Eclipse中的nullpointerexception（android）

Question

运行以下代码时，我从Eclipse中获取了NullPointerException ，无法完全了解它。 这是通过Eclipse btw进行的Android代码。 我曾尝试为移动私有类UpdateTimeTask身边，因为我认为这是问题。

public class ClockWidgetXActivity extends Activity {
private UpdateTimeTask m_updateTime;
private Handler m_handler;
private TextView time;
private final int DELAY = 100;
/** Called when the activity is first created. */

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    String currentDateTimeString = DateFormat.getTimeInstance().format(new Date());
    TextView time = (TextView) findViewById(R.id.time1);
    Typeface font = Typeface.createFromAsset(getAssets(), "Carre.ttf");
    time.setTypeface(font);
    time.setTextSize(65.f);
    time.setText(currentDateTimeString);
    m_updateTime = new UpdateTimeTask();

    m_handler = new Handler();
    m_handler.post(m_updateTime);

}  

private class UpdateTimeTask implements Runnable {
    public void run() {
        String currentDateTimeString = DateFormat.getTimeInstance().format(new Date());
        time.setText(currentDateTimeString);

        m_handler.postDelayed(m_updateTime, DELAY);
    }
}
}

Logcat：

12-01 03:26:54.642: E/AndroidRuntime(673): FATAL EXCEPTION: main
12-01 03:26:54.642: E/AndroidRuntime(673): java.lang.NullPointerException
12-01 03:26:54.642: E/AndroidRuntime(673):  at com.sokydevelopers.clockWidgetX.ClockWidgetXActivity$UpdateTimeTask.run(ClockWidgetXActivity.java:23)
12-01 03:26:54.642: E/AndroidRuntime(673):  at android.os.Handler.handleCallback(Handler.java:605)
12-01 03:26:54.642: E/AndroidRuntime(673):  at android.os.Handler.dispatchMessage(Handler.java:92)
12-01 03:26:54.642: E/AndroidRuntime(673):  at android.os.Looper.loop(Looper.java:137)
12-01 03:26:54.642: E/AndroidRuntime(673):  at android.app.ActivityThread.main(ActivityThread.java:4340)
12-01 03:26:54.642: E/AndroidRuntime(673):  at java.lang.reflect.Method.invokeNative(Native Method)
12-01 03:26:54.642: E/AndroidRuntime(673):  at java.lang.reflect.Method.invoke(Method.java:511)
12-01 03:26:54.642: E/AndroidRuntime(673):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
12-01 03:26:54.642: E/AndroidRuntime(673):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
12-01 03:26:54.642: E/AndroidRuntime(673):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

有可能：

m_updateTime = new UpdateTimeTask();
m_handler = new Handler();

更新为：

m_handler = new Handler();
m_updateTime = new UpdateTimeTask();

首先尝试注释掉此行以确认：

m_handler.postDelayed(m_updateTime, DELAY);

然后取消注释。

Answer 2

可能未初始化任务中使用的time变量。 您最终在onCreate中初始化了本地。

TextView time = (TextView) findViewById(R.id.time1);
    Typeface font = Typeface.createFromAsset(getAssets(), 

改为这样做

 time = (TextView) findViewById(R.id.time1);