Question

我正在创建一个清单，它允许用户将新项目添加到列表中，我试图允许用户在需要时删除项目。因此，当用户长按列表中的项目时，我正在使用this创建一个上下文菜单。现在，它识别出长按但没有任何反应，因此上下文菜单不会出现。

这是我的活动页面：（ViewTask.java）

package com.example.androidhive;

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

import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView.AdapterContextMenuInfo;
import android.widget.ArrayAdapter;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class ViewTask extends Activity {
    protected TaskerDbHelper db;
    List<Task> list;
    MyAdapter adapt;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_view_task);
        db = new TaskerDbHelper(this);
        list = db.getAllTasks();
        adapt = new MyAdapter(this, R.layout.list_inner_view, list);
        ListView listTask = (ListView) findViewById(R.id.listView1);
        listTask.setAdapter(adapt);
    }

    public void addTaskNow(View v) {
        EditText t = (EditText) findViewById(R.id.editText1);
        String s = t.getText().toString();
        if (s.equalsIgnoreCase("")) {
            Toast.makeText(this, "Enter a goal please!",
                    Toast.LENGTH_LONG);
        } else {
            Task task = new Task(s, 0);
            db.addTask(task);
            Log.d("tasker", "data added");
            t.setText("");
            adapt.add(task);
            adapt.notifyDataSetChanged();
        }

    }
    @Override
    public void onCreateContextMenu(ContextMenu menu, View v,
                                    ContextMenuInfo menuInfo) {
        super.onCreateContextMenu(menu, v, menuInfo);
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.layout.cmenu, menu);
    }

    @Override
    public boolean onContextItemSelected(MenuItem item) {
        AdapterContextMenuInfo info = (AdapterContextMenuInfo) item.getMenuInfo();
        switch (item.getItemId()) {
            case R.id.Delete_Task:
                db.deleteTask(info.id);
                return true;
            default:
                return super.onContextItemSelected(item);
        }
    }

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

    private class MyAdapter extends ArrayAdapter<Task> {

        Context context;
        List<Task> taskList = new ArrayList<Task>();
        int layoutResourceId;

        public MyAdapter(Context context, int layoutResourceId,
                List<Task> objects) {
            super(context, layoutResourceId, objects);
            this.layoutResourceId = layoutResourceId;
            this.taskList = objects;
            this.context = context;
        }

        /**
         * This method will DEFINe what the view inside the list view will
         * finally look like Here we are going to code that the checkbox state
         * is the status of task and check box text is the task name
         */
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            CheckBox chk = null;
            if (convertView == null) {
                LayoutInflater inflater = (LayoutInflater) context
                        .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                convertView = inflater.inflate(R.layout.list_inner_view,
                        parent, false);
                chk = (CheckBox) convertView.findViewById(R.id.chkStatus);
                convertView.setTag(chk);

                chk.setOnClickListener(new View.OnClickListener() {

                    public void onClick(View v) {
                        CheckBox cb = (CheckBox) v;
                        Task changeTask = (Task) cb.getTag();
                        changeTask.setStatus(cb.isChecked() == true ? 1 : 0);
                        db.updateTask(changeTask);
                        if(cb.isChecked())
                          {
                           Toast.makeText(
                             getApplicationContext(),
                             "Goal Accomplished!", Toast.LENGTH_LONG).show();
                          }
                    }

                });
            } else {
                chk = (CheckBox) convertView.getTag();
            }
            Task current = taskList.get(position);
            chk.setText(current.getTaskName());
            chk.setChecked(current.getStatus() == 1 ? true : false);
            chk.setTag(current);
            Log.d("listener", String.valueOf(current.getId()));
            return convertView;
        }

    }

}

以下是与此页面关联的xml页面：（activity_view_task.xml）

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#DE8126"
    android:orientation="vertical" >

    <!-- Header Start -->
    <LinearLayout
        android:id="@+id/header"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="@layout/header_gradient"
        android:orientation="vertical"
        android:paddingBottom="5dip"
        android:paddingTop="5dip" >

                <!-- Logo Start -->
        <ImageView
            android:id="@+id/logoButton"
            android:layout_width="match_parent"
            android:layout_height="132dp"
            android:src="@drawable/logo" />
                <!-- Logo Ends -->
    </LinearLayout>
             <!-- Header End -->

             <!-- Goals Title Start -->
      <LinearLayout 
          android:id="@+id/goalsTitle"
          android:layout_width="match_parent"
          android:layout_height="80dp"
          android:paddingTop="5dip"
          android:paddingBottom="5dip">

          <TextView 
              android:id="@+id/gTitle"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
              android:text="My Goals"
              android:textSize="50sp"
              android:textScaleX="1.5"
              android:textStyle="bold"
              android:gravity="center"/>
      </LinearLayout>
            <!-- Goals Title End -->

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ViewTask" >

    <EditText
        android:id="@+id/editText1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:ems="10" >

        <requestFocus />
    </EditText>


    <Button
       android:id="@+id/button1"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_alignParentRight="true"
       android:layout_alignParentTop="true"
       android:layout_marginRight="14dp"
       android:text="@string/Save"
       android:onClick="addTaskNow"/>


    <ListView
        android:id="@+id/listView1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/button1" >
    </ListView>
</RelativeLayout>
</LinearLayout>

这是菜单本身：（cmenu.xml）

<?xml version="1.0" encoding="UTF-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:id="@+id/Edit_Task"></item>
    <item android:id="@+id/Delete_Task"></item>
</menu>

感谢您的回复，现在我无法将该项目实际删除。

这是我的数据库帮助页面：（TaskerDbHelper.java）

package com.example.androidhive;

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

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;


public class TaskerDbHelper extends SQLiteOpenHelper{
    private static final int DATABASE_VERSION = 1;

    // Database Name
    private static final String DATABASE_NAME = "taskerManager";

    // tasks table name
    private static final String TABLE_TASKS = "tasks";

    // tasks Table Columns names
    private static final String KEY_ID = "id";
    private static final String KEY_TASKNAME = "taskName";
    private static final String KEY_STATUS = "status";

    public TaskerDbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        String sql = "CREATE TABLE IF NOT EXISTS " + TABLE_TASKS + " ( "
                + KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
                + KEY_TASKNAME+ " TEXT, "
                + KEY_STATUS + " INTEGER)";
        db.execSQL(sql);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldV, int newV) {
         // Drop older table if existed
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_TASKS);
        // Create tables again
        onCreate(db);
    }

    public void addTask(Task task) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(KEY_TASKNAME, task.getTaskName()); // task name
         // status of task- can be 0 for not done and 1 for done
        values.put(KEY_STATUS, task.getStatus());

        // Inserting Row
        db.insert(TABLE_TASKS, null, values);
        db.close(); // Closing database connection
    }
    public boolean deleteTask(long task) 
    {
        SQLiteDatabase db = this.getWritableDatabase();
        return db.delete(TABLE_TASKS, KEY_TASKNAME + "=" + task, null) > 0;
    }

    public List<Task> getAllTasks() {
        List<Task> taskList = new ArrayList<Task>();
        // Select All Query
        String selectQuery = "SELECT  * FROM " + TABLE_TASKS;
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);
        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {
            do {
                Task task = new Task();
                task.setId(cursor.getInt(0));
                task.setTaskName(cursor.getString(1));
                task.setStatus(cursor.getInt(2));
                // Adding contact to list
                taskList.add(task);
            } while (cursor.moveToNext());
        }
        // return task list
        return taskList;
    }

    public void updateTask(Task task) {
        // updating row
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(KEY_TASKNAME, task.getTaskName());
        values.put(KEY_STATUS, task.getStatus());
        db.update(TABLE_TASKS, values, KEY_ID + " = ?",new String[] {String.valueOf(task.getId())});
        db.close();
    }

}

上面的文件包含我的deleteTask（）。

Answer 1

我在任何地方都看不到registerForContextMenu（）。这对于列表实际上知道它具有上下文菜单是必要的。

  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_view_task);
      db = new TaskerDbHelper(this);
      list = db.getAllTasks();
      adapt = new MyAdapter(this, R.layout.list_inner_view, list);
      ListView listTask = (ListView) findViewById(R.id.listView1);
      listTask.setAdapter(adapt);
      registerForContextMenu(listTask); // <-- Register!
  }

此外，您应该在菜单xml文件中放置一个String值。显然，最好在字符串xml文件中引用实际的字符串。

<item
    android:id="@+id/Edit_Task"
    android:title="Edit">
</item>
<item
    android:id="@+id/Delete_Task"
    android:title="Delete">
</item>

关于删除任务：要从sql数据库中删除任务，您需要某种标识符。据我所知，你只有一个任务名称和一个状态整数。如果允许任务具有相同的名称，则不能将其用作唯一标识符。也许您应该将它添加到您的Task类。然后，您可以使用它来查找和删除数据库中的特定任务。（您的info.id不起作用，因为它只是视图的标识符）您可以使用info.position来检索taskList中Task的位置，或者更具体地说，是适配器中的当前列表。

    case R.id.Delete_Task:
         Task task = list.get(info.position);                
         if (db.deleteTask(task.getUniqueIdentifier())) { // <-- Determine the unique id
             list.Remove(info.position);
             listTask.invalidate();
             return true;
         }
         return false;

我不确定invalidate（）是否会起作用。但试一试。您也可以为适配器提供新列表，并像调用addTaskNow（）一样调用notifyDataSetChanged（）。

Answer 2

您需要将此行添加到onCreate方法

registerForContextMenu(listTask);

你的onCreateContextMenu（）需要看起来像这样

@Override
public void onCreateContextMenu(ContextMenu menu, View v,
        ContextMenuInfo menuInfo) {

    if (v.getId() == R.id.listView1) {  //YOUR VIEW THAT IS ATTACHED TO LISTASK

        AdapterView.AdapterContextMenuInfo info = (AdapterContextMenuInfo) menuInfo;

        menu.setHeaderTitle("Options");
        String[] menuItems = { "Option1", "Option2", "Option3", "Option4"} };
        for (int i = 0; i < menuItems.length; i++) {
            menu.add(Menu.NONE, i, i, menuItems[i]);
        }

    }
}

最后是你的OnContextMenuItemSelected（）

@Override
public boolean onContextItemSelected(android.view.MenuItem item) {

    AdapterView.AdapterContextMenuInfo info = (AdapterContextMenuInfo) item
            .getMenuInfo();
    menuItemIndex = item.getItemId();

    String[] menuItems = { "Option 1, Option 2, Option 3" };
    String menuItemName = menuItems[menuItemIndex];




    return true;
}

在android中长按项目时创建上下文菜单

2 个答案: