打开数据库sqlite android时出错null异常 [英] Error null exception while open database sqlite android

问题描述

大家好，我在尝试在sqlite android中打开数据库时遇到了问题。我想将查询中的数据与来自textview的数据进行匹配，但是当应用程序运行时，强制关闭。我看到了log cat和用于open db的方法是null异常。



这是db类的完整代码

< pre lang =java> public class DBReminder {
私人 SQLiteDatabase db;
private DBHelper helper;
private 上下文konteks;
private static final < span class =code-sdkkeyword> String DBName = db_reminder.db;
private static final < span class =code-sdkkeyword> String TableName = task_table;
public static final < span class =code-sdkkeyword> String ID = id;
public static final < span class =code-sdkkeyword> String LATITUDE = 纬度;
public static final < span class =code-sdkkeyword> String LONGITUDE = 经度;
public static final < span class =code-sdkkeyword> String RADIUS = radius;
public static final < span class =code-sdkkeyword> String ALAMAT = alamat;
public static final < span class =code-sdkkeyword> String KONTEKS_TUGAS = konteks_tugas;
private static final < span class =code-sdkkeyword> String makeTable = create table
+ TableName + （
+ ID + 整数主键自动增量，
+ LATITUDE + integer not null，
+ LONGITUDE + integer not null，
+ RADIUS + integer not null，
+ ALAMAT + varchar（50）not null，
+ KONTEKS_TUGAS + varchar（50）not null
+ ）;;

private static class DBHelper extends SQLiteOpenHelper {
public DBHelper（Context context）{
super （context，DBName，null， 1 ）;
// TODO自动生成的构造函数存根
}

@覆盖
public void onCreate（SQLiteDatabase db）{
// TODO自动生成的方法存根
Log.d（ db， create table）;
db.execSQL（makeTable）;
}

@覆盖
public void onUpgrade（SQLiteDatabase db， int oldVersion， int newVersion）{
// TODO自动生成的方法存根
Log.d （ db， 升级表）;
db.execSQL（ drop table if exists + TableName）;
}
}

public DBReminder（上下文c）{
此 .konteks = c;
helper = new DBHelper（c）;
}

public DBReminder openWrite（Context c） throws SQLException {
helper = new DBHelper（c）;
db = helper.getWritableDatabase（）;
返回 此;
}

public DBReminder openRead（Context c） throws SQLException {
helper = new DBHelper（c）;
db = helper.getReadableDatabase（）;
返回 此;
}

public void closeConn（）{
helper.close（）;
}

public void insertTask（Task tugas）{
openWrite（konteks）;
ContentValues val = new ContentValues（）;
val.put（LATITUDE，tugas.getLatitude（））;
val.put（LONGITUDE，tugas.getLongitude（））;
val.put（RADIUS，tugas.getRadius（））;
val.put（ALAMAT，tugas.getAlamat（））;
val.put（KONTEKS_TUGAS，tugas.getKonteks（））;
db.insert（TableName，null，val）;
closeConn（）;
}
}

我在这个功能中使用它

  public   void  cekPosisi（ String  txtAlamat）{
  if （txtAlamat.toString（）。length（）>  0 ）{
 dbHandler.openRead（getApplicationContext（））; 
 字符串 sql =   select * from task_table其中alamat =' + txtAlamat +  ';; 
光标rs = db.rawQuery（sql，null）; 
  if （rs！= null）{
 rs.moveToFirst（）; 
 字符串 addr = rs.getString（rs.getColumnIndex（  alamat））; 
 Toast.makeText（ this ，  Anda ada tugas di + addr，Toast.LENGTH_LONG）。show（）; 
} 其他 {
 Toast.makeText（此，  Anda tidak ada tugas di lokasi sekarang，Toast.LENGTH_LONG）。show（）; 
} 
 dbHandler.closeConn（）; 
 rs.close（）; 
} 其他 {
 Toast.makeText（此，  Tidak ada alamat，Toast.LENGTH_LONG）。show（）; 
} 
} 

函数cekPosisi用于

  //   cek tugas  
 txtAddr = teksAlamat.getText（）的toString（）; 
  this  .cariTugas.setOnClickListener（ new  OnClickListener（）{
 
  @覆盖 
  public   void  onClick（查看v）{
  //   TODO自动生成的方法存根 
 Log.d（  alamat textView，txtAddr）; 
 cekPosisi（txtAddr）; 
} 
}）; 

请帮助我，谢谢......

解决方案

在

public void cekPosisi（String txtAlamat）



而不是



dbHandler.closeConn（）;

rs.close（）;



试试



rs.close（）;

dbHandler.closeConn（）;





如果这不是我的话你可以粘贴logcat错误行号

Hi everyone, i have a problem while try to open database in sqlite android. I want to match the data in query with the data from textview but when the app run it force close. I saw the log cat and the method that use for open db is null exception.

This is the complete code of db class

public class DBReminder {
	private SQLiteDatabase db;
	private DBHelper helper;
	private Context konteks;
	private static final String DBName = "db_reminder.db";
	private static final String TableName = "task_table";
	public static final String ID = "id";
	public static final String LATITUDE = "latitude";
	public static final String LONGITUDE = "longitude";
	public static final String RADIUS = "radius";
	public static final String ALAMAT = "alamat";
	public static final String KONTEKS_TUGAS = "konteks_tugas";
	private static final String makeTable = "create table "
        + TableName + "("
        + ID + " integer primary key autoincrement,"
        + LATITUDE + " integer not null,"
        + LONGITUDE + " integer not null,"
        + RADIUS + " integer not null,"
        + ALAMAT + " varchar(50) not null,"
        + KONTEKS_TUGAS + " varchar(50) not null"
        + ");";

	private static class DBHelper extends SQLiteOpenHelper {
		public DBHelper(Context context) {
			super(context, DBName, null, 1);
			// TODO Auto-generated constructor stub
		}

		@Override
		public void onCreate(SQLiteDatabase db) {
			// TODO Auto-generated method stub
			Log.d("db", "create table");
			db.execSQL(makeTable);
		}

		@Override
		public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
			// TODO Auto-generated method stub
			Log.d("db", "upgrade table");
			db.execSQL("drop table if exists " + TableName);
		}
	}
	
	public DBReminder(Context c) {
		this.konteks = c;
		helper = new DBHelper(c);
	}
	
	public DBReminder openWrite(Context c) throws SQLException {
		helper = new DBHelper(c);
		db = helper.getWritableDatabase();
		return this;
	}
	
	public DBReminder openRead(Context c) throws SQLException {
		helper = new DBHelper(c);
		db = helper.getReadableDatabase();
		return this;
	}
	
	public void closeConn() {
		helper.close();
	}
	
	public void insertTask(Task tugas) {
		openWrite(konteks);
		ContentValues val = new ContentValues();
		val.put(LATITUDE, tugas.getLatitude());
		val.put(LONGITUDE, tugas.getLongitude());
		val.put(RADIUS, tugas.getRadius());
		val.put(ALAMAT, tugas.getAlamat());
		val.put(KONTEKS_TUGAS, tugas.getKonteks());
		db.insert(TableName, null, val);
		closeConn();
	}
}

And i use that in this function

public void cekPosisi(String txtAlamat) {
		if (txtAlamat.toString().length() > 0) {
			dbHandler.openRead(getApplicationContext());
			String sql = "select * from task_table where alamat = '"+txtAlamat+"';";
			Cursor rs = db.rawQuery(sql, null);
			if(rs != null) {
				rs.moveToFirst();
				String addr = rs.getString(rs.getColumnIndex("alamat"));
				Toast.makeText(this, "Anda ada tugas di " + addr, Toast.LENGTH_LONG).show();
			} else {
				Toast.makeText(this, "Anda tidak ada tugas di lokasi sekarang", Toast.LENGTH_LONG).show();
			}
			dbHandler.closeConn();
			rs.close();
		} else {
			Toast.makeText(this, "Tidak ada alamat", Toast.LENGTH_LONG).show();
		}
	}

The function cekPosisi used in

//cek tugas
		txtAddr = teksAlamat.getText().toString();
		this.cariTugas.setOnClickListener(new OnClickListener() {
			
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				Log.d("alamat textView", txtAddr);
				cekPosisi(txtAddr);
			}
		});

Please help me, thanks...

解决方案

In
public void cekPosisi(String txtAlamat)

instead of

dbHandler.closeConn();
rs.close();

try

rs.close();
dbHandler.closeConn();


and if this doesn''t work can you paste logcat error line number

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