github地址
一、简介
由于近期项目中要做选择收货地址的三级联动滚动选择的效果，所以选择了Numberpicker来做。下面就来讲讲我的实现办法。
二、实现步骤
1、由于收货地址需要用到“省市区”的数据源，所以我先把一个已经做好了的数据库文件放在project下的assets目录下，然后在app初始化的的时候，把assets下的数据库文件拷贝到真机的本地的data/data/包名/databases目录下。(数据库文件放在github地址的assets目录下，有需要的自取)
public static void copyAssetsToDB(Context context, String fileName) throws IOException {
//数据库的存储路径,该路径在：data/data/包名/databases目录下，
String destPath = context.getDatabasePath("").getPath();
Log.i("tag","path---->"+destPath);
File file = new File(destPath);
if (!file.exists()) {
file.mkdirs(); //创建目录
}else {
return;
}
//打开assest文件，获得输入流
InputStream is = context.getAssets().open(fileName);
BufferedInputStream bis = new BufferedInputStream(is);
//获得写入文件的输出流
FileOutputStream fos = new FileOutputStream(destPath +File.separator + fileName);
BufferedOutputStream bos = new BufferedOutputStream(fos);
byte[] data = new byte[2 * 1024];
int len;
while ((len = bis.read(data)) != -1){
bos.write(data, 0, len);
}
bos.flush();
bis.close();
bos.close();
}
2、读取拷贝在真机本地的数据库文件，用于初始化NumberPicker
//打开数据库文件的完整路径，来获得sqlite数据库对象
SQLiteDatabase database = SQLiteDatabase.openOrCreateDatabase(dbPath, null);
//数据库查询操作
Cursor cursor = database.rawQuery(sql, null);
if (cursor != null) {
while (cursor.moveToNext()) {
//......查询结果的操作
}
cursor.close();
}
别急，完整的查询代码放在后面的AddressManager 这个类中
3、设置3个NumberPicker的数据(带联动效果)
布局文件
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.zx.copydatabase.MainActivity"
android:orientation="horizontal"
android:gravity="center"
android:padding="10dp">
android:id="@+id/province_picker"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:focusable="true"
android:focusableInTouchMode="true"/>
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="省"
android:textColor="#000"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"/>
android:id="@+id/city_picker"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:focusable="true"
android:focusableInTouchMode="true"/>
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="市"
android:textColor="#000"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"/>
android:id="@+id/area_picker"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:focusable="true"
android:focusableInTouchMode="true"/>
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="区"
android:textColor="#000"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"/>
MainActivity :
实现这个功能，遇到了的2个问题和坑，文章最后给出详细解决
public class MainActivity extends AppCompatActivity {
private static final String DB_NAME = "mydb.db"; //数据库名称
private NumberPicker provincePicker, cityPicker, areaPicker; //省市区选择器
private AddressManager manager; //自定义的地址管理器
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//拷贝assets下的文件"mydb.db"到 应用的databases目录下
try {
MyUtils.copyAssetsToDB(this, DB_NAME);
} catch (IOException e) {
e.printStackTrace();
}
//初始化“地址管理器”对象
manager = new AddressManager(getDatabasePath(DB_NAME).getPath());
initView();
initProvince();
}
//初始化View
private void initView() {
provincePicker = (NumberPicker) findViewById(R.id.province_picker);
cityPicker = (NumberPicker) findViewById(R.id.city_picker);
areaPicker = (NumberPicker) findViewById(R.id.area_picker);
}
//设置“省份”选择器的数据
private void initProvince() {
List provinceList = manager.getProvinces(); //获取所有的省份
//设置省份的值
final String[] provinces = provinceList.toArray(new String[provinceList.size()]);
provincePicker.setDisplayedValues(provinces);
provincePicker.setMinValue(0); //设置第一个值
provincePicker.setMaxValue(provinces.length - 1); //设置最后一个值
//默认的省份的位置
int defaultProvince = provinces.length / 2 == 0 ? provinces.length / 2 : provinces.length / 2 + 1;
provincePicker.setValue(defaultProvince); //设置当前值
//根据当前默认的省份来设置对应的市
showCityByProvince(provinces[provincePicker.getValue()]);
//省份的选择事件
provincePicker.setOnValueChangedListener(new NumberPicker.OnValueChangeListener() {
@Override
public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
Log.i("tag", "newVal--->" + newVal);
showCityByProvince(provinces[newVal]);
}
});
}
//根据选择的省份名来显示城市名
private void showCityByProvince(String province) {
List cityList = manager.getCities(province);
//设置城市的值
final String[] cities = cityList.toArray(new String[cityList.size()]);
cityPicker.setDisplayedValues(null); //清空之前的选择的数据
cityPicker.setMinValue(0); //设置第一个值
cityPicker.setMaxValue(cities.length - 1); //设置最后一个值
cityPicker.setDisplayedValues(cities);
//根据当前默认的城市来设置对应的区
showAreaByCity(cities[cityPicker.getValue()]);
//城市的选择事件
cityPicker.setOnValueChangedListener(new NumberPicker.OnValueChangeListener() {
@Override
public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
showAreaByCity(cities[newVal]);
}
});
}
//根据选择的城市名来显示区名
private void showAreaByCity(String city) {
List areaList = manager.getAreas(city);
//设置区的值
String[] areas = areaList.toArray(new String[areaList.size()]);
areaPicker.setDisplayedValues(null);
areaPicker.setMinValue(0); //设置第一个值
areaPicker.setMaxValue(areas.length - 1); //设置最后一个值
areaPicker.setDisplayedValues(areas);
}
}
**AddressManager **
public class AddressManager {
//ssq表的字段的名字
private static final String TABLE_NAME = "ssq"; //表名
private static final String PROVINCE = "province"; //省份名称
private static final String CITY = "city"; //市的名称
private static final String AREA = "area"; //区的名称
private SQLiteDatabase database; //sqlite数据库对象
public AddressManager(String dbPath) {
database = SQLiteDatabase.openOrCreateDatabase(dbPath, null);
}
public List getProvinces() {
String sql = "select distinct " + PROVINCE + " from " + TABLE_NAME;
Cursor cursor = database.rawQuery(sql, null);
List provinceList = new ArrayList<>();
if (cursor != null) {
while (cursor.moveToNext()) {
String province = cursor.getString(cursor.getColumnIndex("province"));
Log.i("tag", "province----->" + province);
provinceList.add(province);
}
cursor.close();
}
return provinceList;
}
public List getCities(String province) {
String sql = "select distinct " + CITY + " from " + TABLE_NAME + " where " + PROVINCE + " = ?";
Cursor cursor = database.rawQuery(sql, new String[]{province});
List addressList = new ArrayList<>();
while (cursor.moveToNext()) {
String city = cursor.getString(cursor.getColumnIndex(CITY));
Log.i("tag", "city----->" + city);
addressList.add(city);
}
//关闭游标
cursor.close();
return addressList;
}
public List getAreas(String city) {
//获取指定市的所有区的列表的sql语句
String sql = "select distinct " + AREA + " from " + TABLE_NAME + " where " + CITY + " = ?";
Cursor cursor = database.rawQuery(sql, new String[]{city});
List addressList = new ArrayList<>();
while (cursor.moveToNext()) {
//获取区的名称
String area = cursor.getString(cursor.getColumnIndex(AREA));
Log.i("tag", "area----->" + area);
//把所有的区添加到List集合
addressList.add(area);
}
//关闭游标
cursor.close();
return addressList;
}
}
---------------------------------------到此大功告成----------------------------------------------
效果图：
省市区三级联动效果.PNG
遇到的问题和坑
一、NumberPicker通常是只能显示数字，如何让它显示文字呢？
np = (NumberPicker) findViewById(R.id.numberPicker1);
String[] city = {"北京","上海","广州","深圳","成都","天津"};
np.setDisplayedValues(city);
np.setMinValue(0); //设置显示的第一个数据
np.setMaxValue(city.length - 1); //设置显示的最后一个数据
二、关于NumberPicker滑动选择时出现数组下标越界的问题
解决方案一
1、当前NumberPicker的最大值大于数组大小时，先setMaxValue再setDisplayedValues。
2、当前NumberPicker的最大值小于数组大小时，先setDisplayedValues再setMaxValue。
private void updateCitySelector() {
int oldMax = cityPicker.getMaxValue();
int newMax = mCitys.length - 1;
if(newMax > oldMax) {
cityPicker.setDisplayedValues(mCitys);
cityPicker.setMaxValue(newMax);
} else {
cityPicker.setMaxValue(newMax);
cityPicker.setDisplayedValues(mCitys);
}
}
解决方案二(推荐)：
在设置最大值和最新数组数据前，先将之前设置过的数据设为null。
private void updateCitySelector() {
cityPicker.setDisplayedValues(null);
cityPicker.setMaxValue(mCitys.length - 1);
cityPicker.setDisplayedValues(mCitys);
}