我有三个活动A, B和C,其中A和B是表单,并在数据库(SQLite)中填充和保存表单数据后。我使用意图从A到B,然后从B到C,我想要的是,每次我打开我的应用程序时,我想要C作为我的主屏幕,而不再是A和B。

我想共享偏好可以解决这个问题,但我找不到一个好的例子来给我一个起点。


当前回答

创建SharedPreference和全局使用的最佳方法,你需要创建一个类,如下所示:

public class PreferenceHelperDemo {
    private final SharedPreferences mPrefs;

    public PreferenceHelperDemo(Context context) {
        mPrefs = PreferenceManager.getDefaultSharedPreferences(context);
    }

    private String PREF_Key= "Key";

    public String getKey() {
        String str = mPrefs.getString(PREF_Key, "");
        return str;
    }

    public void setKey(String pREF_Key) {
        Editor mEditor = mPrefs.edit();
        mEditor.putString(PREF_Key, pREF_Key);
        mEditor.apply();
    }

}

其他回答

SharedPreferences sharedPref = getActivity().getPreferences(Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putInt(getString(R.string.saved_high_score), newHighScore);
editor.commit();

我只是发现上面所有的例子都太混乱了,所以我自己写了一个。如果您知道自己在做什么,那么代码片段是很好的,但是像我这样不知道的人呢?

想要一个剪切-粘贴的解决方案?好了,就是这里!

创建一个新的java文件并将其称为Keystore。然后粘贴以下代码:

import android.content.Context;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.util.Log;

public class Keystore { //Did you remember to vote up my example?
    private static Keystore store;
    private SharedPreferences SP;
    private static String filename="Keys";

private Keystore(Context context) {
    SP = context.getApplicationContext().getSharedPreferences(filename,0);
}

public static Keystore getInstance(Context context) {
    if (store == null) {
        Log.v("Keystore","NEW STORE");
        store = new Keystore(context);
    }
    return store;
}

public void put(String key, String value) {//Log.v("Keystore","PUT "+key+" "+value);
    Editor editor = SP.edit();
    editor.putString(key, value);
    editor.commit(); // Stop everything and do an immediate save!
    // editor.apply();//Keep going and save when you are not busy - Available only in APIs 9 and above.  This is the preferred way of saving.
}

public String get(String key) {//Log.v("Keystore","GET from "+key);
    return SP.getString(key, null);

}

public int getInt(String key) {//Log.v("Keystore","GET INT from "+key);
    return SP.getInt(key, 0);
}

public void putInt(String key, int num) {//Log.v("Keystore","PUT INT "+key+" "+String.valueOf(num));
    Editor editor = SP.edit();

    editor.putInt(key, num);
    editor.commit();
}


public void clear(){ // Delete all shared preferences
    Editor editor = SP.edit();

    editor.clear();
    editor.commit();
}

public void remove(){ // Delete only the shared preference that you want
    Editor editor = SP.edit();

    editor.remove(filename);
    editor.commit();
}
}

现在保存那个文件,忘了它吧。你受够了。现在回到你的活动,像这样使用它:

public class YourClass extends Activity{

private Keystore store;//Holds our key pairs

public YourSub(Context context){
    store = Keystore.getInstance(context);//Creates or Gets our key pairs.  You MUST have access to current context!

    int= store.getInt("key name to get int value");
    string = store.get("key name to get string value");

    store.putInt("key name to store int value",int_var);
    store.put("key name to store string value",string_var);
    }
}
SharedPreferences mPref;
SharedPreferences.Editor editor;

public SharedPrefrences(Context mContext) {
    mPref = mContext.getSharedPreferences(Constant.SharedPreferences, Context.MODE_PRIVATE);
    editor=mPref.edit();
}

public void setLocation(String latitude, String longitude) {
    SharedPreferences.Editor editor = mPref.edit();
    editor.putString("latitude", latitude);
    editor.putString("longitude", longitude);
    editor.apply();
}

public String getLatitude() {
    return mPref.getString("latitude", "");
}

public String getLongitude() {
    return mPref.getString("longitude", "");
}

public void setGCM(String gcm_id, String device_id) {
     editor.putString("gcm_id", gcm_id);
    editor.putString("device_id", device_id);
    editor.apply();
}

public String getGCMId() {
    return mPref.getString("gcm_id", "");
}

public String getDeviceId() {
    return mPref.getString("device_id", "");
}


public void setUserData(User user){

    Gson gson = new Gson();
    String json = gson.toJson(user);
    editor.putString("user", json);
    editor.apply();
}
public User getUserData(){
    Gson gson = new Gson();
    String json = mPref.getString("user", "");
    User user = gson.fromJson(json, User.class);
    return user;
}

public void setSocialMediaStatus(SocialMedialStatus status){

    Gson gson = new Gson();
    String json = gson.toJson(status);
    editor.putString("status", json);
    editor.apply();
}
public SocialMedialStatus getSocialMediaStatus(){
    Gson gson = new Gson();
    String json = mPref.getString("status", "");
    SocialMedialStatus status = gson.fromJson(json, SocialMedialStatus.class);
    return status;
}

您可以创建自定义的SharedPreference类

public class YourPreference {   
    private static YourPreference yourPreference;
    private SharedPreferences sharedPreferences;

    public static YourPreference getInstance(Context context) {
        if (yourPreference == null) {
            yourPreference = new YourPreference(context);
        }
        return yourPreference;
    }

    private YourPreference(Context context) {
        sharedPreferences = context.getSharedPreferences("YourCustomNamedPreference",Context.MODE_PRIVATE);
    }

    public void saveData(String key,String value) {
        SharedPreferences.Editor prefsEditor = sharedPreferences.edit();
        prefsEditor .putString(key, value);
        prefsEditor.commit();           
    }

    public String getData(String key) {
        if (sharedPreferences!= null) {
           return sharedPreferences.getString(key, "");
        }
        return "";         
    }
}

你可以像这样获得你的偏好实例:

YourPreference yourPrefrence = YourPreference.getInstance(context);
yourPreference.saveData(YOUR_KEY,YOUR_VALUE);

String value = yourPreference.getData(YOUR_KEY);

您还可以看看我过去为这个目的编写的示例项目。我在本地保存一个名称,并在用户请求或应用程序启动时检索它。

但是,此时最好使用commit(而不是apply)来持久化数据。更多信息请点击这里。