使用简单的游标适配器使用 SQLite 数据库填充 listView
Populating a listView with SQLite database using simple cursor adapter
我有一个包含 3 列和一个 ListView 的 SQLite 数据库。我想用 SQLite 填充 listView。我认为我的编码是正确的，但是当我想查看 listView 时我的应用程序崩溃了。
下面是我的示例代码：
MainActivity.java
public class MainActivity extends ActionBarActivity {
Registration register;
EditText name, grade;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
name = (EditText) findViewById(R.id.editName);
grade = (EditText) findViewById(R.id.editGrade);
register = new Registration(this);
}
public void addButton(View view) {
String eName = name.getText().toString();
String eGrade = grade.getText().toString();
register.insert(eName, eGrade);
name.setText("");
grade.setText("");
Toast.makeText(this, "Item added", Toast.LENGTH_SHORT).show();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
if (id == R.id.sqlView) {
Intent intent = new Intent(this, ViewDatabase.class);
startActivity(intent);
}
return super.onOptionsItemSelected(item);
}}
sqlOpenHelper.java
public class sqlOpenHelper extends SQLiteOpenHelper{
public static final String DATABASE_NAME = "FirstBase.db";
public static final String TABLE_NAME = "First_table";
public static final int VERSION = 1;
public static final String C_KEY_ID = "ID";
public static final String C_name = "Name";
public static final String C_grade = "Grade";
public static final String SCRIPT = "CREATE TABLE " + TABLE_NAME + " ( " +
C_KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
C_name + " TEXT NOT NULL, " +
C_grade + " TEXT NOT NULL " + ");";
public sqlOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(SCRIPT);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
String DELETE_SCRIPT = "DROP TABLE IF EXISTS " + TABLE_NAME;
db.execSQL(DELETE_SCRIPT);
onCreate(db);
}}
Registration.java
public class Registration {
SQLiteDatabase db;
sqlOpenHelper oh;
Context context;
public Registration(Context context) {
this.context = context;
}
public Cursor print() {
oh = new sqlOpenHelper(context, oh.DATABASE_NAME, null, oh.VERSION);
String[] columns = {oh.C_KEY_ID, oh.C_name, oh.C_grade};
db = oh.getWritableDatabase();
Cursor cursor = db.query(sqlOpenHelper.TABLE_NAME, columns, null, null, null, null, null);
return cursor;
}
public void insert(String name, String grade) {
ContentValues values = new ContentValues();
values.put(oh.C_name, name);
values.put(oh.C_grade, grade);
oh = new sqlOpenHelper(context, oh.DATABASE_NAME, null, oh.VERSION);
db = oh.getWritableDatabase();
db.insert(oh.TABLE_NAME, null, values);
db.close();
}}
ViewDatabase.java
public class ViewDatabase extends ActionBarActivity {
private static final String[] from = new String[] {
sqlOpenHelper.C_KEY_ID,
sqlOpenHelper.C_name,
sqlOpenHelper.C_grade};
private static final int[] to = new int[] {
R.id.rId,
R.id.rName,
R.id.rGrade};
Registration register;
sqlOpenHelper oh;
SQLiteDatabase db;
Cursor cursor;
SimpleCursorAdapter cursorAdapter;
ListView list;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_database);
list = (ListView) findViewById(R.id.listView);
oh = new sqlOpenHelper(this, oh.DATABASE_NAME, null, oh.VERSION);
db = oh.getReadableDatabase();
register = new Registration(this);
cursor = register.print();
cursorAdapter = new SimpleCursorAdapter(this, R.layout.rows, cursor, from, to);
list.setAdapter(cursorAdapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_view_database, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}}
activity_main.xml
<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=".MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:paddingTop="10dp"
android:orientation="horizontal"
android:id="@+id/name">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="10dp"
android:text="Name"
android:textSize="20sp" />
<EditText
android:id="@+id/editName"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:ems="10"
android:inputType="textPersonName"
android:hint="Name" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:orientation="horizontal"
android:layout_below="@id/name">
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="10dp"
android:text="Grade"
android:textSize="20sp" />
<EditText
android:id="@+id/editGrade"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:ems="10"
android:inputType="number"
android:hint="Grade"/>
</LinearLayout>
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:text="Add"
android:onClick="addButton"/>
</RelativeLayout>
rows.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<TextView
android:id="@+id/rId"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:textSize="30sp"/>
<TextView
android:id="@+id/rName"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:textSize="30sp"/>
<TextView
android:id="@+id/rGrade"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:textSize="30sp"/>
</LinearLayout>
adtivity_view_database.xml
<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" android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context="com.example.brothers.sql.ViewDatabase">
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/listView"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true" />
</RelativeLayout>
听说是logcat
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.brothers.sql/com.example.brothers.sql.ViewDatabase}: java.lang.IllegalArgumentException: column '_id' does not exist
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2343)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2395)
at android.app.ActivityThread.access0(ActivityThread.java:162)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1364)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5371)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:132)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IllegalArgumentException: column '_id' does not exist
看着你的logcat：
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.brothers.sql/com.example.brothers.sql.ViewDatabase}: java.lang.IllegalArgumentException: column '_id' does not exist
看起来，您的数据库中没有名为 '_id' 的列，但是，您在代码中 using/calling 它。
问题已解决。我在 Content Provider 部分的 developer.android.com 中找到了答案：
Note: A provider isn't required to have a primary key, and it isn't required to use _ID as the column name of a primary key if one is present. However, if you want to bind data from a provider to a ListView, one of the column names has to be _ID. This requirement is explained in more detail in the section Displaying query results.
听说是原文link:
http://developer.android.com/guide/topics/providers/content-provider-basics.html
我有一个包含 3 列和一个 ListView 的 SQLite 数据库。我想用 SQLite 填充 listView。我认为我的编码是正确的，但是当我想查看 listView 时我的应用程序崩溃了。 下面是我的示例代码：
MainActivity.java
public class MainActivity extends ActionBarActivity {
Registration register;
EditText name, grade;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
name = (EditText) findViewById(R.id.editName);
grade = (EditText) findViewById(R.id.editGrade);
register = new Registration(this);
}
public void addButton(View view) {
String eName = name.getText().toString();
String eGrade = grade.getText().toString();
register.insert(eName, eGrade);
name.setText("");
grade.setText("");
Toast.makeText(this, "Item added", Toast.LENGTH_SHORT).show();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
if (id == R.id.sqlView) {
Intent intent = new Intent(this, ViewDatabase.class);
startActivity(intent);
}
return super.onOptionsItemSelected(item);
}}
sqlOpenHelper.java
public class sqlOpenHelper extends SQLiteOpenHelper{
public static final String DATABASE_NAME = "FirstBase.db";
public static final String TABLE_NAME = "First_table";
public static final int VERSION = 1;
public static final String C_KEY_ID = "ID";
public static final String C_name = "Name";
public static final String C_grade = "Grade";
public static final String SCRIPT = "CREATE TABLE " + TABLE_NAME + " ( " +
C_KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
C_name + " TEXT NOT NULL, " +
C_grade + " TEXT NOT NULL " + ");";
public sqlOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(SCRIPT);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
String DELETE_SCRIPT = "DROP TABLE IF EXISTS " + TABLE_NAME;
db.execSQL(DELETE_SCRIPT);
onCreate(db);
}}
Registration.java
public class Registration {
SQLiteDatabase db;
sqlOpenHelper oh;
Context context;
public Registration(Context context) {
this.context = context;
}
public Cursor print() {
oh = new sqlOpenHelper(context, oh.DATABASE_NAME, null, oh.VERSION);
String[] columns = {oh.C_KEY_ID, oh.C_name, oh.C_grade};
db = oh.getWritableDatabase();
Cursor cursor = db.query(sqlOpenHelper.TABLE_NAME, columns, null, null, null, null, null);
return cursor;
}
public void insert(String name, String grade) {
ContentValues values = new ContentValues();
values.put(oh.C_name, name);
values.put(oh.C_grade, grade);
oh = new sqlOpenHelper(context, oh.DATABASE_NAME, null, oh.VERSION);
db = oh.getWritableDatabase();
db.insert(oh.TABLE_NAME, null, values);
db.close();
}}
ViewDatabase.java
public class ViewDatabase extends ActionBarActivity {
private static final String[] from = new String[] {
sqlOpenHelper.C_KEY_ID,
sqlOpenHelper.C_name,
sqlOpenHelper.C_grade};
private static final int[] to = new int[] {
R.id.rId,
R.id.rName,
R.id.rGrade};
Registration register;
sqlOpenHelper oh;
SQLiteDatabase db;
Cursor cursor;
SimpleCursorAdapter cursorAdapter;
ListView list;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_database);
list = (ListView) findViewById(R.id.listView);
oh = new sqlOpenHelper(this, oh.DATABASE_NAME, null, oh.VERSION);
db = oh.getReadableDatabase();
register = new Registration(this);
cursor = register.print();
cursorAdapter = new SimpleCursorAdapter(this, R.layout.rows, cursor, from, to);
list.setAdapter(cursorAdapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_view_database, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}}
activity_main.xml
<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=".MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:paddingTop="10dp"
android:orientation="horizontal"
android:id="@+id/name">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="10dp"
android:text="Name"
android:textSize="20sp" />
<EditText
android:id="@+id/editName"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:ems="10"
android:inputType="textPersonName"
android:hint="Name" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:orientation="horizontal"
android:layout_below="@id/name">
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="10dp"
android:text="Grade"
android:textSize="20sp" />
<EditText
android:id="@+id/editGrade"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:ems="10"
android:inputType="number"
android:hint="Grade"/>
</LinearLayout>
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:text="Add"
android:onClick="addButton"/>
</RelativeLayout>
rows.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<TextView
android:id="@+id/rId"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:textSize="30sp"/>
<TextView
android:id="@+id/rName"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:textSize="30sp"/>
<TextView
android:id="@+id/rGrade"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:textSize="30sp"/>
</LinearLayout>
adtivity_view_database.xml
<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" android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context="com.example.brothers.sql.ViewDatabase">
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/listView"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true" />
</RelativeLayout>
听说是logcat
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.brothers.sql/com.example.brothers.sql.ViewDatabase}: java.lang.IllegalArgumentException: column '_id' does not exist
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2343)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2395)
at android.app.ActivityThread.access0(ActivityThread.java:162)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1364)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5371)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:132)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IllegalArgumentException: column '_id' does not exist
看着你的logcat：
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.brothers.sql/com.example.brothers.sql.ViewDatabase}: java.lang.IllegalArgumentException: column '_id' does not exist
看起来，您的数据库中没有名为 '_id' 的列，但是，您在代码中 using/calling 它。
问题已解决。我在 Content Provider 部分的 developer.android.com 中找到了答案：
Note: A provider isn't required to have a primary key, and it isn't required to use _ID as the column name of a primary key if one is present. However, if you want to bind data from a provider to a ListView, one of the column names has to be _ID. This requirement is explained in more detail in the section Displaying query results.
听说是原文link:
http://developer.android.com/guide/topics/providers/content-provider-basics.html