IllegalStateException：系统服务在 onCreate() 之前对活动不可用答案

【问题标题】：IllegalStateException: System services not available to Activities before onCreate()IllegalStateException：系统服务在 onCreate() 之前对活动不可用
【发布时间】：2012-12-05 09:58:27
【问题描述】：

当我启动我的应用程序时，我不断收到致命的 java.lang.IllegalStateException 错误，但我不知道为什么。基本上我要做的就是每 10 秒返回一次正在运行的进程和任务。

这是我的代码：

public class MainActivity extends Activity {

    Handler h = new Handler();
    public static final String TAG = "MyActivity";
    int s;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Checker();
    }

    public void Checker() {
        Handler h = new Handler();
        h.post(check);
    }

    Runnable check = new Runnable() {
        ActivityManager am = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
        public void run() {
            Processes(am);
            Tasks(am);
            h.postAtTime(check, 10000);
        }
    };

    public void Processes(ActivityManager am) {
        List<ActivityManager.RunningAppProcessInfo> l = am.getRunningAppProcesses();
        s = l.size();
        for(int i = 0; i < s; i++) {
            Log.d(TAG, "Process:  " + l.get(i).processName);
        }
    }

    public void Tasks(ActivityManager am) {
        List<ActivityManager.RunningTaskInfo> l = am.getRunningTasks(1000);
        s = l.size();
        for(int i = 0; i < s; i++) {
            // .baseActivity returns the process that started the Task
            Log.d(TAG, "Task:  " + l.get(i).baseActivity.getPackageName());
        }
    }

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

这是我的日志：

12-18 08:03:53.190: E/AndroidRuntime(1577): FATAL EXCEPTION: main
12-18 08:03:53.190: E/AndroidRuntime(1577): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.androidside/com.example.androidside.MainActivity}: java.lang.IllegalStateException: System services not available to Activities before onCreate()
12-18 08:03:53.190: E/AndroidRuntime(1577):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at android.os.Handler.dispatchMessage(Handler.java:99)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at android.os.Looper.loop(Looper.java:137)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at android.app.ActivityThread.main(ActivityThread.java:5039)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at java.lang.reflect.Method.invokeNative(Native Method)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at java.lang.reflect.Method.invoke(Method.java:511)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at dalvik.system.NativeStart.main(Native Method)
12-18 08:03:53.190: E/AndroidRuntime(1577): Caused by: java.lang.IllegalStateException: System services not available to Activities before onCreate()
12-18 08:03:53.190: E/AndroidRuntime(1577):     at android.app.Activity.getSystemService(Activity.java:4463)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at com.example.androidside.MainActivity$1.<init>(MainActivity.java:54)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at com.example.androidside.MainActivity.<init>(MainActivity.java:53)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at java.lang.Class.newInstanceImpl(Native Method)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at java.lang.Class.newInstance(Class.java:1319)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
12-18 08:03:53.190: E/AndroidRuntime(1577):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
12-18 08:03:53.190: E/AndroidRuntime(1577):     ... 11 more

感谢您的帮助。

【问题讨论】：

标签： java android illegalstateexception

【解决方案1】：

尝试更改您的代码

Handler h ;
    @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            h = new Handler();
            Checker();
        }

【讨论】：

没有用，仍然出现同样的异常，感谢您的尝试。
好吧，当我按照您对处理程序和活动管理器的建议进行操作时，它就起作用了。

【解决方案2】：

首先尝试在需要时初始化变量：

private Handler h;
private Runnable check;

public void Checker() {
    check = new Runnable() {
        ActivityManager am = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
        public void run() {
            Processes(am);
            Tasks(am);
            h.postAtTime(check, 10000);
        }
    };
    h = new Handler();
    h.post(check);
}

public void onResume() {
    super.onResume(); 
    Checker();
}

其次，尝试选择真正能说明它是什么的变量名。例如，将l 更改为taskList，将s 更改为listSize，并将h 更改为handler。此外，方法名称不以大写开头。

【讨论】：