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对不起，这是我第一次在这个网站上提问

我的功能：我设置了两个Button，使用Sharedpreferences功能恢复并保存Spinner和EditText中的信息。

我第一次执行程序。程序会出现错误状态，如果我点击“restore”按钮来恢复Spinner中的信息。但是我在EditText中恢复信息的时候没有遇到这个问题。

这是 Spinner 中的代码

private Spinner.OnItemSelectedListener getfeet = new OnItemSelectedListener() {
    @Override
    public void onItemSelected(AdapterView<?> parent, View v, int position,
            long id) {
        // TODO Auto-generated method stub
        feet_out = parent.getSelectedItemPosition() + 2;
        select_f = feet.getSelectedItemPosition(); //save the position you choose
        Toast.makeText(MainActivity.this,
                "you chose " + parent.getSelectedItem().toString(),
                Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {
        // TODO Auto-generated method stub
    }
};
private Spinner.OnItemSelectedListener getinch = new OnItemSelectedListener() {

    @Override
    public void onItemSelected(AdapterView<?> parent, View v, int position,
            long id) {
        // TODO Auto-generated method stub
        inch_out = parent.getSelectedItemPosition();
        select_i = inch.getSelectedItemPosition(); //save the position you choose
        Toast.makeText(MainActivity.this,
                "you chose " + parent.getSelectedItem().toString(),
                Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {
        // TODO Auto-generated method stub

    }

};

这是在 Sharedpreferences 中执行保存功能的代码

private void save_() {
    settings = getSharedPreferences("DATA", 0);
    settings.edit().putInt("DATA_FEET", select_f) //store the position in DATA_FEET and DATA_INCH
            .putInt("DATA_INCH", select_i)
            .putString("DATA_WEIGHT", weight.getText().toString()).commit();
    Toast.makeText(MainActivity.this, R.string.done, Toast.LENGTH_SHORT) //save done
            .show();
}

这是在 Sharedpreferences 中执行恢复功能的代码

private void restore_() {
    feet.setSelection(settings.getInt("DATA_FEET", select_f)); //restore the position
    inch.setSelection(settings.getInt("DATA_INCH", select_i));
    weight.setText(settings.getString("DATA_WEIGHT", "EMPTY"));

}

我的问题是第一次执行的程序无法使用restore功能。有什么办法可以解决问题吗？？因为在EditText中是正常的，而在Spinner中是异常的。谢谢 ：））

这就是状态。:))

    10-23 23:14:11.677: D/TextLayoutCache(26370): Using debug level: 0 - Debug Enabled: 0
    10-23 23:14:11.747: D/libEGL(26370): loaded /system/lib/egl/libGLES_android.so
    10-23 23:14:11.797: D/libEGL(26370): loaded /system/lib/egl/libEGL_mali.so
    10-23 23:14:11.827: D/libEGL(26370): loaded /system/lib/egl/libGLESv1_CM_mali.so
    10-23 23:14:11.827: D/libEGL(26370): loaded /system/lib/egl/libGLESv2_mali.so
    10-23 23:14:11.887: D/OpenGLRenderer(26370): Enabling debug mode 0
    10-23 23:14:16.762: D/AndroidRuntime(26370): Shutting down VM
    10-23 23:14:16.762: W/dalvikvm(26370): threadid=1: thread exiting with uncaught exception (group=0x40aaa210)
    10-23 23:14:16.802: E/AndroidRuntime(26370): FATAL EXCEPTION: main
    10-23 23:14:16.802: E/AndroidRuntime(26370): java.lang.NullPointerException
    10-23 23:14:16.802: E/AndroidRuntime(26370):    at com.example.bmi.MainActivity.restore_(MainActivity.java:44)
    10-23 23:14:16.802: E/AndroidRuntime(26370):    at com.example.bmi.MainActivity.access$1(MainActivity.java:43)
    10-23 23:14:16.802: E/AndroidRuntime(26370):    at com.example.bmi.MainActivity$2.onClick(MainActivity.java:99)
    10-23 23:14:16.802: E/AndroidRuntime(26370):    at android.view.View.performClick(View.java:3574)
    10-23 23:14:16.802: E/AndroidRuntime(26370):    at android.view.View$PerformClick.run(View.java:14293)
    10-23 23:14:16.802: E/AndroidRuntime(26370):    at android.os.Handler.handleCallback(Handler.java:605)
    10-23 23:14:16.802: E/AndroidRuntime(26370):    at android.os.Handler.dispatchMessage(Handler.java:92)
    10-23 23:14:16.802: E/AndroidRuntime(26370):    at android.os.Looper.loop(Looper.java:137)
    10-23 23:14:16.802: E/AndroidRuntime(26370):    at android.app.ActivityThread.main(ActivityThread.java:4448)
    10-23 23:14:16.802: E/AndroidRuntime(26370):    at java.lang.reflect.Method.invokeNative(Native Method)
    10-23 23:14:16.802: E/AndroidRuntime(26370):    at java.lang.reflect.Method.invoke(Method.java:511)
    10-23 23:14:16.802: E/AndroidRuntime(26370):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:823)
    10-23 23:14:16.802: E/AndroidRuntime(26370):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:590)
    10-23 23:14:16.802: E/AndroidRuntime(26370):    at dalvik.system.NativeStart.main(Native Method)

这是调用 restore_() 的方法

private OnClickListener reback_1 = new OnClickListener() {
    public void onClick(View v) {
        restore_();
    }
};

在我替换select_fand select_iinto之后0，它出现了问题

10-24 00:01:30.957: D/TextLayoutCache(28836): Using debug level: 0 - Debug Enabled: 0
10-24 00:01:31.017: D/libEGL(28836): loaded /system/lib/egl/libGLES_android.so
10-24 00:01:31.037: D/libEGL(28836): loaded /system/lib/egl/libEGL_mali.so
10-24 00:01:31.057: D/libEGL(28836): loaded /system/lib/egl/libGLESv1_CM_mali.so
10-24 00:01:31.057: D/libEGL(28836): loaded /system/lib/egl/libGLESv2_mali.so
10-24 00:01:31.087: D/OpenGLRenderer(28836): Enabling debug mode 0
10-24 00:01:36.262: D/AndroidRuntime(28836): Shutting down VM
10-24 00:01:36.262: W/dalvikvm(28836): threadid=1: thread exiting with uncaught exception (group=0x40aaa210)
10-24 00:01:36.282: E/AndroidRuntime(28836): FATAL EXCEPTION: main
10-24 00:01:36.282: E/AndroidRuntime(28836): java.lang.NullPointerException
10-24 00:01:36.282: E/AndroidRuntime(28836):    at com.example.bmi.MainActivity.restore_(MainActivity.java:44)
10-24 00:01:36.282: E/AndroidRuntime(28836):    at com.example.bmi.MainActivity.access$1(MainActivity.java:43)
10-24 00:01:36.282: E/AndroidRuntime(28836):    at com.example.bmi.MainActivity$2.onClick(MainActivity.java:99)
10-24 00:01:36.282: E/AndroidRuntime(28836):    at android.view.View.performClick(View.java:3574)
10-24 00:01:36.282: E/AndroidRuntime(28836):    at android.view.View$PerformClick.run(View.java:14293)
10-24 00:01:36.282: E/AndroidRuntime(28836):    at android.os.Handler.handleCallback(Handler.java:605)
10-24 00:01:36.282: E/AndroidRuntime(28836):    at android.os.Handler.dispatchMessage(Handler.java:92)
10-24 00:01:36.282: E/AndroidRuntime(28836):    at android.os.Looper.loop(Looper.java:137)
10-24 00:01:36.282: E/AndroidRuntime(28836):    at android.app.ActivityThread.main(ActivityThread.java:4448)
10-24 00:01:36.282: E/AndroidRuntime(28836):    at java.lang.reflect.Method.invokeNative(Native Method)
10-24 00:01:36.282: E/AndroidRuntime(28836):    at java.lang.reflect.Method.invoke(Method.java:511)
10-24 00:01:36.282: E/AndroidRuntime(28836):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:823)
10-24 00:01:36.282: E/AndroidRuntime(28836):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:590)
10-24 00:01:36.282: E/AndroidRuntime(28836):    at dalvik.system.NativeStart.main(Native Method)
10-24 00:01:37.803: I/Process(28836): Sending signal. PID: 28836 SIG: 9
4

1 回答 1

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您使用 SharedPrefs 错误。

feet.setSelection(settings.getInt("DATA_FEET", select_f));

当您尝试从 sharedPref 获取整数值时，您将返回 null！因为我认为您误解了它是如何完成的：

settings.getInt("myKey", defaultValue);

返回键“myKey”的值。如果“myKey”没有设置值，那么它会返回“defaultValue”。在您的情况下，它返回“select_f”的当前值。看起来，当您第一次运行应用程序时，select_f 的值为 null。

因此，您必须决定是在检索 sharedPrefs 之前初始化“select_f”还是在此处输入另一个 defaultValue。

于 2013-10-23T15:36:21.923 回答