点击Android的空指针异常（按钮保存到SQLite数据库）

Question

我得到一个空指针异常，当我点击确认按钮保存配置文件详细信息到sqlite数据库时，我的应用程序关闭。我有一个具有相同的基本编码结构（明显不同的列名等），完美的作品的日志。我似乎无法弄清楚什么是错的。它说这个错误是在ProfileDetailActivity文件的第90行，但我不明白在Logdetail活动中几乎完全相同的结构是如何完美工作的！任何帮助将不胜感激，因为我接近撕裂我的头发！

感谢

ProfileDetailActivity

import java.text.DateFormat; 
import java.text.SimpleDateFormat; 
import java.util.Calendar; 
import michelle.glucose.contentprovider.MyLogContentProvider; 
import android.app.Activity; 
import android.app.DatePickerDialog; 
import android.app.TimePickerDialog; 
import android.content.ContentValues; 
import android.database.Cursor; 
import android.net.Uri; 
import android.os.Bundle; 
import android.support.v4.app.FragmentActivity; 
import android.text.TextUtils; 
import android.view.View; 
import android.widget.Button; 
import android.widget.DatePicker; 
import android.widget.EditText; 
import android.widget.Spinner; 
import android.widget.TextView; 
import android.widget.TimePicker; 
import android.widget.Toast; 


    /* 
    * TodoDetailActivity allows to enter a new todo item 
    * or to change an existing 
    */ 
public class ProfileDetailActivity extends Activity { 
private EditText sms; 
private EditText email ; 
private EditText name; 
private EditText DOB; 
public TextView textView1; 
public TextView textView2 ; 
private Spinner type; 
private Spinner units; 
private Spinner Gender; 

private EditText max; 
private EditText min; 


    private Uri progUri; 
    @Override 
    protected void onCreate(Bundle bundle) { 
super.onCreate(bundle); 
setContentView(R.layout.pro_pref); 


textView1 = (TextView) findViewById(R.id.textView1); 
textView2 = (TextView) findViewById(R.id.textView2); 

type = (Spinner) findViewById(R.id.type); 
units = (Spinner) findViewById(R.id.units); 
Gender = (Spinner) findViewById(R.id.Gender); 
max = (EditText) findViewById(R.id.max); 
min = (EditText) findViewById(R.id.min); 
sms = (EditText) findViewById(R.id.sms); 
email = (EditText) findViewById(R.id.Email); 
DOB = (EditText) findViewById(R.id.dob); 
name = (EditText) findViewById(R.id.name); 



Button confirmButton = (Button) findViewById(R.id.Confirm); 

Bundle extras = getIntent().getExtras(); 

// Check from the saved Instance 
progUri = (bundle == null) ? null : (Uri) bundle 
    .getParcelable(MyLogContentProvider.CONTENT_ITEM_TYPE); 

// Or passed from the other activity 
if (extras != null) { 
    progUri = extras 
     .getParcelable(MyLogContentProvider.CONTENT_ITEM_TYPE); 

    fillData(progUri); 
} 

confirmButton.setOnClickListener(new View.OnClickListener() { 
    public void onClick(View view) { 
    if (TextUtils.isEmpty(DOB.getText().toString())) { SAYS ERROR HERE??? 
     makeToast(); 
    } else { 
     setResult(RESULT_OK); 
     finish(); 
    } 
    } 

    }); 


    } 

    public void fillData(Uri uri) { 
    String[] projection =    {ProTable.COLUMN_NAME,ProTable.COLUMN_DOB, 
    ProTable.COLUMN_GENDER,ProTable.COLUMN_UNIT,     ProTable.COLUMN_MIN,ProTable.COLUMN_MAX,           
      ProTable.COLUMN_TYPE, ProTable.COLUMN_EMAIL,ProTable.COLUMN_NUMBER, 
     ProTable.COLUMN_ID }; 
Cursor cursor = getContentResolver().query(uri, projection, null, null, 
    null); 
if (cursor != null) { 
    cursor.moveToFirst(); 
    String idstr = cursor.getString(cursor.getColumnIndexOrThrow(ProTable.COLUMN_ID)); 

    String u = cursor.getString(cursor 
     .getColumnIndexOrThrow(ProTable.COLUMN_UNIT)); 

    for (int i = 0; i < units.getCount(); i++) { 

    String s = (String) units.getItemAtPosition(i); 
    if (s.equalsIgnoreCase(u)) 
     units.setSelection(i); 
    } 


String g = cursor.getString(cursor.getColumnIndexOrThrow(ProTable.COLUMN_GENDER)); 
    for (int i = 0; i < Gender.getCount(); i++) { 

    String s = (String) Gender.getItemAtPosition(i); 
    if (s.equalsIgnoreCase(g)) { 
     Gender.setSelection(i); 
    } 
    } 



    String t = cursor.getString(cursor.getColumnIndexOrThrow(ProTable.COLUMN_TYPE)); 
    for (int i = 0; i < type.getCount(); i++) { 

    String s = (String) type.getItemAtPosition(i); 
    if (s.equalsIgnoreCase(t)) { 
     type.setSelection(i); 
    } 
    } 


    name.setText(cursor.getString(cursor 
     .getColumnIndexOrThrow(ProTable.COLUMN_NAME))); 
    DOB.setText(cursor.getString(cursor 
     .getColumnIndexOrThrow(ProTable.COLUMN_DOB))); 
    min.setText(cursor.getString(cursor 
      .getColumnIndexOrThrow(ProTable.COLUMN_MIN))); 
     max.setText(cursor.getString(cursor 
      .getColumnIndexOrThrow(ProTable.COLUMN_MAX))); 
     email.setText(cursor.getString(cursor 
       .getColumnIndexOrThrow(ProTable.COLUMN_EMAIL))); 
      sms.setText(cursor.getString(cursor 
       .getColumnIndexOrThrow(ProTable.COLUMN_NUMBER))); 

    // Always close the cursor 
    cursor.close();} 
} 


    protected void onSaveInstanceState(Bundle outState) { 
    super.onSaveInstanceState(outState); 
    saveState(); 
    outState.putParcelable(MyLogContentProvider.CONTENT_ITEM_TYPE, progUri); 
    } 

     @Override 
    protected void onPause() { 
     super.onPause(); 
saveState(); 
    } 

    private void saveState() { 



    String t = (String) type.getSelectedItem(); 
    String u = (String) units.getSelectedItem(); 
String g = (String) Gender.getSelectedItem(); 
String n = name.getText().toString(); 
String d = DOB.getText().toString(); 
String mi = min.getText().toString(); 
String ma = max.getText().toString(); 
String e = email.getText().toString(); 
String s = sms.getText().toString(); 
// Only save if either summary or description 
// is available 

if (d.length() ==0) { 
    return; 
} 


ContentValues values = new ContentValues(); 

values.put(ProTable.COLUMN_NAME, n); 
values.put(ProTable.COLUMN_DOB, d); 
values.put(ProTable.COLUMN_GENDER, g); 
values.put(ProTable.COLUMN_UNIT, u); 
values.put(ProTable.COLUMN_TYPE, t); 
values.put(ProTable.COLUMN_MIN, mi); 
values.put(ProTable.COLUMN_MAX, ma); 
values.put(ProTable.COLUMN_EMAIL, e); 
values.put(ProTable.COLUMN_NUMBER, s); 
if (progUri == null) { 
    // New log 
    progUri = getContentResolver().insert(MyLogContentProvider.CONTENT_URI, values); 
} else { 
    // Update log 
    getContentResolver().update(progUri, values, null, null); 
} 
    } 

private void makeToast() { 
Toast.makeText(ProfileDetailActivity.this, "Please maintain a glucose log", 
    Toast.LENGTH_LONG).show(); 
    } 

数据库内容提供商

import java.util.Arrays; 
import java.util.HashSet; 


    import michelle.glucose.ProTable; 
    import michelle.glucose.ProfileDatabaseHelper; 

    import android.content.ContentProvider; 
import android.content.ContentResolver; 
import android.content.ContentValues; 
import android.content.UriMatcher; 
    import android.database.Cursor; 
    import android.database.sqlite.SQLiteDatabase; 
    import android.database.sqlite.SQLiteQueryBuilder; 
import android.net.Uri; 
import android.text.TextUtils; 


public class MyProfileContentProvider extends ContentProvider { 

    // database 
    private ProfileDatabaseHelper database; 

    // Used for the UriMacher 
    private static final int PRO = 10; 
    private static final int PROD = 20; 


    private static final String AUTHORITY =     
    "michelle.glucose.contentprovider.MyProfileContentProvider"; 

    private static final String BASE_PATH = "pros"; 
    public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY 
    + "/" + BASE_PATH); 

    public static final String CONTENT_TYPE = ContentResolver.CURSOR_DIR_BASE_TYPE 
    + "/pros"; 
public static final String CONTENT_ITEM_TYPE = ContentResolver.CURSOR_ITEM_BASE_TYPE 
    + "/pro"; 

    private static final UriMatcher sURIMatcher = new UriMatcher(UriMatcher.NO_MATCH); 
static { 
    sURIMatcher.addURI(AUTHORITY, BASE_PATH, PRO); 
    sURIMatcher.addURI(AUTHORITY, BASE_PATH + "/#", PROD); 
    } 

@Override 
public boolean onCreate() { 
    database = new ProfileDatabaseHelper(getContext()); 
return false; 
    } 

    @Override 
    public Cursor query(Uri uri, String[] projection, String selection, 
    String[] selectionArgs, String sortOrder) { 

// Uisng SQLiteQueryBuilder instead of query() method 
SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder(); 

// Check if the caller has requested a column which does not exists 
checkColumns(projection); 

// Set the table 
queryBuilder.setTables(ProTable.TABLE_PRO); 

int uriType = sURIMatcher.match(uri); 
switch (uriType) { 
case PRO: 
    break; 
case PROD: 
    // Adding the ID to the original query 
    queryBuilder.appendWhere(ProTable.COLUMN_ID + "=" 
     + uri.getLastPathSegment()); 
    break; 
default: 
    throw new IllegalArgumentException("Unknown URI: " + uri); 
} 

SQLiteDatabase db = database.getWritableDatabase(); 
Cursor cursor = queryBuilder.query(db, projection, selection, 
    selectionArgs, null, null, sortOrder); 
// Make sure that potential listeners are getting notified 
cursor.setNotificationUri(getContext().getContentResolver(), uri); 

return cursor; 
    } 

    @Override 
    public String getType(Uri uri) { 
    return null; 
    } 

    @Override 
    public Uri insert(Uri uri, ContentValues values) { 
    int uriType = sURIMatcher.match(uri); 
    SQLiteDatabase sqlDB = database.getWritableDatabase(); 
    int rowsDeleted = 0; 
    long id = 0; 
    switch (uriType) { 
    case PRO: 
    id = sqlDB.insert(ProTable.TABLE_PRO, null, values); 
    break; 
default: 
    throw new IllegalArgumentException("Unknown URI: " + uri); 
    } 
getContext().getContentResolver().notifyChange(uri, null); 
return Uri.parse(BASE_PATH + "/" + id); 
    } 

    @Override 
public int delete(Uri uri, String selection, String[] selectionArgs) { 
int uriType = sURIMatcher.match(uri); 
SQLiteDatabase sqlDB = database.getWritableDatabase(); 
int rowsDeleted = 0; 
switch (uriType) { 
case PRO: 
    rowsDeleted = sqlDB.delete(ProTable.TABLE_PRO, selection, 
     selectionArgs); 
    break; 
case PROD: 
    String id = uri.getLastPathSegment(); 
    if (TextUtils.isEmpty(selection)) { 
    rowsDeleted = sqlDB.delete(ProTable.TABLE_PRO, 
     ProTable.COLUMN_ID + "=" + id, 
     null); 
    } else { 
    rowsDeleted = sqlDB.delete(ProTable.TABLE_PRO, 
     ProTable.COLUMN_ID + "=" + id 
     + " and " + selection, 
     selectionArgs); 
    } 
    break; 
default: 
    throw new IllegalArgumentException("Unknown URI: " + uri); 
} 
getContext().getContentResolver().notifyChange(uri, null); 
return rowsDeleted; 
} 

    @Override 
    public int update(Uri uri, ContentValues values, String selection, 
    String[] selectionArgs) { 

int uriType = sURIMatcher.match(uri); 
SQLiteDatabase sqlDB = database.getWritableDatabase(); 
int rowsUpdated = 0; 
switch (uriType) { 
case PRO: 
    rowsUpdated = sqlDB.update(ProTable.TABLE_PRO, 
     values, 
     selection, 
     selectionArgs); 
    break; 
case PROD: 
    String id = uri.getLastPathSegment(); 
    if (TextUtils.isEmpty(selection)) { 
    rowsUpdated = sqlDB.update(ProTable.TABLE_PRO, 
     values, 
     ProTable.COLUMN_ID + "=" + id, 
     null); 
    } else { 
    rowsUpdated = sqlDB.update(ProTable.TABLE_PRO, 
     values, 
     ProTable.COLUMN_ID + "=" + id 
     + " and " 
     + selection, 
     selectionArgs); 
    } 
    break; 
default: 
    throw new IllegalArgumentException("Unknown URI: " + uri); 
} 
getContext().getContentResolver().notifyChange(uri, null); 
return rowsUpdated; 
    } 

    private void checkColumns(String[] projection) { 
     String[] available = {ProTable.COLUMN_NAME,ProTable.COLUMN_DOB, 
     ProTable.COLUMN_GENDER,ProTable.COLUMN_TYPE,ProTable.COLUMN_MIN,       

     ProTable.COLUMN_MAX,ProTable.COLUMN_UNIT, 

     ProTable.COLUMN_NUMBER, 
        ProTable.COLUMN_EMAIL, 
    ProTable.COLUMN_ID }; 
    if (projection != null) { 
    HashSet<String> requestedColumns = new HashSet<String>(Arrays.asList(projection)); 
    HashSet<String> availableColumns = new HashSet<String>(Arrays.asList(available)); 
    // Check if all columns which are requested are available 
     if (!availableColumns.containsAll(requestedColumns)) { 
    throw new IllegalArgumentException("Unknown columns in projection"); 
     } 
    } 
    } 

    } 

档案表

import android.content.Context; 
import android.database.Cursor; 
import android.database.sqlite.SQLiteDatabase; 
import android.util.Log; 

public class ProTable { 
private static final String DATABASE_NAME = "protable.db";        
    private static final int DATABASE_VERSION = 1; 
private ProfileDatabaseHelper psqLiteHelper; 
private SQLiteDatabase pdb; 
private Context context; 
    // Database table 
public static final String TABLE_PRO = "pro"; 
public static final String COLUMN_ID = "_id"; 
    public static final String COLUMN_NAME = "name"; 
    public static final String COLUMN_DOB = "dob"; 
public static final String COLUMN_GENDER = "gender"; 
public static final String COLUMN_TYPE = "type"; 
public static final String COLUMN_GLU = "glu"; 
public static final String COLUMN_MIN = "min"; 
public static final String COLUMN_MAX = "max"; 
public static final String COLUMN_EMAIL = "email"; 
public static final String COLUMN_UNIT = "unit"; 
public static final String COLUMN_NUMBER = "number"; 

// Database creation SQL statement 
    private static final 




    String DATABASE_CREATE = "create table " 
    + TABLE_PRO 
    + "(" 
    + COLUMN_ID + " integer primary key autoincrement, " 
    + COLUMN_NAME + " text not null, " 
    + COLUMN_DOB + " text not null," 
    + COLUMN_GENDER + " text not null," 
    + COLUMN_TYPE + " text not null," 
    + COLUMN_MIN + " text not null," 
    + COLUMN_MAX + " text not null," 
    + "COLUMN_UNIT" + "text not null," 
    + COLUMN_EMAIL + " text not null," 
    + COLUMN_NUMBER + " text not null" 
    + ");"; 




    public ProTable(Context ctx) { 
    this.context = ctx; 
    psqLiteHelper = new ProfileDatabaseHelper(context); 
} 

public ProTable openToRead() throws android.database.SQLException { 
     psqLiteHelper = new ProfileDatabaseHelper(context, DATABASE_NAME, null, 
       DATABASE_VERSION); 
     pdb = psqLiteHelper.getReadableDatabase(); 
     return this; } 

    public Cursor getEmail (String email) throws android.database.SQLException{ 
     Cursor mCursor 
     = pdb.query(TABLE_PRO, new String[] {COLUMN_ID, COLUMN_EMAIL },      

     COLUMN_EMAIL + "=" + email , null, null, null, null, null); 
    if (mCursor != null){ 
     mCursor.moveToFirst(); 
    } 
    return mCursor; 

    } 


    public String getSMS() throws android.database.SQLException{ 
     Cursor mCursor 
     = pdb.query(TABLE_PRO, new String[] {COLUMN_ID, COLUMN_NUMBER }, 

     COLUMN_NUMBER + "=" + COLUMN_NUMBER, null, null, null, null, null); 
    if (mCursor != null){ 
     mCursor.moveToFirst(); 

    }String number =mCursor.getString(mCursor.getColumnIndexOrThrow(COLUMN_NUMBER)); 

return number; 

    } 







public static void onCreate(SQLiteDatabase database) { 
    database.execSQL(DATABASE_CREATE); 
    } 

    public static void onUpgrade(SQLiteDatabase database, int oldVersion, 
    int newVersion) { 
    Log.w(ProTable.class.getName(), "Upgrading database from version " 
    + oldVersion + " to " + newVersion 
    + ", which will destroy all old data"); 
    database.execSQL("DROP TABLE IF EXISTS " + TABLE_PRO); 
    onCreate(database); 
    } 
    } 

数据库帮助班组长

import android.content.Context; 
    import android.database.sqlite.SQLiteDatabase; 
    import android.database.sqlite.SQLiteDatabase.CursorFactory; 
    import android.database.sqlite.SQLiteOpenHelper; 

    public class ProfileDatabaseHelper extends SQLiteOpenHelper { 

    private static final String DATABASE_NAME = "protable.db"; 
    private static final int DATABASE_VERSION = 1; 

    public ProfileDatabaseHelper(Context context) { 
    super(context, DATABASE_NAME, null, DATABASE_VERSION); 
     } 

    public ProfileDatabaseHelper(Context context, String databaseName, 
     CursorFactory factory, int databaseVersion) { 
    super(context, databaseName , factory, databaseVersion); 
     } 

    public ProfileDatabaseHelper(Context context, String databaseName, 
    Object factory, int databaseVersion) { 
super(context, DATABASE_NAME, null, DATABASE_VERSION); 
     } 

    // Method is called during creation of the database 
     @Override 
    public void onCreate(SQLiteDatabase database) { 
     ProTable.onCreate(database); 
     } 

    // Method is called during an upgrade of the database, 
    // e.g. if you increase the database version 
    @Override 
    public void onUpgrade(SQLiteDatabase database, int oldVersion, 
    int newVersion) { 
    ProTable.onUpgrade(database, oldVersion, newVersion); 
    } 
    } 

logcat的

E/AndroidRuntime(3797):FATAL EXCEPTION: main 
E/AndroidRuntime(3797): java.lang.NullPointerException 
    E/AndroidRuntime(3797):at      michelle.glucose.ProfileDetailActivity$1.onClick(ProfileDetailActivity.java:90) 
     E/AndroidRuntime(3797):at android.view.View.performClick(View.java:4204) 
E/AndroidRuntime(3797):at android.view.View$PerformClick.run(View.java:17355) 
E/AndroidRuntime(3797):at android.os.Handler.handleCallback(Handler.java:725) 
E/AndroidRuntime(3797): at android.os.Handler.dispatchMessage(Handler.java:92) 
E/AndroidRuntime(3797): at android.os.Looper.loop(Looper.java:137) 
E/AndroidRuntime(3797): at android.app.ActivityThread.main(ActivityThread.java:5041) 
E/AndroidRuntime(3797): at java.lang.reflect.Method.invokeNative(Native Method) 
E/AndroidRuntime(3797): at java.lang.reflect.Method.invoke(Method.java:511) 
E/AndroidRuntime(3797): at 
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
E/AndroidRuntime(3797): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
E/AndroidRuntime(3797): at dalvik.system.NativeStart.main(Native Method) 

Answer 1

老实说，NullPointerException异常是简单的错误，解决一个，它几乎总是在自己的代码中的错误。转到引发nullpointerexception的代码行，并考虑可能导致此问题的原因。我不知道是什么线90在你的来源，但例如如果是下面的代码行：

DOB.getText().toString() 

然后要么出生日期为空，或者DOB.getText（）为null。如果你不能确定哪一个，那么就在该行代码之前打印出值。然后考虑可能导致空指针的情况，或者通过代码回溯到DOB未初始化或其“文本”属性（未设置）的位置。