在Android应用中的共享偏好声明中的NullPointerException？

Question

所以,制作一个应用程序.我添加了大量新代码,现在它已经打开了FC :(

这是logcat:

07-25 16:59:12.490: D/AndroidRuntime(26121): Shutting down VM
07-25 16:59:12.495: W/dalvikvm(26121): threadid=1: thread exiting with uncaught exception (group=0x40a641f8)
07-25 16:59:12.495: E/AndroidRuntime(26121): FATAL EXCEPTION: main
07-25 16:59:12.495: E/AndroidRuntime(26121): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.liamwli.smsbusy/com.liamwli.smsbusy.Sms_busyActivity}: java.lang.NullPointerException
07-25 16:59:12.495: E/AndroidRuntime(26121):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1993)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2104)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at android.app.ActivityThread.access$600(ActivityThread.java:132)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1157)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at android.os.Handler.dispatchMessage(Handler.java:99)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at android.os.Looper.loop(Looper.java:137)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at android.app.ActivityThread.main(ActivityThread.java:4575)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at java.lang.reflect.Method.invokeNative(Native Method)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at java.lang.reflect.Method.invoke(Method.java:511)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at dalvik.system.NativeStart.main(Native Method)
07-25 16:59:12.495: E/AndroidRuntime(26121): Caused by: java.lang.NullPointerException
07-25 16:59:12.495: E/AndroidRuntime(26121):    at android.preference.PreferenceManager.getDefaultSharedPreferencesName(PreferenceManager.java:371)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at android.preference.PreferenceManager.getDefaultSharedPreferences(PreferenceManager.java:366)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at com.liamwli.smsbusy.Sms_busyActivity.<init>(Sms_busyActivity.java:23)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at java.lang.Class.newInstanceImpl(Native Method)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at java.lang.Class.newInstance(Class.java:1319)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at android.app.Instrumentation.newActivity(Instrumentation.java:1023)
07-25 16:59:12.495: E/AndroidRuntime(26121):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1984)
07-25 16:59:12.495: E/AndroidRuntime(26121):    ... 11 more
07-25 16:59:12.940: I/dalvikvm(26121): threadid=3: reacting to signal 3
07-25 16:59:12.950: I/dalvikvm(26121): Wrote stack traces to '/data/anr/traces.txt'
07-25 16:59:13.040: I/dalvikvm(26121): threadid=3: reacting to signal 3
07-25 16:59:13.045: I/dalvikvm(26121): Wrote stack traces to '/data/anr/traces.txt'

Sms_busyActivity.java的第23行是:

SharedPreferences getPrefs = PreferenceManager.getDefaultSharedPreferences(getBaseContext());

我不明白我得到了这个错误.

剩下的活动在下面(非常大):

package com.liamwli.smsbusy;

import android.app.Activity;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.util.Log;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.CompoundButton;
import android.widget.EditText;
import android.widget.Toast;
import android.widget.ToggleButton;
import android.content.IntentFilter;
import android.content.SharedPreferences;

public class Sms_busyActivity extends Activity {
    IntentFilter intentFilter;
    ToggleButton endis;
    EditText message;
    Button smessage;
    SharedPreferences getPrefs = PreferenceManager.getDefaultSharedPreferences(getBaseContext());
    SharedPreferences.Editor editor = getPrefs.edit();

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // Intent i = new Intent("com.liamwli.smsbusy.PREFS");
        // startActivity(i);
        setContentView(R.layout.main);

        endis = (ToggleButton) findViewById(R.id.enableddis);

        smessage = (Button) findViewById(R.id.savemess);

        message = (EditText) findViewById(R.id.message);

        // ---intent to filter for SMS messages received---
        intentFilter = new IntentFilter();
        intentFilter.addAction("SMS_RECEIVED_ACTION");

        endis.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

            @Override
            public void onCheckedChanged(CompoundButton arg0, boolean arg1) {
                // TODO Auto-generated method stub
                Toast.makeText(Sms_busyActivity.this, "App state changed",
                        Toast.LENGTH_LONG).show();
                if (endis.isChecked()){
                    editor.putBoolean("enabled", true);
                    editor.commit();
                }else {
                    editor.putBoolean("enabled", false);
                    editor.commit();
                }

                editor.putString("message", message.getText().toString());
                editor.commit();

            }
        });

        smessage.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub

                editor.putString("message", message.getText().toString());
                editor.commit();

            }
        });

    }

    @SuppressWarnings("deprecation")
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (Integer.parseInt(android.os.Build.VERSION.SDK) < 5
                && keyCode == KeyEvent.KEYCODE_BACK
                && event.getRepeatCount() == 0) {
            Log.d("CDA", "onKeyDown Called");
            onBackPressed();
        }

        return super.onKeyDown(keyCode, event);
    }

    public void onBackPressed() {
        Log.d("CDA", "onBackPressed Called");

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // TODO Auto-generated method stub
        return super.onCreateOptionsMenu(menu);
    }

}

请有人帮帮我吗？

Answer 1

将以下代码移动到onCreate()方法中.

getPrefs = PreferenceManager.getDefaultSharedPreferences(getBaseContext());

原因是,在现有代码中,您getBaseContext()可以在通过调用完全创建之前使用context()super.onCreate().