public class ExternalDbOpenHelper extends SQLiteOpenHelper{
private static final String TABLE_NAME = "hymn";
private final Context myContext;
private static final String TAG = "ExternalDbOpenHelper";
//The Android's default system path of your application database.
private static String DB_PATH = "/data/data/com.catholic_hymnal.arnold/databases/";
public static String HYMN_NAME = "KEY_HYMN";
public static String HYMN_ID = "_id" ;
private SQLiteDatabase myDataBase;
private static String DB_PATH = "/data/data/com.catholic_hymnal.arnold/databases/";
private static String DB_NAME = "hymnals";
public ExternalDbOpenHelper (Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
}
public void createDataBase() throws IOException{
boolean dbExist = checkDataBase();
if(dbExist){
Log.d(TAG, "db exists");
this.getReadableDatabase();
//do nothing - database already exist
}else{
File f = new File(DB_PATH);
if (!f.exists()) {
f.mkdir();
}
this.getReadableDatabase();
try
{
copyDataBase();
}
catch (IOException e)
{
throw new RuntimeException(e);
}
}
}
private boolean checkDataBase() {
File dbFile = new File(DB_PATH + DB_NAME);
return dbFile.exists();
}
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) {
if (newVersion > oldVersion)
Log.v("Database Upgrade」, 「Database version higher than old.", null);
myContext.deleteDatabase(DB_NAME);
}
// 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 Cursor fetchHymnByName(String inputText) throws SQLException {
Log.w(TAG, inputText);
Cursor mCursor = null;
if (inputText == null || inputText.length() == 0) {
mCursor = myDataBase.query(TABLE_NAME, new String[] {HYMN_ID,HYMN_NAME},
null, null, null, null, null);
}
else {
mCursor = myDataBase.query(true, TABLE_NAME, new String[] {HYMN_ID,HYMN_NAME},
HYMN_NAME + " like '%" + inputText + "%'", null,
null, null, null, null);
}
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
public Cursor fetchAllHymns() {
String sql ="SELECT * FROM TABLE_NAME";
Cursor mCur = myDataBase.rawQuery(sql, null);
if (mCur!=null)
{
mCur.moveToNext();
}
return mCur;
}
public boolean deleteAllCountries() {
int doneDelete = 0;
doneDelete = myDataBase.delete(TABLE_NAME, null , null);
Log.w(TAG, Integer.toString(doneDelete));
return doneDelete > 0;
}
}
公共類PrepopSqliteDbActivity延伸活動{我不斷收到java.lang.NullPointerException。請在下面是我的課和日誌貓
// private static final String DB_NAME = "hymnals";
//A good practice is to define database field names as constants
private ExternalDbOpenHelper dbHelper;
private SimpleCursorAdapter dataAdapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//Our key helper
dbHelper = new ExternalDbOpenHelper(this);
try {
try {
//dataabase is created
dbHelper.createDataBase();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
///database is opened
dbHelper.openDataBase();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
//That’s it, the database is open!
displayListView();
dbHelper.deleteAllCountries();
}
private void displayListView() {
//all hymns are fetched
final Cursor cursor = dbHelper.fetchAllHymns();
// The desired columns to be bound
String[] columns = new String[] {
ExternalDbOpenHelper.HYMN_ID,
ExternalDbOpenHelper.HYMN_NAME,
};
// the XML defined views which the data will be bound to
int[] to = new int[] {
R.id.tVid,
R.id.name,
};
// create the adapter using the cursor pointing to the desired data
//as well as the layout information
dataAdapter = new SimpleCursorAdapter(
this, R.layout.country_info,
cursor,
columns,
to,
0);
ListView listView = (ListView) findViewById(R.id.listView1);
// Assign adapter to ListView
listView.setAdapter(dataAdapter);
listView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> listView, View view,
int position, long id) {
// Get the cursor, positioned to the corresponding row in the result set
Cursor cursor = (Cursor) listView.getItemAtPosition(position);
// Get the state's capital from this row in the database.
String countryCode =
cursor.getString(cursor.getColumnIndexOrThrow("code"));
Toast.makeText(getApplicationContext(),
countryCode, Toast.LENGTH_SHORT).show();
}
});
EditText myFilter = (EditText) findViewById(R.id.myFilter);
myFilter.addTextChangedListener(new TextWatcher() {
public void afterTextChanged(Editable s) {
}
public void beforeTextChanged(CharSequence s, int start,
int count, int after) {
}
public void onTextChanged(CharSequence s, int start,
int before, int count) {
dataAdapter.getFilter().filter(s.toString());
}
});
dataAdapter.setFilterQueryProvider(new FilterQueryProvider() {
public Cursor runQuery(CharSequence constraint) {
try {
return dbHelper.fetchHymnByName(constraint.toString());
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return cursor;
}
});
}
// LOgCAts 堆棧跟蹤： // 08-06 13：18：49.946：E/AndroidRuntime（1462 ）：致命例外：main 08-06 13：18：49.946：E/AndroidRuntime（1462）：java.lang.RuntimeException：無法啓動活動ComponentInfo {com.catholic_hymnal.arnold/com.catholic_hymnal.arnold.PrepopSqliteDbActivity}： java.lang.NullPointerException 08-06 13：18：49.946：E/AndroidRuntime（1462）：at android.app.ActivityTh read.performLaunchActivity（ActivityThread.java:2180） 08-06 13：18：49.946：E/AndroidRuntime（1462）：at android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2230） 08-06 13:18： 49.946：E/AndroidRuntime（1462）：at android.app.ActivityThread.access $ 600（ActivityThread.java:141） 08-06 13：18：49.946：E/AndroidRuntime（1462）：at android.app.ActivityThread $ H （Handle.java:99） 08-06 13：18：49.946 ：E/AndroidRuntime（1462）：在android.os.Looper.loop（Looper.java:137） 08-06 13：18：49.946：E/AndroidRuntime（1462）：在android.app.ActivityThread.main（ActivityThread .java：5039） 08-06 13：18：49.946：E/AndroidRuntime（1462）：at java.lang.reflect.Method .invokeNative（Native Method） 08-06 13：18：49.946：E/AndroidRuntime（1462）：at java.lang.reflect.Method.invoke（Method.java:511） 08-06 13：18：49.946： E/AndroidRuntime（1462）：at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:793） 08-06 13：18：49.946：E/AndroidRuntime（1462）：at com.android。 internal.os.ZygoteInit.main（ZygoteInit.java:560） 08-06 13：18：49.946：E/AndroidRuntime（1462）：at dalvik.system.NativeStart.main（Native Method） 08-06 13:18 ：49.946：E/AndroidRuntime（1462）：導致：java.lang.NullPointerException 08-06 13：18：49.946：E/AndroidRuntime（1462）：at com.catholic_hymnal.arnold.PrepopSqliteDbActivity.displayListView（PrepopSqliteDbActivity.java： 65） 08-06 13：18：49.946：E/AndroidRuntime（1462）：at com.catholic_hymnal.arnold.Prepo E/AndroidRuntime（1462）：at android.app.Activity.performCreate（Activity.java:5104） 08-06 13:18： 49.946：E/AndroidRuntime（1462）：在android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1080） 08-06 13：18：49.946：E/AndroidRuntime（1462）：at android.app.ActivityThread.performLaunchActivity ActivityThread.java:2144） 08-06 13：18：49.946：E/AndroidRuntime（1462）：... 11多個
什麼是'PrepopSqliteDbActivity'的65行？ – codeMagic