android - Ecclipse Android Sdk 中的 NullPointerException 不幸的是 myapp 已停止

标签 android nullpointerexception emulation runtimeexception

我是初学者。卡在这个 NullPointerException 上。这是一个简单的按钮程序。一旦我作为 Android 应用程序运行，该项目就会打开并立即关闭，并显示不幸的是我的应用程序已停止。

04-15 17:40:05.656: D/AndroidRuntime(599): Shutting down VM
04-15 17:40:05.656: W/dalvikvm(599): threadid=1: thread exiting with uncaught exception (group=0xb2adcd58)
04-15 17:40:05.666: E/AndroidRuntime(599): FATAL EXCEPTION: main
04-15 17:40:05.666: E/AndroidRuntime(599): Process: com.example.buttona, PID: 599
04-15 17:40:05.666: E/AndroidRuntime(599): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.buttona/com.example.buttona.Buttonwa}: java.lang.NullPointerException
04-15 17:40:05.666: E/AndroidRuntime(599):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2208)
04-15 17:40:05.666: E/AndroidRuntime(599):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2270)
04-15 17:40:05.666: E/AndroidRuntime(599):  at android.app.ActivityThread.access$800(ActivityThread.java:138)
04-15 17:40:05.666: E/AndroidRuntime(599):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1209)
04-15 17:40:05.666: E/AndroidRuntime(599):  at android.os.Handler.dispatchMessage(Handler.java:102)
04-15 17:40:05.666: E/AndroidRuntime(599):  at android.os.Looper.loop(Looper.java:136)
04-15 17:40:05.666: E/AndroidRuntime(599):  at android.app.ActivityThread.main(ActivityThread.java:5042)
04-15 17:40:05.666: E/AndroidRuntime(599):  at java.lang.reflect.Method.invokeNative(Native Method)
04-15 17:40:05.666: E/AndroidRuntime(599):  at java.lang.reflect.Method.invoke(Method.java:515)
04-15 17:40:05.666: E/AndroidRuntime(599):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:776)
04-15 17:40:05.666: E/AndroidRuntime(599):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
04-15 17:40:05.666: E/AndroidRuntime(599):  at dalvik.system.NativeStart.main(Native Method)
04-15 17:40:05.666: E/AndroidRuntime(599): Caused by: java.lang.NullPointerException
04-15 17:40:05.666: E/AndroidRuntime(599):  at com.example.buttona.Buttonwa.onCreate(Buttonwa.java:29)
04-15 17:40:05.666: E/AndroidRuntime(599):  at android.app.Activity.performCreate(Activity.java:5231)
04-15 17:40:05.666: E/AndroidRuntime(599):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
04-15 17:40:05.666: E/AndroidRuntime(599):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2172)
04-15 17:40:05.666: E/AndroidRuntime(599):  ... 11 more
04-15 17:40:11.466: I/Process(599): Sending signal. PID: 599 SIG: 9
04-15 17:57:32.017: D/AndroidRuntime(662): Shutting down VM
04-15 17:57:32.017: W/dalvikvm(662): threadid=1: thread exiting with uncaught exception (group=0xb2adcd58)
04-15 17:57:32.027: E/AndroidRuntime(662): FATAL EXCEPTION: main
04-15 17:57:32.027: E/AndroidRuntime(662): Process: com.example.buttona, PID: 662
04-15 17:57:32.027: E/AndroidRuntime(662): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.buttona/com.example.buttona.Buttonwa}: java.lang.NullPointerException
04-15 17:57:32.027: E/AndroidRuntime(662):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2208)
04-15 17:57:32.027: E/AndroidRuntime(662):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2270)
04-15 17:57:32.027: E/AndroidRuntime(662):  at android.app.ActivityThread.access$800(ActivityThread.java:138)
04-15 17:57:32.027: E/AndroidRuntime(662):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1209)
04-15 17:57:32.027: E/AndroidRuntime(662):  at android.os.Handler.dispatchMessage(Handler.java:102)
04-15 17:57:32.027: E/AndroidRuntime(662):  at android.os.Looper.loop(Looper.java:136)
04-15 17:57:32.027: E/AndroidRuntime(662):  at android.app.ActivityThread.main(ActivityThread.java:5042)
04-15 17:57:32.027: E/AndroidRuntime(662):  at java.lang.reflect.Method.invokeNative(Native Method)
04-15 17:57:32.027: E/AndroidRuntime(662):  at java.lang.reflect.Method.invoke(Method.java:515)
04-15 17:57:32.027: E/AndroidRuntime(662):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:776)
04-15 17:57:32.027: E/AndroidRuntime(662):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
04-15 17:57:32.027: E/AndroidRuntime(662):  at dalvik.system.NativeStart.main(Native Method)
04-15 17:57:32.027: E/AndroidRuntime(662): Caused by: java.lang.NullPointerException
04-15 17:57:32.027: E/AndroidRuntime(662):  at com.example.buttona.Buttonwa.onCreate(Buttonwa.java:29)
04-15 17:57:32.027: E/AndroidRuntime(662):  at android.app.Activity.performCreate(Activity.java:5231)
04-15 17:57:32.027: E/AndroidRuntime(662):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
04-15 17:57:32.027: E/AndroidRuntime(662):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2172)
04-15 17:57:32.027: E/AndroidRuntime(662):  ... 11 more
04-15 17:57:34.957: I/Process(662): Sending signal. PID: 662 SIG: 9

这是 Java 文件。

public class Buttonwa extends Activity {

Button name, surname;
TextView display;

@Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_buttonwa);

    name = (Button) findViewById(R.id.name_button);
    surname = (Button) findViewById(R.id.surname_button);
    display = (TextView) findViewById(R.id.display);
    name.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            display.setText("Your Name Is Shashank Yadav");

        }
    });

    surname.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            display.setText("Your Name Is Yadav Shashank");

        }
    });

这是 xml 文件。

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.buttona.Buttonwa$PlaceholderFragment" >

<TextView
    android:id="@+id/display"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="50dp"
     />
<Button 
android:id="@+id/name_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_marginTop="10dp"
android:text="@string/Name"
/>

<Button 
android:id="@+id/surname_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_below="@+id/name_button"
android:text="@string/Surname"
/>


</RelativeLayout>

最佳答案

问题是您在 fragment 中创建了 View 元素 fragment_main.xml (我认为这就是它的名称，您还没有发布名称)但您的代码期望它们出现在您的 Activity 中。

当你这样做时:

setContentView(R.layout.activity_buttonwa);

name = (Button) findViewById(R.id.name_button);
surname = (Button) findViewById(R.id.surname_button);
display = (TextView) findViewById(R.id.display);

您的意思是，“嘿 Activity，请检查 activity_buttonwa.xml 中的所有这些 View 元素，您会在那里找到它们。

从您的错误消息来看，name是 null因此你会得到 NullPointerException当您尝试设置OnClickListener时在上面。这是null因为它不在你的 activity_buttonwa.xml 中文件。

要修复此问题，您可以或者将所有 xml 移至 activity_buttonwa.xml 或者您可以将通货膨胀代码移动到您的 fragment 中:

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment {

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);

        name = (Button) rootView.findViewById(R.id.name_button);
        surname = (Button) rootView.findViewById(R.id.surname_button);
        display = (TextView) rootView.findViewById(R.id.display);

        // Add OnClickListeners, etc.

        return rootView;
    }
}

我想说最好将通货膨胀代码移动到您的 fragment 中，如上所述。

关于android - Ecclipse Android Sdk 中的 NullPointerException 不幸的是 myapp 已停止，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/23091832/

上一篇：android - 下载文件到内部存储

下一篇：android - Admob 梯度依赖

相关文章：

java - Android 存储 - 即使设置了权限，也无法读取应用程序目录之外的目录文件

java - 如何使用 Spinner(s) 值更新 Button Click 上的 TextView

JavaFx 节点集.....() -> NullPointer 异常

android - 挂载Android模拟器创建的qcow2镜像

android - 有没有办法在 Windows 程序中模拟 Android 应用程序？

android - Android 10 中的应用程序图标有时是错误的

android - Calabash Android 未找到查询 : textView marked: 的元素

java - 为什么这个查询返回NULL？

java - 单击后退按钮会导致强制关闭/NullPointerException

javascript - Protractor :如何拉伸(stretch)和替换元素？

©2024 IT工具网  联系我们