每当我启动数据库时，我的应用程序就会崩溃。我已经为此工作了几天。 (我在这里只输入了我的 databaseAdapter.java 文件的重要代码 fragment )。我在 getWritableDatabase() 中收到错误:NullPointerException。
private SQLiteDatabase db;
static final boolean assertionsDisabled = false;
private DBHelper dbHelper;
// private Context context;
public DatabaseAdapter(Context context) {
dbHelper = new DBHelper(context, DATABASE_NAME, null, DATABASE_VERSION);
}
private static class DBHelper extends SQLiteOpenHelper {
public DBHelper(Context context, String name, CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
try {
db.execSQL(CREATE_TABLE_ENTRIES);
//db = DBHelper.getWritableDatabase();
} catch (SQLException e) {
e.printStackTrace();
}
}
@Override
public void onUpgrade(SQLiteDatabase db, int i, int j)
{
Log.w("mytag", (new StringBuilder("Upgrading from version ")).append(i).append(" to ").append(j).append(", which will destroy all old data").toString());
db.execSQL("DROP TABLE IF EXISTS CREATE TABLE IF NOT EXISTS entries (_id INTEGER PRIMARY KEY AUTOINCREMENT, input_type INTEGER NOT NULL, activity_type INTEGER NOT NULL, date_time DATETIME NOT NULL, duration INTEGER NOT NULL, distance FLOAT, avg_pace INTEGER, avg_speed INTEGER,calories INTEGER, climb INTEGER, avg_heartrate INTEGER, comment TEXT, privacy INTEGER, gps_data BLOB );");
onCreate(db);
}
}
public DatabaseAdapter open()
throws SQLException
{
db = dbHelper.getWritableDatabase();
return this;
}
/////////////////////////////////////////////////////////////////
编辑 1:我从 ActivityManualInput.java 代码调用 databaseAdapter.java //////////////////////这是 ActivityManualInput.java 中调用 databaseAdapter 的代码 fragment
public class ActivityManualInput extends ListActivity {
// Some code here
private Context mContext;
// Some code here
protected void onCreate(Bundle savedInstanceState) {
//TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.xml.manualinput);
// Some code here
Button btn = ((Button) findViewById(R.id.btnSave));
View.OnClickListener myListener;
myListener= new View.OnClickListener(){
@Override
public void onClick(View v)
{
// mDateTime = new GregorianCalendar(mYear, mMonth, mDay, mHour, mMinute);
mDateTime = new GregorianCalendar(2, 3, 1, 4,5);
db = new DatabaseAdapter(mContext);
db.open();
// long id = db.insertEntry(mInputType, mActivityType, mDateTime, mDuration, mDistance, mCalories, mComment);
long id = db.insertEntry(3, 3, mDateTime, 4, 5, 5, "ant");
db.close();
Toast.makeText(getApplicationContext(), "Entry #" + id + "Saved!", Toast.LENGTH_SHORT)
.show();
finish();
}
};
btn.setOnClickListener(myListener);
/////////日志文件......////////////////////
12-03 06:03:00.318: W/dalvikvm(270): threadid=3: thread exiting with uncaught exception (group=0x4001b188)
12-03 06:03:00.318: E/AndroidRuntime(270): Uncaught handler: thread main exiting due to uncaught exception
12-03 06:03:00.398: E/AndroidRuntime(270): java.lang.NullPointerException
12-03 06:03:00.398: E/AndroidRuntime(270): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:98)
12-03 06:03:00.398: E/AndroidRuntime(270): at com.android.saud.lab3.DatabaseAdapter.open(DatabaseAdapter.java:147)
12-03 06:03:00.398: E/AndroidRuntime(270): at com.android.saud.lab3.ActivityManualInput$1.onClick(ActivityManualInput.java:85)
12-03 06:03:00.398: E/AndroidRuntime(270): at android.view.View.performClick(View.java:2364)
12-03 06:03:00.398: E/AndroidRuntime(270): at android.view.View.onTouchEvent(View.java:4179)
12-03 06:03:00.398: E/AndroidRuntime(270): at android.widget.TextView.onTouchEvent(TextView.java:6541)
12-03 06:03:00.398: E/AndroidRuntime(270): at android.view.View.dispatchTouchEvent(View.java:3709)
12-03 06:03:00.398: E/AndroidRuntime(270): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
12-03 06:03:00.398: E/AndroidRuntime(270): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
12-03 06:03:00.398: E/AndroidRuntime(270): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
12-03 06:03:00.398: E/AndroidRuntime(270): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
12-03 06:03:00.398: E/AndroidRuntime(270): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
12-03 06:03:00.398: E/AndroidRuntime(270): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1659)
12-03 06:03:00.398: E/AndroidRuntime(270): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1107)
12-03 06:03:00.398: E/AndroidRuntime(270): at android.app.Activity.dispatchTouchEvent(Activity.java:2061)
12-03 06:03:00.398: E/AndroidRuntime(270): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1643)
12-03 06:03:00.398: E/AndroidRuntime(270): at android.view.ViewRoot.handleMessage(ViewRoot.java:1691)
12-03 06:03:00.398: E/AndroidRuntime(270): at android.os.Handler.dispatchMessage(Handler.java:99)
12-03 06:03:00.398: E/AndroidRuntime(270): at android.os.Looper.loop(Looper.java:123)
12-03 06:03:00.398: E/AndroidRuntime(270): at android.app.ActivityThread.main(ActivityThread.java:4363)
12-03 06:03:00.398: E/AndroidRuntime(270): at java.lang.reflect.Method.invokeNative(Native Method)
12-03 06:03:00.398: E/AndroidRuntime(270): at java.lang.reflect.Method.invoke(Method.java:521)
12-03 06:03:00.398: E/AndroidRuntime(270): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
12-03 06:03:00.398: E/AndroidRuntime(270): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
12-03 06:03:00.398: E/AndroidRuntime(270): at dalvik.system.NativeStart.main(Native Method)
12-03 06:03:00.418: I/dalvikvm(270): threadid=7: reacting to signal 3
12-03 06:03:00.418: E/dalvikvm(270): Unable to open stack trace file '/data/anr/traces.txt': Permission denied
12-03 06:08:00.478: I/Process(270): Sending signal. PID: 270 SIG: 9
编辑 #2:上述错误已解决。现在我得到的应用程序不会崩溃。但是数据没有存储在数据库中。错误在返回 db.insert(TABLE_NAME_ENTRIES, null, contentvalues); databaseadapter.java 文件行
public long insertEntry(int i, int j, GregorianCalendar gregoriancalendar, long l, double d,
int k, String s)
{
ContentValues contentvalues = new ContentValues();
contentvalues.put(KEY_INPUT_TYPE, Integer.valueOf(i));
contentvalues.put(KEY_ACTIVITY_TYPE, Integer.valueOf(j));
contentvalues.put(KEY_DATE_TIME, Long.valueOf(gregoriancalendar.getTimeInMillis() / 1000L));
contentvalues.put(KEY_DURATION, Long.valueOf(l));
contentvalues.put(KEY_DISTANCE, Double.valueOf(d));
contentvalues.put(KEY_CALORIES, Integer.valueOf(k));
contentvalues.put(KEY_COMMENT, s);
return db.insert(TABLE_NAME_ENTRIES, null, contentvalues); // Logcat is howing
error here
}
这是日志
12-03 08:51:10.608: E/Database(327): Error inserting input_type=3 calories=5 distance=5.0 duration=4 comment=ant date_time=-62096464100 activity_type=3
12-03 08:51:10.608: E/Database(327): android.database.sqlite.SQLiteException: no such table: entries: , while compiling: INSERT INTO entries(input_type, calories, distance, duration, comment, date_time, activity_type) VALUES(?, ?, ?, ?, ?, ?, ?);
12-03 08:51:10.608: E/Database(327): at android.database.sqlite.SQLiteProgram.native_compile(Native Method)
12-03 08:51:10.608: E/Database(327): at android.database.sqlite.SQLiteProgram.compile(SQLiteProgram.java:110)
最佳答案
原始错误
您还没有发布 LogCat 错误，但这是一个典型的错误。我猜您正试图按照评论中的描述错误地将 DatabaseAdapter 创建为字段变量。
public class MainActivity extends Activity {
// Do not do this!
// This will case a NullPointerException later when your call getWritableDatabase()...
//DatabaseAdapter dba = new DatabaseAdapter(this);
// Do this instead:
DatabaseAdapter dba;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dba = new DatabaseAdapter(this); // Right way!
this 引用的上下文在注释掉的代码中无效。您必须等到上下文有效。您获得的第一个机会是在 onCreate() 中。
添加
在这种情况下，您使用的是 new DatabaseAdapter(mContext); 但忘记初始化 mContext 所以它是 null...
新的 LogCat 显示表条目不存在，原因是您不能将这些 SQL 命令链接在一起:
db.execSQL("DROP TABLE IF EXISTS CREATE TABLE IF NOT EXISTS entries ...
这是一个语法错误，因此从未构建表 entries。这些必须是单独的命令:
db.execSQL("DROP TABLE IF EXISTS entries");
db.execSQL("CREATE TABLE IF NOT EXISTS entries ...
不要忘记增加 DATABASE_VERSION，这样表将在 onUpgrade() 中创建。
希望这已经解决了您当前的问题。如果您遇到更多异常，请随时提出新问题。 祝你好运! :)
关于android - getWritableDatabase() -Nullpoiter 异常 (android)，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/13674758/