I'm new in Android studio I want to send data from Arduino to the android via Bluetooth HC-06 I begin my code from the template(Navigation Drawer Activity) of AndroidStudio. At first everything was okay, but nightmares begin when I wanted to add Bluetooth button with the help SetOnClickListener to my code. 1. Its appearance changed from thisenter image description here
to this enter image description here. For clarity: Navigation bar and other tools disappeared, instead only home fragment is appeared. 2. When push the Bluetooth button on this fragment, my app closed. I try to follow logcat , but can't fix the problem.
Please, help me with advice Best Regard p.s. Below is my MainActivity.java file
package com.example.myecg2;
import android.content.Intent;
import android.os.Bundle;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.view.View;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProviders;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;
import com.google.android.material.navigation.NavigationView;
import androidx.drawerlayout.widget.DrawerLayout;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import android.view.Menu;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import java.util.Set;
public class MainActivity extends AppCompatActivity {
private AppBarConfiguration mAppBarConfiguration;
private TextView Tekst;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Savollaringiz bo\'lsa Xat yozing", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
DrawerLayout drawer = findViewById(R.id.drawer_layout);
NavigationView navigationView = findViewById(R.id.nav_view);
mAppBarConfiguration = new AppBarConfiguration.Builder(
R.id.nav_home, R.id.nav_gallery, R.id.nav_slideshow,
R.id.nav_tools, R.id.nav_share, R.id.nav_send)
.setDrawerLayout(drawer)
.build();
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
NavigationUI.setupActionBarWithNavController(this, navController, mAppBarConfiguration);
NavigationUI.setupWithNavController(navigationView, navController);
final int REQUEST_ENABLE_BT = 1;
setContentView(R.layout.fragment_home);
final BluetoothAdapter btAdapter = BluetoothAdapter.getDefaultAdapter();
Button button =findViewById(R.id.button6);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (btAdapter == null) {
Tekst.setText("Bluetooth NOT support");
return;
} else {
if (btAdapter.isEnabled()) {
Tekst.setText("Bluetooth is currently in device discovery process.");
Tekst.append("\nPaired Devices are:");
Set<BluetoothDevice> devices = btAdapter.getBondedDevices();
for (BluetoothDevice device : devices) {
Tekst.append("\nDevice" + device.getName() + "," + device);
}
} else {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
}
}
}
}
);}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onSupportNavigateUp() {
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
return NavigationUI.navigateUp(navController, mAppBarConfiguration)
|| super.onSupportNavigateUp();
}
}<?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">
<TextView
android:id="@+id/text_home"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:textAlignment="center"
android:textSize="20sp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/textView8"
android:layout_width="394dp"
android:layout_height="218dp"
android:text="@string/matn"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toBottomOf="@+id/button6" />
<Button
android:id="@+id/button6"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="116dp"
android:text="@string/LeadI"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toBottomOf="@+id/text_home"/>
</androidx.constraintlayout.widget.ConstraintLayout>and errors given in LogCat 2019-11-30 02:09:01.342 13088-13088/com.example.myecg2 D/AndroidRuntime: Shutting down VM 2019-11-30 02:09:01.343 13088-13088/com.example.myecg2 E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.myecg2, PID: 13088 java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference at com.example.myecg2.MainActivity$2.onClick(MainActivity.java:75) at android.view.View.performClick(View.java:6256) at android.view.View$PerformClick.run(View.java:24701) at android.os.Handler.handleCallback(Handler.java:789) at android.os.Handler.dispatchMessage(Handler.java:98) at android.os.Looper.loop(Looper.java:164) at android.app.ActivityThread.main(ActivityThread.java:6541) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
