将变量从一个活动传递到另一个

我尝试从一个活动发送一个变量到另一个，但我得到一个错误。我使用这个，因为我想发送有关菜单的每个项目的一些数据到另一个活动，然后修改根据收到的数据进行文本查看。我已经把它贴只有一个，我要送这是标题信息.. 我已经附上了我的活动和logcat的错误：将变量从一个活动传递到另一个

MainActivity

 Bundle bundle= new Bundle(); 
     bundle.putString("Title", lessons_titles[position]);         

     Intent intent = new Intent(context, Example1.class); 

     intent.putExtras(bundle); 
     context.startActivity(intent);

传递活动

Bundle bundle = getIntent().getExtras(); 
    String title = bundle.getString("Title");       
    title_view.setText(title);

logcat的错误

03-12 17:18:31.529: E/AndroidRuntime(1873): FATAL EXCEPTION: main 
03-12 17:18:31.529: E/AndroidRuntime(1873): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.test/com.example.test.Example1}: java.lang.NullPointerException 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2137) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at android.app.ActivityThread.access$600(ActivityThread.java:141) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at android.os.Handler.dispatchMessage(Handler.java:99) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at android.os.Looper.loop(Looper.java:137) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at android.app.ActivityThread.main(ActivityThread.java:5103) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at java.lang.reflect.Method.invokeNative(Native Method) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at java.lang.reflect.Method.invoke(Method.java:525) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at dalvik.system.NativeStart.main(Native Method) 
03-12 17:18:31.529: E/AndroidRuntime(1873): Caused by: java.lang.NullPointerException 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at android.app.Activity.findViewById(Activity.java:1853) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at com.example.test.Example1.<init>(Example1.java:10) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at java.lang.Class.newInstanceImpl(Native Method) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at java.lang.Class.newInstance(Class.java:1130) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at android.app.Instrumentation.newActivity(Instrumentation.java:1061) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2128) 
03-12 17:18:31.529: E/AndroidRuntime(1873):  ... 11 more 
03-12 17:21:55.112: E/AndroidRuntime(2031): FATAL EXCEPTION: main 
03-12 17:21:55.112: E/AndroidRuntime(2031): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.test/com.example.test.Example1}: java.lang.NullPointerException 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2137) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at android.app.ActivityThread.access$600(ActivityThread.java:141) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at android.os.Handler.dispatchMessage(Handler.java:99) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at android.os.Looper.loop(Looper.java:137) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at android.app.ActivityThread.main(ActivityThread.java:5103) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at java.lang.reflect.Method.invokeNative(Native Method) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at java.lang.reflect.Method.invoke(Method.java:525) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at dalvik.system.NativeStart.main(Native Method) 
03-12 17:21:55.112: E/AndroidRuntime(2031): Caused by: java.lang.NullPointerException 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at android.app.Activity.findViewById(Activity.java:1853) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at com.example.test.Example1.<init>(Example1.java:10) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at java.lang.Class.newInstanceImpl(Native Method) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at java.lang.Class.newInstance(Class.java:1130) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at android.app.Instrumentation.newActivity(Instrumentation.java:1061) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2128) 
03-12 17:21:55.112: E/AndroidRuntime(2031):  ... 11 more 
03-12 17:22:02.132: E/AndroidRuntime(2050): FATAL EXCEPTION: main 
03-12 17:22:02.132: E/AndroidRuntime(2050): java.lang.RuntimeException: Unable to  instantiate activity ComponentInfo{com.example.test/com.example.test.Example1}: java.lang.NullPointerException 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2137) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at android.app.ActivityThread.access$600(ActivityThread.java:141) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at android.os.Handler.dispatchMessage(Handler.java:99) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at android.os.Looper.loop(Looper.java:137) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at android.app.ActivityThread.main(ActivityThread.java:5103) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at java.lang.reflect.Method.invokeNative(Native Method) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at java.lang.reflect.Method.invoke(Method.java:525) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at dalvik.system.NativeStart.main(Native Method) 
03-12 17:22:02.132: E/AndroidRuntime(2050): Caused by: java.lang.NullPointerException 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at android.app.Activity.findViewById(Activity.java:1853) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at com.example.test.Example1.<init>(Example1.java:10) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at java.lang.Class.newInstanceImpl(Native Method) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at java.lang.Class.newInstance(Class.java:1130) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at android.app.Instrumentation.newActivity(Instrumentation.java:1061) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2128) 
03-12 17:22:02.132: E/AndroidRuntime(2050):  ... 11 more

来源

2014-03-12 Victor Mihaita

什么是Example1.java的第10行？它看起来像你可能在调用setContentView之前从你的构造函数调用findViewById，这是无效的。活动视图尚未设置。 – goto10

TextView title_view =（TextView）findViewById（R.id.titleView）; –

这是行10 –

您正在从您的Activity构造函数调用findViewById。在通过调用setContentView设置活动视图之后，您才能拨打findViewById，这应在onCreate中完成。例如：

class MyActivity extends Activity { 
    public MyActivity() { 
     // Do not do anything with views here 
    } 

    public void onCreate(final Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.myLayout); 
     // Now you can do stuff with your views 
     final TextView title_view = (TextView)findViewById(R.id.titleView); 
    } 
}

来源

2014-03-12 22:24:17 goto10

感谢您的回复。我发现了错误，你是对的。再次感谢：） –

将变量从一个活动传递到另一个

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