NullPointerException异常复选框共享preferences [英] NullPointerException checkbox sharedpreferences
问题描述
我试图挽救从位于layout.xml文件不同的复选框中的值,使用共享preferences。
I am trying to save the values from different checkboxes located in a layout.xml file, using sharedpreferences.
但是,当我编译程序我得到一个NullPointerException异常,根据logcat的原因是行463,标志着我的code。
But when i compile the program i get a NullPointerException, according Logcat the cause is in line 463, marked in my code.
我试过sevaral东西,但我不能老是摆脱例外。
I tried sevaral things, but i can`t get rid of the exception.
有人能帮帮我吗?
从logcat中的异常:
The Exception from Logcat:
10-29 23:35:31.556: E/AndroidRuntime(3292): FATAL EXCEPTION: main
10-29 23:35:31.556: E/AndroidRuntime(3292): java.lang.RuntimeException: Unable to resume activity {com.sencide/com.sencide.AndroidLogin}: java.lang.NullPointerException
10-29 23:35:31.556: E/AndroidRuntime(3292): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2241)
10-29 23:35:31.556: E/AndroidRuntime(3292): at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2256)
10-29 23:35:31.556: E/AndroidRuntime(3292): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1789)
10-29 23:35:31.556: E/AndroidRuntime(3292): at android.app.ActivityThread.access$1500(ActivityThread.java:123)
10-29 23:35:31.556: E/AndroidRuntime(3292): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:939)
10-29 23:35:31.556: E/AndroidRuntime(3292): at android.os.Handler.dispatchMessage(Handler.java:99)
10-29 23:35:31.556: E/AndroidRuntime(3292): at android.os.Looper.loop(Looper.java:130)
10-29 23:35:31.556: E/AndroidRuntime(3292): at android.app.ActivityThread.main(ActivityThread.java:3835)
10-29 23:35:31.556: E/AndroidRuntime(3292): at java.lang.reflect.Method.invokeNative(Native Method)
10-29 23:35:31.556: E/AndroidRuntime(3292): at java.lang.reflect.Method.invoke(Method.java:507)
10-29 23:35:31.556: E/AndroidRuntime(3292): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:847)
10-29 23:35:31.556: E/AndroidRuntime(3292): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605)
10-29 23:35:31.556: E/AndroidRuntime(3292): at dalvik.system.NativeStart.main(Native Method)
10-29 23:35:31.556: E/AndroidRuntime(3292): Caused by: java.lang.NullPointerException
10-29 23:35:31.556: E/AndroidRuntime(3292): at com.sencide.AndroidLogin.onResume(AndroidLogin.java:463)
10-29 23:35:31.556: E/AndroidRuntime(3292): at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1150)
10-29 23:35:31.556: E/AndroidRuntime(3292): at android.app.Activity.performResume(Activity.java:3832)
10-29 23:35:31.556: E/AndroidRuntime(3292): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2231)
10-29 23:35:31.556: E/AndroidRuntime(3292): ... 12 more
的code在我的主程序XML部分:
Part of the code in my Main program xml:
在创建和设置值:
public static final String PREFS_NAME = "SharedPrefsDemoPreferences";
public static final String PREF_BOOL = "PrefBool";
private SharedPreferences mPrefs;
private CheckBox mCheckBox;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mPrefs = getSharedPreferences(PREFS_NAME, 0);
mCheckBox = (CheckBox)findViewById(R.id.nieuwbel);// in layout.xml
在将OnPause和OnResume:
The OnPause and OnResume:
@Override
protected void onResume() {
mCheckBox.setChecked(mPrefs.getBoolean(PREF_BOOL, false)); <-- Line 463
super.onResume();}
@Override
protected void onPause() {
Editor e = mPrefs.edit();
e.putBoolean(PREF_BOOL, mCheckBox.isChecked());
e.commit();
Toast.makeText(this, "Settings Saved.", Toast.LENGTH_SHORT).show();
super.onPause(); }
与复选框的布局文件:
The layout file with the checkbox:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<CheckBox
android:id="@+id/nieuwbel"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:checked="true"
android:text="Nieuw beltegoed" />
<CheckBox
android:id="@+id/vorige"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:checked="true"
android:text="Tegoed vorige periode" />
等等...
and so on...
推荐答案
您需要再次获得共享preferences。在这一点上
米preFS
可也空对象。也可以尝试reinstatiating的 mCheckBox
。出现这种情况,如果该活动从的onPause()
到 onResume()
不叫的onCreate去( )
再次,你有两个instatiation对象正常。
You need to get SharedPreferences
again. At that point mPrefs
can be also null object. Also try reinstatiating the mCheckBox
. This happens if the activity went from onPause()
to onResume()
not calling onCreate()
again where you have instatiation of both object properly.
编辑:
@Override
protected void onResume() {
mPrefs = getSharedPreferences(PREFS_NAME, 0);
mCheckBox = (CheckBox)findViewById(R.id.nieuwbel);
if(mPrefs!=null) //check in case there are no prefs saved, due some reason
mCheckBox.setChecked(mPrefs.getBoolean(PREF_BOOL, false));
else
mCheckBox.setChecked(true); //here put default value if there are no preferences saved
super.onResume();
}
编辑2:充气的其他XML
Edit 2: Inflating the other xml.
您把这个里面onResume()
You put this inside onResume()
LayoutInflater inflater = (LayoutInflater)getSystemService
(Context.LAYOUT_INFLATER_SERVICE);
View v = inflater.inflate(R.layout.layout, null); // you have the xml as a view from which you can extract the checkbox
mCheckBox = (CheckBox)v.findViewById(R.id.nieuwbel);
.... do the rest of the coding in the first edit :)
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