如何在片段内的SharedPreferences中获取pref_name的值？
如何在片段内的SharedPreferences中获取pref_name的值？
提问于 2018-07-29 00:13:26
我一直在尝试从SharedPreferences中获取一个字符串形式的键的值，这样我就可以修改连接到片段的布局中的数据。
下面是我的OneFragment.java代码
public class OneFragment extends Fragment{
private TextView mText;
public OneFragment() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_one, container, false);
SharedPreferences prefs = getActivity().getSharedPreferences("EID", Context.MODE_PRIVATE);
String value = prefs.getString("EID", "0");
mText = (TextView) view.findViewById(R.id.textView2);
mText.setText(value);
return view;
}
}该应用程序表示，它在打开时已停止。我从Main activity中调用片段。
制片厂说：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.dell.tab2, PID: 3857
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.dell.tab2/com.example.dell.tab2.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content.Context.getSharedPreferences(java.lang.String, int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2548)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content.Context.getSharedPreferences(java.lang.String, int)' on a null object reference
at android.content.ContextWrapper.getSharedPreferences(ContextWrapper.java:164)
at com.example.dell.tab2.MainActivity.<init>(MainActivity.java:31)
at java.lang.Class.newInstance(Native Method)
at android.app.Instrumentation.newActivity(Instrumentation.java:1078)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2538)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755) 回答 2
Stack Overflow用户
回答已采纳
发布于 2018-07-29 00:44:34
如果您不能以片段形式获取此值，则可以从您的活动中获取此值。在片段中调用：
String value = ((YourActivityName)getActivity()).getValuePreference();并在您的活动中添加方法：
public String getValuePreference(){
SharedPreferences preferences = getSharedPreferences("SharedPreferences", Context.MODE_PRIVATE);
return preferences.getString("EID", "0");
}Stack Overflow用户
发布于 2018-07-29 00:23:45
试试这个：
在片段中添加以下代码
Context context;
@Override
public void onAttach(Context context) {
super.onAttach(context);
this.context = context;
}在onCreateView中，用context替换getActivity()
SharedPreferences prefs = context.getSharedPreferences("EID", Context.MODE_PRIVATE);
String value = prefs.getString("EID", "0");页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/51573103
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