Question

所以我有一个Activity并调用另一个类，一旦它尝试获取共享首选项就崩溃了。

以下是我在Activity中调用的代码

Methods_play test1 = new Methods_play(); 
String[] tmp1 = test1.pewpew(level);

这里是我的方法类的代码

package


import android.app.Activity;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;

    public class Methods_play extends Activity {

        public String[] pewpew(int level) {

            //GETS STUFF
            Random rn = new Random(); 
            !!!HERE IS THE ERROR!!!    SharedPreferences prefs = getSharedPreferences(getResources().getString(R.string.preferences), MODE_PRIVATE);
            Editor editor = prefs.edit();

            //SOME CODE

            //RETRUNS ARRAY
            String ar[] = new String[2];
            ar[0]= button1text;
            ar[1]= button2text;
            return ar;

        }

    }

我做错了什么？我已经在清单文件中声明了它（我没有，但它仍然崩溃了）。在正常活动上，获取共享首选项代码有效。

这是我第一次尝试在android中使用方法类，所以我很确定我搞砸了。

旁注：有没有关于此的好教程？

感谢您的帮助！

编辑（第23行是我说崩溃的地方，159是对方法的调用，143是对活动的oncreate方法中的defineqacall方法的调用）：

09-03 01:36:01.742: E/AndroidRuntime(14001): FATAL EXCEPTION: main
09-03 01:36:01.742: E/AndroidRuntime(14001): Process: eu.jbr.quizexo, PID: 14001
09-03 01:36:01.742: E/AndroidRuntime(14001): java.lang.RuntimeException: Unable to start activity ComponentInfo{eu.jbr.quizexo/eu.jbr.quizexo.Career_Play}: java.lang.NullPointerException
09-03 01:36:01.742: E/AndroidRuntime(14001):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2212)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2271)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at android.app.ActivityThread.access$800(ActivityThread.java:144)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at android.os.Handler.dispatchMessage(Handler.java:102)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at android.os.Looper.loop(Looper.java:136)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at android.app.ActivityThread.main(ActivityThread.java:5146)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at java.lang.reflect.Method.invokeNative(Native Method)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at java.lang.reflect.Method.invoke(Method.java:515)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:796)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:612)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at dalvik.system.NativeStart.main(Native Method)
09-03 01:36:01.742: E/AndroidRuntime(14001): Caused by: java.lang.NullPointerException
09-03 01:36:01.742: E/AndroidRuntime(14001):    at android.content.ContextWrapper.getSharedPreferences(ContextWrapper.java:173)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at eu.jbr.quizexo.Methods_play.defineqa(Methods_play.java:23)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at eu.jbr.quizexo.Career_Play.defineqacall(Career_Play.java:159)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at eu.jbr.quizexo.Career_Play.onCreate(Career_Play.java:143)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at android.app.Activity.performCreate(Activity.java:5231)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
09-03 01:36:01.742: E/AndroidRuntime(14001):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2169)
09-03 01:36:01.742: E/AndroidRuntime(14001):    ... 11 more

Answer 1

由于Methods_play extends Activity您必须实施某些方法，例如onCreate(Bundle myBundle)。此外，SharedPreferences需要Context，因此您无法在 onCreate()之前将其初始化，因为没有Context可用。尝试像

这样的东西
// declare it SharedPreferences prefs; public class Methods_play extends Activity { public void onCreate(Bundle someBundle) { super.onCreate(someBundle); //initialize it prefs = getSharedPreferences(getResources().getString(R.string.preferences), MODE_PRIVATE);

正如MikeM在评论中指出的那样，您似乎不需要扩展Activity。不要扩展任何内容，创建构造函数，将其传递给Activity Context，然后使用它来访问SharedPreferences。

public class Methods_play { // create a member variable for your context Context mContext; //Create the constructor which takes a context public void Methods_play(Context c) { mContext = c; } public String[] pewpew(int level) { //GETS STUFF Random rn = new Random(); // Use your context below SharedPreferences prefs = mContext.getSharedPreferences(getResources() .getString(R.string.preferences), MODE_PRIVATE); Editor editor = prefs.edit();

方法类在共享偏好上崩溃

1 个答案: