我有一个像这样的DatabaseHelper类：
public class DataBaseHelper extends SQLiteOpenHelper
{
// The Android's default system path of your application database.
private static String DB_PATH = android.os.Environment.getExternalStorageDirectory() + "/FitnessData/";
private static String DB_NAME = "OFSDb.db";
private SQLiteDatabase myDataBase;
private final Context myContext;
/**
* Constructor Takes and keeps a reference of the passed context in order to
* access to the application assets and resources.
*
* @param context
*/
public DataBaseHelper(Context context)
{
super(context, DB_NAME, null, 1);
this.myContext = context;
}
/**
* Creates a empty database on the system and rewrites it with your own
* database.
* */
public void createDataBase() throws IOException
{
boolean dbExist = checkDataBase();
if (dbExist)
{
// do nothing - database already exist
}
else
{
// By calling this method and empty database will be created into
// the default system path
// of your application so we are gonna be able to overwrite that
// database with our database.
this.getReadableDatabase();
try
{
copyDataBase();
}
catch (IOException e)
{
throw new Error("Error copying database");
}
}
}
/**
* Check if the database already exist to avoid re-copying the file each
* time you open the application.
*
* @return true if it exists, false if it doesn't
*/
private boolean checkDataBase()
{
SQLiteDatabase checkDB = null;
try
{
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}
catch (SQLiteException e)
{
// database does't exist yet.
}
if (checkDB != null)
{
checkDB.close();
}
return checkDB != null ? true : false;
}
/**
* Copies your database from your local assets-folder to the just created
* empty database in the system folder, from where it can be accessed and
* handled. This is done by transfering bytestream.
* */
private void copyDataBase() throws IOException
{
// Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(DB_NAME);
// Path to the just created empty db
String outFileName = DB_PATH + DB_NAME;
// Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
// transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0)
{
myOutput.write(buffer, 0, length);
}
// Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
public void openDataBase() throws SQLException
{
// Open the database
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}
@Override
public synchronized void close()
{
if (myDataBase != null)
myDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db)
{
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
}
// Add your public helper methods to access and get content from the
// database.
// You could return cursors by doing "return myDataBase.query(....)" so it'd
// be easy
// to you to create adapters for your views.
public VehicleData getInfo(String regno)
{
VehicleData vData = new VehicleData();
String selectQuery = "SELECT * FROM" + DB_NAME + " WHERE FIT_REF_NO = " + regno;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst())
{
do
{
vData.regno = cursor.getString(1);
vData.ownername = cursor.getString(2);
vData.makername = cursor.getString(3);
vData.makermodel = cursor.getString(4);
}
while (cursor.moveToNext());
}
return vData;
}
}
VehicleData类类似于：
public class VehicleData
{
public String regno;
public String ownername;
public String makername;
public String makermodel;
public String picsnum;
public String status;
}
我尝试使用Database Helper中的方法的类如下所示：
public class Reference extends Activity
{
public static String rslt = "";
public static String picsNumber = "";
public static String ipAdress;
Button bproceed;
Button bSendRef;
TextView regno;
TextView ownername;
TextView vmake;
TextView vmodel;
DataBaseHelper controller;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.reference);
// set color for fields
regno = ((TextView) findViewById(R.id.regnum));
regno.setTextColor(Color.parseColor("#34afdd"));
ownername = (TextView) findViewById(R.id.ownername);
ownername.setTextColor(Color.parseColor("#34afdd"));
vmake = ((TextView) findViewById(R.id.vmake));
vmake.setTextColor(Color.parseColor("#34afdd"));
vmodel = ((TextView) findViewById(R.id.vmodel));
vmodel.setTextColor(Color.parseColor("#34afdd"));
HideStaticTexts();
final TextView tvNotif = (TextView) findViewById(R.id.tvNotif);
tvNotif.setVisibility(View.INVISIBLE);
// disable proceed button until data recieved from web service
bproceed = (Button) findViewById(R.id.bproceed);
bSendRef = (Button) findViewById(R.id.bSendRef);
bproceed.setEnabled(false);
bproceed.setClickable(false);
/* Get data Against Ref Number using button Submit */
DataBaseHelper myDbHelper = new DataBaseHelper(this);
try
{
myDbHelper.createDataBase();
}
catch (IOException ioe)
{
throw new Error("Unable to create database");
}
try
{
myDbHelper.openDataBase();
}
catch (SQLException sqle)
{
throw sqle;
}
// handling send from keyboard
final EditText edt = (EditText) findViewById(R.id.editText1);
edt.setOnEditorActionListener(new OnEditorActionListener()
{
@Override
public boolean onEditorAction(TextView v, int actionId, KeyEvent event)
{
boolean handled = false;
if (actionId == EditorInfo.IME_ACTION_SEND)
{
bSendRef.callOnClick();
handled = true;
}
return handled;
}
});
((Button) findViewById(R.id.bSendRef)).setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
// TODO Auto-generated method stub
String searchUser = edt.getText().toString();
VehicleData response = controller.getInfo(searchUser);
ShowStaticTexts();
((TextView) findViewById(R.id.regnumval)).setText(response.regno); /*
* Regn
* No
*/
((TextView) findViewById(R.id.ownerNameVal)).setText(response.ownername); /*
* Owner
* name
*/
((TextView) findViewById(R.id.vehicleMakeVal)).setText(response.makername); /*
* Manufacturer
* Name
*/
((TextView) findViewById(R.id.vehicleModelVal)).setText(response.makermodel); /*
* Maker
* Name
*/
picsNumber = response.picsnum;
Toast.makeText(Reference.this.getApplicationContext(), picsNumber + " images will be clicked", Toast.LENGTH_LONG).show();
tvNotif.setVisibility(View.VISIBLE);
tvNotif.setText(picsNumber + " IMAGES WILL BE CLICKED ");
bproceed.setEnabled(true);
bproceed.setClickable(true);
}
});
/* Start Camera Using Proceed Button */
bproceed.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
// TODO Auto-generated method stub
if (picsNumber.equals("4"))
{
Intent intent = new Intent(Reference.this, Camera.class);
// ---use putExtra() to add new key/value pairs---
intent.putExtra("refnum", ((EditText) findViewById(R.id.editText1)).getText().toString());
intent.putExtra("regno", ((TextView) findViewById(R.id.regnumval)).getText().toString());
intent.putExtra("picnum", picsNumber);
startActivity(intent);
finish();
}
else
{
Intent intent = new Intent(Reference.this, Camera2.class);
// ---use putExtra() to add new key/value pairs---
intent.putExtra("refnum", ((EditText) findViewById(R.id.editText1)).getText().toString());
intent.putExtra("regno", ((TextView) findViewById(R.id.regnumval)).getText().toString());
intent.putExtra("picnum", picsNumber);
startActivity(intent);
finish();
}
}
});
/* Clear form using Clear Button */
((Button) findViewById(R.id.bclear)).setOnLongClickListener(new OnLongClickListener()
{
@Override
public boolean onLongClick(View v)
{
// TODO Auto-generated method stub
Intent intent = new Intent(Reference.this, Settings.class);
String reset = "RESET";
intent.putExtra("reSet", reset);
startActivity(intent);
return true;
}
});
/* Clear All Controls Using Clear Button */
((Button) findViewById(R.id.bclear)).setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
((EditText) findViewById(R.id.editText1)).setText("");
clearAllControls();
// force keyboard to show up when reset is called
edt.requestFocus();
InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
imm.showSoftInput(edt, InputMethodManager.SHOW_IMPLICIT);
tvNotif.setVisibility(View.INVISIBLE);
HideStaticTexts();
}
});
}
private void HideStaticTexts()
{
// TODO Auto-generated method stub
regno.setVisibility(View.INVISIBLE);
ownername.setVisibility(View.INVISIBLE);
vmake.setVisibility(View.INVISIBLE);
vmodel.setVisibility(View.INVISIBLE);
}
private void ShowStaticTexts()
{
// TODO Auto-generated method stub
regno.setVisibility(View.VISIBLE);
ownername.setVisibility(View.VISIBLE);
vmake.setVisibility(View.VISIBLE);
vmodel.setVisibility(View.VISIBLE);
}
public void clearAllControls()
{
((TextView) findViewById(R.id.regnumval)).setText("");
((TextView) findViewById(R.id.ownerNameVal)).setText("");
((TextView) findViewById(R.id.vehicleMakeVal)).setText("");
((TextView) findViewById(R.id.vehicleModelVal)).setText("");
}
public static void hideSoftKeyboard(Activity activity, View view)
{
InputMethodManager imm = (InputMethodManager) activity.getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(view.getApplicationWindowToken(), 0);
}
}
当我在editText中输入字符串并按下按钮时，应用程序挂起。甚至无法读取LogCat。请帮我？
"SELECT * FROM" + DB_NAME + " WHERE FIT_REF_NO = " + regno;……崩溃！
1-在FROM
2之后您错过了一个空格-DB_NAME应该是YOUR_TABLE_NAME
尝试：
"SELECT * FROM " + YOUR_TABLE_NAME + " WHERE FIT_REF_NO = " + regno;
另请注意，列基于0。我希望您没有检索到另一个索引为0的列：
if (cursor.moveToFirst())
{
do
{
//vData.XYX = cursor.getString(0);
vData.regno = cursor.getString(1);
vData.ownername = cursor.getString(2);
vData.makername = cursor.getString(3);
vData.makermodel = cursor.getString(4);
}
while (cursor.moveToNext());
但是，按索引检索列值不是一件好事，尤其是如果您使用星号（*）代替指定字段名（永远不能保证总是将列提取到列集中的某个位置）。
您可以选择或者两者兼而有之：
1-指定所有列名称insetad为*，以确保按此顺序获取它们。
2-使用cursor.getString（cursor.getColumnIndex（“ columnName”））;
此外，如果regno为string，则应将其值用单引号引起来，例如：
"SELECT * FROM " + YOUR_TABLE_NAME + " WHERE FIT_REF_NO = '" + regno + "'";
但是，如果您绑定参数，那就更好了，例如：
"SELECT * FROM " + YOUR_TABLE_NAME + " WHERE FIT_REF_NO = ?";
//...
Cursor cursor = db.rawQuery(selectQuery, new String[]{regno});
希望我能帮上忙。
[编辑]
指定数据库路径绝不是一个好主意。
Android在其默认路径下自动处理数据库：
/data/data/your.app.name/databases/your.db
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我来说两句