我的应用程序运行正常。但由于某些原因我不得不在我的项目中实现SQLiteOpenHelper。我不知道SQLiteOpenHelper。我在数据库的自定义列表视图中成功显示了产品。但是点击它应该显示的listview项目它的详细信息来自database.But崩溃我的设备。请帮助。我不知道如何在那里实现SQLteOpenHelper。
DataBaseHelper.java
public class DataBaseHandler extends SQLiteOpenHelper{
public static final String DATABASE_NAME = "products.db";
public static final String CONTACTS_TABLE_NAME = "product";
public static final String CONTACTS_COLUMN_ID = "pid";
public static final String CONTACTS_COLUMN_NAME = "pname";
public static final String CONTACTS_COLUMN_EMAIL = "pspec";
public static final String CONTACTS_COLUMN_STREET = "pprice";
public static final String CONTACTS_COLUMN_CITY = "pfeature";
public static final String CONTACTS_COLUMN_PHONE = "pimage";
public DataBaseHandler(Context context, String name, CursorFactory factory,
int version) {
super(context, name, factory, version);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL("CREATE TABLE IF NOT EXISTS product(pimage BLOB,pid INTEGER PRIMARY KEY,pname TEXT,pprice NUMERIC,pspec TEXT,pfeature TEXT)");
db.execSQL("INSERT INTO product(pname,pprice,pspec) VALUES('Candle stick 3',4000,'Solar garden / pathway light,Solar Panel:1pc crystal silicon solar cell, Battery:1pc 1.2V Ni-MH/Ni-CD AA battery 600MA ,Material:Stainless steel ,WaterProof and safe ')");
db.execSQL("INSERT INTO product(pname,pprice,pspec) VALUES('Candle stick 4',4500,'Solar garden / pathway light, Solar Panel:1pc crystal silicon solar cell, Battery:1pc 1.2V Ni-MH/Ni-CD AA battery 600MA, Material:Stainless steel, WaterProof and safe IP44 ')");
db.execSQL("INSERT INTO product(pname,pprice,pspec) VALUES('Candle stick 5',3500,'Solar garden / pathway light, Solar Panel:1pc crystal silicon solar cell, Battery:1pc 1.2V Ni-MH/Ni-CD AA battery 600MA, Material:Stainless steel, WaterProof and safe IP44 ')");
db.execSQL("INSERT INTO product(pname,pprice,pspec) VALUES('Candle stick 6',6000,'Solar garden / pathway light, Solar Panel:1pc crystal silicon solar cell, Battery:1pc 1.2V Ni-MH/Ni-CD AA battery 600MA, Material:Stainless steel, WaterProof and safe IP44 ')");
db.execSQL("INSERT INTO product(pname,pprice,pspec) VALUES('lawn Delight',8800,'Solar garden / pathway light, Solar Panel:1pc crystal silicon solar cell, Battery:1pc 1.2V Ni-MH/Ni-CD AA battery 600MA, Material:Stainless steel, WaterProof and safe IP44 ')");
db.execSQL("INSERT INTO product(pname,pprice,pspec) VALUES('SGLC10',4500,'Solar garden / pathway light, Solar Panel:1pc crystal silicon solar cell, Battery:1pc 1.2V Ni-MH/Ni-CD AA battery 600MA, Material:Stainless steel, WaterProof and safe IP44 ')");
db.execSQL("INSERT INTO product(pname,pprice,pspec) VALUES('Senson',4500,'Solar garden / pathway light, Solar Panel:1pc crystal silicon solar cell, Battery:1pc 1.2V Ni-MH/Ni-CD AA battery 600MA, Material:Stainless steel, WaterProof and safe IP44 ')");
db.execSQL("INSERT INTO product(pname,pprice,pspec) VALUES('Thejus',7500,'Solar garden / pathway light, Solar Panel:1pc crystal silicon solar cell, Battery:1pc 1.2V Ni-MH/Ni-CD AA battery 600MA, Material:Stainless steel, WaterProof and safe IP44 ')");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
}
Product_display.java
public class product_display extends Activity {
ListView prd_list;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.product_disply);
prd_list = (ListView) findViewById(R.id.list);
DataBaseHandler dbh = new DataBaseHandler(this);
Intent in=getIntent();
Bundle bundle=in.getExtras();
final String list=bundle.getString("key");
SQLiteDatabase db = dbh.getWritableDatabase();
Cursor cr = db.rawQuery("SELECT * FROM product", null);
final String[] pname = new String[cr.getCount()];
String[] price = new String[cr.getCount()];
int i = 0;
while(cr.moveToNext())
{
String name = cr.getString(cr.getColumnIndex("pname"));
String prprice = cr.getString(cr.getColumnIndex("pprice"));
pname[i] = name;
price[i] = prprice;
i++;
}
ListAdapter adapter = new com.example.login_signup.ListAdapter(this, pname, price);
prd_list.setAdapter(adapter);
prd_list.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
long arg3) {
// TODO Auto-generated method stub
String nme = pname[arg2];
Bundle bun = new Bundle();
bun.putString("key",list);
Bundle bn = new Bundle();
bn.putString("name",nme);
Intent in = new Intent(product_display.this, Product_Details.class);
in.putExtras(bun);
in.putExtras(bn);
startActivity(in);
}
});
}
}
product_dtls.java
public class Product_Details extends Activity{
TextView name,price,specification,feature;
String nme;
String pname;
String prprice;
String pspec;
String pfeature;
Button add2cart,by_nw;
ImageView image;
ImageButton imgbtn;
DataBaseHandler dbh = new DataBaseHandler(this);
SQLiteDatabase db = dbh.getWritableDatabase();
Integer [] pmge ={R.drawable.candle1,R.drawable.candl3,
R.drawable.candl4,R.drawable.candl5,R.drawable.candl6,
R.drawable.lawn,R.drawable.sglc10,R.drawable.senson,R.drawable.thejus6669};
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.product_dtls);
image=(ImageView)findViewById(R.id.pr_img);
name = (TextView) findViewById(R.id.txtPr_name);
price = (TextView) findViewById(R.id.txtprice);
specification=(TextView)findViewById(R.id.txtPr_spec);
feature=(TextView)findViewById(R.id.txtPr_feature);
imgbtn=(ImageButton)findViewById(R.id.cartimg);
add2cart=(Button)findViewById(R.id.add2cart);
by_nw=(Button)findViewById(R.id.buy_nw);
Intent in = getIntent();
Bundle bn = in.getExtras();
Bundle bun=in.getExtras();
final String dtl=bun.getString("key");
nme = bn.getString("name");
Cursor cr = db.rawQuery("SELECT * FROM product WHERE pname = '"+nme+"'", null);
while(cr.moveToNext())
{
String name = cr.getString(cr.getColumnIndex("pname"));
String pr1price = cr.getString(cr.getColumnIndex("pprice"));
String prspc=cr.getString(cr.getColumnIndex("pspec"));
String prfeature=cr.getString(cr.getColumnIndex("pfeature"));
pname = name;
prprice = pr1price;
pspec=prspc;
pfeature=prfeature;
}
name.setText(pname);
price.setText("Rs " +prprice + "/-");
specification.setText(pspec);
feature.setText(pfeature);
add2cart.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
boolean incart=false;
String nm=name.getText().toString();
db=Product_Details.this.openOrCreateDatabase("addcart", MODE_PRIVATE, null);
Cursor cur=db.rawQuery("select * from add2cart where pnme='"+nm+"'",null);
if (cur.moveToFirst()){
String prdname=cur.getString(cur.getColumnIndex("pnme"));
if (nm.equals(prdname)){
add2cart.setText("Already in Cart");
incart=true;
}
}
if(incart==false){
db.execSQL("INSERT INTO add2cart (pnme,prate)VALUES('"+nm+"','"+prprice+"')");
Toast.makeText(getApplicationContext(),"added to cart",Toast.LENGTH_SHORT).show();
}
}
});
}
}
logcat的
01-20 04:48:56.315: E/AndroidRuntime(19864): FATAL EXCEPTION: main
01-20 04:48:56.315: E/AndroidRuntime(19864): Process: com.example.login_signup, PID: 19864
01-20 04:48:56.315: E/AndroidRuntime(19864): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.login_signup/com.example.login_signup.Product_Details}: java.lang.NullPointerException
01-20 04:48:56.315: E/AndroidRuntime(19864): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2102)
01-20 04:48:56.315: E/AndroidRuntime(19864): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
01-20 04:48:56.315: E/AndroidRuntime(19864): at android.app.ActivityThread.access$700(ActivityThread.java:135)
01-20 04:48:56.315: E/AndroidRuntime(19864): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
01-20 04:48:56.315: E/AndroidRuntime(19864): at android.os.Handler.dispatchMessage(Handler.java:102)
01-20 04:48:56.315: E/AndroidRuntime(19864): at android.os.Looper.loop(Looper.java:137)
01-20 04:48:56.315: E/AndroidRuntime(19864): at android.app.ActivityThread.main(ActivityThread.java:4998)
01-20 04:48:56.315: E/AndroidRuntime(19864): at java.lang.reflect.Method.invokeNative(Native Method)
01-20 04:48:56.315: E/AndroidRuntime(19864): at java.lang.reflect.Method.invoke(Method.java:515)
01-20 04:48:56.315: E/AndroidRuntime(19864): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
01-20 04:48:56.315: E/AndroidRuntime(19864): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
01-20 04:48:56.315: E/AndroidRuntime(19864): at dalvik.system.NativeStart.main(Native Method)
01-20 04:48:56.315: E/AndroidRuntime(19864): Caused by: java.lang.NullPointerException
01-20 04:48:56.315: E/AndroidRuntime(19864): at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:256)
01-20 04:48:56.315: E/AndroidRuntime(19864): at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224)
01-20 04:48:56.315: E/AndroidRuntime(19864): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
01-20 04:48:56.315: E/AndroidRuntime(19864): at com.example.login_signup.Product_Details.<init>(Product_Details.java:29)
答案 0 :(得分：1)
移入onCreate(..)
DataBaseHandler dbh = new DataBaseHandler(this);
SQLiteDatabase db = dbh.getWritableDatabase();