NullPointerException：println需要一条消息

Question

我知道我有一个空指针，但我不知道它在哪里发生或为什么。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); 
} 

文件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) 

Answer 1

你的错误是很明显的

E/AndroidRuntime(909): java.lang.NullPointerException: println needs a message 02-27 11:03:42.058: 

必须为日志消息提供消息。它不能为空。

Log.i(course.getcoursename(), null); 

应该

Log.i(course.getcoursename(), "Some not null string");