Android ListView数据更新问题：updateData和deleteData无法正常工作

在Android应用中使用ListView展示数据，并通过ContentProvider进行数据增删改查操作时，有时会遇到updateData和deleteData按钮无法实现预期功能，并且程序闪退的问题。本文将分析代码问题，并提供详细的解决方案。

问题代码：

class MainActivity : AppCompatActivity() {
    var bookId: String? = null
    private lateinit var adapter: ArrayAdapter<String>
    private val dataList = mutableListOf<String>()
    private val bookSet = mutableSetOf<String>()
    @SuppressLint("Range")

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        adapter = ArrayAdapter(this, android.R.layout.simple_list_item_1, dataList)
        val listView: ListView = findViewById(R.id.bookslistview)
        listView.adapter = adapter
        val addData:Button=findViewById(R.id.addData)
        addData.setOnClickListener {
            // 添加数据
            val uri = Uri.parse("content://com.example.shiyan2app_a.provider/book")
            val values = contentValuesOf("name" to "A Clash of Kings", "author" to "George Martin", "pages" to 1040, "price" to 22.85)
            val newUri = contentResolver.insert(uri, values)
            bookId = newUri?.pathSegments?.get(1)
            // 将数据添加到列表中
            if (bookId != null && !bookSet.contains(bookId)) {
                val bookInfo = "${values["name"]}- ${values["author"]}- ${values["pages"]}Info)"
                bookSet.add(bookId!!)
                adapter.notifyDataSetChanged()
            }
        }
        val queryData:Button=findViewById(R.id.queryData)
        queryData.setOnClickListener {
            dataList.clear()
            bookSet.clear()
            // 查询数据
            val uri = Uri.parse("content://com.example.shiyan2app_a.provider/book")
            contentResolver.query(uri, null, null, null, null)?.apply {
                while (moveToNext()) {
                    val name = getString(getColumnIndex("name"))
                    val author = getString(getColumnIndex("author"))
                    val pages = getInt(getColumnIndex("pages"))
                    val price = getDouble(getColumnIndex("price"))
                    Log.d("MainActivity", "book name is $name")
                    Log.d("MainActivity", "book author is $author")
                    Log.d("MainActivity", "book pages is $pages")
                    Log.d("MainActivity", "book price is $price")
                    val bookInfo = "$name - $author - $pages - $price"
                    dataList.add(bookInfo)
                    bookId?.let { it1 -> bookSet.add(it1) }
                }
                adapter.notifyDataSetChanged() // 通知适配器数据发生变化，更新ListView的显示
                close()
            }
        }
        val updateData:Button=findViewById(R.id.updateData)
        updateData.setOnClickListener {
            // 更新数据
            val uri = Uri.parse("content://com.example.shiyan2app_a.provider/book")
            contentResolver.query(uri, null, null, null, null)?.use { cursor ->
                while (cursor.moveToNext()) {
                    val bookId = cursor.getString(cursor.getColumnIndex("_id"))
                    if (bookSet.contains(bookId)) {
                        val values = contentValuesOf("name" to "A Storm of Swords", "author" to "George Martin", "pages" to 1216, "price" to 24.05)
                        contentResolver.update(Uri.parse("$uri/$bookId"), values, null, null)
                        val updatedBookInfo = "${values["name"]}- ${values["author"]}- ${values["pages"]} - ${values["price"]}"
                        val bookIndex = dataList.indexOfFirst { it.startsWith(bookId) }
                        if (bookIndex != -1) {
                            dataList[bookIndex] = updatedBookInfo
                        }
                    }
                }
                adapter.notifyDataSetChanged()
            }
        }

        val deleteData:Button=findViewById(R.id.deleteData)
        deleteData.setOnClickListener {
            // 删除数据
            bookId?.let { 
                val uri = Uri.parse("content://com.example.shiyan2app_a.provider/ book/$it")
                contentResolver.delete(uri, null, null)
            }
        }
    }
}

问题分析：

该代码存在以下几个问题，导致updateData和deleteData按钮无法正常工作，并且程序闪退：

添加数据时，没有将bookInfo添加到dataList中，导致列表没有更新。
查询数据时，没有将bookInfo添加到dataList中，导致列表没有更新。
更新数据时，没有将更新后的bookInfo添加到dataList中，导致列表没有更新。
删除数据时，删除的uri路径中有多余的空格。

解决方案：

添加数据时，将bookInfo添加到dataList中。

if (bookId != null && !bookSet.contains(bookId)) {
    val bookInfo = "${values["name"]}- ${values["author"]}- ${values["pages"]} - ${values["price"]}"
    bookSet.add(bookId!!)
    dataList.add(bookInfo) // 添加到dataList中
    adapter.notifyDataSetChanged()
}

查询数据时，将bookInfo添加到dataList中。

while (moveToNext()) {
    ...
    val bookInfo = "$name - $author - $pages - $price"
    dataList.add(bookInfo) // 添加到dataList中
    bookId?.let { it1 -> bookSet.add(it1) }
}
adapter.notifyDataSetChanged()

更新数据时，将更新后的bookInfo添加到dataList中。

while (cursor.moveToNext()) {
    ...
    val updatedBookInfo = "${values["name"]}- ${values["author"]}- ${values["pages"]} - ${values["price"]}"
    val bookIndex = dataList.indexOfFirst { it.startsWith(bookId) }
    if (bookIndex != -1) {
        dataList[bookIndex] = updatedBookInfo // 更新dataList中的数据
    }
}
adapter.notifyDataSetChanged()

删除数据时，删除的uri路径中有多余的空格。

val uri = Uri.parse("content://com.example.shiyan2app_a.provider/book/$it")

修改完毕后的代码：

class MainActivity : AppCompatActivity() {
    var bookId: String? = null
    private lateinit var adapter: ArrayAdapter<String>
    private val dataList = mutableListOf<String>()
    private val bookSet = mutableSetOf<String>()
    @SuppressLint("Range")

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        adapter = ArrayAdapter(this, android.R.layout.simple_list_item_1, dataList)
        val listView: ListView = findViewById(R.id.bookslistview)
        listView.adapter = adapter
        val addData: Button = findViewById(R.id.addData)
        addData.setOnClickListener {
            // 添加数据
            val uri = Uri.parse("content://com.example.shiyan2app_a.provider/book")
            val values = contentValuesOf("name" to "A Clash of Kings", "author" to "George Martin", "pages" to 1040, "price" to 22.85)
            val newUri = contentResolver.insert(uri, values)
            bookId = newUri?.pathSegments?.get(1)
            // 将数据添加到列表中
            if (bookId != null && !bookSet.contains(bookId)) {
                val bookInfo = "${values["name"]}- ${values["author"]}- ${values["pages"]} - ${values["price"]}"
                bookSet.add(bookId!!)
                dataList.add(bookInfo)
                adapter.notifyDataSetChanged()
            }
        }
        val queryData: Button = findViewById(R.id.queryData)
        queryData.setOnClickListener {
            dataList.clear()
            bookSet.clear()
            // 查询数据
            val uri = Uri.parse("content://com.example.shiyan2app_a.provider/book")
            contentResolver.query(uri, null, null, null, null)?.apply {
                while (moveToNext()) {
                    val name = getString(getColumnIndex("name"))
                    val author = getString(getColumnIndex("author"))
                    val pages = getInt(getColumnIndex("pages"))
                    val price = getDouble(getColumnIndex("price"))
                    Log.d("MainActivity", "book name is $name")
                    Log.d("MainActivity", "book author is $author")
                    Log.d("MainActivity", "book pages is $pages")
                    Log.d("MainActivity", "book price is $price")
                    val bookInfo = "$name - $author - $pages - $price"
                    dataList.add(bookInfo)
                    bookId?.let { it1 -> bookSet.add(it1) }
                }
                adapter.notifyDataSetChanged()
                close()
            }
        }
        val updateData: Button = findViewById(R.id.updateData)
        updateData.setOnClickListener {
            // 更新数据
            val uri = Uri.parse("content://com.example.shiyan2app_a.provider/book")
            contentResolver.query(uri, null, null, null, null)?.use { cursor ->
                while (cursor.moveToNext()) {
                    val bookId = cursor.getString(cursor.getColumnIndex("_id"))
                    if (bookSet.contains(bookId)) {
                        val values = contentValuesOf("name" to "A Storm of Swords", "author" to "George Martin", "pages" to 1216, "price" to 24.05)
                        contentResolver.update(Uri.parse("$uri/$bookId"), values, null, null)
                        val updatedBookInfo = "${values["name"]}- ${values["author"]}- ${values["pages"]} - ${values["price"]}"
                        val bookIndex = dataList.indexOfFirst { it.startsWith(bookId) }
                        if (bookIndex != -1) {
                            dataList[bookIndex] = updatedBookInfo
                        }
                    }
                }
                adapter.notifyDataSetChanged()
            }
        }

        val deleteData: Button = findViewById(R.id.deleteData)
        deleteData.setOnClickListener {
            // 删除数据
            bookId?.let { 
                val uri = Uri.parse("content://com.example.shiyan2app_a.provider/book/$it")
                contentResolver.delete(uri, null, null)
            }
        }
    }
}

总结：

通过以上修改，可以解决updateData和deleteData按钮无法正常工作，并且程序闪退的问题。在开发Android应用时，需要注意数据更新和删除操作时，及时更新ListView数据，并确保URI路径正确，避免出现错误。

Android ListView数据更新问题：updateData和deleteData无法正常工作