Intent isn't working, on clicking on the button2, application crashes

Question

I am not able to switch between activities, when I click on the button2, the application crashes down.

MainActivity.Java

<pre>package com.example.againtry;

    import java.util.Random;

    import android.app.Activity;
    import android.content.Intent;
    import android.os.Bundle;
    import android.view.Menu;
    import android.view.View;
    import android.widget.Button;
    import android.widget.TextView;

    public class MainActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Declare our View Variables and assign them the Views from the layout file

        final TextView answerLabel = (TextView) findViewById(R.id.textView1);
        Button getAnswerButton = (Button) findViewById(R.id.button1);

        getAnswerButton.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View arg0) {
    // The Button was clicked, so the update the answer label with an answer

         String answer = "";
    // Randomly select one of three answers: Yes, No or May be

    // Update the label with our dynamic answer

    Random randomGenerator = new Random(); // Construct a new Random number Generator
    int randomNumber = randomGenerator.nextInt(3);
    answer = Integer.toString(randomNumber);
    // update the label with our dynamic answer

    answerLabel.setText(answer);
    }});

        Button btnSimple= (Button) findViewById(R.id.button2);
        btnSimple.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View v) {

    // From One Activity to another
    Intent intent = new Intent(MainActivity.this, SendMessageActivity.class);
    startActivity(intent);

    }});
    }



    @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;
    }}</pre>

This is my Second Activity

SendMessageActivity.Java
<pre>package com.example.againtry;

    import android.app.Activity;
    import android.os.Bundle;
    import android.telephony.SmsManager;
    import android.view.Menu;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.Toast;

    public class SendMessageActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.send_message);

        final EditText editSMS = (EditText) findViewById(R.id.editText1);
        final EditText editPhoneNum = (EditText) findViewById(R.id.phoneNum);
        Button getSendButton = (Button) findViewById(R.id.button1);



        getSendButton.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View v) {
    String phoneNo = editPhoneNum.getText().toString();
    String sms = editSMS.getText().toString();

    try {
    SmsManager smsManager = SmsManager.getDefault();
    smsManager.sendTextMessage(phoneNo, null, sms, null, null);
    Toast.makeText(getApplicationContext(), "SMS Sent!",
    Toast.LENGTH_LONG).show();
    } catch (Exception e) {
    Toast.makeText(getApplicationContext(),
    "SMS faild, please try again later!",
    Toast.LENGTH_LONG).show();
    e.printStackTrace();
    }

    }
    });

    }


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


Manifest
    <pre> <?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.againtry"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="10"
        android:targetSdkVersion="10" />
    <uses-permission android:maxSdkVersion="10" android:name="android.permission.READ_CONTACTS"/>
    <uses-permission android:maxSdkVersion="10" android:name="android.permission.SEND_SMS"/>
    <uses-permission android:maxSdkVersion="10" android:name="android.permission.READ_SMS"/>

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

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.example.againtry.SendMessageActivity"
            android:label="@string/title_activity_send_message" >
        </activity>
    </application>

    </manifest></pre>

activity_main<pre>

    <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:gravity="bottom"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/button1"
        style="@android:style/ButtonBar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textView1"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="70dp"
        android:text="Enlighten Me!" />

     <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="177dp"
        android:textSize="32sp" />

       <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/button1"
        android:layout_alignLeft="@+id/button1"
        android:layout_marginBottom="44dp"
        android:text="Message" />

    </RelativeLayout></pre>

send_message.xml<pre>

    <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"
    tools:context=".SendMessageActivity" >

    <EditText
        android:id="@+id/editText1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:ems="10"
        android:hint="Enter your message" >

        <requestFocus />
    </EditText>

    <Button
        android:id="@+id/sendButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/editText1"
        android:layout_alignBottom="@+id/editText1"
        android:layout_alignParentRight="true"
        android:text="@string/button_send" />

    <TextView
        android:id="@+id/messageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/editText1"
        android:layout_alignParentTop="true"
        android:layout_marginTop="77dp"
        android:text="TextView" />

    <EditText
        android:id="@+id/phoneNum"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/messageView1"
        android:layout_alignParentTop="true"
        android:layout_marginTop="18dp"
        android:text="Enter Phone Number" android:inputType="number"/>
    </RelativeLayout></pre>

Answer 1

there is mistake in mapping of control in SendMessageActivity

  public class SendMessageActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.send_message);

    final EditText editSMS = (EditText) findViewById(R.id.editText1);
    final EditText editPhoneNum = (EditText) findViewById(R.id.phoneNum);
    Button getSendButton = (Button) findViewById(R.id.button1);

instead of button1 it should be R.id.sendButton

Answer 2

You have to assign onclick to a particular button which i don't see in your activity_main xml.

just add onclick event to your button and remove onclicklistener and it should work.

to add onclick listener you can go to designer page and in properties you will find a tag as onclick.Just assign the onlick method to that tag using dropdown.

Answer 3

In the layout of SendMessageActivity (i.e send_message.xml), you have no buttons with id "button1". So when doing :

Button getSendButton = (Button) findViewById(R.id.button1);

findViewById returns null and hence getSendButton.setOnClickListener(/***/); throws a NullPointerException.

It should be :

Button getSendButton = (Button) findViewById(R.id.sendButton);