如果在 SQLite 中值为空，则跳过插入

Question

插入Android SQLite数据库时，我想跳过用户未填写的值。 但是我得到空指针异常。

在我的DBHelper课程中，我尝试了两个"...不为空"，没有不为空选项，但我认为这不是解决方案。

public void addToDb(View view) {
SharedPreferences sharedPreferences = getSharedPreferences("entry",0);
float  lastlatitude = sharedPreferences.getFloat("latitude",0f);
float lastlongitude =  sharedPreferences.getFloat("longitude",0f);
if (mTitleInput.getText().length() == 0 ||
mEntryInput.getText().length() == 0) {
return;
}
try {
Date a = new Date();
SimpleDateFormat sdf = new SimpleDateFormat("EEE, MMM d, ''yy");
String o = sdf.format(a);
title = mTitleInput.getText().toString();
entry = mEntryInput.getText().toString();
dateStr = o;
image = getApplicationContext().getFilesDir().getAbsolutePath() + String.valueOf(System.currentTimeMillis()) + ".jpg";
rating = mRatingBar.getRating();
latitude = lastlatitude;
longitude = lastlongitude;
} catch (NumberFormatException ex) {
Log.e(LOG_TAG, "Failed to parse party size text to number: " + ex.getMessage());
}
// Add to mDb
addNewEntry(title, entry, dateStr, image, rating, latitude, longitude);

//clear UI text fields
mTitleInput.getText().clear();
mEntryInput.getText().clear();
}

编辑 1：堆栈跟踪。

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.aok.secretdiarywithlock, PID: 29148
java.lang.NullPointerException: Attempt to invoke virtual method 'long android.database.sqlite.SQLiteDatabase.insert(java.lang.String, java.lang.String, android.content.ContentValues)' on a null object reference
at com.aok.secretdiarywithlock.CreateEntry.addNewEntry(CreateEntry.java:157)
at com.aok.secretdiarywithlock.CreateEntry.addToDb(CreateEntry.java:139)
at com.aok.secretdiarywithlock.CreateEntry$1.onClick(CreateEntry.java:93)
at android.view.View.performClick(View.java:6597)
at android.view.View.performClickInternal(View.java:6574)
at android.view.View.access$3100(View.java:778)
at android.view.View$PerformClick.run(View.java:25885)
at android.os.Handler.handleCallback(Handler.java:873)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

编辑 2：错误代码

private long addNewEntry(String title, String entry, String date, String image, Float rate, Float latitude, Float longitude){
ContentValues cv = new ContentValues();
cv.put(EntryContract.EntryEntry.COLUMN_TITLE,title);
cv.put(EntryContract.EntryEntry.COLUMN_TEXT,entry);
cv.put(EntryContract.EntryEntry.COLUMN_DATE,date);
cv.put(EntryContract.EntryEntry.COLUMN_IMAGE,image);
cv.put(EntryContract.EntryEntry.COLUMN_TEXT,entry);
cv.put(EntryContract.EntryEntry.COLUMN_RATING,rate);
cv.put(EntryContract.EntryEntry.COLUMN_LOCATION_LAT,latitude);
cv.put(EntryContract.EntryEntry.COLUMN_LOCATION_LONG,longitude);
//        Next line is throwing error
return mDb.insert(EntryContract.EntryEntry.TABLE_NAME, null, cv);
}

Answer 1

嗨，您必须检查它们是否为空，例如

dateStr = o == null ? "" : o;

这将检查o是否为空，如果是，它将 dateStr 设置为空，如果不是，它将使用 o。