Using Intent.putextra

Question

String sRow = SignIn.getRow(email);    
Intent intent = new Intent(SignIn.this,HomePage.class); 
       intent.putExtra("rowID", sRow); 
       startActivity(intent); 

此代码在我的SignIn活动中，我想将String值sRow传递给HomePage类。

Bundle extras = getIntent().getExtras(); 
    String rowID = extras.getString("rowID"); 

从我的HomePage类，我用它来调用sRow的值并将其分配给rowID。我做得对吗？因为我收到和错误的调用HomePage.class;

的logcat：

10-27 02:55:19.040: D/dalvikvm(1722): Not late-enabling CheckJNI (already on) 

10-27 02:55:19.380: D/(1722): HostConnection::get() New Host Connection established 0xb96340e0, tid 1722 

10-27 02:55:19.650: W/EGL_emulation(1722): eglSurfaceAttrib not implemented 

10-27 02:55:19.780: D/OpenGLRenderer(1722): Enabling debug mode 0 

10-27 02:55:19.800: D/dalvikvm(1722): GC_CONCURRENT freed 131K, 8% free 3092K/3348K, paused 1ms+1ms, total 4ms 

10-27 02:55:52.960: W/EGL_emulation(1722): eglSurfaceAttrib not implemented 

10-27 02:56:00.141: W/EGL_emulation(1722): eglSurfaceAttrib not implemented 

10-27 02:56:00.181: D/AndroidRuntime(1722): Shutting down VM 

10-27 02:56:00.181: W/dalvikvm(1722): threadid=1: thread exiting with uncaught exception (group=0xb0cacb20) 

10-27 02:56:00.181: E/AndroidRuntime(1722): FATAL EXCEPTION: main 

10-27 02:56:00.181: E/AndroidRuntime(1722): Process: com.example.packageit, PID: 1722 

10-27 02:56:00.181: E/AndroidRuntime(1722): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.packageit/com.example.packageit.HomePage}: java.lang.NullPointerException 

10-27 02:56:00.181: E/AndroidRuntime(1722):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121) 

10-27 02:56:00.181: E/AndroidRuntime(1722):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245) 

10-27 02:56:00.181: E/AndroidRuntime(1722):  at android.app.ActivityThread.access$800(ActivityThread.java:135) 
10-27 02:56:00.181: E/AndroidRuntime(1722):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
10-27 02:56:00.181: E/AndroidRuntime(1722):  at android.os.Handler.dispatchMessage(Handler.java:102) 
10-27 02:56:00.181: E/AndroidRuntime(1722):  at android.os.Looper.loop(Looper.java:136) 
10-27 02:56:00.181: E/AndroidRuntime(1722):  at android.app.ActivityThread.main(ActivityThread.java:5017) 
10-27 02:56:00.181: E/AndroidRuntime(1722):  at java.lang.reflect.Method.invokeNative(Native Method) 
10-27 02:56:00.181: E/AndroidRuntime(1722):  at java.lang.reflect.Method.invoke(Method.java:515) 
10-27 02:56:00.181: E/AndroidRuntime(1722):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) 
10-27 02:56:00.181: E/AndroidRuntime(1722):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) 
10-27 02:56:00.181: E/AndroidRuntime(1722):  at dalvik.system.NativeStart.main(Native Method) 
10-27 02:56:00.181: E/AndroidRuntime(1722): Caused by: java.lang.NullPointerException 
10-27 02:56:00.181: E/AndroidRuntime(1722):  at com.example.packageit.HomePage.<init>(HomePage.java:14) 
10-27 02:56:00.181: E/AndroidRuntime(1722):  at java.lang.Class.newInstanceImpl(Native Method) 
10-27 02:56:00.181: E/AndroidRuntime(1722):  at java.lang.Class.newInstance(Class.java:1208) 
10-27 02:56:00.181: E/AndroidRuntime(1722):  at android.app.Instrumentation.newActivity(Instrumentation.java:1061) 
10-27 02:56:00.181: E/AndroidRuntime(1722):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112) 
10-27 02:56:00.181: E/AndroidRuntime(1722):  ... 11 more 

Answer 1

Try this help you 

HomePage class: 

Intent intent = getIntent(); 
Bundle extras = intent.getExtras(); 
String rowID = extras.getString("rowID"); 

Answer 2

你做了一个非常小的错误。

你把字符串额外的意图直接不捆绑。当你检索你使用捆绑。

所以干脆写这种方式。

String rowID = getIntent().getStringExtra("rowID"); 

Answer 3

虽然HomePage类获得ROWID，具体操作如下：

Intent intent = getIntent(); 
String rowID = intent.getStringExtra("rowID"); 

希望这会工作精绝。

也请检查清单以确认HomePage.class是否已注册。