获取savedInstanceState值，NullPointerException异常 [英] fetching savedInstanceState values, nullpointerexception

问题描述

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main2);
    savedInstanceState.putString("foo", "bar");
}

@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
  super.onRestoreInstanceState(savedInstanceState);

  String myString = savedInstanceState.getString("foo");

  Log.i("debug", "saved data: " + myString);
}

我试着去preserve一些值一个活动，但我收到以下错误： 23 06-23：09：44.038：E / AndroidRuntime（17584）：了java.lang.RuntimeException ：无法启动活动ComponentInfo {se.johanberntsson.activitytest / se.johanberntsson.activitytest.TestActivity}：显示java.lang.NullPointerException

我错过了什么吗？谢谢

推荐答案

覆盖的onSaveInstanceState 在savedInstanceState捆绑储蓄值：

Override onSaveInstanceState for saving values in savedInstanceState Bundle as:

public String strfoo="";
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main2);
            //comment this line you only fatch values from savedInstanceState
            String myString = savedInstanceState.getString("foo");
            Log.i("debug", "saved data: " + myString);
            // savedInstanceState.putString("foo", "bar");
            strfoo="bar"; set value here
        }

        @Override
        public void onRestoreInstanceState(Bundle savedInstanceState) {
          super.onRestoreInstanceState(savedInstanceState);
          String myString = savedInstanceState.getString("foo");
          Log.i("debug", "saved data: " + myString);
        }

      @Override

      public void onSaveInstanceState(Bundle savedInstanceState) {
         savedInstanceState.putString("foo", strfoo);
         super.onSaveInstanceState(savedInstanceState);

       } 

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