java - Android Studio 删除 Reyclerview 和 Sqlitedb 中的所有行

Question

在 MarkerDisplayActivity 内部我试图确认用户想要 要从行和数据库中删除所有列出的项目，你该怎么做？我 尝试了clear()和其他类型，行被删除，但如果我返回 然后再次转到 RV，删除的行又回来了，因为它们仍然被保存 在数据库中。

这是我的代码:

package elevatesecurity.myapplication;

import android.app.Dialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;
import android.widget.Toolbar;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GoogleApiAvailability;

import java.util.ArrayList;
import java.util.List;

import elevatesecurity.myapplication.Adapters.MarkerAdapter;
import elevatesecurity.myapplication.Model.MarkerModel;
import elevatesecurity.myapplication.Utilities.MarkerDatabaseHelper;

public class MarkerDisplayActivity extends AppCompatActivity {

    RecyclerView recyclerView;
    MarkerAdapter markerAdapter;
    ArrayList<MarkerModel> modelArrayList;
//    private ArrayList<MarkerModel> marker_list = new ArrayList<>();
    MarkerDatabaseHelper markerDatabaseHelper;
    TextView textView;
    Toolbar toolBar;
    List<MarkerModel> markerList;

    private static final int ERROR_DIALOG_REQUEST = 9001;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_marker_display);
        textView = (TextView)findViewById(R.id.markerInfotxt);
        markerDatabaseHelper = new MarkerDatabaseHelper(this);
        recyclerView = (RecyclerView)findViewById(R.id.recyclerview);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        modelArrayList = markerDatabaseHelper.getAllMarkers();

        android.support.v7.widget.Toolbar toolBar = (android.support.v7.widget.Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolBar);
        if (isServicesOk()) {
        }



        if(modelArrayList.size()>0)
        {
            textView.setVisibility(View.GONE);

            markerAdapter = new MarkerAdapter(this,modelArrayList);
            recyclerView.setAdapter(markerAdapter);
            markerAdapter.notifyDataSetChanged();
        }



    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu_marker, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item)
    {
        switch (item.getItemId())
        {
            case R.id.action_removeAll:
                android.support.v7.app.AlertDialog.Builder builder;
                builder = new android.support.v7.app.AlertDialog.Builder(MarkerDisplayActivity.this);

                builder.setTitle("Confirm!")
                        .setMessage("Are You Sure You Want To Remove All Saved Locations?")
                        .setPositiveButton(android.R.string.yes, new DialogInterface.OnClickListener()
                        {
                            public void onClick(DialogInterface dialog, int which)
                            {


                                modelArrayList.clear();
                                markerAdapter.notifyDataSetChanged();

                            }
                        })
                        .setNegativeButton(android.R.string.no, new DialogInterface.OnClickListener()
                        {
                            public void onClick(DialogInterface dialog, int which)
                            {
                                return;
                            }
                        })
                        .setIcon(android.R.drawable.ic_dialog_alert)
                        .show();

                break;
        }

        return super.onOptionsItemSelected(item);
    }

    public boolean isServicesOk()
    {
        Log.d("", "ifServicesOk: checking google services version");

        int available = GoogleApiAvailability.getInstance()
                .isGooglePlayServicesAvailable(MarkerDisplayActivity.this);

        if (available == ConnectionResult.SUCCESS) {
            // Everything is fine and the user can make a map request
            Log.d("", "ifServicesOk: Google play services is working");
            return true;
        } else if (GoogleApiAvailability.getInstance().isUserResolvableError(available)) {
            // An error occurred but we can resolve it
            Log.d("", "ifServicesOk: An error occurred but we can fix it");
            Dialog dialog = GoogleApiAvailability.getInstance().getErrorDialog
                    (MarkerDisplayActivity.this, available, ERROR_DIALOG_REQUEST);
            dialog.show();
        } else {
            Toast.makeText(this, "You can't make a map request"
                    , Toast.LENGTH_SHORT).show();
        }
        return false;
    }

}

public class MarkerDatabaseHelper extends SQLiteOpenHelper
{

public static final String DB_NAME = "markers.db";
public static final int DB_VERSION = 1;
public static final String TABLE_NAME = "markertable";
public static final String COLUMN_ID  = "id";
public static final String COLUMN_LAT = "lat";
public static final String COLUMN_LNG = "lng";
public static final String COLUMN_TITLE = "title";



public MarkerDatabaseHelper(Context context) {
    super(context, TABLE_NAME, null, DB_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL("create table " + TABLE_NAME + "(id INTEGER PRIMARY KEY AUTOINCREMENT," +
            "lat TEXT, "+
            "lng TEXT, title TEXT)");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
    onCreate(db);
}



public boolean insertMarker(String lat,String lng,String title)
{
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put(COLUMN_LAT, lat);
    contentValues.put(COLUMN_LNG, lng);
    contentValues.put(COLUMN_TITLE, title);
    // Insert the row into your table
    long ins = db.insert(TABLE_NAME, null, contentValues);

    if (ins == -1) return false;
    else return true;
}


public ArrayList<MarkerModel> getAllMarkers()
{
    ArrayList<MarkerModel> arrayListMarkers = new ArrayList<>();
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.rawQuery("Select * from "+TABLE_NAME,null);
    while(cursor.moveToNext())
    {
        int id = cursor.getInt(0);
        String lat = cursor.getString(1);
        String lng = cursor.getString(2);
        String title = cursor.getString(3);

        MarkerModel markerModel = new MarkerModel(id,lat,lng,title);

        arrayListMarkers.add(markerModel);
    }
    cursor.close();

    return arrayListMarkers;
}

public void deleteRow(int value)
{
    SQLiteDatabase db = this.getWritableDatabase();
    db.execSQL("DELETE FROM " + TABLE_NAME+ " WHERE "+COLUMN_ID+"='"+value+"'");
}

public void deleteRows(int value)
{
    SQLiteDatabase db = this.getWritableDatabase();
    db.execSQL("DELETE * FROM " + TABLE_NAME + " WHERE " + COLUMN_ID + " =' " + value + " ' ");
}
}









package elevatesecurity.myapplication.Adapters;


public class MarkerAdapter extends RecyclerView.Adapter<MarkerAdapter.MarkerViewHolder> {

// The MarkerModel is the name of the existed activity called MarkerModel
List<MarkerModel> markerList;
Context mCtx;


public MarkerAdapter(Context mCtx, List<MarkerModel> markerList)
{
    this.mCtx = mCtx;
    this.markerList = markerList;

}

@Override
public MarkerViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view= LayoutInflater.from(mCtx).inflate(R.layout.item_marker,parent,false);
    return new MarkerViewHolder(view);
}

@Override
public void onBindViewHolder(MarkerViewHolder holder, int position) {

    holder.titleTxt.setText(markerList.get(position).getTitle());

}

@Override
public int getItemCount() {

    return markerList.size();
}

public class MarkerViewHolder extends RecyclerView.ViewHolder
{

    TextView titleTxt;
    Button buttonOptions;

    public MarkerViewHolder(final View itemView)
    {
        super(itemView);
        titleTxt = (TextView)itemView.findViewById(R.id.titleTxt);
        buttonOptions = (Button)itemView.findViewById(R.id.buttonOptions);
        itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
               MarkerModel markerModel = markerList.get(getAdapterPosition());

                Intent i = new Intent(mCtx, DisplayMapActivity.class);
                i.putExtra("lat",markerModel.getLat());
                i.putExtra("lng",markerModel.getLng());
                i.putExtra("title",markerModel.getTitle());
                mCtx.startActivity(i);
            }
        });





        buttonOptions.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    PopupMenu popupMenu = new PopupMenu(mCtx, buttonOptions);
                    popupMenu.getMenuInflater().inflate(R.menu.menu_contextual, popupMenu.getMenu());
                    popupMenu.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
                        @Override
                        public boolean onMenuItemClick(MenuItem item) {


                            MarkerDatabaseHelper db = new MarkerDatabaseHelper(mCtx);
                            db.deleteRow(markerList.get(getAdapterPosition()).getId());
                            markerList.remove(getAdapterPosition());
                            //       Recent_Adapter.this.notify();
                            notifyDataSetChanged();
                            notifyItemRemoved(getAdapterPosition());

                            return true;
                        }
                    });
                    popupMenu.show();
                }catch(Exception e)
                {
                    e.printStackTrace();
                }
            }
        });


    }


}
}

Answer 1

在您的 MarkerDatabaseHelper 类中创建此方法:

public void deleteAllRows() {
    SQLiteDatabase db = this.getWritableDatabase();
    db.execSQL("DELETE FROM " + TABLE_NAME);
}

并从您的 Activity 类中调用它:

db.deleteAllRows();

因为这些行:

modelArrayList.clear();
markerAdapter.notifyDataSetChanged();

对数据库没有影响，它们只会清除附加到适配器的列表。

删除所有行而不创建方法的另一种方法是调用:

int counter = db.delete(TABLE_NAME, null, null);

这还将返回已删除的行数。