SQLiteExample.java
package com.example.myfirstapp;
import android.app.Activity;
import android.app.Dialog;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class SQLiteExample extends Activity implements OnClickListener {
EditText sqlName, sqlHotness;
Button sqlUpdate, sqlView;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.sqliteexample);
sqlName = (EditText) findViewById(R.id.etName);
sqlHotness = (EditText) findViewById(R.id.etSQLHotness);
sqlUpdate = (Button) findViewById(R.id.bSQLUpdate);
sqlView = (Button) findViewById(R.id.bSQLOpenView);
sqlUpdate.setOnClickListener(this);
sqlView.setOnClickListener(this);
}
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
switch (arg0.getId()) {
case R.id.bSQLUpdate:
boolean didItWork = true;
try {
String name;
name = sqlName.getText().toString();
String hot;
hot = sqlHotness.getText().toString();
HotOrNot entry = new HotOrNot(SQLiteExample.this);
entry.open();
entry.createEntry(name, hot);
entry.close();
} catch (Exception e) {
didItWork = false;
String error;
error = e.toString();
Dialog d = new Dialog(this);
TextView tv = new TextView(this);
d.setTitle("Nop");
tv.setText(error);
d.setContentView(tv);
d.show();
} finally {
if (didItWork) {
Dialog d = new Dialog(this);
TextView tv = new TextView(this);
d.setTitle("YAY");
tv.setText("Success");
d.setContentView(tv);
d.show();
}
}
/*
*
* boolean didwork = true; try{ String name =
* sqlName.getText().toString(); String hotness =
* sqlHotness.getText().toString();
*
* HotOrNot entry = new HotOrNot(SQLiteExample.this); entry.open();
* entry.createEntry(name,hotness); entry.close(); }catch (Exception
* e){ didwork = false; }finally{ if (didwork){ /*Dialog d = new
* Dialog(this); d.setTitle("Heck Ya!!"); TextView tv = new
* TextView(this); tv.setText("Success"); d.setContentView(tv);
* d.show();
*/
/*
* Toast t = Toast.makeText(SQLiteExample.this, "Success",
* Toast.LENGTH_LONG); t.show(); } else{ Toast t =
* Toast.makeText(SQLiteExample.this, "Fail", Toast.LENGTH_LONG);
* t.show(); } }
*/
break;
case R.id.bSQLOpenView:
break;
}
}
}
HotOrNot.java
package com.example.myfirstapp;
import android.app.Activity;
import android.content.ContentValues;
import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class HotOrNot extends Activity{
public static final String KEY_ROWID = "_id";
public static final String KEY_NAME = "persons_name";
public static final String KEY_HOTNESS = "persons_hotness";
private static final String DATABASE_NAME = "HotOrNotdb.db";
private static final String DATABASE_TABLE = "peopleTable";
private static final int DATABASE_VERSION = 1;
private DbHelper ourHelper;
private final Context ourContext;
private SQLiteDatabase ourDatabase;
private static class DbHelper extends SQLiteOpenHelper {
public DbHelper(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
db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" + KEY_ROWID
+ " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_NAME
+ " TEXT NOT NULL, " + KEY_HOTNESS + " TEXT NOT NULL);");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
onCreate(db);
}
}
public HotOrNot(Context c) {
ourContext = c;
}
public HotOrNot open() throws SQLException {
ourHelper = new DbHelper(ourContext);
ourDatabase = ourHelper.getWritableDatabase();
return this;
}
public void close() {
ourHelper.close();
}
public long createEntry(String name, String hotness) {
// TODO Auto-generated method stub
ContentValues cv = new ContentValues();
cv.put(KEY_NAME, name);
cv.put(KEY_HOTNESS, hotness);
return ourDatabase.insert(DATABASE_TABLE, null, cv);
}
}
sqlite示例
<?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="vertical" >
<TextView
android:id="@+id/textView21"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Name" />
<EditText
android:id="@+id/etSQLName"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10" >
</EditText>
<TextView
android:id="@+id/textView12"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hotness scale 1-10" />
<EditText
android:id="@+id/etSQLHotness"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10" />
<Button
android:id="@+id/bSQLUpdate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Update SQLite Database" />
<Button
android:id="@+id/bSQLOpenView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="View" />
</LinearLayout>
我有这两个类文件和xml，没有任何错误。但是，当尝试更新 SQLite 数据库时，我设置的对话框会引发错误：java.lang.NullPointerException。我对此很陌生，并且一直在关注 youtube 上的教程。（http://www.youtube.com/watch?v=9ew_Ajpqwqg&list=EC2F07DBCDCC01493A）
任何帮助是极大的赞赏。