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Android中奇怪的NullPointerException

android

Android中奇怪的NullPointerException,android,nullpointerexception,Android,Nullpointerexception,我认为下面的问题会很傻（我只是一个编码初学者），但我已经在上面坐了很长时间，最后决定把它挂起来。我有一个类级的getName（）方法，它访问string.xml文件并从中获取一个条目 代码： public String getName() { String name = null; try { System.out.println("Inside getName"); String app_id = Main

我认为下面的问题会很傻（我只是一个编码初学者），但我已经在上面坐了很长时间，最后决定把它挂起来。我有一个类级的getName（）方法，它访问string.xml文件并从中获取一个条目

代码：

public String getName()
    {
        String name = null;
        try {
            System.out.println("Inside getName");
            String app_id = MainActivity.this.getResources().getString(R.string.app_id);
            System.out.println(app_id);
            fb = new Facebook(app_id);
            System.out.println("Before the JSON");
            String jsonUser = fb.request("me");
            System.out.println("Successful in fb.request");
            obj=Util.parseJson(jsonUser);
            System.out.println("Successful in parsejson");
            name = obj.optString("username");
} catch...
}

  12-26 17:24:07.330: W/dalvikvm(23184): threadid=1: thread exiting with uncaught exception (group=0x4118d438)
12-26 17:24:07.330: E/AndroidRuntime(23184): FATAL EXCEPTION: main
12-26 17:24:07.330: E/AndroidRuntime(23184): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.facebook_integration/com.example.facebook_integration.SQLiteDemoActivity}: java.lang.NullPointerException
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2099)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.access$600(ActivityThread.java:138)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.os.Handler.dispatchMessage(Handler.java:99)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.os.Looper.loop(Looper.java:137)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.main(ActivityThread.java:4954)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at java.lang.reflect.Method.invokeNative(Native Method)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at java.lang.reflect.Method.invoke(Method.java:511)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:798)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:565)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at dalvik.system.NativeStart.main(Native Method)
12-26 17:24:07.330: E/AndroidRuntime(23184): Caused by: java.lang.NullPointerException
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.example.facebook_integration.SQLiteDemoActivity.onCreate(SQLiteDemoActivity.java:33)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.Activity.performCreate(Activity.java:5252)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1082)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2038)
12-26 17:24:07.330: E/AndroidRuntime(23184):    ... 11 more

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">Facebook_Integration</string>
    <string name="action_settings">Settings</string>
    <string name="app_id">594458613962731</string>
    <string name="hello_world">Hello world!</string>
    <string name="title_activity_snap__image_view">Snap_ImageView</string>
    <string name="album_name">San_Pictures</string>
    <string name="title_activity_android_custom_gallery">AndroidCustomGalleryActivity</string>
    <string name="title_activity_full_screen">FullScreen</string>
    <string name="title_activity_sqlite_demo">SQLiteDemoActivity</string>

</resources>
当我调用上述方法时，它在

   String app_id = getString(R.string.app_id);

String app_id = MainActivity.this.getResources().getString(R.string.app_id);
有趣且最好的是，我在onCreate（）方法中有相同的行，如下所示：

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv = (TextView) findViewById(R.id.name_text_view);
        b = (ImageView) findViewById(R.id.postbutton);
        snap = (ImageView) findViewById(R.id.camera_image_view);
        sp = getPreferences(MODE_PRIVATE);
        **String app_id = getString(R.string.app_id);**
        fb = new Facebook(app_id);
        System.out.println("The app_id is " + app_id);
        String access_token = sp.getString("access_token", null);
        long expires = sp.getLong("access_expires", 0);
}
这不会引发任何空指针异常。我的问题是，为什么它只在getName（）方法上抛出NullPointerException。这与R的范围有关吗？我在这里完全迷失了方向，我真的很难为情地提出这样的问题，但也无法接受这样一个事实，那就是它给了我这个愚蠢的错误。任何帮助都会得到疯狂的感激

更新：

Logcat:

public String getName()
    {
        String name = null;
        try {
            System.out.println("Inside getName");
            String app_id = MainActivity.this.getResources().getString(R.string.app_id);
            System.out.println(app_id);
            fb = new Facebook(app_id);
            System.out.println("Before the JSON");
            String jsonUser = fb.request("me");
            System.out.println("Successful in fb.request");
            obj=Util.parseJson(jsonUser);
            System.out.println("Successful in parsejson");
            name = obj.optString("username");
} catch...
}

  12-26 17:24:07.330: W/dalvikvm(23184): threadid=1: thread exiting with uncaught exception (group=0x4118d438)
12-26 17:24:07.330: E/AndroidRuntime(23184): FATAL EXCEPTION: main
12-26 17:24:07.330: E/AndroidRuntime(23184): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.facebook_integration/com.example.facebook_integration.SQLiteDemoActivity}: java.lang.NullPointerException
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2099)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.access$600(ActivityThread.java:138)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.os.Handler.dispatchMessage(Handler.java:99)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.os.Looper.loop(Looper.java:137)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.main(ActivityThread.java:4954)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at java.lang.reflect.Method.invokeNative(Native Method)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at java.lang.reflect.Method.invoke(Method.java:511)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:798)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:565)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at dalvik.system.NativeStart.main(Native Method)
12-26 17:24:07.330: E/AndroidRuntime(23184): Caused by: java.lang.NullPointerException
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.example.facebook_integration.SQLiteDemoActivity.onCreate(SQLiteDemoActivity.java:33)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.Activity.performCreate(Activity.java:5252)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1082)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2038)
12-26 17:24:07.330: E/AndroidRuntime(23184):    ... 11 more

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">Facebook_Integration</string>
    <string name="action_settings">Settings</string>
    <string name="app_id">594458613962731</string>
    <string name="hello_world">Hello world!</string>
    <string name="title_activity_snap__image_view">Snap_ImageView</string>
    <string name="album_name">San_Pictures</string>
    <string name="title_activity_android_custom_gallery">AndroidCustomGalleryActivity</string>
    <string name="title_activity_full_screen">FullScreen</string>
    <string name="title_activity_sqlite_demo">SQLiteDemoActivity</string>

</resources>
更新2:

public String getName()
    {
        String name = null;
        try {
            System.out.println("Inside getName");
            String app_id = MainActivity.this.getResources().getString(R.string.app_id);
            System.out.println(app_id);
            fb = new Facebook(app_id);
            System.out.println("Before the JSON");
            String jsonUser = fb.request("me");
            System.out.println("Successful in fb.request");
            obj=Util.parseJson(jsonUser);
            System.out.println("Successful in parsejson");
            name = obj.optString("username");
} catch...
}

  12-26 17:24:07.330: W/dalvikvm(23184): threadid=1: thread exiting with uncaught exception (group=0x4118d438)
12-26 17:24:07.330: E/AndroidRuntime(23184): FATAL EXCEPTION: main
12-26 17:24:07.330: E/AndroidRuntime(23184): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.facebook_integration/com.example.facebook_integration.SQLiteDemoActivity}: java.lang.NullPointerException
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2099)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.access$600(ActivityThread.java:138)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.os.Handler.dispatchMessage(Handler.java:99)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.os.Looper.loop(Looper.java:137)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.main(ActivityThread.java:4954)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at java.lang.reflect.Method.invokeNative(Native Method)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at java.lang.reflect.Method.invoke(Method.java:511)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:798)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:565)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at dalvik.system.NativeStart.main(Native Method)
12-26 17:24:07.330: E/AndroidRuntime(23184): Caused by: java.lang.NullPointerException
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.example.facebook_integration.SQLiteDemoActivity.onCreate(SQLiteDemoActivity.java:33)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.Activity.performCreate(Activity.java:5252)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1082)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2038)
12-26 17:24:07.330: E/AndroidRuntime(23184):    ... 11 more

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">Facebook_Integration</string>
    <string name="action_settings">Settings</string>
    <string name="app_id">594458613962731</string>
    <string name="hello_world">Hello world!</string>
    <string name="title_activity_snap__image_view">Snap_ImageView</string>
    <string name="album_name">San_Pictures</string>
    <string name="title_activity_android_custom_gallery">AndroidCustomGalleryActivity</string>
    <string name="title_activity_full_screen">FullScreen</string>
    <string name="title_activity_sqlite_demo">SQLiteDemoActivity</string>

</resources>
Strings.xml:

public String getName()
    {
        String name = null;
        try {
            System.out.println("Inside getName");
            String app_id = MainActivity.this.getResources().getString(R.string.app_id);
            System.out.println(app_id);
            fb = new Facebook(app_id);
            System.out.println("Before the JSON");
            String jsonUser = fb.request("me");
            System.out.println("Successful in fb.request");
            obj=Util.parseJson(jsonUser);
            System.out.println("Successful in parsejson");
            name = obj.optString("username");
} catch...
}

  12-26 17:24:07.330: W/dalvikvm(23184): threadid=1: thread exiting with uncaught exception (group=0x4118d438)
12-26 17:24:07.330: E/AndroidRuntime(23184): FATAL EXCEPTION: main
12-26 17:24:07.330: E/AndroidRuntime(23184): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.facebook_integration/com.example.facebook_integration.SQLiteDemoActivity}: java.lang.NullPointerException
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2099)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.access$600(ActivityThread.java:138)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.os.Handler.dispatchMessage(Handler.java:99)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.os.Looper.loop(Looper.java:137)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.main(ActivityThread.java:4954)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at java.lang.reflect.Method.invokeNative(Native Method)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at java.lang.reflect.Method.invoke(Method.java:511)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:798)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:565)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at dalvik.system.NativeStart.main(Native Method)
12-26 17:24:07.330: E/AndroidRuntime(23184): Caused by: java.lang.NullPointerException
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.example.facebook_integration.SQLiteDemoActivity.onCreate(SQLiteDemoActivity.java:33)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.Activity.performCreate(Activity.java:5252)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1082)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2038)
12-26 17:24:07.330: E/AndroidRuntime(23184):    ... 11 more

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">Facebook_Integration</string>
    <string name="action_settings">Settings</string>
    <string name="app_id">594458613962731</string>
    <string name="hello_world">Hello world!</string>
    <string name="title_activity_snap__image_view">Snap_ImageView</string>
    <string name="album_name">San_Pictures</string>
    <string name="title_activity_android_custom_gallery">AndroidCustomGalleryActivity</string>
    <string name="title_activity_full_screen">FullScreen</string>
    <string name="title_activity_sqlite_demo">SQLiteDemoActivity</string>

</resources>
如果有人处理过这样的情况，请让我知道

更新4:

public String getName()
    {
        String name = null;
        try {
            System.out.println("Inside getName");
            String app_id = MainActivity.this.getResources().getString(R.string.app_id);
            System.out.println(app_id);
            fb = new Facebook(app_id);
            System.out.println("Before the JSON");
            String jsonUser = fb.request("me");
            System.out.println("Successful in fb.request");
            obj=Util.parseJson(jsonUser);
            System.out.println("Successful in parsejson");
            name = obj.optString("username");
} catch...
}

  12-26 17:24:07.330: W/dalvikvm(23184): threadid=1: thread exiting with uncaught exception (group=0x4118d438)
12-26 17:24:07.330: E/AndroidRuntime(23184): FATAL EXCEPTION: main
12-26 17:24:07.330: E/AndroidRuntime(23184): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.facebook_integration/com.example.facebook_integration.SQLiteDemoActivity}: java.lang.NullPointerException
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2099)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.access$600(ActivityThread.java:138)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.os.Handler.dispatchMessage(Handler.java:99)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.os.Looper.loop(Looper.java:137)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.main(ActivityThread.java:4954)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at java.lang.reflect.Method.invokeNative(Native Method)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at java.lang.reflect.Method.invoke(Method.java:511)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:798)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:565)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at dalvik.system.NativeStart.main(Native Method)
12-26 17:24:07.330: E/AndroidRuntime(23184): Caused by: java.lang.NullPointerException
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.example.facebook_integration.SQLiteDemoActivity.onCreate(SQLiteDemoActivity.java:33)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.Activity.performCreate(Activity.java:5252)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1082)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2038)
12-26 17:24:07.330: E/AndroidRuntime(23184):    ... 11 more

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">Facebook_Integration</string>
    <string name="action_settings">Settings</string>
    <string name="app_id">594458613962731</string>
    <string name="hello_world">Hello world!</string>
    <string name="title_activity_snap__image_view">Snap_ImageView</string>
    <string name="album_name">San_Pictures</string>
    <string name="title_activity_android_custom_gallery">AndroidCustomGalleryActivity</string>
    <string name="title_activity_full_screen">FullScreen</string>
    <string name="title_activity_sqlite_demo">SQLiteDemoActivity</string>

</resources>
MyApp的结构：

public String getName()
    {
        String name = null;
        try {
            System.out.println("Inside getName");
            String app_id = MainActivity.this.getResources().getString(R.string.app_id);
            System.out.println(app_id);
            fb = new Facebook(app_id);
            System.out.println("Before the JSON");
            String jsonUser = fb.request("me");
            System.out.println("Successful in fb.request");
            obj=Util.parseJson(jsonUser);
            System.out.println("Successful in parsejson");
            name = obj.optString("username");
} catch...
}

  12-26 17:24:07.330: W/dalvikvm(23184): threadid=1: thread exiting with uncaught exception (group=0x4118d438)
12-26 17:24:07.330: E/AndroidRuntime(23184): FATAL EXCEPTION: main
12-26 17:24:07.330: E/AndroidRuntime(23184): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.facebook_integration/com.example.facebook_integration.SQLiteDemoActivity}: java.lang.NullPointerException
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2099)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.access$600(ActivityThread.java:138)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.os.Handler.dispatchMessage(Handler.java:99)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.os.Looper.loop(Looper.java:137)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.main(ActivityThread.java:4954)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at java.lang.reflect.Method.invokeNative(Native Method)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at java.lang.reflect.Method.invoke(Method.java:511)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:798)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:565)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at dalvik.system.NativeStart.main(Native Method)
12-26 17:24:07.330: E/AndroidRuntime(23184): Caused by: java.lang.NullPointerException
12-26 17:24:07.330: E/AndroidRuntime(23184):    at com.example.facebook_integration.SQLiteDemoActivity.onCreate(SQLiteDemoActivity.java:33)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.Activity.performCreate(Activity.java:5252)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1082)
12-26 17:24:07.330: E/AndroidRuntime(23184):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2038)
12-26 17:24:07.330: E/AndroidRuntime(23184):    ... 11 more

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">Facebook_Integration</string>
    <string name="action_settings">Settings</string>
    <string name="app_id">594458613962731</string>
    <string name="hello_world">Hello world!</string>
    <string name="title_activity_snap__image_view">Snap_ImageView</string>
    <string name="album_name">San_Pictures</string>
    <string name="title_activity_android_custom_gallery">AndroidCustomGalleryActivity</string>
    <string name="title_activity_full_screen">FullScreen</string>
    <string name="title_activity_sqlite_demo">SQLiteDemoActivity</string>

</resources>
以下是我的应用程序的要点

1.登录facebook

2.拍照

3.将拍摄的照片的用户名和路径存储在数据库中

最初，我的主要活动有facebook图像，它会将我记录在facebook内并检索用户名，从而在同一主要活动的文本视图中设置它。 其次是一个相机按钮，它可以带我到相机前拍照。
拍摄完照片后，第三个活动应显示用户名和存储照片的路径。（这是我无法再次获取用户名的地方）。

在此，您应提供应用程序或活动上下文以获取资源值，如下所示：

String app_id=youractivity.this.getString(R.string.app_name);

public class MainActivity extends Activity {

    Resources res = this.getResources(); //you cannot use like this
这种方法很简单。希望这有帮助…

首先必须检查strings.xml文件中的应用程序id是否正确

如果是的话，那就改变

 String app_id = getResources().getString(R.string.app_id);
我发现这发生在我身上的是一个破损的布局。不用担心。我正在尽力给你解决办法

解决方案

确保R.链接到的任何内容都没有损坏。修复XML文件中的所有错误。如果ADK中的任何东西损坏，R将无法再生

如果您在活动中找到了某个内容并创建了import android.R，请将其删除。 运行Project->Clean。这将删除并重新生成R和BuildConfig

确保自动勾选了项目->构建。如果没有，请通过菜单->项目->构建项目手动构建。

等待几秒钟，让错误消失

如果不起作用，请删除/gen/文件夹中的所有内容

如果仍然不起作用，请尝试右键单击项目->Android工具->修复项目属性

检查*.properties文件（位于应用程序文件夹的根文件夹中），确保其中的链接未断开

右键单击您的项目>属性>Android

查看页面右侧的项目构建目标和库部分。构建目标应与AndroidManifest.xml中的目标匹配。因此，如果在AndroidManifest中设置为target 17，请确保目标名称为Android4.2。如果您的库在引用下有一个X，请删除并重新添加该库，直到出现绿色勾号。如果您移动了一些文件和文件夹，可能会发生这种情况

如果R不能重新生成，该怎么办

这通常发生在xml文件损坏时

检查XML文件中的错误，主要是/res/文件夹中的错误

常见的位置是/layout/和/values/，尤其是最近更改了其中一个位置时

检查AndroidManifest.xml，我发现我经常更改字符串，而忘记更改AndroidManifest.xml中的字符串名称

检查是否安装了Android SDK构建工具窗口->Android SDK管理器->工具->Android SDK构建工具

确保在更新Android SDK工具时，还更新了Android SDK平台工具和Android ASK构建工具。如果它们不匹配，构建将以静默方式失败

如果找不到问题，请右键单击/gen/->从本地历史还原…->勾选R.java->单击还原。这并不能解决问题，但会清除额外的错误，使问题更容易找到

希望它能帮助你。：）

我不知道到底是什么问题，但我可以为您提供更好的解决方案

尝试将此应用程序id保存在共享首选项中，然后您可以随时随地访问它

或者在任何类中创建一个静态字符串（我总是为所有常量和静态变量创建一个特殊类），然后您也可以随时随地调用此变量：）

我根据更新修改的答案：

恐怕活动的创造不仅仅局限于活动的创造 对象然后是各种初始化和setter调用，它们 Android系统可以，这将为活动生成完整的上下文。 例如：当您的MainActivity由Android系统创建时，MainActivity 对象，然后进行初始化，初始化还包括绑定 对象与资源。 当您在应用程序中创建MainActivity对象时，这些初始化都不会发生，因此，您无法访问资源（以及许多其他内容）。这个物体 不是Android意义上的真正活动对象。它只是一个未初始化的对象 主要活动类

在您的情况下，可以通过应用程序访问资源中的字符串值， 在使用当前活动上下文的所有活动中。你可以支持