setText(text);
b.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent goBack = new Intent("ed.letslearn.com.appone");
goBack.putExtra("result", "Sent from App two");
setResult(Activity.RESULT_OK, goBack);
finish();
}
});
}
}
I'm not getting the returned string from app two in app one. Any help please ?

How to show a picture in a class, which I saved in another class

I got an application where you can make and save a picture. Now I when this picture to display in another class. I just started programming in java and have no idea how to do this.
FotoMaker.java:
package com.example.random;
import java.io.FileNotFoundException;
import android.app.Activity;
import android.content.ContentValues;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.provider.MediaStore;
import android.util.Log;
import android.net.Uri;
import android.view.View;
import android.view.Window;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
public class FotoMaker extends Activity
{
ImageView iv;
Uri uriOfPicture;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.addpictolist);
iv = (ImageView) findViewById(R.id.imageView);
Button btn = (Button) findViewById(R.id.button1);
btn.setOnClickListener(new OnClickListener()
{
#Override
public void onClick (View v){
takeImageFromCamera();
}
});
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
if(requestCode == 0)
{
Bitmap image=createBitmapFromURI(uriOfPicture);
iv.setImageBitmap(image);
}
}
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
if (uriOfPicture != null) {
outState.putString("cameraImageUri", uriOfPicture.toString());
}
}
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
if (savedInstanceState.containsKey("cameraImageUri")) {
uriOfPicture = Uri.parse(savedInstanceState.getString("cameraImageUri"));
}
}
public void takeImageFromCamera(){
String fileName = "new-photo-name.jpg";
ContentValues values = new ContentValues();
values.put(MediaStore.Images.Media.TITLE, fileName);
values.put(MediaStore.Images.Media.DESCRIPTION,
"Image captured by camera");
uriOfPicture = getContentResolver()
.insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
values);
Log.i("uri",uriOfPicture.toString());
Intent intent = new Intent(
MediaStore.ACTION_IMAGE_CAPTURE);
intent.putExtra(MediaStore.EXTRA_OUTPUT, uriOfPicture);
intent.putExtra(MediaStore.EXTRA_VIDEO_QUALITY, 1);
startActivityForResult(intent,
0);
}
public Bitmap createBitmapFromURI(Uri uri) {
Bitmap bitmap = null;
try {
bitmap = BitmapFactory.decodeStream(getApplicationContext()
.getContentResolver().openInputStream(uri));
} catch (FileNotFoundException e) {
e.printStackTrace();
}
if (bitmap != null)
return Bitmap.createScaledBitmap(bitmap, 100, 100, true);
else {
return null;
}
}
}
ShowPhoto.java:
package com.example.random;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
public class ShowPhoto extends Activity{
ImageView iv;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.watch_pic);
iv = (ImageView) findViewById(R.id.imageView1);
}
}

You can pass the URI to the new activity once you have it. So, in your FotoMaker's onActivityResult just start the ShowPhoto activity and send the uriOfPicture in an extra.
Intent intent = new Intent(this, ShowPhoto.class);
intent.putExtra("uri", uriOfPicture);
startActivity(intent);
In your ShowPhoto activity just catch the argument and show it:
String uriOfPicture = getIntent().getStringExtra("uri");
Bitmap image = createBitmapFromURI(uriOfPicture);
iv.setImageBitmap(image);
I'm assuming most of your code already works.

Playing a video in android

Im implementing a video playback in android im completely new to android, and this is the bit of code i have gathered so far.
according to the logic it should play a video. don't know where im doing wrong.
package com.themetanoia.readfilefromsdc;
import java.io.File;
import android.app.ListActivity;
import android.content.Context;
import android.content.Intent;
import android.graphics.PixelFormat;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.MediaController;
import android.widget.TextView;
import android.widget.Toast;
import android.widget.VideoView;
import android.widget.AdapterView.OnItemClickListener;
public class ReadFileFromSDCActivity extends ListActivity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//Get the file path for external storage
String a = Environment.getExternalStorageDirectory().getAbsolutePath();
final String finalPath = a+"/Videos";
//Define new file function
File f=new File(finalPath);
if(f.isDirectory()){
//Define arrayadapter
setListAdapter(new ArrayAdapter<String>(this, R.layout.listview,files));
//Define listview
ListView listview = getListView();
listview.setTextFilterEnabled(true);
//Onclick list item event
listview.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
//get selected items
String selectedValue = (String) getListAdapter().getItem(position);
Uri uri = Uri.parse(finalPath);
MediaController mediaController = new MediaController(getBaseContext());
mediaController.setAnchorView(mVideoView);
Uri video = Uri.parse(finalPath+"/"+selectedValue);
mVideoView.setMediaController(mediaController);
mVideoView.setVideoURI(video);
mVideoView.start();
}
});
}
}
}

<VideoView
android:id="#+id/videoView1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
/>
VideoView vv = (VideoView) findViewById(R.id.videoView1);
uri = "your video uri";
vv.setVideoURI(Uri.parse(uri));
vv.start();
vv.setOnCompletionListener(new OnCompletionListener() {
#Override
public void onCompletion(MediaPlayer mp) {
finish();
}
});