我是新手。我试图从一个字符串的Edittext中获取输入,并在另一个edittext中显示它。该应用程序在开始时运行良好,但是当我在下面插入代码时,我开始出现错误“应用程序意外停止”,之后当我删除此代码时出现错误,我仍然遇到相同的错误。我完全感到困惑。
这是我完整的课程代码:
public class IOActivity extends Activity {
/** Called when the activity is first created. */
Button button=(Button) findViewById(R.id.button1);
EditText edtxt1=(EditText) findViewById(R.id.editText1);
EditText edtxt2=(EditText) findViewById(R.id.editText2);
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
String a=edtxt1.getText().toString();
edtxt2.setText(a);
}
});
}
}
我的Android.Manifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.IO"
android:versionCode="1"
android:versionName="1.0">
<uses-sdk android:minSdkVersion="9" />
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".IOActivity" android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
我的Logcat显示以下错误:
03-19 18:30:17.938: ERROR/Zygote(32): setreuid() failed. errno: 2
03-19 18:30:29.179: ERROR/Zygote(32): setreuid() failed. errno: 17
03-19 18:30:30.868: ERROR/BatteryService(60): usbOnlinePath not found
03-19 18:30:30.868: ERROR/BatteryService(60): batteryVoltagePath not found
03-19 18:30:30.868: ERROR/BatteryService(60): batteryTemperaturePath not found
03-19 18:30:30.888: ERROR/SurfaceFlinger(60): Couldn't open /sys/power/wait_for_fb_sleep or /sys/power/wait_for_fb_wake
03-19 18:30:31.128: ERROR/SensorService(60): couldn't open device for module sensors (Invalid argument)
03-19 18:30:40.158: ERROR/System(60): Failure starting core service
03-19 18:30:40.158: ERROR/System(60): java.lang.SecurityException
03-19 18:30:40.158: ERROR/System(60): at android.os.BinderProxy.transact(Native Method)
03-19 18:30:40.158: ERROR/System(60): at android.os.ServiceManagerProxy.addService(ServiceManagerNative.java:146)
03-19 18:30:40.158: ERROR/System(60): at android.os.ServiceManager.addService(ServiceManager.java:72)
03-19 18:30:40.158: ERROR/System(60): at com.android.server.ServerThread.run(SystemServer.java:206)
03-19 18:30:40.188: ERROR/EventHub(60): could not get driver version for /dev/input/mouse0, Not a typewriter
03-19 18:30:40.188: ERROR/EventHub(60): could not get driver version for /dev/input/mice, Not a typewriter
03-19 18:30:40.738: ERROR/SoundPool(60): error loading /system/media/audio/ui/Effect_Tick.ogg
03-19 18:30:40.748: ERROR/SoundPool(60): error loading /system/media/audio/ui/KeypressStandard.ogg
03-19 18:30:40.748: ERROR/SoundPool(60): error loading /system/media/audio/ui/KeypressSpacebar.ogg
03-19 18:30:40.748: ERROR/SoundPool(60): error loading /system/media/audio/ui/KeypressDelete.ogg
03-19 18:30:40.758: ERROR/SoundPool(60): error loading /system/media/audio/ui/KeypressReturn.ogg
03-19 18:30:40.808: ERROR/UsbObserver(60): java.lang.NullPointerException
03-19 18:30:40.808: ERROR/UsbObserver(60): at
com.android.server.UsbObserver.init(UsbObserver.java:131)
03-19 18:30:40.808: ERROR/UsbObserver(60): at com.android.server.UsbObserver.<init>(UsbObserver.java:65)
03-19 18:30:40.808: ERROR/UsbObserver(60): at com.android.server.ServerThread.run(SystemServer.java:402)
03-19 18:30:41.748: ERROR/ThrottleService(60): Could not open GPS configuration file /etc/gps.conf
03-19 18:30:41.998: ERROR/logwrapper(132): executing /system/bin/tc failed: No such file or directory
03-19 18:30:42.070: ERROR/logwrapper(134): executing /system/bin/tc failed: No such file or directory
03-19 18:30:42.118: ERROR/logwrapper(135): executing /system/bin/tc failed: No such file or directory
03-19 18:31:06.573: ERROR/MediaProvider(257): Illegal update request: can't downgrade from 305 to 92. Did you forget to wipe data?
03-19 18:31:06.823: ERROR/MediaScannerService(257): exception in MediaScanner.scan()
03-19 18:31:06.823: ERROR/MediaScannerService(257): java.lang.IllegalArgumentException
03-19 18:31:06.823: ERROR/MediaScannerService(257): at com.android.providers.media.MediaProvider.updateDatabase(MediaProvider.java:379)
03-19 18:31:06.823: ERROR/MediaScannerService(257): at com.android.providers.media.MediaProvider.access$200(MediaProvider.java:83)
03-19 18:31:06.823: ERROR/MediaScannerService(257): at com.android.providers.media.MediaProvider$DatabaseHelper.onUpgrade(MediaProvider.java:201)
03-19 18:31:06.823: ERROR/MediaScannerService(257): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:132)
03-19 18:31:06.823: ERROR/MediaScannerService(257): at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:187)
03-19 18:31:06.823: ERROR/MediaScannerService(257): at com.android.providers.media.MediaProvider.query(MediaProvider.java:1290)
03-19 18:31:06.823: ERROR/MediaScannerService(257): at android.content.ContentProvider$Transport.query(ContentProvider.java:187)
03-19 18:31:06.823: ERROR/MediaScannerService(257): at android.media.MediaScanner.prescan(MediaScanner.java:911)
03-19 18:31:06.823: ERROR/MediaScannerService(257): at android.media.MediaScanner.scanDirectories(MediaScanner.java:1184)
03-19 18:31:06.823: ERROR/MediaScannerService(257): at com.android.providers.media.MediaScannerService.scan(MediaScannerService.java:111)
03-19 18:31:06.823: ERROR/MediaScannerService(257): at com.android.providers.media.MediaScannerService.access$200(MediaScannerService.java:48)
03-19 18:31:06.823: ERROR/MediaScannerService(257): at com.android.providers.media.MediaScannerService$ServiceHandler.handleMessage(MediaScannerSe
rvice.java:267)
03-19 18:31:06.823: ERROR/MediaScannerService(257): at android.os.Handler.dispatchMessage(Handler.java:99)
03-19 18:31:06.823: ERROR/MediaScannerService(257): at android.os.Looper.loop(Looper.java:123)
03-19 18:31:06.823: ERROR/MediaScannerService(257): at com.android.providers.media.MediaScannerService.run(MediaScannerService.java:188)
03-19 18:31:06.823: ERROR/MediaScannerService(257): at java.lang.Thread.run(Thread.java:1019)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): FATAL EXCEPTION: main
03-19 18:31:14.083: ERROR/AndroidRuntime(332): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.IO/com.example.IO.IOActivity}: java.lang.NullPointerException
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1544)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1638)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:928)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at android.os.Handler.dispatchMessage(Handler.java:99)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at android.os.Looper.loop(Looper.java:123)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at android.app.ActivityThread.main(ActivityThread.java:3647)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at java.lang.reflect.Method.invokeNative(Native Method)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at java.lang.reflect.Method.invoke(Method.java:507)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at dalvik.system.NativeStart.main(Native Method)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): Caused by: java.lang.NullPointerException
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at android.app.Activity.findViewById(Activity.java:1647)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at com.example.IO.IOActivity.<init>(IOActivity.java:14)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at java.lang.Class.newInstanceImpl(Native Method)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at java.lang.Class.newInstance(Class.java:1409)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1536)
03-19 18:31:14.083: ERROR/AndroidRuntime(332): ... 11 more
最佳答案
您正在尝试使按钮槽
Button myButton = (Button) findViewById(R.id.my_button);
您必须确保在setContentView调用之后执行此操作
setContentView(R.layout.layoutcontainingbutton);
因此会出错,因为您试图在加载这些视图之前调用findViewById。
关于java - Android:应用程序意外停止,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/9771376/