我正在尝试使用Android将记录插入到SQLite数据库中。这是我的按钮onClick时的代码，它将执行插入查询：
public void btnClick(View view) {
String todayAsString = new SimpleDateFormat("yyyy-MM-dd HH:mm")
.format(new Date());
// Insert record into database
DatabaseAdapter dbAdapt = new DatabaseAdapter(Exercise.this);
dbAdapt.bookExercise(userName, exerciseIDList, todayAsString);
Toast.makeText(getBaseContext(), "Show Results Clicked",
Toast.LENGTH_SHORT).show();
startActivity((new Intent(this.getBaseContext(), Results.class)));
}
在我的DatabaseAdapter中：
public class DatabaseAdapter {
protected static final String TAG = "DatabaseAdapter";
private final Context mContext;
private SQLiteDatabase mDb;
private DataBaseHelper mDbHelper;
public DatabaseAdapter(Context context) {
this.mContext = context;
mDbHelper = new DataBaseHelper(mContext);
}
public DatabaseAdapter createDatabase() throws SQLException {
try {
mDbHelper.createDataBase();
Log.e(TAG, "Database Created");
} catch (IOException mIOException) {
Log.e(TAG, mIOException.toString() + " UnableToCreateDatabase");
throw new Error("UnableToCreateDatabase");
}
return this;
}
public SQLiteDatabase open() throws SQLException {
try {
mDbHelper.openDataBase();
mDbHelper.close();
mDb = mDbHelper.getReadableDatabase();
Log.e(TAG, "Database Open");
} catch (SQLException mSQLException) {
Log.e(TAG, "open >>" + mSQLException.toString());
throw mSQLException;
}
return mDb;
}
public void close() {
mDbHelper.close();
}
public long bookExercise(String userName, ArrayList<String> exerciseIDList, String todayAsString)
{
ContentValues newEntryValues = new ContentValues();
for (int i = 0; i < exerciseIDList.size(); i++) {
try {
newEntryValues.put("userName", userName);
newEntryValues.put("exerciseID", exerciseIDList.get(i));
newEntryValues.put("bookedTime", todayAsString);
} catch (Exception ex) {
}
}
return mDb.insert("bookedExercise", null, newEntryValues);
}
DatabaseHelper：
public class DataBaseHelper extends SQLiteOpenHelper {
private static String TAG = "DataBaseHelper"; // Tag just for the LogCat
// window
// destination path (location) of our database on device
private static String DB_PATH = "";
private static String DB_NAME = "schoolAssignment";// Database name
private SQLiteDatabase mDataBase;
private final Context mContext;
public DataBaseHelper(Context context) {
super(context, DB_NAME, null, 1);// 1? its Database Version
DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
this.mContext = context;
try
{
createDataBase();
}
catch (Exception e)
{
Log.e(TAG,"DatabaseHelper_constuctor createDataBase :" + e.fillInStackTrace());
}
}
public void createDataBase() throws IOException {
// If database not exists copy it from the assets
Log.e(TAG, "CreateDataBase()");
boolean mDataBaseExist = checkDataBase();
if (!mDataBaseExist) {
this.getReadableDatabase();
this.close();
try {
// Copy the database from assests
copyDataBase();
Log.e(TAG, "createDatabase database created");
} catch (IOException mIOException) {
throw new Error("ErrorCopyingDataBase");
}
}
}
// Check that the database exists here: /data/data/your package/databases/Database
// Name
private boolean checkDataBase() {
File dbFile = new File(DB_PATH + DB_NAME);
Log.e("dbFile", dbFile + " "+ dbFile.exists());
return dbFile.exists();
}
// Copy the database from assets
private void copyDataBase() throws IOException {
InputStream mInput = mContext.getAssets().open(DB_NAME);
String outFileName = DB_PATH + DB_NAME;
OutputStream mOutput = new FileOutputStream(outFileName);
byte[] mBuffer = new byte[1024];
int mLength;
while ((mLength = mInput.read(mBuffer)) > 0) {
mOutput.write(mBuffer, 0, mLength);
}
mOutput.flush();
mOutput.close();
mInput.close();
}
// Open the database, so we can query it
public boolean openDataBase() throws SQLException {
String mPath = DB_PATH + DB_NAME;
// Log.v("mPath", mPath);
mDataBase = SQLiteDatabase.openDatabase(mPath, null,
SQLiteDatabase.CREATE_IF_NECESSARY);
// mDataBase = SQLiteDatabase.openDatabase(mPath, null,
// SQLiteDatabase.NO_LOCALIZED_COLLATORS);
return mDataBase != null;
}
@Override
public synchronized void close() {
if (mDataBase != null)
mDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase arg0) {
// TODO Auto-generated method stub
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
但是，我收到的错误消息是LogCat：
08-02 11:59:16.497: E/AndroidRuntime(24821): FATAL EXCEPTION: main
08-02 11:59:16.497: E/AndroidRuntime(24821): java.lang.IllegalStateException: Could not execute method of the activity
08-02 11:59:16.497: E/AndroidRuntime(24821): at android.view.View$1.onClick(View.java:3098)
08-02 11:59:16.497: E/AndroidRuntime(24821): at android.view.View.performClick(View.java:3620)
08-02 11:59:16.497: E/AndroidRuntime(24821): at android.view.View$PerformClick.run(View.java:14292)
08-02 11:59:16.497: E/AndroidRuntime(24821): at android.os.Handler.handleCallback(Handler.java:605)
08-02 11:59:16.497: E/AndroidRuntime(24821): at android.os.Handler.dispatchMessage(Handler.java:92)
08-02 11:59:16.497: E/AndroidRuntime(24821): at android.os.Looper.loop(Looper.java:137)
08-02 11:59:16.497: E/AndroidRuntime(24821): at android.app.ActivityThread.main(ActivityThread.java:4512)
08-02 11:59:16.497: E/AndroidRuntime(24821): at java.lang.reflect.Method.invokeNative(Native Method)
08-02 11:59:16.497: E/AndroidRuntime(24821): at java.lang.reflect.Method.invoke(Method.java:511)
08-02 11:59:16.497: E/AndroidRuntime(24821): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:982)
08-02 11:59:16.497: E/AndroidRuntime(24821): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:749)
08-02 11:59:16.497: E/AndroidRuntime(24821): at dalvik.system.NativeStart.main(Native Method)
08-02 11:59:16.497: E/AndroidRuntime(24821): Caused by: java.lang.reflect.InvocationTargetException
08-02 11:59:16.497: E/AndroidRuntime(24821): at java.lang.reflect.Method.invokeNative(Native Method)
08-02 11:59:16.497: E/AndroidRuntime(24821): at java.lang.reflect.Method.invoke(Method.java:511)
08-02 11:59:16.497: E/AndroidRuntime(24821): at android.view.View$1.onClick(View.java:3093)
08-02 11:59:16.497: E/AndroidRuntime(24821): ... 11 more
08-02 11:59:16.497: E/AndroidRuntime(24821): Caused by: java.lang.NullPointerException
08-02 11:59:16.497: E/AndroidRuntime(24821): at edu.nyp.project.DatabaseAdapter.bookExercise(DatabaseAdapter.java:62)
08-02 11:59:16.497: E/AndroidRuntime(24821): at edu.nyp.project.Exercise.btnClick(Exercise.java:97)
08-02 11:59:16.497: E/AndroidRuntime(24821): ... 14 more
08-02 11:59:48.208: I/Process(24821): Sending signal. PID: 24821 SIG: 9
08-02 11:59:48.521: D/dalvikvm(25205): GC_CONCURRENT freed 75K, 11% free 9489K/10567K, paused 5ms+2ms
08-02 11:59:48.536: D/dalvikvm(25205): GC_FOR_ALLOC freed 0K, 11% free 9489K/10567K, paused 15ms
08-02 11:59:48.536: I/dalvikvm-heap(25205): Grow heap (frag case) to 10.749MB for 642004-byte allocation
08-02 11:59:48.552: D/dalvikvm(25205): GC_FOR_ALLOC freed 1K, 10% free 10114K/11207K, paused 14ms
08-02 11:59:48.583: D/dalvikvm(25205): GC_CONCURRENT freed 279K, 13% free 9840K/11207K, paused 2ms+3ms
08-02 11:59:48.701: D/TextLayoutCache(25205): Using debug level: 0 - Debug Enabled: 0
08-02 11:59:48.763: D/dalvikvm(25205): GC_FOR_ALLOC freed 67K, 12% free 9910K/11207K, paused 15ms
08-02 11:59:48.763: I/dalvikvm-heap(25205): Grow heap (frag case) to 11.375MB for 868016-byte allocation
08-02 11:59:48.810: D/dalvikvm(25205): GC_CONCURRENT freed 3K, 12% free 10754K/12103K, paused 2ms+6ms
08-02 11:59:48.833: D/dalvikvm(25205): GC_FOR_ALLOC freed 0K, 12% free 10755K/12103K, paused 15ms
08-02 11:59:48.833: I/dalvikvm-heap(25205): Grow heap (frag case) to 13.236MB for 1953016-byte allocation
08-02 11:59:48.857: D/dalvikvm(25205): GC_FOR_ALLOC freed 0K, 10% free 12662K/14023K, paused 17ms
08-02 11:59:48.888: D/dalvikvm(25205): GC_CONCURRENT freed 0K, 10% free 12662K/14023K, paused 2ms+2ms
08-02 11:59:49.099: D/CLIPBOARD(25205): Hide Clipboard dialog at Starting input: finished by someone else... !
08-02 11:59:56.185: D/CLIPBOARD(25205): Hide Clipboard dialog at Starting input: finished by someone else... !
任何指南？提前谢谢。
答案 0 :(得分：1)
可能mDb实例是null，因为在调用{方法open()方法之前调用insert method.Call bookExercise方法之前没有初始化为：DatabaseAdapter： / p>
DatabaseAdapter dbAdapt = new DatabaseAdapter(Exercise.this);
dbAdapt.open(); // open db connection here
dbAdapt.bookExercise(userName, exerciseIDList, todayAsString);
// close db connection here