小贝子编程

无法使用光标从数据库中成功检索微调器所选项目文本以填充我的应用中的联系人列表项目



我的应用有一个献血者的注册屏幕，血型字段是一个微调器。我将所有捐赠者信息保存在SQLite数据库中。现在我需要检索它并将其显示为一个列表，该列表显示了所有注册的献血者及其血型。

我该怎么做？

我在下面附加了我的所有代码。主要问题出现在RegisterActivity.java和DonorList.java中。

注册活动.java

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.Toast;
public class RegisterActivity extends AppCompatActivity {
EditText edtname, edtnumber;
Spinner spblood;
Button btnregister, btnlist;
public static SQLiteHelper sqLiteHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
init();
Spinner spinner = findViewById(R.id.blood_selector);
// Create an ArrayAdapter using the string array and a default spinner layout
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,
R.array.blood_type, android.R.layout.simple_spinner_item);
// Specify the layout to use when the list of choices appears
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
// Apply the adapter to the spinner
spinner.setAdapter(adapter);
sqLiteHelper = new SQLiteHelper(this, "Donors.sqlite", null, 1);
sqLiteHelper.queryData("CREATE TABLE IF NOT EXISTS DONORS (Id INTEGER PRIMARY KEY AUTOINCREMENT, name VARCHAR, number VARCHAR, blood VARCHAR)");
btnregister.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
try {
sqLiteHelper.insertData(
edtname.getText().toString().trim(),
edtnumber.getText().toString().trim(),
spblood
);
}
catch (Exception e) {
e.printStackTrace();
}
}
});
btnlist.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(RegisterActivity.this, DonorList.class);
startActivity(intent);
}
});
}
private void init() {
edtname = findViewById(R.id.name_input);
edtnumber = findViewById(R.id.numberinput);
spblood = findViewById(R.id.blood_selector);
btnregister = findViewById(R.id.register_button);
btnlist = findViewById(R.id.list_button);
}
}

捐赠者名单.java

import android.database.Cursor;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.widget.ListView;
import android.widget.Spinner;
import java.util.ArrayList;
public class DonorList extends AppCompatActivity {
ListView listView;
ArrayList<Donor> list;
DonorListAdapter adapter = null;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.contacts_list);
list = new ArrayList<>();
adapter = new DonorListAdapter(this, R.layout.activity_main, list);
listView.setAdapter(adapter);
Cursor cursor = RegisterActivity.sqLiteHelper.getData("SELECT * FROM DONORS");
list.clear();
while (cursor.moveToNext()) {
String name = cursor.getString(1);
String number = cursor.getString(2);
String blood = cursor.getString(3);
list.add(new Donor(name, number, blood));
}
adapter.notifyDataSetChanged();
}
}

捐赠者.java

import android.widget.Spinner;
public class Donor {
private String name;
private String number;
private Spinner blood;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
public Spinner getBlood() {
return blood;
}
public void setBlood(Spinner blood) {
this.blood = blood;
}
public Donor(String name, String number, Spinner blood) {
this.name = name;
this.number = number;
this.blood = blood;
}
}

SQLiteHelper.java

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteStatement;
import android.widget.Spinner;
public class SQLiteHelper extends SQLiteOpenHelper {
public SQLiteHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
public void queryData(String sql) {
SQLiteDatabase database = getWritableDatabase();
database.execSQL(sql);
}
public void insertData(String name, String number, Spinner blood) {
SQLiteDatabase database = getWritableDatabase();
String sql = "INSERT INTO DONORS (name, number, blood) values (?, ?, ?)";
SQLiteStatement statement = database.compileStatement(sql);
statement.clearBindings();
statement.bindString(1, name);
statement.bindString(2, number);
statement.bindString(3, blood.getSelectedItem().toString());
statement.executeInsert();
}
public Cursor getData(String sql) {
SQLiteDatabase database = getReadableDatabase();
return database.rawQuery(sql, null);
}
}

DonorListAdapter.java

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
import java.util.ArrayList;
public class DonorListAdapter extends BaseAdapter {
private Context context;
private int layout;
private ArrayList<Donor> donorList;
public DonorListAdapter(Context context, int layout, ArrayList<Donor> donorList) {
this.context = context;
this.layout = layout;
this.donorList = donorList;
}
@Override
public int getCount() {
return donorList.size();
}
@Override
public Object getItem(int position) {
return donorList.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
private class ViewHolder {
TextView txtname, txtnumber, txtblood;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View row = convertView;
ViewHolder holder = new ViewHolder();
if (row == null) {
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
if (inflater != null) {
row = inflater.inflate(layout, null);
}
if (row != null) {
holder.txtname = row.findViewById(R.id.name_input);
}
if (row != null) {
holder.txtnumber = row.findViewById(R.id.numberinput);
}
if (row != null) {
holder.txtblood = (TextView) row.findViewById(R.id.blood_selector);
}
if (row != null) {
row.setTag(holder);
}
}
else {
holder = (ViewHolder) row.getTag();
}
Donor donor = donorList.get(position);
holder.txtname.setText(donor.getName());
holder.txtnumber.setText(donor.getNumber());
holder.txtblood.setText(donor.getBlood().toString());
return row;
}
}

activity_main.xml

<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.lumen.dayem.blooddonor.MainActivity">

<ListView
android:id="@+id/contacts_list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:choiceMode="singleChoice">
</ListView>
</LinearLayout>

activity_register.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<EditText
android:id="@+id/name_input"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/person_name"
android:ems="10"
android:inputType="textCapWords"
android:layout_marginBottom="5sp" />
<EditText
android:id="@+id/numberinput"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/hint"
android:ems="10"
android:inputType="phone"
android:layout_marginBottom="5sp" />
<TextView
android:id="@+id/blood"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/blood_type"
android:layout_marginBottom="10sp"/>
<Spinner
android:id="@+id/blood_selector"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:entries="@array/blood_type"
android:prompt="@string/blood_select"
android:layout_marginBottom="5sp"/>
<Button
android:id="@+id/register_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/register" />
<Button
android:id="@+id/list_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/show_donors" />
</LinearLayout>

contact_item.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/contact_name"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="@string/contact_name"
android:textSize="22sp"/>
<TextView
android:id="@+id/contact_number"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textAppearance="?android:textAppearanceSmall"
android:text="@string/contact_number"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginLeft="29sp"
android:layout_marginStart="29sp"
android:layout_marginTop="31sp" />
<TextView
android:id="@+id/contact_blood"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textAppearance="?android:textAppearanceMedium"
android:text="@string/blood_type"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginLeft="300sp"
android:layout_marginStart="300sp"
android:layout_marginTop="30sp"/>
</RelativeLayout>

你的类Donor似乎有Spinner型的野外血统。我将类型更改为String，因为数据类不应包含任何View：

public class Donor
{
private String name;
private String number;
private String blood;
// Getters and Setters here...
public Donor(String name, String number, String blood) {
this.name = name;
this.number = number;
this.blood = blood;
}
}

SQLiteHelper应具有静态getInstance()方法，因此您可以避免将其作为RegisterActivity中的静态字段。另外，我认为应该封装数据库设置。Activity不需要了解有关数据库实现的任何信息。所以我把DDL移到了SQLiteHelper的onCreate()上，并删除了queryData()。出于同样的原因，我将getData(String sql)更改为getDonors()。最后，insertData()应该将数据作为参数，而不是Views。因此，不应传递Spinner，而应传递所选项目的值。

我的 SQLiteHelper 版本.java：

public class SQLiteHelper extends SQLiteOpenHelper{
private static SQLiteHelper sqliteHelper;
private static String dbName = "Donors.sqlite";
private static int version = 1;
private static final String CREATE_TABLE_DONORS = "CREATE TABLE IF NOT EXISTS DONORS (Id INTEGER PRIMARY KEY AUTOINCREMENT, name VARCHAR, number VARCHAR, blood VARCHAR)";
/**
* We use the application Context under the hood because this helps to avoid Exceptions
* @param ctx
*/
private SQLiteHelper(Context ctx){
super(ctx.getApplicationContext(), dbName, null, version);
}
/**
* SQLiteHelper as a Singleton
* @param ctx any Context
* @return x
*/
public static SQLiteHelper getInstance(Context ctx)
{
if(sqliteHelper == null){
sqliteHelper = new SQLiteHelper(ctx);
}
return sqliteHelper;
}
@Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(CREATE_TABLE_DONORS);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
// necessary if you have a new database version
}
public void insertData(String name, String number, String blood) {
SQLiteDatabase database = getWritableDatabase();
String sql = "INSERT INTO DONORS (name, number, blood) values (?, ?, ?)";
SQLiteStatement statement = database.compileStatement(sql);
statement.clearBindings();
statement.bindString(1, name);
statement.bindString(2, number);
statement.bindString(3, blood);
statement.executeInsert();
}
public Cursor getDonors() {
String sql = "SELECT * FROM DONORS";
SQLiteDatabase database = getReadableDatabase();
return database.rawQuery(sql, null);
}
}

更新的 RegisterActivity.java(请注意，我摆脱了局部变量微调器，只使用了spblood)：

public class RegisterActivity extends AppCompatActivity
{
private EditText edtname, edtnumber;
private Spinner spblood;
private Button btnregister, btnlist;
private SQLiteHelper sqLiteHelper;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
init();
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,
R.array.blood_type, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spblood.setAdapter(adapter);
sqLiteHelper = SQLiteHelper.getInstance(this);
btnregister.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
try {
sqLiteHelper.insertData(
edtname.getText().toString().trim(),
edtnumber.getText().toString().trim(),
spblood.getSelectedItem().toString()
);
}
catch (Exception e) {
e.printStackTrace();
}
}
});
btnlist.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(RegisterActivity.this, DonorList.class);
startActivity(intent);
}
});
}
private void init() {
edtname = findViewById(R.id.name_input);
edtnumber = findViewById(R.id.numberinput);
spblood = findViewById(R.id.blood_selector);
btnregister = findViewById(R.id.register_button);
btnlist = findViewById(R.id.list_button);
}
}

对DonorList和适配器的更改是由于我对SQLiteHelper和Donor所做的更改。除此之外，还需要将列表行的资源 ID 传递给适配器的构造函数，而不是活动布局的资源 ID。同样，R.id...列表行中TextView的值必须与 contact_item.xml 中的值匹配

捐赠者名单.java

public class DonorList extends AppCompatActivity
{
private ListView listView;
private ArrayList<Donor> list;
private DonorListAdapter adapter = null;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.contacts_list);
list = new ArrayList<>();
adapter = new DonorListAdapter(this, R.layout.contact_item, list);
listView.setAdapter(adapter);
Cursor cursor = SQLiteHelper.getInstance(this).getDonors();
list.clear();
while (cursor.moveToNext()) {
String name = cursor.getString(1);
String number = cursor.getString(2);
String blood = cursor.getString(3);
list.add(new Donor(name, number, blood));
}
adapter.notifyDataSetChanged();
}
}

最后，适配器：

public class DonorListAdapter extends BaseAdapter
{
private Context context;
private int layout;
private ArrayList<Donor> donorList;
public DonorListAdapter(Context context, int layout, ArrayList<Donor> donorList) {
this.context = context;
this.layout = layout;
this.donorList = donorList;
}
@Override
public int getCount() {
return donorList.size();
}
@Override
public Object getItem(int position) {
return donorList.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
private class ViewHolder {
TextView txtname, txtnumber, txtblood;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View row = convertView;
if (row == null) {
ViewHolder holder = new ViewHolder();
row = LayoutInflater.from(context).inflate(layout, null);
holder.txtname = (TextView)row.findViewById(R.id.contact_name);
holder.txtnumber = (TextView)row.findViewById(R.id.contact_number);
holder.txtblood = (TextView) row.findViewById(R.id.contact_blood);
row.setTag(holder);
}
ViewHolder viewHolder = (ViewHolder) row.getTag();
Donor donor = donorList.get(position);
viewHolder.txtname.setText(donor.getName());
viewHolder.txtnumber.setText(donor.getNumber());
viewHolder.txtblood.setText(donor.getBlood());
return row;
}
}

享受！

相关内容

最新更新


热门标签：

javascript python java c# php android html jquery c++ css ios sql mysql arrays asp.net json python-3.x ruby-on-rails .net sql-server django objective-c excel regex ruby linux ajax iphone xml vba spring asp.net-mvc database wordpress string postgresql wpf windows xcode bash git oracle list vb.net multithreading eclipse algorithm macos powershell visual-studio image forms numpy scala function api selenium