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Android 发布时间：2022-04-28 发布网站：大佬教程 code.js-code.com

大佬教程收集整理的这篇文章主要介绍了android – Room Invalidation tracker初始化两次，大佬教程大佬觉得挺不错的，现在分享给大家，也给大家做个参考。

我有一个水平回收站视图,其中包含自定义项目.每个项目都可以在Recycler视图中保存当前项目的位置.我想使用拖放移动项目时更新项目位置.但是当水平视图中有三个以上的项目时,数据会被删除.请帮帮我.
Source Code

这是我在Logcat中得到的：@H_@L_262_5@_4@

在onCreate中初始化数据库.@H_@L_262_5@_4@

db = Room.databaseBuilder(getApplicationContext(),ApPDAtabase.class,db_name)
                .fallBACkToDestructiveMigration()
                .allowMainThreadQueries()
                .build();

RecyclerView适配器代码.@H_@L_262_5@_4@

@Override
public Boolean onItemMove(int fromPosition,int toPosition) {
    String name = dataSet.get(fromPosition).getName();
    //this will make "Add item" do not move from its first position..
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODEs.KITKAT) {
        if (!(Objects.equals(name,"Add") || (toPosition == 0 && fromPosition == 1))) {
            Collections.swap(dataSet,fromPosition,toPosition);
            MoveItem(fromPosition,toPosition);
            notifyItemMoved(fromPosition,toPosition);
            return true;
        }
    }
    return false;
}

移动项目时更新数据的代码.@H_@L_262_5@_4@

public static void MoveItem(int fromPosition,int toPosition){
        String name = data.get(fromPosition).getName(); //This gets the current item name in the view 
        String nexName = data.get(toPosition).getName(); //This gets the next item name in the view 

        ContentValues fromContentValues = new ContentValues();
        fromContentValues.put("posItem",toPosition); //adding data to ContentValues
        ContentValues toContentValues = new ContentValues();
        toContentValues.put("posItem",fromPosition);
        Log.e("Item moved",name + "from" + fromPosition + "\n" + "next item:" + "to" + toPosition);

        db.begintransaction();
        try {
        db.getOpenHelper().getWritableDatabase().update(name,fromContentValues,"posItem =" + fromPosition,null);

        db.getOpenHelper().getWritableDatabase().update(nexName,toContentValues,"posItem =" + toPosition,null);
        db.settransactionsuccessful(); //setTing transaction successful
        } finally {
            db.endtransaction(); // commit or rollBACk
            db.close(); //closing database
        }
    }