数据未保存在Commit上的共享首选项中

Question

我正在尝试将片段接收的数据保存到共享首选项中，以便在重新创建相同片段时可以重用存储在共享首选项中的数据。但不知何故，数据没有被保存，并且首选项的默认值被返回到我的片段。 下面是代码。 实施SharePreference的片段

import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;

public class StreamFragment extends Fragment {

    public String streamUrl=null;
    TextView textView;
    public static final String playerData="pData";
    SharedPreferences playerSettings;
    public StreamFragment(){};

   @Override
    public void onCreate(Bundle state) {
        super.onCreate(state);
        SharedPreferences playerSettings = getActivity().getSharedPreferences(playerData, Context.MODE_PRIVATE);
        streamUrl = playerSettings.getString(streamUrl,"No Link Found");
    }

    @Override
    public View onCreateView( LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
        View view =  inflater.inflate(R.layout.fragment_stream, container, false);
        playerSettings = getActivity().getSharedPreferences(playerData, Context.MODE_PRIVATE);
        streamUrl = playerSettings.getString("streamLink","No Link Found");
        //getData();
        Toast.makeText(getActivity(),"Stream Saved"+streamUrl,Toast.LENGTH_LONG).show();
        return view;
    }       

    public void getUrl(String data)
    {
        streamUrl=data;
        playerSettings = this.getActivity().getSharedPreferences(playerData, Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = playerSettings.edit();
        editor.putString("streamLink", streamUrl);
        editor.commit();
        Toast.makeText(getActivity(),"Stream Saved"+streamUrl,Toast.LENGTH_LONG).show();
    }
}

提前致谢！

Answer 1

而不是streamUrl = playerSettings.getString(streamUrl,"No Link Found");

你应该使用

streamUrl = playerSettings.getString("streamLink","No Link Found");

并且还使用apply而不是commit

Answer 2

我试着解释一下这一点：

参考此图片：

如您所见，onCreate在onCreateview之前被解雇。

让我们分析您的代码：

public class StreamFragment extends Fragment {

    public String streamUrl=null;
    TextView textView;
    public static final String playerData="pData";
    SharedPreferences playerSettings;
    public StreamFragment(){};

此处，您的streamUrl为null。

 @Override
    public void onCreate(Bundle state) {
        super.onCreate(state);
        /*SharedPreferences -- no needed*/playerSettings = getActivity().getSharedPreferences(playerData, Context.MODE_PRIVATE);
        streamUrl = playerSettings.getString(/*streamUrl -- replace with a key value*/,"No Link Found");
    }

这是第一种被解雇的方法。在这里，您尝试从String获取sharedPref，该null应命名为getString。这一点是错误的。 SharedPreferences上的第一个参数应该是一个键，并且对于相同的值，唯一应该是

。

另一件事是你正在使用相同的名称来表示另一个 @Override public View onCreateView( LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) { View view = inflater.inflate(R.layout.fragment_stream, container, false); //playerSettings = getActivity().getSharedPreferences(playerData, Context.MODE_PRIVATE); -- they are already istantiated streamUrl = playerSettings.getString(/*streamUrl -- replace with a key value*/,"No Link Found"); //getData(); Toast.makeText(getActivity(),"Stream Saved"+streamUrl,Toast.LENGTH_LONG).show(); return view; } 的距离，所以删除istantiation中的强制转换。

streamUrl

现在，您要将sharedPreferences's设置为使用相同变量streamUrl命名的streamUrl /*which is currently null*/ = playerSettings.getString(null, "No Link Found"); 值。这意味着：

key

您仍应将streamUrl从static unique field替换为public void getUrl(String data) { streamUrl=data; //playerSettings = this.getActivity().getSharedPreferences(playerData, Context.MODE_PRIVATE); -- already done above SharedPreferences.Editor editor = playerSettings.edit(); editor.putString("streamLink", streamUrl); //editor.commit(); --replace with apply Toast.makeText(getActivity(),"Stream Saved"+streamUrl,Toast.LENGTH_LONG).show(); } 。

"streamLink"

}

这应该是您保存值的点，因此import android.content.Context; import android.content.SharedPreferences; import android.os.Bundle; import android.support.v4.app.Fragment; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.TextView; import android.widget.Toast; public class StreamFragment extends Fragment { public String streamUrl=null; TextView textView; public static final String playerData="pData"; public static final String valueKey="streamLink"; SharedPreferences playerSettings; public StreamFragment(){}; @Override public void onCreate(Bundle state) { super.onCreate(state); playerSettings = getActivity().getSharedPreferences(playerData, Context.MODE_PRIVATE); streamUrl = playerSettings.getString(valueKey,"No Link Found"); } @Override public View onCreateView( LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) { View view = inflater.inflate(R.layout.fragment_stream, container, false); streamUrl = playerSettings.getString(valueKey,"No Link Found"); //getData(); Toast.makeText(getActivity(),"Stream Saved"+streamUrl,Toast.LENGTH_LONG).show(); return view; } public void getUrl(String data) { streamUrl=data; SharedPreferences.Editor editor = playerSettings.edit(); editor.putString(valueKey, streamUrl); editor.apply(); Toast.makeText(getActivity(),"Stream Saved"+streamUrl,Toast.LENGTH_LONG).show(); } } 应该是上面使用的密钥。

使用apply替换commit并删除istantiation，因为它已经完成

现在......说这应该是这样的：

echo 'system("ls *ZIP,*zip")' | ruby

希望这可以帮到你。

Answer 3

您的偏好值的键不正确。请注意以下行。

streamUrl = playerSettings.getString(streamUrl,"No Link Found");

使用一些常量值作为键。

private static final String STREAM_URL = "stream_url";

并使用常量作为密钥，如下所述。

streamUrl = playerSettings.getString(STREAM_URL,"No Link Found");

Answer 4

未调用getUrl(String)方法。因此，您的共享偏好值未存储，在playerSettings.getString(streamUrl,"No Link Found");之前调用它 您还要创建＆＃34; SharedPreferences＆＃34;的实例。两次，从onCreateView中移除。使用editor.apply()代替editor.commit()。

Answer 5

你正在使用两个SharedPreferences playerSettings;一个全局，一个在onCreate，你正在使用未初始化的上一个

   import android.content.Context;
    import android.content.SharedPreferences;
    import android.os.Bundle;
    import android.support.v4.app.Fragment;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.TextView;
    import android.widget.Toast;

    public class StreamFragment extends Fragment {

        public String streamUrl=null;
        TextView textView;
        public static final String playerData="pData";
        SharedPreferences playerSettings;
        public StreamFragment(){};

       @Override
        public void onCreate(Bundle state) {
            super.onCreate(state);
            playerSettings = getActivity().getSharedPreferences(playerData, Context.MODE_PRIVATE);
            streamUrl = playerSettings.getString("streamLink","No Link Found");
        }

        @Override
        public View onCreateView( LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
            View view =  inflater.inflate(R.layout.fragment_stream, container, false);
            playerSettings = getActivity().getSharedPreferences(playerData, Context.MODE_PRIVATE);
            streamUrl = playerSettings.getString("streamLink","No Link Found");
            //getData();
            Toast.makeText(getActivity(),"Stream Saved"+streamUrl,Toast.LENGTH_LONG).show();
            return view;
        }       

        public void getUrl(String data)
        {
            streamUrl=data;
            playerSettings = this.getActivity().getSharedPreferences(playerData, Context.MODE_PRIVATE);
            SharedPreferences.Editor editor = playerSettings.edit();
            editor.putString("streamLink", streamUrl);
            editor.commit();
            Toast.makeText(getActivity(),"Stream Saved"+streamUrl,Toast.LENGTH_LONG).show();
        }
    }