Link two layouts in android

Question

I am trying to link my two Android layout and make the process.

MainActivity.java

public class MainActivity extends AppCompatActivity {


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });



    }

    public void open(View view){
        AlertDialog.Builder alb=new AlertDialog.Builder(this);
        alb.setMessage("Are You Sure Do You Want This");
        alb.setPositiveButton("yes", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
           Toast.makeText(MainActivity.this,"You Clicked Yes Button",Toast.LENGTH_LONG).show();
            }
        });

        alb.setNegativeButton("NO", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                Toast.makeText(MainActivity.this,"You Clicked Yes Button",Toast.LENGTH_LONG).show();
                //finish();
            }
        });
        AlertDialog al=alb.create();
        al.show();
    }


    public void clockwise(View view){
        ImageView iv=(ImageView) findViewById(R.id.imageView);
        Animation animation = AnimationUtils.loadAnimation(getApplicationContext(),R.anim.myanimation);
        iv.startAnimation(animation);
    }
    public void zoom(View view){
ImageView iv=(ImageView) findViewById(R.id.imageView);
        Animation animation=AnimationUtils.loadAnimation(getApplicationContext(),R.anim.clockwise);
        iv.startAnimation(animation);
    }

    public void fade(View view){
        ImageView iv=(ImageView) findViewById(R.id.imageView);
        Animation animation=AnimationUtils.loadAnimation(getApplicationContext(),R.anim.fade);
        iv.startAnimation(animation);
    }

    public void blink(View view){
        ImageView iv=(ImageView)findViewById(R.id.imageView);
        Animation animation=AnimationUtils.loadAnimation(getApplicationContext(),R.anim.blink);
        iv.startAnimation(animation);
    }

    public void move(View view){
        ImageView iv=(ImageView)findViewById(R.id.imageView);
        Animation animation=AnimationUtils.loadAnimation(getApplicationContext(),R.anim.move);
        iv.startAnimation(animation);
    }

    public void slide(View view){
        ImageView iv=(ImageView)findViewById(R.id.imageView);
        Animation animation=AnimationUtils.loadAnimation(getApplicationContext(),R.anim.slide);
        iv.startAnimation(animation);
    }






public void next(View v){
   // setContentView(R.layout.recording);
   Intent inent = new Intent(this, RecordActivity.class);

  startActivity(inent);
}

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

RecordActivity.java

public class RecordActivity extends Activity {
    private MediaRecorder mr;
    Button play,record,stop;
    private String outputFile=null;
    @Override
   public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.recording);

        play=(Button)findViewById(R.id.button3);
        stop=(Button)findViewById(R.id.button2);
        record=(Button)findViewById(R.id.button);
        stop.setEnabled(false);
        play.setEnabled(false);

        outputFile= Environment.getExternalStorageDirectory().getAbsolutePath()+"/recording.3gp";
        mr=new MediaRecorder();
        mr.setAudioSource(MediaRecorder.AudioSource.MIC);
        mr.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
        mr.setAudioEncoder(MediaRecorder.OutputFormat.AMR_NB);
        mr.setOutputFile(outputFile);

    }


    public void Record(View v){
        try{
            mr.prepare();
            mr.start();
        }
        catch (Exception e){
            e.printStackTrace();
        }
        record.setEnabled(false);
        stop.setEnabled(true);


    }


    public void stop(View v){
        mr.stop();
        mr.release();
        mr=null;
        stop.setEnabled(false);
        play.setEnabled(true);
        Toast.makeText(getApplicationContext(),"AudioRecorded Sucessfully",Toast.LENGTH_LONG);

    }

    public void play(View v){
        MediaPlayer mp=new MediaPlayer();
        try{
            mp.setDataSource(outputFile);
            mp.prepare();
        }
        catch (Exception e){
            e.printStackTrace();
        }
        mp.start();
        Toast.makeText(getApplicationContext(),"Playing Audio",Toast.LENGTH_LONG);
    }

}

content_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.example.admin.alertapplication.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Alert Dialog"
        android:id="@+id/textView"
        android:textSize="35dp"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Raptor"
        android:id="@+id/textView2"
        android:textColor="#da644860"
        android:textSize="35dp"
        android:layout_below="@+id/textView"
        android:layout_centerHorizontal="true" />

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/imageView"
        android:src="@drawable/logo"
        android:layout_below="@+id/textView2"
        android:layout_alignLeft="@+id/textView"
        android:layout_alignStart="@+id/textView"
        android:layout_alignRight="@+id/button2"
        android:layout_alignEnd="@+id/button2" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="zoom"
        android:id="@+id/button"
        android:layout_below="@+id/imageView"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="40dp"
        android:onClick="clockwise"/>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="clockwise"
        android:id="@+id/button2"
        android:layout_alignTop="@+id/button"
        android:layout_centerHorizontal="true"
        android:onClick="zoom"/>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="fade"
        android:id="@+id/button3"
        android:layout_alignTop="@+id/button2"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:onClick="fade"/>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="blink"
        android:onClick="blink"
        android:id="@+id/button4"
        android:layout_below="@+id/button"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="move"
        android:onClick="move"
        android:id="@+id/button5"
        android:layout_below="@+id/button2"
        android:layout_alignRight="@+id/button2"
        android:layout_alignEnd="@+id/button2"
        android:layout_alignLeft="@+id/button2"
        android:layout_alignStart="@+id/button2" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="slide"
        android:onClick="slide"
        android:id="@+id/button6"
        android:layout_below="@+id/button3"
        android:layout_toRightOf="@+id/textView"
        android:layout_toEndOf="@+id/textView" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Next"
        android:onClick="next"
        android:id="@+id/button61"
        android:layout_below="@+id/button4"
        android:layout_alignRight="@+id/button4"
        android:layout_alignEnd="@+id/button4" />

</RelativeLayout>

recording.xml

<?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"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:weightSum="1">

    <TextView
        android:layout_width="234dp"
        android:layout_height="112dp"
        android:text="Android Audio Recording"
        android:id="@+id/textView3"
        android:layout_gravity="center_horizontal"

        android:textSize="30dp"
        android:textColor="#d50c0c"
        android:layout_weight="0.01" />

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="86dp"
        android:id="@+id/imageView2"
        android:src="@drawable/logo"
        android:layout_gravity="center_horizontal"
        />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Record"
        android:id="@+id/button7"
        android:layout_below="@+id/imageView2"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="59dp"
        android:onClick="Record"
        />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Stop"
        android:id="@+id/button8"
        android:layout_alignTop="@+id/button"
        android:layout_centerHorizontal="true"
        android:layout_gravity="center_horizontal"
        android:onClick="stop"
        />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="play"
        android:id="@+id/button9"
        android:layout_alignTop="@+id/button8"
        android:layout_alignRight="@+id/textView3"
        android:layout_alignEnd="@+id/textView3"
        android:layout_gravity="right"
        android:onClick="play"
        />

</LinearLayout>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.admin.alertapplication">
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.RECORD_AUDIO"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <activity
            android:name=".RecordActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.VIEW" />
            </intent-filter>
        </activity>


    </application>

</manifest>

stack trace 04-22 14:24:09.415 4470-4470/com.example.admin.alertapplication E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.admin.alertapplication, PID: 4470 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.admin.alertapplication/com.example.admin.alertapplication.RecordActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setEnabled(boolean)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) at android.app.ActivityThread.access$800(ActivityThread.java:151) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5254) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setEnabled(boolean)' on a null object reference at com.example.admin.alertapplication.RecordActivity.onCreate(RecordActivity.java:27) at android.app.Activity.performCreate(Activity.java:5990) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)  at android.app.ActivityThread.access$800(ActivityThread.java:151)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)  at android.os.Handler.dispatchMessage(Handler.java:102)  at android.os.Looper.loop(Looper.java:135)  at android.app.ActivityThread.main(ActivityThread.java:5254)  at java.lang.reflect.Method.invoke(Native Method)  at java.lang.reflect.Method.invoke(Method.java:372)  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 

I am using the above code to for linking the two layouts when next button was clicked next() function will be called after that Unfortunately application has stopped why it's happening can any one help me to fix this

Answer 1

The reason is in RecordActivity in this line
play=(Button)findViewById(R.id.button3);
Because recording.xml doesn't contain button3 so play(Button) will be null
Then you call play.setEnabled(false); => your app crash by NullPointerException