线程：崩溃并显示消息“ java.lang.RuntimeException：无法实例化活动”

Question

i know this question has been treated so much time, but i really don't find the answer to my problem. This is an application which connect to a server, so, there's a socket, that's why i'm using thread (i can't do anything else since android 4.0), but even if i'm disable the code of my socket, it still crash.

Here's the logCat error :

04-08 08:36:39.366: D/AndroidRuntime(16604): Shutting down VM
04-08 08:36:39.366: W/dalvikvm(16604): threadid=1: thread exiting with uncaught                exception (group=0x4122f300)
04-08 08:36:39.366: E/AndroidRuntime(16604): FATAL EXCEPTION: main
04-08 08:36:39.366: E/AndroidRuntime(16604): java.lang.RuntimeException: Unable to   instantiate activity   ComponentInfo{com.example.projetlyres2013/com.example.projetlyres2013.PlanDMX}:   java.lang.NullPointerException
04-08 08:36:39.366: E/AndroidRuntime(16604):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at android.app.ActivityThread.access$600(ActivityThread.java:130)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at android.os.Handler.dispatchMessage(Handler.java:99)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at android.os.Looper.loop(Looper.java:137)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at android.app.ActivityThread.main(ActivityThread.java:4745)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at java.lang.reflect.Method.invokeNative(Native Method)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at java.lang.reflect.Method.invoke(Method.java:511)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at dalvik.system.NativeStart.main(Native Method)
04-08 08:36:39.366: E/AndroidRuntime(16604): Caused by: java.lang.NullPointerException
04-08 08:36:39.366: E/AndroidRuntime(16604):    at android.app.Activity.findViewById(Activity.java:1825)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at com.example.projetlyres2013.PlanDMX.<init>(PlanDMX.java:27)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at java.lang.Class.newInstanceImpl(Native Method)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at java.lang.Class.newInstance(Class.java:1319)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
04-08 08:36:39.366: E/AndroidRuntime(16604):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
04-08 08:36:39.366: E/AndroidRuntime(16604):    ... 11 more
04-08 08:36:41.326: I/Process(16604): Sending signal. PID: 16604 SIG: 9
04-08 08:46:26.556: D/AndroidRuntime(16825): Shutting down VM

///////// Manifest /////////

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.projetlyres2013"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="16" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.example.projetlyres2013.PlanDMX"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

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

</application>

</manifest>

I don't know what's happened when i want to launch it on my tablet (android 4.1). I really need help for that :/

Thanks

Answer 1

NullPointer here means that you did not set your layout XML as contentView to your Activity. Inside onCreate(...) method of Activity add

setContentView(R.layout.some_layout-file)