Develop Reference

seekbar not working with video view when handle and move it

I am building a simple video player Ui and I have a : seekbar and two buttons to controle the video view, when I click on any point of seekbar every thing is ok and video view progress will be the same with seekbar and the buttons is working too ! but,when I handle the seekbar thumb and move it ,then leave it, every thing messing up and the seekbar and the buttons will never work again, so I am not getting an Exception error it's just will not work again. why that happening?
Activity
public class Player extends AppCompatActivity {
View controller;
Handler handler;
SeekBar seekBar;
VideoView videoView;
ImageButton play_btn, pause_btn;
ImageButton forward_btn, replay_btn;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_player);
handler = new Handler();
videoView = (VideoView) findViewById(R.id.videoView);
controller = findViewById(R.id.player_controller); // the controller View
hideController(controller);
forward_btn = (ImageButton) findViewById(R.id.playerController_forward_10_Button);
replay_btn = (ImageButton) findViewById(R.id.playerController_replay_10_Button);
forward_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
forward_10_sec();
}
});
replay_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
reply_10_sec();
}
});
play_btn = (ImageButton) findViewById(R.id.playerController_playButton);
pause_btn = (ImageButton) findViewById(R.id.playerController_pauseButton);
play_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
play();
}
});
pause_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
pause();
}
});
seekBar = findViewById(R.id.playerController_seekBar); // video seekBar
seekBar.setOnSeekBarChangeListener(onSeekBarChangeListener);
videoView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if (controller.getVisibility() == View.INVISIBLE)
showController(controller);
else
hideController(controller);
}
});
Intent intent = getIntent();
if (intent != null)
setVideoSource(intent);
}
private void play() {
if(!videoView.isPlaying()) {
videoView.start();
play_btn.setVisibility(View.INVISIBLE);
pause_btn.setVisibility(View.VISIBLE);
}
}
private void pause() {
if(videoView.isPlaying()) {
videoView.pause();
pause_btn.setVisibility(View.INVISIBLE);
play_btn.setVisibility(View.VISIBLE);
}
}
private void forward_10_sec() {
if (videoView.canSeekForward())
videoView.seekTo(videoView.getCurrentPosition() + 1000);
}
private void reply_10_sec() {
if (videoView.canSeekBackward())
videoView.seekTo(videoView.getCurrentPosition() - 1000);
}
// to show the controllers
private void showController(View controller) {
controller.setVisibility(View.VISIBLE);
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
hideController(controller);
}
}, 6000);
}
// to hide the controllers
private void hideController(View controller) {
controller.setVisibility(View.INVISIBLE);
}
// to set video source from the main app or file manager
private void setVideoSource(Intent intent) {
... some codes to set path ...
play();
showController(controller);
updateSeekBarProgress();
}
// to move seekBar to real video progress
private void updateSeekBarProgress() {
Player.this.runOnUiThread(updateSeekBar);
}
private Runnable updateSeekBar = new Runnable() {
#Override
public void run() {
seekBar.setMax(videoView.getDuration() / 1000);
seekBar.setProgress(videoView.getCurrentPosition() / 1000);
seekBar.postDelayed(this,500);
}
};
SeekBar.OnSeekBarChangeListener onSeekBarChangeListener = new SeekBar.OnSeekBarChangeListener() {
#Override
public void onProgressChanged(SeekBar seekBar, int i, boolean b) {
if (b) {
videoView.seekTo(i*1000);
}
}
#Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
#Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
};
}
activity_player
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/black"
tools:context=".Player">
<VideoView
android:id="#+id/videoView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<include
android:id="#+id/player_controller"
layout="#layout/player_controller" />
</androidx.constraintlayout.widget.ConstraintLayout>
player_controller
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/transparent_black">
<ImageButton
android:id="#+id/playerController_playButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#null"
android:src="#drawable/play_icon_48"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<ImageButton
android:id="#+id/playerController_pauseButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#null"
android:src="#drawable/pause_icon_48"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<ImageButton
android:id="#+id/playerController_replay_10_Button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#null"
android:src="#drawable/replay_10_icon_48"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="#id/playerController_playButton"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<ImageButton
android:id="#+id/playerController_forward_10_Button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#null"
android:src="#drawable/forward_10_icon_48"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="#id/playerController_playButton"
app:layout_constraintTop_toTopOf="parent" />
<SeekBar
android:id="#+id/playerController_seekBar"
android:layout_width="0dp"
android:layout_height="50dp"
android:layout_marginStart="5dp"
android:layout_marginEnd="5dp"
android:progressBackgroundTint="#color/white"
android:progressTint="#color/white"
android:secondaryProgressTint="#color/light_purple"
android:thumbTint="#color/white"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#id/playerController_playButton" />
</androidx.constraintlayout.widget.ConstraintLayout>
so, in a simple way : I want to set video view progress like seekbar progress with any way that I move the seek bar with.
(now it's just works when click on it and when handle and move it , nothing works again).
thanks...

It's finally has been done with that :
SeekBar.OnSeekBarChangeListener onSeekBarChangeListener = new SeekBar.OnSeekBarChangeListener() {
#Override
public void onProgressChanged(SeekBar seekBar, int i, boolean b) {
if (b) {
videoView.seekTo(i * 1000);
}
}
#Override
public void onStartTrackingTouch(SeekBar seekBar) {
handler.removeCallbacks(updateSeekBar);
pause();
}
#Override
public void onStopTrackingTouch(SeekBar seekBar) {
videoView.seekTo(seekBar.getProgress()*1000);
play();
updateSeekBarProgress();
}
};

How to call Custom Activity inside onCreate method

I am developing a simple app that has two activities, MainActivity and SecondActivity and a transparent CustomActivity that extends Dialog. The
MainActivity has two buttons (Yes_button and No_button).
When user clicks Yes_button, the SecondActivity is called via Intent and the
CustomActivity will be in front of it.
When user clicks No_button the SecondActivity will also be called but the CustomActivity will not be called alongside with it.
The calling of the CustomActivity is based on if-else statement expressions. The CustomActivity has a skip button, when clicked the CustomActivity will close only then can the SecondActivity be accessible to the user. The SecondActivity has just one button that calls the MainActivity and the cycle continues.
Problem
When the app launches and a user clicks on the No_button, the SecondActivity will be called without the CustomActivity (as expected!), but ONCE a user
clicks on the Yes_button, the SecondActivity will keep on displaying alongside the CustomActivity EVEN when the No_button is clicked.
Expectation
I want the SecondActivity to be called alongside the CustomActivity each time the Yes_button is clicked and also let only the SecondActivity be called when ever the No_button is click.
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
xml:toos="http://schemas.android.com/tools">
<TextView
android:id="#+id/text"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/text" />
<Button
android:id="#+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/button1" />
</RelativeLayout>
MainActivity.java
public class MainActivity extends BaseActivity implements View.OnClickListener {
private static int getNumber;
Button Yes_button;
Button No_button;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Yes_button = findViewById(R.id.button1);
No_button = findViewById(R.id.button2);
Yes_button.setOnClickListener(this);
No_button.setOnClickListener(this);
}
#Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.button1:
int get_input = 1; // will be use in if else statement.
getNumber = get_input;
Intent intent = new Intent(MainActivity.this, SecondActivity.class);
startActivity(intent);
break;
case R.id.button2:
Intent intent2 = new Intent(MainActivity.this, SecondActivity.class);
startActivity(intent2);
break;
}
}
public static int get_Logic() {
return getNumber;
}
}
activity_second_activity.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
xml:toos="http://schemas.android.com/tools">
<TextView
android:id="#+id/text"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/text"
android:onClick="Click"
android:text="Click" />
</RelativeLayout>
SecondActivity.java
public class SecondActivity extends AppCompatActivity {
private static int output;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second_activity);
int received = MainActivity.get_Logic();
output = received;
Display();
}
public final void Display() {
if (output == 1) {
CustomActivity custom = new CustomActivity(SecondActivity.this);
custom.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
custom.show();
} else {
CustomActivity custom = new CustomActivity(SecondActivity.this);
custom.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
custom.cancel();
}
}
public void Click(View view) {
Intent intent = new Intent(SecondActivity.this, MainActivity.class);
startActivity(intent);
}
}
activity_custom_activity.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="180dp"
android:layout_height="250dp"
xml:toos="http://schemas.android.com/tools">
<TextView
android:id="#+id/text"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<Button
android:id="#+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/text"
android:text="Skip" />
</RelativeLayout>
CustomActivity.java
class CustomActivity extends Dialog {
Button SkipButton;
private Activity main;
public CustomActivity(Activity constr) {
super(constr);
this.main = constr;
}
#Override
protected void onCreate(Bundle saveInstanceState) {
super.onCreate(saveInstanceState);
setCancelable(false);
setContentView(R.layout.activity_custom_activity);
SkipButton = findViewById(R.id.button);
SkipButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
dismiss();
}
});
}
}
checking.xml
<?XML version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item>
<shape>
<solid android:color="#FFFF" />
<corners android:radius="20dp" />
<stroke android:width="4dp" android:color="#color/colorPrimary" />
<gradient />
</shape>
</item>
</selector>

In Android, to pass data from an activity to another, you don't need to declare a static variable (getNumber in MainActivity), you should use Intent and Bundle together. See the below solution.
MainActivity.java
public class MainActivity extends BaseActivity implements View.OnClickListener {
Button Yes_button;
Button No_button;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Yes_button = findViewById(R.id.button1);
No_button = findViewById(R.id.button2);
Yes_button.setOnClickListener(this);
No_button.setOnClickListener(this);
}
#Override
public void onClick(View v) {
int input = v.getId() == R.id.button1 ? 1 : 0;
Intent intent = new Intent(MainActivity.this, SecondActivity.class);
intent.putExtra("input", input);
startActivity(intent);
}
}
SecondActivity.java
public class SecondActivity extends AppCompatActivity {
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second_activity);
Display();
}
public final void Display() {
int input = getIntent().getIntExtra("input", 0);
CustomActivity custom = new CustomActivity(SecondActivity.this);
custom.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
if (input == 1) {
custom.show();
} else {
custom.cancel();
}
}
public void Click(View view) {
finish();
}
}

Android Progress Bar not working

I have made a progress bar in Android but it is not at all working. What am I doing wrong? I have just started to learn android. Below is my code.
MainActivity.java-
public class MainActivity extends AppCompatActivity {
ProgressBar progressBar;
int mporgress=0;
EditText time;
private Handler mHandler = new Handler();
private static final int PROGRESS = 0x1;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void Startbuttononclick(View view){
Button startbutton=(Button) findViewById(R.id.button);
startbutton.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View v) {
mporgress = Integer.parseInt(time.getText().toString());
progressBar.setProgress(mporgress);
new Thread(new Runnable() {
public void run() {
while (mporgress < 100) {
// Update the progress bar
mHandler.post(new Runnable() {
public void run() {
progressBar.setProgress(mporgress);
mporgress = doWork();
try{
Thread.sleep(1000);
}catch (InterruptedException e){}
}
});
}
}
}).start();
}
});
}
public void doprogress(View view) {
}
public int doWork(){
mporgress++;
return mporgress;
}
}
Activity_main.xml-
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.android.progressbar.MainActivity">
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Enter the time:"
android:inputType="number"
android:id="#+id/editText" />
<ProgressBar
style="?android:attr/progressBarStyleLarge"
android:layout_width="500dp"
android:layout_height="200dp"
android:id="#+id/progressBar4"
android:layout_gravity="center"
android:scrollbarSize="500dp" />
<Button
android:text="START"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/button"
android:layout_gravity="center"
android:onClick="Startbuttononclick" />
</LinearLayout>
Check out this image below-
- https://i.stack.imgur.com/2TBIb.png
Note- Enter the time in this image is an EditText with a hint and not a TextView.
It is appearing but not working.
I have done these changes so far.-
https://i.stack.imgur.com/UujpB.png
But still the progress bar is still continuously rotating.

Seems you forgot to initialize EditText -time and ProgressBar. Init it inside onCreate:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
progressBar =(ProgressBar) findViewById(R.id.progressBar4);
time = (EditText) findViewById(R.id.editText); //here
}
Also inside button click the bar:
progressBar = new ProgressBar(this);
mporgress = Integer.parseInt(time.getText().toString());
................
.............

menu using clickable images?

I'm trying to create a menu using clickable images, but they don't seem to be working? I was following a tutorial and it uses something like
Intent biodata = new Intent(mainActivity.this, profile.class);
but it's not working so I tried to look for something else and someone said to use v.getContext() instad of ....this
it works on my other page but it doesn't work on this page?
mainActivity.java
package skripsi.garden;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageButton;
public class mainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public ImageButton buttonBio;
public void init(){
buttonBio= (ImageButton)findViewById(R.id.buttonBio);
buttonBio.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent biodata = new Intent(v.getContext(), profile.class);
startActivity(biodata);
}
}
);
}
public ImageButton buttonList;
public void tombollist(){
buttonList=(ImageButton)findViewById(R.id.buttonList);
buttonList.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent listTaman = new Intent(v.getContext(), gardenlist.class);
startActivity(listTaman);
}
}
);
}
public ImageButton buttonWeather;
public void tombolcuaca(){
buttonWeather=(ImageButton)findViewById(R.id.buttonWeather);
buttonWeather.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent cuaca = new Intent(v.getContext(), weather.class);
startActivity(cuaca);
}
}
);
}
}
and this is the xml
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:background="#drawable/foliagemain"
tools:context="skripsi.garden.mainActivity">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/imageView3"
android:src="#drawable/selamatdatang"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/buttonBio"
android:src="#drawable/buttonbiodata"
android:layout_above="#+id/buttonList"
android:layout_alignRight="#+id/buttonWeather"
android:layout_alignEnd="#+id/buttonWeather" />
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/buttonList"
android:src="#drawable/buttondaftartaman"
android:layout_above="#+id/buttonHelp"
android:layout_alignLeft="#+id/buttonHelp"
android:layout_alignStart="#+id/buttonHelp" />
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/buttonHelp"
android:src="#drawable/buttonhelp"
android:layout_above="#+id/buttonWeather"
android:layout_alignLeft="#+id/buttonBio"
android:layout_alignStart="#+id/buttonBio" />
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/buttonWeather"
android:src="#drawable/buttoncuaca"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true" />
</RelativeLayout>

Put your buttons in your onCreate method. They do not need to be in their own method.
public class mainActivity extends AppCompatActivity {
public ImageButton buttonBio;
public ImageButton buttonList;
public ImageButton buttonWeather;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
buttonBio= (ImageButton) findViewById(R.id.buttonBio);
buttonBio.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent biodata = new Intent(mainActivity.this, profile.class);
startActivity(biodata);
}
});
buttonList=(ImageButton)findViewById(R.id.buttonList);
buttonList.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent listTaman = new Intent(mainActivity.this, gardenlist.class);
startActivity(listTaman);
}
});
buttonWeather=(ImageButton)findViewById(R.id.buttonWeather);
buttonWeather.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent cuaca = new Intent(mainActivity.this, weather.class);
startActivity(cuaca);
}
});
}
}

You could just call your methods init(), tombollist() and tombolcuaca() in onCreate method of your activity after setting the layout.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
init();
tombollist();
tombolcuaca()
}
This would initialise the button to do the action written inside the onClick.
If the methods are not called, the button would not be initialised and hence the click will not work.
You could also use android:clickable="true" in your imageButtons, and then assign the click function init() to the button in your layout xml.
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/buttonBio"
android:src="#drawable/buttonbiodata"
android:layout_above="#+id/buttonList"
android:layout_alignRight="#+id/buttonWeather"
android:layout_alignEnd="#+id/buttonWeather"
android:clickable="true"
android:onClick="init"/>
Then you wouldn't need to initialise the buttons in your activity. On click of the button, the method would be called.

Button is set to Null and NullPointerException is generated in Android [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 6 years ago.
I'm trying to make an app with different intents. I've got two of the ready. I want that a button in the 1st intent makes the 2nd intent to appear.
The issue is that the button is always set to null and throws a NullPointerException when the app is run
My .java classes are:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(vocabulario);
//....
Button buttonVocabulary = (Button) findViewById(R.id.buttonVocabulary);
Button holaPlayerBtn = (Button) findViewById(R.id.holaPlayerBtn);
//...
buttonVocabulary.setOnClickListener(new OnClickListener(){
#Override
public void onClick(View view)
{
//Se abre un nuevo Intent con el primer botón
try
{
{
Intent myIntent = new Intent(view.getContext(), Vocabulario.class);
startActivityForResult(myIntent, 0);}
} catch (Exception e) {
e.printStackTrace();
}
}});
My main.xml file is:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<RelativeLayout
android:id="#+id/adViewContainer"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_alignParentBottom="true"
/>
<Button
android:id="#+id/buttonVocabulary"
android:text="#string/vocabulario"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:nestedScrollingEnabled="true" />
</LinearLayout>
</LinearLayout>
In my AndroidManifest.xml there is an element that says:
<activity android:name=".Vocabulario"
android:label="#string/vocabulario"/>
There's something I'm doing wrong. Could you help me with this issue?
Thanks in advance.

change
setContentView(vocabulario);
To
setContentView(R.layout.main);

In your onCreate method you should set the view to the layout:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
...
}

#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main); //set layout id
//...
findViewById(R.id.buttonVocabulary).setOnClickListener(new OnClickListener(){
#Override
public void onClick(View view){
try {
Intent i = new Intent(view.getContext(), Vocabulario.class);
startActivityForResult(i, 0);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}