SharedPreferences save list ＜ bean ＞ to local and solve com google. gson. internal. Linkedtreemap cannot be cast to exception

I haven't blogged recently , Job hopping. , Turned a direction , It's the field I've always wanted to go to , I also prepared for a while , Find a job in this direction , Good luck. , Met a good boss , I have made plans for these days , Follow up plan for this year , from 2 Aspect departure , On the one hand, record daily problems , On the one hand, sort out the source code

Today's post says what I met , About the scene , We need to talk about one List <Bean > Save locally SP, I found many posts on the Internet , Originally, I wanted to find someone who didn't use GSON Of , But I really didn't find , It should be in SystemUI Layer modification , There's no way back , I am here android.bp It's added to the file

java_import {

    name: "core-settings",

    jars: ["libs/core.jar"],

    sdk_version: "current",

}

Continue to say , Methods found online

public class ListDataSave {
    private SharedPreferences preferences;
    private SharedPreferences.Editor editor;

    public ListDataSave(Context mContext) {
        preferences = mContext.getSharedPreferences("stock_info", Context.MODE_PRIVATE);
        editor = preferences.edit();
    }

    /**
     *  preservation List
     * @param tag
     * @param datalist
     */
   public <T> void setDataList(String tag, List<T> datalist) {
		if (null == datalist || datalist.size() <= 0)
			return;
 
		Gson gson = new Gson();
		// convert to json data , Save again 
		String strJson = gson.toJson(datalist);
		editor.clear();
		editor.putString(tag, strJson);
		editor.commit();
 
	}
 

    /**
     *  obtain List
     * @param tag
     * @return
     */
   public <T> List<T> getDataList(String tag) {
		List<T> datalist=new ArrayList<T>();
		String strJson = preferences.getString(tag, null);
		if (null == strJson) {
			return datalist;
		}
		Gson gson = new Gson();
		datalist = gson.fromJson(strJson, new TypeToken<List<T>>() {
		}.getType());
		return datalist;
 
	 

    }
}
 

The problem is ：

After running this code , I found something unusual ：

java.lang.ClassCastException: com.google.gson.internal.LinkedTreeMap cannot be cast to 

Then I read it and sent it , The reason why this exception is thrown is because it is used when fetching Gson analysis Json In the data process , Running charge throws such a problem exception , Simply put, it is to have Generic when ,gson Unable to recognize the generics, it turned into LinkenTreeMap The type of .

The solution is ： In the process of using generics , It must be specific to a certain class , Instead of using generics .

Let's go up there T Change it to what you want bean It can be solved