Java Android应用程序持续崩溃，严重异常

我正在做一个笔记应用程序，在那里我做笔记它被存储在

数据库中，我可以编辑和删除它，所以，我正要继续我的编辑和删除冒险，我想我会运行这个应用程序，看看它是否正常，它刚刚崩溃

数据库处理程序

  package com.example.quicknotetaker;

  import java.util.ArrayList;

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

 public class DatabaseHandler extends SQLiteOpenHelper {

// All Static variables
// Database Version
private static final int DATABASE_VERSION = 1;

// Database Name
private static final String DATABASE_NAME = "Qdatabase";

// Contacts table name
private static final String DATABASE_TABLE = "qtable";

// Contacts Table Columns names
private static final String KEY_ID = "id";
private static final String KEY_TITLE = "title";
private static final String KEY_NOTE = "note";
private final ArrayList<Editablegetset> titlenoteslist = new ArrayList<Editablegetset>();

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

// Creating Tables
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_DATABASE_TABLE = "CREATE TABLE " + DATABASE_TABLE + "("
    + KEY_ID + " INTEGER PRIMARY KEY," + KEY_TITLE + " TEXT,"
    + KEY_NOTE + " TEXT,)";
db.execSQL(CREATE_DATABASE_TABLE);
}

// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Drop older table if existed
db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);

// Create tables again
onCreate(db);
}

/**
 * All CRUD(Create, Read, Update, Delete) Operations
 */

// Adding new contact
public void Add_titlenotes(Editablegetset editablegetset) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_TITLE, editablegetset.getTitle()); // Contact Name
values.put(KEY_NOTE, editablegetset.getNote()); // Contact Phone

// Inserting Row
db.insert(DATABASE_TABLE, null, values);
db.close(); // Closing database connection
}

// Getting single data
Editablegetset Get_Set(int id) {
SQLiteDatabase db = this.getReadableDatabase();

Cursor cursor = db.query(DATABASE_TABLE, new String[] { KEY_ID,
    KEY_TITLE, KEY_NOTE}, KEY_ID + "=?",
    new String[] { String.valueOf(id) }, null, null, null);
if (cursor != null)
    cursor.moveToFirst();

Editablegetset editablegetset = new Editablegetset(Integer.parseInt(cursor.getString(0)),
    cursor.getString(1), cursor.getString(2));
// return contact
cursor.close();
db.close();

return editablegetset;
}

// Getting All Contacts
public ArrayList<Editablegetset> Get_Set() {
try {
    titlenoteslist.clear();

    // Select All Query
    String selectQuery = "SELECT  * FROM " + DATABASE_TABLE;

    SQLiteDatabase db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery(selectQuery, null);

    // looping through all rows and adding to list
    if (cursor.moveToFirst()) {
    do {
        Editablegetset editablegetset = new Editablegetset();
        editablegetset.setID(Integer.parseInt(cursor.getString(0)));
        editablegetset.setTitle(cursor.getString(1));
        editablegetset.setNote(cursor.getString(2));

        // Adding to list
        titlenoteslist.add(editablegetset);
    } while (cursor.moveToNext());
    }

    // return list
    cursor.close();
    db.close();
    return titlenoteslist;
} catch (Exception e) {
    // TODO: handle exception
    Log.e("all title and notes", "" + e);
}

return titlenoteslist;
}

// Updating individual notes
public int Update_Contact(Editablegetset editablegetset) {
SQLiteDatabase db = this.getWritableDatabase();

ContentValues values = new ContentValues();
values.put(KEY_TITLE, editablegetset.getTitle());
values.put(KEY_NOTE, editablegetset.getNote());


// updating row
return db.update(DATABASE_TABLE, values, KEY_ID + " = ?",
    new String[] { String.valueOf(editablegetset.getID()) });
}

// Deleting single notes
public void Delete_Contact(int id) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete(DATABASE_TABLE, KEY_ID + " = ?",
    new String[] { String.valueOf(id) });
db.close();
}

// Getting notes Count
public int totalnotes() {
String countQuery = "SELECT  * FROM " + DATABASE_TABLE;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(countQuery, null);
cursor.close();

// return count
return cursor.getCount();
}

}

这是我的获取集方法

package com.example.quicknotetaker;

public class Editablegetset {

// private variables
public int _id;
public String _title;
public String _note;


public Editablegetset() {
}

// constructor
public Editablegetset(int id, String title, String note) {
this._id = id;
this._title = title;
this._note = note;


}

// constructor
public Editablegetset(String title, String note) {
this._title = title;
this._note = note;

}

// getting ID
public int getID() {
return this._id;
}

// setting id
public void setID(int id) {
this._id = id;
}

// getting title
public String getTitle() {
return this._title;
}

// setting title
public void setTitle(String title) {
this._title = title;
}

// getting note
public String getNote() {
return this._note;
}

// setting note
public void setNote(String note) {
this._note = note;
}



}

Logcat

03-20 07:48:37.458: D/AndroidRuntime(23951): Shutting down VM
03-20 07:48:37.458: W/dalvikvm(23951): threadid=1: thread exiting with uncaught       exception (group=0x4170ad40)  
03-20 07:48:37.460: E/AndroidRuntime(23951): FATAL EXCEPTION: main 
03-20 07:48:37.460: E/AndroidRuntime(23951): Process: com.example.quicknotetaker, PID: 23951 
03-20 07:48:37.460: E/AndroidRuntime(23951): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.quicknotetaker/com.example.quicknotetaker.Mainnote}: java.lang.NullPointerException 
03-20 07:48:37.460: E/AndroidRuntime(23951):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209) 
03-20 07:48:37.460: E/AndroidRuntime(23951):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2269) 
03-20 07:48:37.460: E/AndroidRuntime(23951):    at android.app.ActivityThread.access$800(ActivityThread.java:139) 
03-20 07:48:37.460: E/AndroidRuntime(23951):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1210) 
03-20 07:48:37.460: E/AndroidRuntime(23951):    at android.os.Handler.dispatchMessage(Handler.java:102) 
03-20 07:48:37.460: E/AndroidRuntime(23951):    at android.os.Looper.loop(Looper.java:136)
03-20 07:48:37.460: E/AndroidRuntime(23951):    at android.app.ActivityThread.main(ActivityThread.java:5102) 
03-20 07:48:37.460: E/AndroidRuntime(23951):    at java.lang.reflect.Method.invokeNative(Native Method) 
03-20 07:48:37.460: E/AndroidRuntime(23951):    at java.lang.reflect.Method.invoke(Method.java:515) 
03-20 07:48:37.460: E/AndroidRuntime(23951):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785) 
03-20 07:48:37.460: E/AndroidRuntime(23951):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) 
03-20 07:48:37.460: E/AndroidRuntime(23951):    at dalvik.system.NativeStart.main(Native Method) 
03-20 07:48:37.460: E/AndroidRuntime(23951): Caused by: java.lang.NullPointerException 
03-20 07:48:37.460: E/AndroidRuntime(23951):    at com.example.quicknotetaker.Mainnote.onCreate(Mainnote.java:30) 
03-20 07:48:37.460: E/AndroidRuntime(23951):    at android.app.Activity.performCreate(Activity.java:5248) 
03-20 07:48:37.460: E/AndroidRuntime(23951):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1110) 
03-20 07:48:37.460: E/AndroidRuntime(23951):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2173) 
03-20 07:48:37.460: E/AndroidRuntime(23951):    ... 11 more

我真的需要帮助我花了很多时间在这上面谢谢logcat：

Caused by: java.lang.NullPointerException
  at com.example.quicknotetaker.Mainnote.onCreate(Mainnote.java:30)

您的
onCreate（）
只能在这里进行NPE：

ab.setOnClickListener(...);

当
ab
为空时。您可以使用
findViewById（）
初始化它，如果找不到视图，它将返回
null

确保您的
activity\u main note
layout确实有一个id为
addnote
的
按钮
，“noteid”的值为0，并且您可能没有值为0的密钥id。数据库查询可能不返回任何行。所以Editablegetset类被设置为null。所以当你调用edtitle.setText（ed.getTitle（））时；您将获得NullPointerException，因为ed为null。在从Editablegetset类获取值之前添加一个空检查，如下代码所示

  if(ed!=null)
  {
  edtitle.setText(ed.getTitle());
  enotes.setText(ed.getNote());         
  }

同时正确设置“noteid”以匹配db值。
基于代码中的我的视图。在main中的int变量noteid中获得空指针

试着用这个

int noteid = 0;

希望这能对您有所帮助。
例外情况是？当我在android手机上运行它时，它只是说-不幸的是，Quick Note taker已经停止。你需要从logcat发布堆栈跟踪。这将显示错误的确切位置。我现在添加了logcate，因为
onCreate（）
中有一个NPE，布局可能没有id为
addnote
的视图。您的权利。布局有问题。对不起，我已经起床很长时间了。你能看到addbutton有什么错误吗？当我按下它的时候，应用程序崩溃了。开始调试它，logcat中的stacktrace也出现了异常。它会说03-20 08:19:46.698:E/OpenGLRenderer（26027）：GL\u无效\u操作你认为如果我添加自动增量，它会解决问题吗？你确定吗？但根据我的经验。如果我遇到空指针异常，我总是初始化我的变量。除了我，我无法检查你的指针。如果初始化变量，效果会更好：）
int noteid = 0;