```public class Login extends Activity{
EditText txtlogin,txtpwd;
Button btnzhuceButton, btndenglButton;
Tb_user tb_user=new Tb_user();
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.login);
txtlogin = (EditText) findViewById(R.id.logintext);
txtpwd =(EditText)findViewById(R.id.passwordtext);
btnzhuceButton = (Button) findViewById(R.id.zhuce);
btndenglButton = (Button) findViewById(R.id.denglu);
tb_user.setusername(txtlogin.getText().toString());
tb_user.setPassword(txtpwd.getText().toString());
btndenglButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
String str=txtlogin.getText().toString();
Intent intent = new Intent(Login.this, MainActivity.class);
userDAO userdao = new userDAO(Login.this);
Tb_user user=userdao.find(str);
if (user.getusername()
.equals(txtlogin.getText().toString())) {
if(user.getPassword()
.equals(txtpwd.getText().toString())){
startActivity(intent);
}else if(txtlogin.getText().toString().isEmpty()){
Toast.makeText(Login.this, "请输入用户名!",Toast.LENGTH_SHORT).show();
}else if(txtpwd.getText().toString().isEmpty()){
Toast.makeText(Login.this, "请输入密码!",Toast.LENGTH_SHORT).show();
}else {
Toast.makeText(Login.this, "请输入正确的密码",
Toast.LENGTH_SHORT).show();
}
}else {
Toast.makeText(Login.this, "请输入正确的用户名!",Toast.LENGTH_SHORT).show();
txtpwd.setText("");
txtlogin.setText("");}
}
});
btnzhuceButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
Intent intent= new Intent(Login.this,zhuce.class);
startActivity(intent);
}
});
}
}
public class Tb_user {
private int _id;
private String username;
private String password;
public Tb_user(){
super();
}
public Tb_user(int _id,String username,String password){
super();
this._id = _id;
this.username = username;
this.password = password;
}
public int getid() {
return _id;
}
public void setid(int _id) {
this._id=_id;
}
public String getusername(){
return username;
}
public void setusername(String username){
this.username = username;
}
public String getPassword(){
return password;
}
public void setPassword(String password){
this.password = password;
}
}
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import model.Tb_user;
public class userDAO {
private DBOpenHelper helper;
private SQLiteDatabase db;
public userDAO(Context context){
helper = new DBOpenHelper(context);
db = helper.getWritableDatabase();
}
public void add(Tb_user tb_user) {
db.execSQL("insert into tb_user (_id,username,password) values (?,?,?)",
new Object[] {tb_user.getid(),tb_user.getusername(),tb_user.getPassword()});
}
public void update(Tb_user tb_user) {
db.execSQL("update tb_user set password = ?",new Object[] { tb_user.getPassword() });
db.execSQL("update tb_user set username = ?",new Object[] { tb_user.getusername() });
}
public Tb_user find(String username) {
Cursor cursor = db.rawQuery("select _id from tb_user where username = ?",new String[]{username});
if (cursor.moveToNext()){
return new Tb_user(
cursor.getInt(cursor.getColumnIndex("_id")),
cursor.getString(cursor.getColumnIndex("username")),
cursor.getString(cursor.getColumnIndex("password")));
}
cursor.close();
return null;
}
public long getCount() {
Cursor cursor = db.rawQuery("select count(password) from tb_user", null);
if (cursor.moveToNext()){
return cursor.getLong(0);
}
cursor.close();
return 0;
}
public int getMaxId() {
Cursor cursor = db.rawQuery("select max(_id) from tb_user", null);
while (cursor.moveToLast()) {
return cursor.getInt(0);
}
cursor.close();
return 0;
}
}
06-17 09:07:03.690: E/AndroidRuntime(18694): at com.example.eddapp.Login$1.onClick(Login.java:39)
if (user.getusername()这行代码有空指针?