Question

我创建了一个使用SharedPreferences的课程。在我的Activity中，我正在尝试添加项目并收到以下错误...

06-05 17:01:53.950: E/AndroidRuntime(3488): FATAL EXCEPTION: main
06-05 17:01:53.950: E/AndroidRuntime(3488): java.lang.NullPointerException
06-05 17:01:53.950: E/AndroidRuntime(3488):     at com.xcxcxc.helpers.Prefs.init(Prefs.java:16)
06-05 17:01:53.950: E/AndroidRuntime(3488):     at com.xcxcxc.helpers.Prefs.addStringProperty(Prefs.java:30)
06-05 17:01:53.950: E/AndroidRuntime(3488):     at com.xcxcxc.usersadapter.SplashActivity$1.callback(SplashActivity.java:78)
06-05 17:01:53.950: E/AndroidRuntime(3488):     at com.xcxcxc.usersadapter.SplashActivity$1.callback(SplashActivity.java:1)

这是我处理SharedPreferences ...

的代码

import android.content.Context;
import android.content.SharedPreferences;

public class Prefs {

    public static final String STORAGE_NAME = "ApplicationPrefs";

    private static SharedPreferences settings = null;
    private static SharedPreferences.Editor editor = null;
    private static Context context = null;

    public static void init(Context cntxt) {
        context = cntxt;
    }

    private static void init() {
        settings = context.getSharedPreferences(STORAGE_NAME, 0);
        editor = settings.edit();
    }

    /* String values */
    public static void addStringProperty(String name, String value) {
        if (settings == null || editor == null) {
            init();
        }
        editor.putString(name, value);
        editor.commit();
    }

    public static String getStringProperty(String name) {
        if (settings == null || editor == null) {
            init();
        }
        return settings.getString(name, null);
    }
}

这是我在Activity ...

中调用的代码

Prefs.addStringProperty("client_id", "1JDkv9sdfj8sf63rjs");

Answer 1

看起来Context是null。在addStringProperty（..）

之前设置Context

Prefs.init(getApplicationContext());
Prefs.addStringProperty("client_id", "1JDkv9sdfj8sf63rjs");

Answer 2

context似乎 null 。试着打电话

public static void init(Context cntxt)

第一

Answer 3

settings = context.getSharedPreferences(STORAGE_NAME, 0);

该声明必须引起NPE 您如何以及在何处调用init(Context cntxt)方法。

除非初始化上下文对象，否则您将获得NPE。先修复它。

Answer 4

context可能为null，这就是你得到空指针异常的原因：

private static void init() {
    settings = context.getSharedPreferences(STORAGE_NAME, 0);
    editor = settings.edit();
}

首先调用public static void init(Context cntxt)或处理空值：

private static void init() {
    if(context != null){
       settings = context.getSharedPreferences(STORAGE_NAME, 0);
       editor = settings.edit();
    }
}

带有context.getSharedPreferences的java.lang.NullPointerException（STORAGE_NAME，0）

4 个答案: