具有共享首选项的 LiveData [英] LiveData with shared preferences

问题描述

我有一个设置屏幕，用于设置一些值.当我设置这些值时，它会保存在共享首选项中，并且这些值在我的请求网络api调用作为参数.

I have a settings screen where I am setting some values. When I set those values it gets saved in shared preferences and these values are needed in my request to the network api call as parameters.

现在我可以在我的活动中使用共享首选项的侦听器，然后进行 api 调用并获取新数据，但我想将它与 LiveData 一起使用.

Now I can use a listener for shared preferences in my activity then make an api call and get fresh data, but I want to use this with LiveData.

如何使用 LiveData 侦听共享首选项的更改，然后使用新参数进行网络调用.

How can I listen for changes in the shared preferences using LiveData and then make the network call using the new parameters.

推荐答案

Java 代码 by <一个 href="https://stackoverflow.com/users/1203043/idish">Idish，虽然他在这里评论，但不确定，为什么他没有将其添加为答案.

Java Code by Idish, though he commented here, but not sure, why he didn't add it as answer.

在下面粘贴相同的代码:

Pasting the same code below:

public abstract class SharedPreferenceLiveData<T> extends LiveData<T> {

SharedPreferences sharedPrefs;
String key;
public T defValue;

public SharedPreferenceLiveData(SharedPreferences prefs, String key, T defValue) {
    this.sharedPrefs = prefs;
    this.key = key;
    this.defValue = defValue;
}

private SharedPreferences.OnSharedPreferenceChangeListener preferenceChangeListener = new SharedPreferences.OnSharedPreferenceChangeListener() {
    @Override
    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
        if (SharedPreferenceLiveData.this.key.equals(key)) {
            setValue(getValueFromPreferences(key, defValue));
        }
    }
};
abstract T getValueFromPreferences(String key, T defValue);

@Override
protected void onActive() {
    super.onActive();
    setValue(getValueFromPreferences(key, defValue));
    sharedPrefs.registerOnSharedPreferenceChangeListener(preferenceChangeListener);
}

@Override
protected void onInactive() {
    sharedPrefs.unregisterOnSharedPreferenceChangeListener(preferenceChangeListener);
    super.onInactive();
}
public SharedPreferenceLiveData<Boolean> getBooleanLiveData(String key, Boolean defaultValue) {
    return new SharedPreferenceBooleanLiveData(sharedPrefs,key, defaultValue);
}
}

SharedPreferenceBooleanLiveData 类

SharedPreferenceBooleanLiveData class

public class SharedPreferenceBooleanLiveData extends SharedPreferenceLiveData<Boolean>{

public SharedPreferenceBooleanLiveData(SharedPreferences prefs, String key, Boolean defValue) {
    super(prefs, key, defValue);
}

@Override
Boolean getValueFromPreferences(String key, Boolean defValue) {
    return sharedPrefs.getBoolean(key, defValue);
}

}

像下面这个链接中提到的代码一样调用它:

Calling this like the below code mentioned in this link:

 SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
 SharedPreferenceStringLiveData sharedPreferenceStringLiveData = new SharedPreferenceStringLiveData(preferences, "cid", "");
 sharedPreferenceStringLiveData.getStringLiveData("cid", "").observe(this, cid -> {
            Toast.makeText(this, "Change in CID "+cid, Toast.LENGTH_SHORT).show();
 });

同样，如果使用 Preference Helper 类，该类可以如下调用:只是一个示例:

Again if using a Preference Helper class, the class can be called as below: Just a sample:

public class PreferenceManager {
private SharedPreferenceBooleanLiveData sharedPreferenceLiveData;

public SharedPreferenceBooleanLiveData getSharedPrefs(){
        return sharedPreferenceLiveData;
    }

public void setSharedPreferences(String key, boolean value) {

        SharedPreferences userDetails = context.getSharedPreferences(APP_PREFERENCE,
            Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = userDetails.edit();
        editor.putBoolean(key, value);
        editor.apply();
        sharedPreferenceLiveData = new SharedPreferenceBooleanLiveData(userDetails,key,value);
    }
}

在活动类中调用如下:创建一个对象:

And in the activity class call it as below: Create an object:

SharedPreferenceBooleanLiveData sharedPreferenceLiveData;
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    sharedPreferenceLiveData = preferenceManager.getSharedPrefs();
}

并观察如下:

sharedPreferenceLiveData.getBooleanLiveData(PreferenceKey.KEY_LOCATION_PERMISSION,false).observe(this,check->{
        if(check){
            setPermissionGranted(check);
        }
    });

这篇关于具有共享首选项的 LiveData的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！