NullPointerException：println需要一条消息
我知道我有一个空指针，但我不知道它的发生位置或原因。 希望能在这里得到一些帮助。
Button add = (Button) findViewById(R.id.addfencebutton); add.setOnClickListener(new OnClickListener() { @Override public void onClick(View add) { //code to store in fence locations database createData(); } }); } public void createData(){ Course course = new Course(); course.setcoursename("courseNamefield"); course.setfencename("fenceNamefield"); course.setAlocation("standardAfield"); course.setBlocation("standardBfield"); course = datasource.create(course); Log.i(course.getcoursename(), null); //Log.i("course created with id" + course.getcourseid(), null); // Log.i("course name is " + course.getcoursename(), null); } file courseDBopenHelper
public class courseDBOpenHelper extends SQLiteOpenHelper { private static final String LOGTAG = "courseDatabase"; private static final String DATABASE_NAME = "courses.db"; private static final int DATABASE_VERSION = 1; public static final String TABLE_COURSES = "courses"; public static final String COLUMN_ID = "coursesID"; public static final String COLUMN_COURSENAME = "coursename"; public static final String COLUMN_FENCENAME = "fencename"; public static final String COLUMN_ALOCATION = "alocation"; public static final String COLUMN_BLOCATION = "blocation"; private static final String TABLE_CREATE = "CREATE TABLE " + TABLE_COURSES + " (" + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + COLUMN_COURSENAME + " TEXT, " + COLUMN_FENCENAME + " TEXT, " + COLUMN_ALOCATION + " NUMERIC, " + COLUMN_BLOCATION + " NUMBERIC " + ")"; public courseDBOpenHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(TABLE_CREATE); Log.i(LOGTAG, "table created"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { db.execSQL("DROP TABLE IF EXISTS" + TABLE_COURSES); onCreate(db); } }
courseDataSource.java
public class courseDataSource { public static final String LOGTAG = "courseDatabase"; SQLiteOpenHelper dbhelper; SQLiteDatabase database; public courseDataSource(Context context) { dbhelper = new courseDBOpenHelper(context); database = dbhelper.getWritableDatabase(); } public void open(){ Log.i(LOGTAG, "database open"); database = dbhelper.getWritableDatabase(); } public void close(){ Log.i(LOGTAG, "database closed"); dbhelper.close(); } public Course create(Course course) { ContentValues values = new ContentValues(); values.put(courseDBOpenHelper.COLUMN_COURSENAME, course.getcourseid()); values.put(courseDBOpenHelper.COLUMN_FENCENAME, course.getcoursename()); values.put(courseDBOpenHelper.COLUMN_ALOCATION, course.getAlocation()); values.put(courseDBOpenHelper.COLUMN_BLOCATION, course.getBlocation()); long insertid = database.insert(courseDBOpenHelper.TABLE_COURSES, null, values); course.setcourseid(insertid); return course; } }
course.java
public class Course { private long courseid; private String coursename; private String fencename; private String Alocation; private String Blocation; public long getcourseid(){ return courseid; } public void setcourseid(long courseid) { this.courseid = courseid; } public String getcoursename(){ return coursename; } public void setcoursename(String string){ this.coursename = coursename; } public String getfencename(){ return fencename; } public void setfencename(String fencename){ this.fencename = fencename; } public String getAlocation(){ return Alocation; } public void setAlocation(String view){ this.Alocation = view; } public String getBlocation(){ return Blocation; } public void setBlocation(String view){ this.Blocation = view; } }
错误日志
02-27 11:03:42.058: E/AndroidRuntime(909): FATAL EXCEPTION: main 02-27 11:03:42.058: E/AndroidRuntime(909): java.lang.NullPointerException: println needs a message 02-27 11:03:42.058: E/AndroidRuntime(909): at android.util.Log.println_native(Native Method) 02-27 11:03:42.058: E/AndroidRuntime(909): at android.util.Log.i(Log.java:159) 02-27 11:03:42.058: E/AndroidRuntime(909): at com.greygoosefarmpa.fencecoursebuilder.addFence.createData(addFence.java:155) 02-27 11:03:42.058: E/AndroidRuntime(909): at com.greygoosefarmpa.fencecoursebuilder.addFence$4.onClick(addFence.java:140) 02-27 11:03:42.058: E/AndroidRuntime(909): at android.view.View.performClick(View.java:4202) 02-27 11:03:42.058: E/AndroidRuntime(909): at android.view.View$PerformClick.run(View.java:17340) 02-27 11:03:42.058: E/AndroidRuntime(909): at android.os.Handler.handleCallback(Handler.java:725) 02-27 11:03:42.058: E/AndroidRuntime(909): at android.os.Handler.dispatchMessage(Handler.java:92) 02-27 11:03:42.058: E/AndroidRuntime(909): at android.os.Looper.loop(Looper.java:137) 02-27 11:03:42.058: E/AndroidRuntime(909): at android.app.ActivityThread.main(ActivityThread.java:5039) 02-27 11:03:42.058: E/AndroidRuntime(909): at java.lang.reflect.Method.invokeNative(Native Method) 02-27 11:03:42.058: E/AndroidRuntime(909): at java.lang.reflect.Method.invoke(Method.java:511) 02-27 11:03:42.058: E/AndroidRuntime(909): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 02-27 11:03:42.058: E/AndroidRuntime(909): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 02-27 11:03:42.058: E/AndroidRuntime(909): at dalvik.system.NativeStart.main(Native Method)
你的错误非常明显
E/AndroidRuntime(909): java.lang.NullPointerException: println needs a message 02-27 11:03:42.058:
您必须提供日志消息的消息。 它不能为空。
Log.i(course.getcoursename(), null);
应该
Log.i(course.getcoursename(), "Some not null string");