Android - Intent putExtra 需要空指针

Question

我在 android 中遇到了问题。在我的程序中有一个包含 4 个片段的活动。从其中一个片段中，我想调用一个对话活动，并发送一个变量。这是我的代码：

 Intent popup = new Intent(getActivity().getApplicationContext(),
 PopUpWifi.class); popup.putExtra("WiFiID", String.valueOf(name));
 startActivity(popup);

这是弹出活动的代码：

public class PopUpWifi extends Activity { 
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.popupwifi);

         TextView TVWifi = (TextView) findViewById(R.id.TVWifi);
         EditText ETJelszo = (EditText) findViewById(R.id.ETJelszo);

         String value = getIntent().getStringExtra("WiFiID");
         TVWifi.setText(value);
     } }

这里是 pupupwifi.xml：

   <LinearLayout
   xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:orientation="vertical">
   <TextView
       android:layout_width="fill_parent"
       android:layout_height="wrap_content"
       android:text="Wi-fi hálózat neve"
       android:textSize="@dimen/NewSize" />
   <TextView
       android:name="@+id/TVWifi"
       android:layout_width="fill_parent"
       android:layout_height="wrap_content"
       android:text="Wi-fi"
       android:textSize="@dimen/NewSize" />
   <TextView
       android:layout_width="fill_parent"
       android:layout_height="wrap_content"
       android:text="Kérem adja meg a jelszót:"
       android:textSize="@dimen/NewSize" />
   <EditText
       android:id="@+id/ETJelszo"
       android:layout_width="fill_parent"
       android:layout_height="wrap_content"
       android:textSize="@dimen/NewSize" />
   <Button
       android:layout_width="fill_parent"
       android:layout_height="wrap_content"
       android:text="Bevitel"
       android:textSize="@dimen/NewSize" /> 
   </LinearLayout>

但我可以尝试任何方法，它会引发空指针异常：

 FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.sss.home/com.sss.home.PopUpWifi}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2372)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2424)
            at android.app.ActivityThread.access$600(ActivityThread.java:162)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1364)
            at android.os.Handler.dispatchMessage(Handler.java:107)
            at android.os.Looper.loop(Looper.java:194)
            at android.app.ActivityThread.main(ActivityThread.java:5400)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:525)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:837)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:604)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.sss.home.PopUpWifi.onCreate(PopUpWifi.java:20)
            at android.app.Activity.performCreate(Activity.java:5122)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1084)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2336)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2424)
            at android.app.ActivityThread.access$600(ActivityThread.java:162)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1364)
            at android.os.Handler.dispatchMessage(Handler.java:107)
            at android.os.Looper.loop(Looper.java:194)
            at android.app.ActivityThread.main(ActivityThread.java:5400)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:525)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:837)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:604)
            at dalvik.system.NativeStart.main(Native Method)

感谢您的帮助。

Answer 1

尝试使用android:id="@+id/TVWifi" 而不是android:name="@+id/TVWifi"