我的Log cat：
10-14 14:56:15.527: I/dalvikvm(1283): threadid=3: reacting to signal 3
10-14 14:56:15.857: I/dalvikvm(1283): Wrote stack traces to '/data/anr/traces.txt'
10-14 14:56:16.037: I/dalvikvm(1283): threadid=3: reacting to signal 3
10-14 14:56:16.107: I/dalvikvm(1283): Wrote stack traces to '/data/anr/traces.txt'
10-14 14:56:16.296: D/AndroidRuntime(1283): Shutting down VM
10-14 14:56:16.296: W/dalvikvm(1283): threadid=1: thread exiting with uncaught exception (group=0x409bf1f8)
10-14 14:56:16.316: E/AndroidRuntime(1283): FATAL EXCEPTION: main
10-14 14:56:16.316: E/AndroidRuntime(1283): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.lpu/com.example.lpu.MainActivity}: java.lang.NullPointerException
10-14 14:56:16.316: E/AndroidRuntime(1283): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
10-14 14:56:16.316: E/AndroidRuntime(1283): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
10-14 14:56:16.316: E/AndroidRuntime(1283): at android.app.ActivityThread.access$600(ActivityThread.java:123)
10-14 14:56:16.316: E/AndroidRuntime(1283): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
10-14 14:56:16.316: E/AndroidRuntime(1283): at android.os.Handler.dispatchMessage(Handler.java:99)
10-14 14:56:16.316: E/AndroidRuntime(1283): at android.os.Looper.loop(Looper.java:137)
10-14 14:56:16.316: E/AndroidRuntime(1283): at android.app.ActivityThread.main(ActivityThread.java:4424)
10-14 14:56:16.316: E/AndroidRuntime(1283): at java.lang.reflect.Method.invokeNative(Native Method)
10-14 14:56:16.316: E/AndroidRuntime(1283): at java.lang.reflect.Method.invoke(Method.java:511)
10-14 14:56:16.316: E/AndroidRuntime(1283): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
10-14 14:56:16.316: E/AndroidRuntime(1283): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
10-14 14:56:16.316: E/AndroidRuntime(1283): at dalvik.system.NativeStart.main(Native Method)
10-14 14:56:16.316: E/AndroidRuntime(1283): Caused by: java.lang.NullPointerException
10-14 14:56:16.316: E/AndroidRuntime(1283): at com.example.lpu.MainActivity.onCreate(MainActivity.java:29)
10-14 14:56:16.316: E/AndroidRuntime(1283): at android.app.Activity.performCreate(Activity.java:4466)
10-14 14:56:16.316: E/AndroidRuntime(1283): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
10-14 14:56:16.316: E/AndroidRuntime(1283): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
10-14 14:56:16.316: E/AndroidRuntime(1283): ... 11 more
10-14 14:56:16.547: I/dalvikvm(1283): threadid=3: reacting to signal 3
10-14 14:56:16.577: I/dalvikvm(1283): Wrote stack traces to '/data/anr/traces.txt'
10-14 14:56:16.866: I/dalvikvm(1283): threadid=3: reacting to signal 3
10-14 14:56:16.886: I/dalvikvm(1283): Wrote stack traces to '/data/anr/traces.txt'
10-14 14:57:06.806: I/dalvikvm(1330): threadid=3: reacting to signal 3
10-14 14:57:07.136: I/dalvikvm(1330): Wrote stack traces to '/data/anr/traces.txt'
10-14 14:57:07.277: I/dalvikvm(1330): threadid=3: reacting to signal 3
10-14 14:57:07.407: I/dalvikvm(1330): Wrote stack traces to '/data/anr/traces.txt'
10-14 14:57:07.736: D/dalvikvm(1330): GC_FOR_ALLOC freed 65K, 3% free 9119K/9347K, paused 78ms
10-14 14:57:07.806: I/dalvikvm(1330): threadid=3: reacting to signal 3
10-14 14:57:08.026: I/dalvikvm-heap(1330): Grow heap (frag case) to 16.883MB for 8294416-byte allocation
10-14 14:57:08.087: I/dalvikvm(1330): Wrote stack traces to '/data/anr/traces.txt'
10-14 14:57:08.207: D/dalvikvm(1330): GC_CONCURRENT freed 1K, 2% free 17217K/17479K, paused 6ms+19ms
10-14 14:57:08.307: I/dalvikvm(1330): threadid=3: reacting to signal 3
10-14 14:57:08.337: I/dalvikvm(1330): Wrote stack traces to '/data/anr/traces.txt'
10-14 14:57:08.826: I/dalvikvm(1330): threadid=3: reacting to signal 3
10-14 14:57:08.866: I/dalvikvm(1330): Wrote stack traces to '/data/anr/traces.txt'
10-14 14:57:09.301: D/gralloc_goldfish(1330): Emulator without GPU emulation detected.
10-14 14:57:09.316: I/dalvikvm(1330): threadid=3: reacting to signal 3
10-14 14:57:09.357: I/dalvikvm(1330): Wrote stack traces to '/data/anr/traces.txt'
10-14 14:57:12.797: I/dalvikvm(1330): threadid=3: reacting to signal 3
10-14 14:57:12.849: I/dalvikvm(1330): Wrote stack traces to '/data/anr/traces.txt'
10-14 14:57:13.306: I/dalvikvm(1330): threadid=3: reacting to signal 3
10-14 14:57:13.326: I/dalvikvm(1330): Wrote stack traces to '/data/anr/traces.txt'
10-14 14:57:18.666: I/dalvikvm(1330): threadid=3: reacting to signal 3
10-14 14:57:18.697: I/dalvikvm(1330): Wrote stack traces to '/data/anr/traces.txt'
10-14 15:01:11.557: I/dalvikvm(1371): threadid=3: reacting to signal 3
10-14 15:01:11.807: I/dalvikvm(1371): Wrote stack traces to '/data/anr/traces.txt'
10-14 15:01:12.046: I/dalvikvm(1371): threadid=3: reacting to signal 3
10-14 15:01:12.097: I/dalvikvm(1371): Wrote stack traces to '/data/anr/traces.txt'
10-14 15:01:12.137: D/AndroidRuntime(1371): Shutting down VM
10-14 15:01:12.147: W/dalvikvm(1371): threadid=1: thread exiting with uncaught exception (group=0x409bf1f8)
10-14 15:01:12.157: E/AndroidRuntime(1371): FATAL EXCEPTION: main
10-14 15:01:12.157: E/AndroidRuntime(1371): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.lpu/com.example.lpu.MainActivity}: java.lang.NullPointerException
10-14 15:01:12.157: E/AndroidRuntime(1371): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
10-14 15:01:12.157: E/AndroidRuntime(1371): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
10-14 15:01:12.157: E/AndroidRuntime(1371): at android.app.ActivityThread.access$600(ActivityThread.java:123)
10-14 15:01:12.157: E/AndroidRuntime(1371): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
10-14 15:01:12.157: E/AndroidRuntime(1371): at android.os.Handler.dispatchMessage(Handler.java:99)
10-14 15:01:12.157: E/AndroidRuntime(1371): at android.os.Looper.loop(Looper.java:137)
10-14 15:01:12.157: E/AndroidRuntime(1371): at android.app.ActivityThread.main(ActivityThread.java:4424)
10-14 15:01:12.157: E/AndroidRuntime(1371): at java.lang.reflect.Method.invokeNative(Native Method)
10-14 15:01:12.157: E/AndroidRuntime(1371): at java.lang.reflect.Method.invoke(Method.java:511)
10-14 15:01:12.157: E/AndroidRuntime(1371): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
10-14 15:01:12.157: E/AndroidRuntime(1371): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
10-14 15:01:12.157: E/AndroidRuntime(1371): at dalvik.system.NativeStart.main(Native Method)
10-14 15:01:12.157: E/AndroidRuntime(1371): Caused by: java.lang.NullPointerException
10-14 15:01:12.157: E/AndroidRuntime(1371): at com.example.lpu.MainActivity.onCreate(MainActivity.java:29)
10-14 15:01:12.157: E/AndroidRuntime(1371): at android.app.Activity.performCreate(Activity.java:4466)
10-14 15:01:12.157: E/AndroidRuntime(1371): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
10-14 15:01:12.157: E/AndroidRuntime(1371): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
10-14 15:01:12.157: E/AndroidRuntime(1371): ... 11 more
10-14 15:01:12.547: I/dalvikvm(1371): threadid=3: reacting to signal 3
10-14 15:01:12.586: I/dalvikvm(1371): Wrote stack traces to '/data/anr/traces.txt'
10-14 15:01:12.816: I/dalvikvm(1371): threadid=3: reacting to signal 3
10-14 15:01:12.826: I/dalvikvm(1371): Wrote stack traces to '/data/anr/traces.txt'
10-14 15:04:31.236: I/Process(1371): Sending signal. PID: 1371 SIG: 9
xml文件：
<?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"
android:background="@drawable/game" >
<TextView
android:id="@+id/textView5"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView4"
android:layout_below="@+id/textView4"
android:text="• Game Development"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textSize="13dp" />
<TextView
android:id="@+id/textView6"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView5"
android:layout_below="@+id/textView5"
android:layout_marginTop="21dp"
android:text="BS Information Technology major in"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textColor="#FDFEFE"
android:textSize="15dp"
android:textStyle="bold|italic" />
<TextView
android:id="@+id/textView7"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView6"
android:layout_below="@+id/textView6"
android:text="PACUCOA Level II Reaccredited Status)"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textSize="13dp"
android:textStyle="italic" />
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginLeft="12dp"
android:layout_marginTop="18dp"
android:text="COMPUTER STUDIES"
android:textAppearance="?android:attr/textAppearanceLarge"
android:textColor="#FDFEFE"
android:textSize="20sp"
android:textStyle="bold" />
<TextView
android:id="@+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView1"
android:layout_below="@+id/textView2"
android:layout_marginTop="16dp"
android:text="BS Computer Science major in"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textColor="#FDFEFE"
android:textSize="15dp"
android:textStyle="bold|italic" />
<TextView
android:id="@+id/textView4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView3"
android:layout_below="@+id/textView3"
android:layout_marginTop="14dp"
android:text="• Mobile Application Development"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textSize="13dp" />
<TextView
android:id="@+id/textView10"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView9"
android:layout_below="@+id/textView9"
android:layout_marginTop="16dp"
android:text="Associate in Computer Technology"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textColor="#FDFEFE"
android:textStyle="bold|italic" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView1"
android:layout_below="@+id/textView1"
android:text="(Bs Computer Science - PACUCOA level III Reacrideted Status)"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textSize="13sp"
android:textStyle="italic" />
<TextView
android:id="@+id/textView9"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView8"
android:layout_below="@+id/textView8"
android:text="• Digital Animation"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textSize="13dp" />
<TextView
android:id="@+id/textView8"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView7"
android:layout_centerVertical="true"
android:text="• Multimedia Technologies"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textSize="13dp" />
</RelativeLayout>
主要活动：
package com.example.lpu;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageButton;
public class MainActivity extends Activity implements OnClickListener {
Button button1;
Button button2;
ImageButton imageButton1;
Intent intent;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button1 = (Button)findViewById(R.id.button1);
button2 = (Button)findViewById(R.id.button2);
imageButton1 = (ImageButton)findViewById(R.id.imageButton1);
button1.setOnClickListener(this);
button2.setOnClickListener(this);
imageButton1.setOnClickListener(this);
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.button1:
Intent intent = new Intent(MainActivity.this,BUTTON.class);
this.startActivity(intent);
break;
case R.id.button2:
Intent intent2 = new Intent(MainActivity.this,BUTOON.class);
this.startActivity(intent2);
break;
case R.id.imageButton1:
Intent intent3 = new Intent(MainActivity.this,CCS.class);
this.startActivity(intent3);
break;
}
}
}
这是Android Manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.lpu"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="15"
android:targetSdkVersion="15" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".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=".BUTTON"></activity>
<activity android:name=".BUTOON"></activity>
<activity android:name=".CCS"></activity>
</application>
</manifest>
答案 0 :(得分：0)
您的日志文件指出了问题：
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.lpu/com.example.lpu.MainActivity}: java.lang.NullPointerException
...
10-14 14:56:16.316: E/AndroidRuntime(1283): Caused by: java.lang.NullPointerException
10-14 14:56:16.316: E/AndroidRuntime(1283): at com.example.lpu.MainActivity.onCreate(MainActivity.java:29)
从最后一行可以看出，MainActivity类的第29行有一个空指针异常。看起来你正试图错误地设置onClickListener。而不是
imageButton1.setOnClickListener(this);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// Perform action on click
}
});
根据Android文档：https://developer.android.com/reference/android/widget/Button.html
答案 1 :(得分：0)
您的xml缺少要将OnClickListener添加到的元素。
您需要将一个标识为R.id.button1的按钮，另一个标识为R.id.button2的按钮和一个标识为R.id.imageButton1的imageButton添加到您的activity_main xml文件中。
在relativeLayout中添加类似的内容：
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="button1"
android:id="@+id/button1"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="button2"
android:id="@+id/button2"
/>
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="imageButton1"
android:id="@+id/imageButton1"
/>