学习Android的第十七天

目录

Android ListView 添加插入数据

添加记录

在指定位置插入数据

Android ListView 删除数据

ListView 删除数据

ListView 清空数据

Android ListView 更改数据

ListView 数据更新

Android ListView 查询数据

ListView 数据查询

Android ListView 添加插入数据

添加记录

我们在顶部添加一个按钮，每次点击添加一条记录，并且数据为空时提示用户没数据

XML 布局文件（activity_main.xml）：

Java 代码（MainActivity.java）：

package com.example.myapplication;import android.os.Bundle;import android.view.View;import android.widget.ArrayAdapter;import android.widget.Button;import android.widget.ListView;import android.widget.TextView;import androidx.appcompat.app.AppCompatActivity;import java.util.ArrayList;public class MainActivity extends AppCompatActivity {private ArrayList dataList;private ArrayAdapter adapter;private TextView noDataText;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Button addButton = findViewById(R.id.addButton);ListView listView = findViewById(R.id.listView);noDataText = findViewById(R.id.noDataText);dataList = new ArrayList();adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, dataList);listView.setAdapter(adapter);addButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {addRecord();}});}private void addRecord() {// 在这里添加记录dataList.add("新建记录 " + (dataList.size() + 1));adapter.notifyDataSetChanged();// 如果有数据，则隐藏文本消息if (!dataList.isEmpty()) {noDataText.setVisibility(View.GONE);}}@Overrideprotected void onResume() {super.onResume();// 在 onResume 中检查数据列表是否为空，并根据情况显示或隐藏文本消息if (dataList.isEmpty()) {noDataText.setVisibility(View.VISIBLE);} else {noDataText.setVisibility(View.GONE);}}}

在指定位置插入数据

要在指定位置插入数据，可以添加一个编辑框让用户输入要插入的位置，然后添加一个按钮来触发插入操作。

XML 布局文件（activity_main.xml）：

Java 代码（MainActivity.java）：

package com.example.myapplication;import android.os.Bundle;import android.view.View;import android.widget.ArrayAdapter;import android.widget.Button;import android.widget.EditText;import android.widget.ListView;import android.widget.TextView;import android.widget.Toast;import androidx.appcompat.app.AppCompatActivity;import java.util.ArrayList;public class MainActivity extends AppCompatActivity {private ArrayList dataList;private ArrayAdapter adapter;private TextView noDataText;private EditText positionEditText;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Button addButton = findViewById(R.id.addButton);Button insertButton = findViewById(R.id.insertButton);ListView listView = findViewById(R.id.listView);noDataText = findViewById(R.id.noDataText);positionEditText = findViewById(R.id.positionEditText);dataList = new ArrayList();adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, dataList);listView.setAdapter(adapter);addButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {addRecord();}});insertButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {insertRecord();}});}private void addRecord() {dataList.add("新建记录 " + (dataList.size() + 1));adapter.notifyDataSetChanged();toggleNoDataTextVisibility();}private void insertRecord() {try {int position = Integer.parseInt(positionEditText.getText().toString());if (position >= 0 && position <= dataList.size()) {dataList.add(position, "插入记录 " + (dataList.size() + 1));adapter.notifyDataSetChanged();toggleNoDataTextVisibility();} else {Toast.makeText(this, "位置无效", Toast.LENGTH_SHORT).show();}} catch (NumberFormatException e) {Toast.makeText(this, "请输入有效的位置", Toast.LENGTH_SHORT).show();}}private void toggleNoDataTextVisibility() {if (dataList.isEmpty()) {noDataText.setVisibility(View.VISIBLE);} else {noDataText.setVisibility(View.GONE);}}}

Android ListView 删除数据

ListView 删除数据

从 ListView 中删除某项数据有两种方法

• 根据对象删除
• 根据游标(position) 删除

例子：

XML 布局文件（activity_main.xml）：

Java 代码（MainActivity.java）：

package com.example.myapplication;import android.os.Bundle;import android.view.View;import android.widget.ArrayAdapter;import android.widget.Button;import android.widget.ListView;import android.widget.TextView;import android.widget.Toast;import androidx.appcompat.app.AppCompatActivity;import java.util.ArrayList;public class MainActivity extends AppCompatActivity {private ArrayList dataList;private ArrayAdapter adapter;private TextView noDataText;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Button addButton = findViewById(R.id.addButton);Button deleteByObjectButton = findViewById(R.id.deleteByObjectButton);Button deleteByPositionButton = findViewById(R.id.deleteByPositionButton);ListView listView = findViewById(R.id.listView);noDataText = findViewById(R.id.noDataText);dataList = new ArrayList();adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, dataList);listView.setAdapter(adapter);addButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {addRecord();}});deleteByObjectButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {deleteByObject();}});deleteByPositionButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {deleteByPosition();}});}private void addRecord() {dataList.add("新建记录 " + (dataList.size() + 1));adapter.notifyDataSetChanged();toggleNoDataTextVisibility();}private void deleteByObject() {if (!dataList.isEmpty()) {// 根据对象删除最后一项数据dataList.remove(dataList.size() - 1);adapter.notifyDataSetChanged();toggleNoDataTextVisibility();} else {Toast.makeText(this, "无数据可删除", Toast.LENGTH_SHORT).show();}}private void deleteByPosition() {if (!dataList.isEmpty()) {// 根据游标(position)删除第一项数据dataList.remove(0);adapter.notifyDataSetChanged();toggleNoDataTextVisibility();} else {Toast.makeText(this, "无数据可删除", Toast.LENGTH_SHORT).show();}}private void toggleNoDataTextVisibility() {if (dataList.isEmpty()) {noDataText.setVisibility(View.VISIBLE);} else {noDataText.setVisibility(View.GONE);}}}

ListView 清空数据

清空 ListView 数据有两种方式

• 调用 remove() 方法一项一项的删除
• 调用 clear() 方法一次性删除

下面我们就写二个按钮 来演示下这两种方法

XML 布局文件（activity_main.xml）：

Java 代码（MainActivity.java）：

package com.example.myapplication;import android.os.Bundle;import android.view.View;import android.widget.ArrayAdapter;import android.widget.Button;import android.widget.ListView;import android.widget.TextView;import android.widget.Toast;import androidx.appcompat.app.AppCompatActivity;import java.util.ArrayList;public class MainActivity extends AppCompatActivity {private ArrayList dataList;private ArrayAdapter adapter;private TextView noDataText;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Button addButton = findViewById(R.id.addButton);Button removeOneByOneButton = findViewById(R.id.removeOneByOneButton);Button clearAllButton = findViewById(R.id.clearAllButton);ListView listView = findViewById(R.id.listView);noDataText = findViewById(R.id.noDataText);dataList = new ArrayList();adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, dataList);listView.setAdapter(adapter);addButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {addRecord();}});removeOneByOneButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {removeOneByOne();}});clearAllButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {clearAll();}});}private void addRecord() {dataList.add("新建记录 " + (dataList.size() + 1));adapter.notifyDataSetChanged();toggleNoDataTextVisibility();}private void removeOneByOne() {if (!dataList.isEmpty()) {dataList.remove(dataList.size() - 1);adapter.notifyDataSetChanged();toggleNoDataTextVisibility();} else {Toast.makeText(this, "无数据可删除", Toast.LENGTH_SHORT).show();}}private void clearAll() {if (!dataList.isEmpty()) {dataList.clear();adapter.notifyDataSetChanged();toggleNoDataTextVisibility();} else {Toast.makeText(this, "无数据可清空", Toast.LENGTH_SHORT).show();}}private void toggleNoDataTextVisibility() {if (dataList.isEmpty()) {noDataText.setVisibility(View.VISIBLE);} else {noDataText.setVisibility(View.GONE);}}}

Android ListView 更改数据

ListView 数据更新

更新 ListView 中的数据有两种办法

• 根据对象更新
• 根据游标(pos) 更新

例子：

XML 布局文件（activity_main.xml）：

Java 代码（MainActivity.java）：

package com.example.myapplication;import android.os.Bundle;import android.view.View;import android.widget.ArrayAdapter;import android.widget.Button;import android.widget.ListView;import android.widget.TextView;import android.widget.Toast;import androidx.appcompat.app.AppCompatActivity;import java.util.ArrayList;public class MainActivity extends AppCompatActivity {private ArrayList dataList;private ArrayAdapter adapter;private ListView listView;private TextView noDataText;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Button addButton = findViewById(R.id.addButton);Button updateByObjectButton = findViewById(R.id.updateByObjectButton);Button updateByPositionButton = findViewById(R.id.updateByPositionButton);listView = findViewById(R.id.listView);noDataText = findViewById(R.id.noDataText);dataList = new ArrayList();adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, dataList);listView.setAdapter(adapter);addButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {addRecord();}});updateByObjectButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {updateByObject();}});updateByPositionButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {updateByPosition();}});}private void addRecord() {dataList.add("新记录 " + (dataList.size() + 1));adapter.notifyDataSetChanged();toggleNoDataTextVisibility();}private void updateByObject() {if (!dataList.isEmpty()) {// 根据对象更新第一个数据项dataList.set(0, "更新的记录 1");adapter.notifyDataSetChanged();Toast.makeText(this, "根据对象更新成功", Toast.LENGTH_SHORT).show();} else {Toast.makeText(this, "没有可更新的数据", Toast.LENGTH_SHORT).show();}}private void updateByPosition() {if (!dataList.isEmpty()) {// 根据游标更新第二个数据项int position = 1; // 第二个位置if (position >= 0 && position < dataList.size()) {dataList.set(position, "更新的记录 2");adapter.notifyDataSetChanged();Toast.makeText(this, "根据游标更新成功", Toast.LENGTH_SHORT).show();} else {Toast.makeText(this, "位置无效", Toast.LENGTH_SHORT).show();}} else {Toast.makeText(this, "没有可更新的数据", Toast.LENGTH_SHORT).show();}}private void toggleNoDataTextVisibility() {if (dataList.isEmpty()) {noDataText.setVisibility(View.VISIBLE);} else {noDataText.setVisibility(View.GONE);}}}

Android ListView 查询数据

ListView 数据查询

例子：

XML 布局文件（activity_main.xml）：

Java 代码（MainActivity.java）：

package com.example.myapplication;import android.os.Bundle;import android.text.Editable;import android.text.TextWatcher;import android.view.View;import android.widget.ArrayAdapter;import android.widget.Button;import android.widget.EditText;import android.widget.ListView;import android.widget.TextView;import androidx.appcompat.app.AppCompatActivity;import java.util.ArrayList;import java.util.List;public class MainActivity extends AppCompatActivity {private ArrayList dataList;private ArrayList originalDataList; // 保存原始数据private ArrayAdapter adapter;private ListView listView;private TextView noDataText;private EditText searchEditText;private Button searchButton;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Button addButton = findViewById(R.id.addButton);searchEditText = findViewById(R.id.searchEditText);searchButton = findViewById(R.id.searchButton);listView = findViewById(R.id.listView);noDataText = findViewById(R.id.noDataText);dataList = new ArrayList();originalDataList = new ArrayList(); // 初始化原始数据列表adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, dataList);listView.setAdapter(adapter);addButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {addRecord();}});searchButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {searchRecords();}});searchEditText.addTextChangedListener(textWatcher);}private final TextWatcher textWatcher = new TextWatcher() {@Overridepublic void beforeTextChanged(CharSequence s, int start, int count, int after) {}@Overridepublic void onTextChanged(CharSequence s, int start, int before, int count) {}@Overridepublic void afterTextChanged(Editable s) {// 每次文本发生变化时不自动查询}};private void addRecord() {originalDataList.add("新记录 " + (originalDataList.size() + 1)); // 添加记录到原始数据列表if (searchEditText.getText().toString().isEmpty()) {// 如果查询条件为空，则更新列表updateList(originalDataList);}searchRecords(); // 执行查询操作}private void searchRecords() {String query = searchEditText.getText().toString().trim().toLowerCase();List filteredList = new ArrayList();for (String record : originalDataList) {if (record.toLowerCase().contains(query)) {filteredList.add(record);}}updateList(filteredList);}private void updateList(List records) {dataList.clear();dataList.addAll(records);adapter.notifyDataSetChanged();toggleNoDataTextVisibility();}private void toggleNoDataTextVisibility() {noDataText.setVisibility(dataList.isEmpty() ? View.VISIBLE : View.GONE);}}