Question

我有一个列表视图，其中填充了一个简单的游标适配器，它反映了数据库中的条目。我想从我创建的上下文菜单中删除项目。我写了下面的代码，但它似乎没有工作。单击“编辑”或“删除”时，即使我在单击每个菜单项时写了一行以显示祝酒，也没有任何反应。以下是代码。

// MainActivity

package com.apps.katz.doer;

import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.widget.SimpleCursorAdapter;
import android.support.v7.app.AlertDialog;
import android.view.ContextMenu;
import android.view.View;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Toast;

import java.util.List;

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {

    private ListView taskListView;
    private DataModel data;
    DatabaseHandler db = new DatabaseHandler(this);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);



        taskListView = (ListView) findViewById(R.id.task_list_view);
        Cursor cursor = db.queueAllTasks();
        String[] from = new String[] {"taskName"};
        int[] to = new int[] {R.id.text};
        SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, R.layout.row_item, cursor, from, to);
        taskListView.setAdapter(adapter);

        registerForContextMenu(taskListView);

    }

    @Override
    public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
        int currentPosition;
        super.onCreateContextMenu(menu, v, menuInfo);
        AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) menuInfo;
        menu.setHeaderTitle(R.string.task_options);
        menu.add(0, v.getId(), 0, R.string.edit_task);
        menu.add(0, v.getId(), 0, R.string.delete_task);
    }

    @Override
    public boolean onContextItemSelected(MenuItem item) {
        int position;
        super.onContextItemSelected(item);
        if (item.getTitle()=="Edit") {

        } else if (item.getTitle()=="Delete") {
            Toast.makeText(getBaseContext(),"Task Deleted  ",Toast.LENGTH_LONG).show();
            AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
            position = (int)info.id;
            db.deleteTask(position);
        } else {
            return false;
        }
        return true;
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        if (id == R.id.action_add_new_task) {
            startActivity(new Intent(MainActivity.this, AddTask.class));
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();

        if (id == R.id.nav_camera) {
            // Handle the camera action
        } else if (id == R.id.nav_gallery) {

        } else if (id == R.id.nav_slideshow) {

        } else if (id == R.id.nav_manage) {

        } else if (id == R.id.nav_share) {

        } else if (id == R.id.nav_send) {

        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }
}

DataBase处理程序删除方法

public void deleteTask(int id) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(TABLE_NAME, KEY_ID + " =?",
                new String[] {String.valueOf(id)});
        db.close();
    }

// DataModel类

package com.apps.katz.doer;

/**
 * Created by katz on 14/4/16.
 */
public class DataModel {

    int id;
    private String taskTitle;

    public DataModel(){

    }

    public DataModel(int id) {
        this.id=id;
    }

    public DataModel(int id, String taskTitle){
        this.id=id;
        this.taskTitle=taskTitle;
    }

    public DataModel(String taskTitle) {
        this.taskTitle = taskTitle;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getTaskTitle() {
        return taskTitle;
    }

    public void setTaskTitle(String taskTitle) {
        this.taskTitle = taskTitle;
    }
}

Answer 1

试试这个：

@Override
public boolean onContextItemSelected(MenuItem item) {
    super.onContextItemSelected(item);

    int id = item.getItemId();
    if (id == R.id.edit) {
        // code
        return true;
    } else if (id == R.id.delete) {
        // code
        return true;
    }
    return false;
}

Answer 2

通过创建方法refreshListView（）并在onCreate中调用它然后在我从上下文菜单中选择“删除”的代码中解决它。这是onContextItemSelected方法的代码。

@Override
    public boolean onContextItemSelected(MenuItem item) {
        AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
        switch (item.getItemId()) {
            case R.id.edit:
                Toast.makeText(this,"You chose Edit",Toast.LENGTH_LONG).show();
                return true;
            case R.id.delete:
                Toast.makeText(this,"Task Deleted",Toast.LENGTH_LONG).show();
                db.deleteTask((int)info.id);
                refreshListView();
                return true;
            default:
                return super.onContextItemSelected(item);
        }
    }

这是方法的代码，refreshListView（）。

private void refreshListView() {

        taskListView = (ListView) findViewById(R.id.task_list_view);
        cursor = db.queueAllTasks();
        String[] from = new String[] {"taskName"};
        int[] to = new int[] {R.id.text};
        adapter = new SimpleCursorAdapter(this, R.layout.row_item, cursor, from, to);
        taskListView.setAdapter(adapter);

        registerForContextMenu(taskListView);

    }

从android列表视图中删除数据库条目并更新它

2 个答案: