Button的新setText属性出现空指针异常，原因不明

Question

这只是我的应用程序中一个活动的代码，它的基本功能是根据位置提供紧急情况下要联系的人员列表。然而，我最近收到了一些要添加到应用程序中的新数据，现在我不得不在布局中再添加几个按钮(最初只有2个按钮(，出于某种原因，我添加的新按钮上出现了nullpointer异常。我为什么会出现这样的异常，这毫无意义，因为我相信我已经正确初始化了按钮。任何帮助都将不胜感激！

联系人.java

import android.net.Uri;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.content.Intent;
import android.widget.Button;
import android.view.View;
import android.widget.TextView;
import android.widget.RelativeLayout;
public class Contacts extends ActionBarActivity {
    Button bt1;
    Button bt2;
    Button bt3;
    Button bt4;
    Button bt5;
    Button bt6;
    TextView t1;
    TextView t2;
    TextView t3;
    TextView t4;
    TextView t5;
    TextView t6;
    private String num1;
    private String num2;
    private String num3;
    private String num4;
    private String num5;
    private String num6;
   // RelativeLayout myLayout;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_contacts);
        Intent intent = getIntent();
        Bundle extras = intent.getExtras();
        String branch = extras.getString("branch");
        String level = extras.getString("level");
        bt1 = (Button) findViewById(R.id.contact_button1);
        bt2 = (Button) findViewById(R.id.contact_button2);
        bt3 = (Button) findViewById(R.id.contact_button3);
        bt4 = (Button) findViewById(R.id.contact_button4);
        bt5 = (Button) findViewById(R.id.contact_button5);
        bt6 = (Button) findViewById(R.id.contact_button6);
        t1 = (TextView) findViewById(R.id.textView1);
        t2 = (TextView) findViewById(R.id.textView2);
        t3 = (TextView) findViewById(R.id.textView3);
        t4 = (TextView) findViewById(R.id.textView4);
        t5 = (TextView) findViewById(R.id.textView5);
        t6 = (TextView) findViewById(R.id.textView6);
        if(branch.contentEquals("Hoody") && level.contentEquals("Safety In Charge"))
        {
            bt1.setText("Javaji P");
            bt2.setText("H S Rao");
            bt3.setText("Sunil KB");
            bt4.setText("K Kishor");
            bt5.setText("Vincent");
            bt6.setText("Sreenivas K");
            num1 = "[phone]";
            num2 = "[phone]";
            num3 = "[phone]";
            num4 = "[phone]";
            num5 = "[phone]";
            num6 = "[phone]";
        }
        if(branch.contentEquals("Hoody") && level.contentEquals("Fire/Accident/Ambulance"))
        {
            bt1.setText("Security");
            bt2.setVisibility(View.GONE);
            bt3.setVisibility(View.GONE);
            bt4.setVisibility(View.GONE);
            bt5.setVisibility(View.GONE);
            bt6.setVisibility(View.GONE);
           // t1.setVisibility(View.GONE);
          //  t2.setVisibility(View.GONE);
           /// t3.setVisibility(View.GONE);
          //  t4.setVisibility(View.GONE);
        //    t5.setVisibility(View.GONE);
         //   t6.setVisibility(View.GONE);
            num1 = "08022979333";
        }
        if(branch.contentEquals("Hoody") && level.contentEquals("Emergency Declarer"))
        {
            bt1.setText("B S Lokeshwaran(Head-Admin)");
            bt2.setText("Philip Mammen(Head-HR)");
            bt3.setVisibility(View.GONE);
            bt4.setVisibility(View.GONE);
            bt5.setVisibility(View.GONE);
            bt6.setVisibility(View.GONE);
        //    t1.setVisibility(View.GONE);
         //   t2.setVisibility(View.GONE);
        //    t3.setVisibility(View.GONE);
        //    t4.setVisibility(View.GONE);
        //    t5.setVisibility(View.GONE);
        //    t6.setVisibility(View.GONE);
            num1 = "[phone]";
            num2 = "[phone]";
        }
        if(branch.contentEquals("BTP") && level.contentEquals("Safety In Charge"))
        {
            bt1.setText("Javaji P");
            bt2.setText("H S Rao");
            bt3.setText("Sunil KB");
            bt4.setText("K Kishor");
            bt5.setText("Roshan");
            bt6.setText("Varghese M");
            num1 = "[phone]";
            num2 = "[phone]";
            num3 = "[phone]";
            num4 = "[phone]";
            num5 = "[phone]";
            num6 = "[phone]";
        }
        if(branch.contentEquals("BTP") && level.contentEquals("Fire/Accident/Ambulance"))
        {
            bt1.setText("Security");
            bt2.setVisibility(View.GONE);
            bt3.setVisibility(View.GONE);
            bt4.setVisibility(View.GONE);
            bt5.setVisibility(View.GONE);
            bt6.setVisibility(View.GONE);
            num1 = "08022984000";
        }
        if(branch.contentEquals("BTP") && level.contentEquals("Emergency Declarer"))
        {
            bt1.setText("B S Lokeshwaran(Head-Admin)");
            bt2.setText("Philip Mammen(Head-HR)");
            bt3.setVisibility(View.GONE);
            bt4.setVisibility(View.GONE);
            bt5.setVisibility(View.GONE);
            bt6.setVisibility(View.GONE);
            num1 = "[phone]";
            num2 = "[phone]";
        }
        if(branch.contentEquals("TD") && level.contentEquals("Safety In Charge"))
        {
            bt1.setText("Javaji P");
            bt2.setText("H S Rao");
            bt3.setText("Sunil KB");
            bt4.setText("K Kishor");
            bt5.setText("Anitha S");
            bt6.setText("Sreenivas K");
            num1 = "[phone]";
            num2 = "[phone]";
            num3 = "[phone]";
            num4 = "[phone]";
            num5 = "[phone]";
            num6 = "[phone]";
        }
        if(branch.contentEquals("TD") && level.contentEquals("Fire/Accident/Ambulance"))
        {
            bt1.setText("Security");
            bt2.setVisibility(View.GONE);
            bt3.setVisibility(View.GONE);
            bt4.setVisibility(View.GONE);
            bt5.setVisibility(View.GONE);
            bt6.setVisibility(View.GONE);
            num1 = "08022979761";
        }
        if(branch.contentEquals("TD") && level.contentEquals("Emergency Declarer"))
        {
            bt1.setText("B S Lokeshwaran(Head-Admin)");
            bt2.setText("Philip Mammen(Head-HR)");
            bt3.setVisibility(View.GONE);
            bt4.setVisibility(View.GONE);
            bt5.setVisibility(View.GONE);
            bt6.setVisibility(View.GONE);
            num1 = "[phone]";
            num2 = "[phone]";
        }
        if((branch.contentEquals("Neyyar") && level.contentEquals("Safety In Charge")) || (branch.contentEquals("Leela") && level.contentEquals("Safety In Charge")) || (branch.contentEquals("Gayathri") && level.contentEquals("Safety In Charge")))
        {
            bt1.setText("Tony");
            bt2.setText("Jossy Joseph");
            num1 = "[phone]";
            num2 = "[phone]";
        }
        if((branch.contentEquals("Neyyar")||branch.contentEquals("Leela")|| branch.contentEquals("Gayathri")) && level.contentEquals("Fire/Accident/Ambulance"))
        {
            bt1.setText("Security");
            bt2.setVisibility(View.GONE);
            num1 = "04716661000";
        }
        if((branch.contentEquals("Neyyar")||branch.contentEquals("Leela")|| branch.contentEquals("Gayathri")) && level.contentEquals("Emergency Declarer"))
        {
            bt1.setText("Sreekumar.V(Centre Head)");
            bt2.setText("Ajish MJ(Head-HR)");
            num1 = "[phone]";
            num2 = "[phone]";
        }
        if(branch.contentEquals("Chennai") && level.contentEquals("Safety In Charge"))
        {
            bt1.setText("Meeran");
            bt2.setVisibility(View.GONE);
            num1 = "[phone]";

        }
        if(branch.contentEquals("Chennai") && level.contentEquals("Fire/Accident/Ambulance"))
        {
            bt1.setText("Security");
            bt2.setVisibility(View.GONE);
            num1 = "08022979761";
        }
        if(branch.contentEquals("Chennai") && level.contentEquals("Emergency Declarer"))
        {
            bt1.setText("Jayendran.G(Center Head)");
            bt2.setVisibility(View.GONE);
            num1 = "[phone]";

        }
        if((branch.contentEquals("Alpha 1 & 2") || branch.contentEquals("SEZ")) && level.contentEquals("Safety In Charge"))
        {
            bt1.setText("Laxman Jadhav");
            bt2.setVisibility(View.GONE);
            num1 = "[phone]";
        }
        if((branch.contentEquals("Alpha 1 & 2") || branch.contentEquals("SEZ")) && level.contentEquals("Fire/Accident/Ambulance"))
        {
            bt1.setText("Security");
            bt2.setVisibility(View.GONE);
            bt3.setVisibility(View.GONE);
            bt4.setVisibility(View.GONE);
            bt5.setVisibility(View.GONE);
            bt6.setVisibility(View.GONE);
            num1 = "02066060033";
        }
        if((branch.contentEquals("Alpha 1 & 2") || branch.contentEquals("SEZ")) && level.contentEquals("Emergency Declarer"))
        {
            bt1.setText("Mr.Vasant Shah(Center Head)");
            bt2.setText("Ms.Simrit Dhindasa(Sr.Executive-HR)");
            num1 = "[phone]";
            num2 = "[phone]";
        }
        if(branch.contentEquals("Mumbai") && level.contentEquals("Safety In Charge"))
        {
            bt1.setText("Naveen Dighe");
            bt2.setVisibility(View.GONE);
            num1 = "[phone]";
        }
        if(branch.contentEquals("Mumbai") && level.contentEquals("Emergency Declarer"))
        {
            bt1.setText("Nagarajan(Center Head)");
            bt2.setVisibility(View.GONE);
            num1 = "[phone]";
        }
        if(branch.contentEquals("Mumbai") && level.contentEquals("Fire/Accident/Ambulance"))
        {
            bt1.setText("Security");
            bt2.setVisibility(View.GONE);
            num1 = "0226822145";
        }
    }
    public void launchDialer(String number)
    {
        String numberToDial = "tel:"+number;
        startActivity(new Intent(Intent.ACTION_DIAL, Uri.parse(numberToDial)));
    }
    public void onClickbt1(View view)
    {
    launchDialer(num1);
    }
    public void onClickbt2(View view)
    {
        launchDialer(num2);
    }
    public void onClickbt3(View view)
    {
        launchDialer(num3);
    }
    public void onClickbt4(View view)
    {
        launchDialer(num4);
    }
    public void onClickbt5(View view)
    {
        launchDialer(num5);
    }
    public void onClickbt6(View view)
    {
        launchDialer(num6);
    }

    @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_contacts, 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);
    }
}

activity_contacts.xml

<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:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context="com.prashanth.emergencycontacts.Contacts"
    android:background="@drawable/bg"
    android:id="@+id/layout1">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="CONTACT 1"
        android:id="@+id/contact_button1"
        android:onClick="onClickbt1"
        android:background="@android:drawable/dialog_holo_light_frame"
        android:layout_alignParentTop="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="CONTACT 2"
        android:id="@+id/contact_button2"
        android:layout_marginTop="40dp"
        android:onClick="onClickbt2"
        android:background="@android:drawable/dialog_holo_light_frame"
        android:layout_below="@+id/contact_button1"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:layout_alignLeft="@+id/contact_button1"
        android:layout_alignStart="@+id/contact_button1" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="CONTACT 3"
        android:id="@+id/contact_button3"
        android:onClick="onClickbt3"
        android:layout_marginTop="40dp"
        android:layout_below="@+id/contact_button2"
        android:layout_alignLeft="@+id/contact_button2"
        android:layout_alignStart="@+id/contact_button2"
        android:layout_alignRight="@+id/contact_button2"
        android:layout_alignEnd="@+id/contact_button2"
        android:background="@android:drawable/dialog_holo_light_frame" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="CONTACT 4"
        android:id="@+id/contact_button4"
        android:onClick="onClickbt4"
        android:layout_below="@+id/contact_button3"
        android:layout_alignLeft="@+id/contact_button3"
        android:layout_alignStart="@+id/contact_button3"
        android:layout_marginTop="40dp"
        android:layout_alignRight="@+id/contact_button3"
        android:layout_alignEnd="@+id/contact_button3"
        android:background="@android:drawable/dialog_holo_light_frame" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="CONTACT 5"
        android:id="@+id/contact_button5"
        android:onClick="onClickbt5"
        android:layout_below="@+id/contact_button4"
        android:layout_alignLeft="@+id/contact_button4"
        android:layout_alignStart="@+id/contact_button4"
        android:layout_marginTop="40dp"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:background="@android:drawable/dialog_holo_light_frame" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="CONTACT 6"
        android:id="@+id/contact_button6"
        android:onClick="onClickbt6"
        android:layout_below="@+id/contact_button5"
        android:layout_alignLeft="@+id/contact_button5"
        android:layout_alignStart="@+id/contact_button5"
        android:layout_marginTop="40dp"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:background="@android:drawable/dialog_holo_light_frame" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Security"
        android:id="@+id/textView1"
        android:layout_above="@+id/contact_button2"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Health &amp; Safety"
        android:id="@+id/textView2"
        android:layout_alignBottom="@+id/contact_button2"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Transport"
        android:id="@+id/textView3"
        android:layout_above="@+id/contact_button4"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Maintenance"
        android:id="@+id/textView4"
        android:layout_alignBottom="@+id/contact_button4"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Housekeeping"
        android:id="@+id/textView5"
        android:layout_alignBottom="@+id/contact_button5"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="IT"
        android:id="@+id/textView6"
        android:layout_alignBottom="@+id/contact_button6"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />
</RelativeLayout>

Logcat-

07-06 22:23:37.574  24510-24510/com.prashanth.emergencycontacts I/Timeline﹕ Timeline: Activity_launch_request id:com.prashanth.emergencycontacts time:14497951
07-06 22:23:37.601  24510-24510/com.prashanth.emergencycontacts I/ViewRootImpl﹕ CPU Rendering VSync enable = true
07-06 22:23:37.637  24510-24510/com.prashanth.emergencycontacts I/Timeline﹕ Timeline: Activity_idle id: android.os.BinderProxy@2f428e3d time:14498015
07-06 22:23:37.662  24510-24528/com.prashanth.emergencycontacts D/OpenGLRenderer﹕ endAllStagingAnimators on 0xa18af280 (ListView) with handle 0xaec2ce40
07-06 22:23:38.413  24510-24510/com.prashanth.emergencycontacts I/Timeline﹕ Timeline: Activity_launch_request id:com.prashanth.emergencycontacts time:14498790
07-06 22:23:38.472  24510-24510/com.prashanth.emergencycontacts D/AndroidRuntime﹕ Shutting down VM
07-06 22:23:38.473  24510-24510/com.prashanth.emergencycontacts E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.prashanth.emergencycontacts, PID: 24510
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.prashanth.emergencycontacts/com.prashanth.emergencycontacts.Contacts}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setText(java.lang.CharSequence)' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2354)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2416)
            at android.app.ActivityThread.access$900(ActivityThread.java:153)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1319)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5287)
            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:904)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setText(java.lang.CharSequence)' on a null object reference
            at com.prashanth.emergencycontacts.Contacts.onCreate(Contacts.java:65)
            at android.app.Activity.performCreate(Activity.java:6041)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2307)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2416)
            at android.app.ActivityThread.access$900(ActivityThread.java:153)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1319)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5287)
            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:904)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)

任何帮助都将不胜感激！

Answer 1

崩溃日志清楚地告诉我们出了什么问题。

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setText(java.lang.CharSequence)' on a null object reference
            at com.prashanth.emergencycontacts.Contacts.onCreate(Contacts.java:65)

您正试图在为null的Button上调用setText()。它还告诉你它在哪条线上崩溃

Contacts.onCreate(Contacts.java:65)

这意味着，您需要检查第65行。第65行为

bt1.setText("Javaji P");

即CCD_ 3是CCD_。但是你在下面的行中找到了bt1

bt1 = (Button) findViewById(R.id.contact_button1);

因此，这意味着bt1不存在于activity_contacts.xml布局中，或者id contact_button1是错误的。

请试着了解崩溃日志是如何工作的，因为这是一个非常基本的崩溃，你应该知道如何快速修复它。

Answer 2

在布局文件中，您使用@+id引用现有元素id，例如：

android:layout_alignLeft="@+id/contact_button1">

创建新id时，您应该使用@+id。在引用已创建的id时使用@id，例如：

android:layout_alignLeft="@id/contact_button1">