Android App NullPointerException on SharedPreferences按鈕

Question

我在sharedpreferences上遇到了問題，在第43行出現了NullPointerException錯誤，我將提供所需的所有信息，我厭倦了試圖解決它數小時的問題。

我有3個活動，帶有2個按鈕的主活動=查看和編輯。

這個應用程序是關於什么的。 用戶打開應用程序，然后按我說的獲得2個按鈕，即“查看和編輯”。 當他按下“編輯”時，他會輸入一些信息，例如姓名，姓氏，尼克，地址，電話，電子郵件。 當他按下“保存”按鈕時，他進入“查看活動”並查看他剛剛輸入的信息。

編輯按鈕JAVA是這樣的：

public class Editaremesaj extends ActionBarActivity {

    public static final String PREFS_NAME = "MyPreferencesFile";

    EditText name = null;
    EditText lastname = null;
    EditText nickname = null;
    EditText adress = null;
    EditText phone = null;
    EditText myemail = null;
    EditText mylevel = null;
    Button btn = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_editaremesaj);

        name = (EditText)findViewById(R.id.name);
        lastname = (EditText)findViewById(R.id.lastname);
        nickname = (EditText)findViewById(R.id.nickname);
        adress = (EditText)findViewById(R.id.adress);
        phone = (EditText)findViewById(R.id.phone);
        myemail = (EditText)findViewById(R.id.email);
        mylevel = (EditText)findViewById(R.id.level);

         btn = (Button)findViewById(R.id.btnshared);
         btn.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    // TODO Auto-generated method stub

                    SharedPreferences settings = getSharedPreferences (PREFS_NAME,0);
                    SharedPreferences.Editor editor = settings.edit();

                    editor.putString("name", name.getText().toString());
                    editor.putString("lastname", lastname.getText().toString());
                    editor.putString("nickname", nickname.getText().toString());
                    editor.putString("adress", adress.getText().toString());
                    editor.putString("phone", phone.getText().toString());
                    editor.putString("myemail", myemail.getText().toString());
                    editor.putString("mylevel", mylevel.getText().toString());

                    editor.commit();

                    Intent intent = new Intent(getApplicationContext(), Aratamesaj.class);
                    startActivity(intent);
                }
            });

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.editaremesaj, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * 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_editaremesaj,
                    container, false);
            return rootView;
        }
    }

}

編輯活動的XML是這樣的：

<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.citiresiscriere.Editaremesaj$PlaceholderFragment" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="38dp"
        android:layout_marginTop="28dp"
        android:text="Name:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <EditText
        android:id="@+id/name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textView1"
        android:layout_marginLeft="21dp"
        android:layout_toRightOf="@+id/textView1"
        android:ems="10" android:inputType="text">

        <requestFocus />
    </EditText>

    <EditText
        android:id="@+id/nickname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/textView3"
        android:layout_alignBottom="@+id/textView3"
        android:layout_alignLeft="@+id/lastname"
        android:ems="10" android:inputType="text"/>

    <EditText
        android:id="@+id/lastname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textView2"
        android:layout_alignLeft="@+id/name"
        android:ems="10" android:inputType="text"/>

    <TextView
        android:id="@+id/textView4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/textView3"
        android:layout_below="@+id/nickname"
        android:layout_marginTop="28dp"
        android:text="Adress:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <EditText
        android:id="@+id/adress"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textView4"
        android:layout_alignLeft="@+id/nickname"
        android:ems="10" android:inputType="text"/>

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView1"
        android:layout_marginTop="24dp"
        android:layout_toLeftOf="@+id/name"
        android:text="Lastname:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView2"
        android:layout_marginTop="21dp"
        android:layout_toLeftOf="@+id/name"
        android:text="Nick-name:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textView5"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView4"
        android:layout_marginTop="30dp"
        android:layout_toLeftOf="@+id/name"
        android:text="Phone:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <EditText
        android:id="@+id/phone"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textView5"
        android:layout_alignLeft="@+id/adress"
        android:ems="10" 
        android:inputType="text"/>

    <TextView
        android:id="@+id/textView6"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView5"
        android:layout_marginTop="26dp"
        android:layout_toLeftOf="@+id/name"
        android:text="E-mail:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <EditText
        android:id="@+id/email"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textView6"
        android:layout_alignLeft="@+id/phone"
        android:ems="10" android:inputType="text"/>

    <TextView
        android:id="@+id/textView7"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView6"
        android:layout_marginTop="28dp"
        android:layout_toLeftOf="@+id/name"
        android:text="Level:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <EditText
        android:id="@+id/level"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textView7"
        android:layout_alignLeft="@+id/email"
        android:ems="10" android:inputType="text"/>

    <Button
        android:id="@+id/btnshared"
        style="?android:attr/buttonStyleSmall"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignRight="@+id/level"
        android:layout_marginBottom="24dp"
        android:text="@string/salveaza" />

</RelativeLayout>

和LogCat：

04-11 08:20:37.144: I/dalvikvm(597): Could not find method android.content.pm.PackageManager.getActivityLogo, referenced from method android.support.v7.internal.widget.ActionBarView.<init>
04-11 08:20:37.144: W/dalvikvm(597): VFY: unable to resolve virtual method 323: Landroid/content/pm/PackageManager;.getActivityLogo (Landroid/content/ComponentName;)Landroid/graphics/drawable/Drawable;
04-11 08:20:37.144: D/dalvikvm(597): VFY: replacing opcode 0x6e at 0x008b
04-11 08:20:37.144: I/dalvikvm(597): Could not find method android.content.pm.ApplicationInfo.loadLogo, referenced from method android.support.v7.internal.widget.ActionBarView.<init>
04-11 08:20:37.144: W/dalvikvm(597): VFY: unable to resolve virtual method 319: Landroid/content/pm/ApplicationInfo;.loadLogo (Landroid/content/pm/PackageManager;)Landroid/graphics/drawable/Drawable;
04-11 08:20:37.144: D/dalvikvm(597): VFY: replacing opcode 0x6e at 0x0099
04-11 08:20:37.164: D/dalvikvm(597): VFY: dead code 0x008e-0092 in Landroid/support/v7/internal/widget/ActionBarView;.<init> (Landroid/content/Context;Landroid/util/AttributeSet;)V
04-11 08:20:37.164: D/dalvikvm(597): VFY: dead code 0x009c-00a0 in Landroid/support/v7/internal/widget/ActionBarView;.<init> (Landroid/content/Context;Landroid/util/AttributeSet;)V
04-11 08:20:38.454: D/dalvikvm(597): GC_FOR_MALLOC freed 4374 objects / 272672 bytes in 69ms
04-11 08:20:38.554: D/AndroidRuntime(597): Shutting down VM
04-11 08:20:38.554: W/dalvikvm(597): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
04-11 08:20:38.564: E/AndroidRuntime(597): FATAL EXCEPTION: main
04-11 08:20:38.564: E/AndroidRuntime(597): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.citiresiscriere/com.example.citiresiscriere.Editaremesaj}: java.lang.NullPointerException
04-11 08:20:38.564: E/AndroidRuntime(597):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
04-11 08:20:38.564: E/AndroidRuntime(597):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
04-11 08:20:38.564: E/AndroidRuntime(597):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
04-11 08:20:38.564: E/AndroidRuntime(597):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
04-11 08:20:38.564: E/AndroidRuntime(597):  at android.os.Handler.dispatchMessage(Handler.java:99)
04-11 08:20:38.564: E/AndroidRuntime(597):  at android.os.Looper.loop(Looper.java:123)
04-11 08:20:38.564: E/AndroidRuntime(597):  at android.app.ActivityThread.main(ActivityThread.java:4627)
04-11 08:20:38.564: E/AndroidRuntime(597):  at java.lang.reflect.Method.invokeNative(Native Method)
04-11 08:20:38.564: E/AndroidRuntime(597):  at java.lang.reflect.Method.invoke(Method.java:521)
04-11 08:20:38.564: E/AndroidRuntime(597):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
04-11 08:20:38.564: E/AndroidRuntime(597):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
04-11 08:20:38.564: E/AndroidRuntime(597):  at dalvik.system.NativeStart.main(Native Method)
04-11 08:20:38.564: E/AndroidRuntime(597): Caused by: java.lang.NullPointerException
04-11 08:20:38.564: E/AndroidRuntime(597):  at com.example.citiresiscriere.Editaremesaj.onCreate(Editaremesaj.java:43)
04-11 08:20:38.564: E/AndroidRuntime(597):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
04-11 08:20:38.564: E/AndroidRuntime(597):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
04-11 08:20:38.564: E/AndroidRuntime(597):  ... 11 more

第43行在這里：

 btn = (Button)findViewById(R.id.btnshared);
         btn.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    // TODO Auto-generated method stub

                    SharedPreferences settings = getSharedPreferences (PREFS_NAME,0);
                    SharedPreferences.Editor editor = settings.edit();

在btn.setOnClickListener(new View.OnClickListener() {

顯示按鈕Java文件：

public class Aratamesaj extends ActionBarActivity {


    public static final String PREFS_NAME = "MyPreferencesFile";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_aratamesaj);

        TextView name = (TextView)findViewById(R.id.textViewname);
        TextView lastname = (TextView)findViewById(R.id.textViewlastname);
        TextView nickname = (TextView)findViewById(R.id.textViewnick);
        TextView adress = (TextView)findViewById(R.id.textViewadress);
        TextView phone = (TextView)findViewById(R.id.textViewphone);
        TextView email = (TextView)findViewById(R.id.textViewemail);
        TextView level = (TextView)findViewById(R.id.textViewlevel);


        SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);

        name.setText(settings.getString("name","ERROR"));
        lastname.setText(settings.getString("lastname", "ERROR"));
        nickname.setText(settings.getString("nickname", "ERROR"));
        adress.setText(settings.getString("adress", "ERROR"));
        phone.setText(settings.getString("phone", "ERROR"));
        email.setText(settings.getString("myemail", "ERROR"));
        level.setText(settings.getString("mylevel", "ERROR"));

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.aratamesaj, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * 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_aratamesaj,
                    container, false);
            return rootView;
        }
    }

}

和XML：

<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.citiresiscriere.Aratamesaj$PlaceholderFragment" >

    <TextView
        android:id="@+id/textView7"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/textView6"
        android:layout_below="@+id/textView6"
        android:layout_marginTop="26dp"
        android:text="Level:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/textView2"
        android:layout_marginTop="24dp"
        android:text="Nick-name:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textView4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/textView3"
        android:layout_below="@+id/textView3"
        android:layout_marginTop="19dp"
        android:text="Adress:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textView5"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/textView4"
        android:layout_below="@+id/textView4"
        android:layout_marginTop="22dp"
        android:text="Phone:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textView6"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/textView5"
        android:layout_below="@+id/textView5"
        android:layout_marginTop="22dp"
        android:text="E-mail:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/textView3"
        android:layout_below="@+id/textView1"
        android:layout_marginTop="20dp"
        android:text="Lastname:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_alignRight="@+id/textView2"
        android:layout_marginTop="40dp"
        android:text="Name:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textViewname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/textView1"
        android:layout_alignBottom="@+id/textView1"
        android:layout_alignParentRight="true"
        android:layout_marginRight="46dp"
        android:text=""
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textViewlastname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textView2"
        android:layout_alignLeft="@+id/numecitire"
        android:text=""
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textViewnick"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/textView3"
        android:layout_alignBottom="@+id/textView3"
        android:layout_alignLeft="@+id/textView9"
        android:text=""
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textViewadress"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/textView4"
        android:layout_alignBottom="@+id/textView4"
        android:layout_alignLeft="@+id/textView10"
        android:text=""
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textViewphone"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/textView5"
        android:layout_alignBottom="@+id/textView5"
        android:layout_alignLeft="@+id/textView11"
        android:text=""
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textViewemail"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textView6"
        android:layout_alignLeft="@+id/textView12"
        android:text=""
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textViewlevel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textView7"
        android:layout_alignLeft="@+id/textView13"
        android:text=""
        android:textAppearance="?android:attr/textAppearanceMedium" />

</RelativeLayout>

謝謝你，祝你有美好的一天。

Answer 1

只有在Activity上調用了onCreate( ）之后，才能調用getSharedPreferences() 。

Answer 2

嘗試通過以下方式獲得編輯器：

SharedPreferences.Editor editor = PreferenceManager.getDefaultSharedPreferences(context).edit();