1
我的应用程序包含MainActivity类和几个片段。 其中一个是我希望它能够与我的数据库进行交互的注册片段，它应该只包含一个名为USERS的表，我将向其中CRUD。 我已经打开了MySQLiteOpenHelper类，它扩展了SQLiteOpenHelper并创建了一个User类。 我已经声明：从片段访问SQLite数据库
MySQLiteOpenHelper db = new MySQLiteOpenHelper(this);
。 我的问题是我如何与碎片交互这个数据库？ 我试着下面的代码，但它不工作：
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
public class registration extends Fragment {
public registration() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.registration, container,
false);
return rootView;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onActivityCreated(savedInstanceState);
final EditText etFirstName = (EditText) getActivity().findViewById(
R.id.etFirstName);
final EditText etLastName = (EditText) getActivity().findViewById(
R.id.etLastName);
final EditText etEmail = (EditText) getActivity().findViewById(
R.id.etEmail);
final EditText etUsername = (EditText) getActivity().findViewById(
R.id.etUsername);
final EditText etPassword = (EditText) getActivity().findViewById(
R.id.etPassword);
Button bDone = (Button) getActivity().findViewById(R.id.bDone);
bDone.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
MySQLiteOpenHelper db = new MySQLiteOpenHelper(null);//do I need this??
db.addUser(new User(etFirstName.getText().toString(),
etLastName.getText().toString(), etEmail.getText()
.toString(), etUsername.getText().toString(),
etPassword.getText().toString()));
}
});
}
}
现在发生的是那一刻我点击完成按钮的应用程序的迷恋...... 感谢的！
MySQLiteOpenHelper看起来是这样的：
import java.util.LinkedList;
import java.util.List;
import android.R.string;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class MySQLiteOpenHelper extends SQLiteOpenHelper {
private static final int DATABASE_VERSION=1;
private static final String DATABASE_NAME="MyDB";
private static final String TABLE_USERS="USERS";
private static final String FIRST_NAME="First_name";
private static final String LAST_NAME="Last_name";
private static final String EMAIL="Email";
private static final String USERNAME="Username";
private static final String PASSWORD="Password";
private static final String COLUMNS[]={FIRST_NAME, LAST_NAME, EMAIL, USERNAME, PASSWORD};
public MySQLiteOpenHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
String CREATE_MyDB_TABLE = "CREATE TABLE USERS (" +
"First_name TEXT, " +
"Last_name TEXT, "+
"Email KEY TEXT NOT NULL, "+
"Username TEXT NOT NULL, "+
"Password TEXT NOT NULL)";
db.execSQL(CREATE_MyDB_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS USERS");
this.onCreate(db);
}
public void addUser(User user){
Log.d("addUser", user.toString());
SQLiteDatabase db=this.getWritableDatabase();
ContentValues values=new ContentValues();
values.put(FIRST_NAME, user.getFirstName());
values.put(LAST_NAME, user.getLastName());
values.put(EMAIL, user.getEmail());
values.put(USERNAME, user.getUsername());
values.put(PASSWORD, user.getPassword());
db.insert(TABLE_USERS, null, values);
db.close();
}
public User getUser(String Email){
SQLiteDatabase db=this.getReadableDatabase();
Cursor cursor=
db.query(TABLE_USERS, COLUMNS, "Email =?", new String[] {String.valueOf(Email)}, null, null, null);
if (cursor != null)
cursor.moveToFirst();
User user=new User();
user.setFirstName(cursor.getString(0));
user.setLastName(cursor.getString(1));
user.setEmail(cursor.getString(2));
user.setUsername(cursor.getString(3));
user.setPassword(cursor.getString(4));
Log.d("getUser ("+Email+")", user.toString());
return user;
}
public List<User> getAllUsers(){
List<User> users=new LinkedList<User>();
String query="SELECT * FROM "+TABLE_USERS;
SQLiteDatabase db=this.getWritableDatabase();
Cursor cursor= db.rawQuery(query, null);
User user=null;
if (cursor.moveToFirst()){
do{
user=new User();
user.setFirstName(cursor.getString(0));
user.setLastName(cursor.getString(1));
user.setEmail(cursor.getString(2));
user.setUsername(cursor.getString(3));
user.setPassword(cursor.getString(4));
users.add(user);
} while (cursor.moveToNext());
}
Log.d("getAllUsers", users.toString());
return users;
}
public int updateUser(User user){
SQLiteDatabase db=this.getWritableDatabase();
ContentValues values=new ContentValues();
values.put(FIRST_NAME, user.getFirstName());
values.put(LAST_NAME, user.getLastName());
values.put(EMAIL, user.getEmail());
values.put(USERNAME, user.getUsername());
values.put(PASSWORD, user.getPassword());
int i=db.update(TABLE_USERS, values, "Email =?", new String[]{String.valueOf(user.getEmail())});
db.close();
return i;
}
public void deleteUser(User user){
SQLiteDatabase db=this.getWritableDatabase();
db.delete(TABLE_USERS, "Email =?", new String[]{String.valueOf(user.getEmail())});
db.close();
Log.d("deleteUser", user.toString());
}
}
的logcat：
04-18 12:16:09.132: E/Trace(1051): error opening trace file: No such file or directory (2)
04-18 12:16:09.404: D/libEGL(1051): loaded /system/lib/egl/libEGL_emulation.so
04-18 12:16:09.416: D/(1051): HostConnection::get() New Host Connection established 0xb9324060, tid 1051
04-18 12:16:09.492: D/libEGL(1051): loaded /system/lib/egl/libGLESv1_CM_emulation.so
04-18 12:16:09.492: D/libEGL(1051): loaded /system/lib/egl/libGLESv2_emulation.so
04-18 12:16:09.672: W/EGL_emulation(1051): eglSurfaceAttrib not implemented
04-18 12:16:09.708: D/OpenGLRenderer(1051): Enabling debug mode 0
04-18 12:16:09.800: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb931a8e0): name, size, mSize = 1, 1048576, 1048576
04-18 12:16:09.960: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9331d10): name, size, mSize = 2, 5184, 1053760
04-18 12:16:10.068: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9309b60): name, size, mSize = 4, 20736, 1074496
04-18 12:16:10.072: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb932d4b8): name, size, mSize = 5, 9216, 1083712
04-18 12:16:10.140: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9312810): name, size, mSize = 7, 7488, 1091200
04-18 12:16:10.152: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9325d70): name, size, mSize = 8, 100, 1091300
04-18 12:16:10.212: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb93176a0): name, size, mSize = 10, 7488, 1098788
04-18 12:16:10.252: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9373798): name, size, mSize = 11, 7488, 1106276
04-18 12:16:10.336: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9315840): name, size, mSize = 12, 2304, 1108580
04-18 12:16:42.528: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9378b38): name, size, mSize = 78, 7488, 1116068
04-18 12:16:42.800: D/dalvikvm(1051): GC_CONCURRENT freed 142K, 3% free 8216K/8391K, paused 14ms+0ms, total 25ms
04-18 12:16:44.200: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9308998): name, size, mSize = 85, 7488, 1123556
04-18 12:16:44.216: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9316848): name, size, mSize = 86, 7488, 1131044
04-18 12:16:53.192: D/addUser(1051): First name: dsfLast name: dsfdsfEmail: dsfdsfUsername: Password:
04-18 12:16:53.196: D/AndroidRuntime(1051): Shutting down VM
04-18 12:16:53.196: W/dalvikvm(1051): threadid=1: thread exiting with uncaught exception (group=0xa627b288)
04-18 12:16:53.200: E/AndroidRuntime(1051): FATAL EXCEPTION: main
04-18 12:16:53.200: E/AndroidRuntime(1051): java.lang.NullPointerException
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224)
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
04-18 12:16:53.200: E/AndroidRuntime(1051): at com.craftyonhand.www.MySQLiteOpenHelper.addUser(MySQLiteOpenHelper.java:60)
04-18 12:16:53.200: E/AndroidRuntime(1051): at com.craftyonhand.www.registration$1.onClick(registration.java:47)
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.view.View.performClick(View.java:4084)
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.view.View$PerformClick.run(View.java:16966)
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.os.Handler.handleCallback(Handler.java:615)
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.os.Handler.dispatchMessage(Handler.java:92)
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.os.Looper.loop(Looper.java:137)
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.app.ActivityThread.main(ActivityThread.java:4745)
04-18 12:16:53.200: E/AndroidRuntime(1051): at java.lang.reflect.Method.invokeNative(Native Method)
04-18 12:16:53.200: E/AndroidRuntime(1051): at java.lang.reflect.Method.invoke(Method.java:511)
04-18 12:16:53.200: E/AndroidRuntime(1051): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
04-18 12:16:53.200: E/AndroidRuntime(1051): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
04-18 12:16:53.200: E/AndroidRuntime(1051): at dalvik.system.NativeStart.main(Native Method)
04-18 12:16:55.792: I/Process(1051): Sending signal. PID: 1051 SIG: 9
你好！我是否也应该在活动中保留声明？ – evyamiz
如果你需要它，你可以保留它。如果你不这样做，你可以删除它。 – laalto
我明白你的意思，如果我不打算与活动中的数据库进行交互，我可以删除这个声明？！太棒了，我会删除它！ – evyamiz