能不能使用sharedpreference

-1

過程中添加最喜愛的清單：com.example.sonu.travelfreak，PID：在com.example.sonu 15374 顯示java.lang.NullPointerException 。在android.view.android.widget.CompoundButton.performClick（CompoundButton.java:100） android.view.View.performClick（View.java:4438）。查看$ PerformClick.run（View.java:18422） at android.os.Handler .handleCallback（Handler.java:733） at android.os.Handler.dispatchMessage（Handler.java:95） at android.os.Looper.loop（Looper.java:136） at android.app.ActivityThread.main （ActivityThread.java:5001） at java.lang.reflect.Method.invokeNative（Native Method） at java.lang.reflect.Method.invoke（Method.java:515） at com.android.internal.os。 ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:785）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:601）在dalvik.system.NativeStart.main（本機方法）

類，添加自己喜歡的

public class PlaceView extends AppCompatActivity{ 
TextView textView1; 
TextView textView2; 
ToggleButton toggleButton; 
SharedPreference sharedPreference; 
@Override 
protected void onCreate(final Bundle savedInstanceState) { 

    super.onCreate(savedInstanceState); 
    setContentView(R.layout.place_view); 

    textView1= (TextView) findViewById(R.id.textViewActivity); 
    textView2= (TextView) findViewById(R.id.detail); 
    Intent intent=getIntent(); 
    final Bundle bundle=intent.getExtras(); 
    textView1.setText(bundle.getString("Activity")); 
    textView2.setText(bundle.getString("Detail")); 
    toggleButton= (ToggleButton) findViewById(R.id.toggleButton1); 

    toggleButton.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      if(toggleButton.isChecked()){ 
       Log.d("check",bundle.getString("position name")); 
       Toast.makeText(getApplicationContext(), 
         "Added as favorites", 
         Toast.LENGTH_SHORT).show(); 
       sharedPreference.addFavorite(getApplicationContext(),bundle.getString("position name")); 

     } 
      else{ 

       } 

      } 


    }); 

}

}

類的recyclerview的每一行設定值

public class fav_info { 
String string; 
public String getname(){ 
    return string; 
} 
public void setname(String name){ 
    this.string=name; 
}}

sharedpreference類處理添加，刪除，保存收藏

import android.content.Context; 
import android.content.SharedPreferences; 
import android.content.SharedPreferences.Editor; 
import com.google.gson.Gson; 
import java.util.ArrayList; 
import java.util.Arrays; 
import java.util.List; 
public class SharedPreference { 
public static final String PREFS_NAME = "PRODUCT_APP"; 
public static final String FAVORITES = "Product_Favorite"; 

public SharedPreference() { 
    super(); 
} 


public void saveFavorites(Context context, List<fav_info> favorites) { 
    SharedPreferences settings; 
    Editor editor; 

    settings = context.getSharedPreferences(PREFS_NAME, 
      Context.MODE_PRIVATE); 
    editor = settings.edit(); 

    Gson gson = new Gson(); 
    String jsonFavorites = gson.toJson(favorites); 

    editor.putString(FAVORITES, jsonFavorites); 

    editor.commit(); 
} 

public void addFavorite(Context context, String string) { 
    fav_info fi=new fav_info(); 
    fi.setname(string); 
    List<fav_info> favorites = getFavorites(context); 
    if (favorites == null) 
     favorites = new ArrayList<fav_info>(); 
    favorites.add(fi); 
    saveFavorites(context, favorites); 
} 

public void removeFavorite(Context context, fav_info fav_info) { 
    ArrayList<fav_info> favorites = getFavorites(context); 
    if (favorites != null) { 
     favorites.remove(fav_info); 
     saveFavorites(context, favorites); 
    } 
} 

public ArrayList<fav_info> getFavorites(Context context) { 
    SharedPreferences settings; 
    List<fav_info> favorites; 

    settings = context.getSharedPreferences(PREFS_NAME, 
      Context.MODE_PRIVATE); 

    if (settings.contains(FAVORITES)) { 
     String jsonFavorites = settings.getString(FAVORITES, null); 
     Gson gson = new Gson(); 
     fav_info[] favoriteItems = gson.fromJson(jsonFavorites, 
       fav_info[].class); 

     favorites = Arrays.asList(favoriteItems); 
     favorites = new ArrayList<fav_info>(favorites); 
    } else 
     return null; 

    return (ArrayList<fav_info>) favorites; 
}}

來源

2016-07-01 sonu kumar prashant

你我已經錯過了nyway thnx –

您可以選擇使用它的對象

訪問sharedPreference對象之前，所以加這行之前，實例化SharedPreference類，

SharedPreference sharedPreference = new SharedPreference();

我想你忘了添加此行..

注意：您代碼已宣佈SharedPreference作爲一個類的屬性，所以下面的線就可以了，

sharedPreference = new SharedPreference();

感謝

來源

2016-07-01 16:02:50 sam

能不能使用sharedpreference

回答

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