空对象引用错误:Android Studio使用SQLite
因此,我尝试改编本教程: 我自己的项目。它是Android/Java中的一个基本注册和登录,使用SQLite和Volley通过PHP登录到SQL服务器。 我可以得到书面工作没有问题的教程。然而,在将其转移到我的项目时,我遇到了崩溃空对象引用错误:Android Studio使用SQLite,android,sqlite,android-volley,Android,Sqlite,Android Volley,因此,我尝试改编本教程: 我自己的项目。它是Android/Java中的一个基本注册和登录,使用SQLite和Volley通过PHP登录到SQL服务器。 我可以得到书面工作没有问题的教程。然而,在将其转移到我的项目时,我遇到了崩溃 05-12 01:18:05.763 1965-1965/com.disclosure_scots.disclosure_scots E/AndroidRuntime? FATAL EXCEPTION: main Process: com.disclosure_
05-12 01:18:05.763 1965-1965/com.disclosure_scots.disclosure_scots E/AndroidRuntime? FATAL EXCEPTION: main
Process: com.disclosure_scots.disclosure_scots, PID: 1965
java.lang.NullPointerException: Attempt to invoke virtual method 'void com.disclosure_scots.disclosure_scots.AppController.addToRequestQueue(com.android.volley.Request, java.lang.String)' on a null object reference
at com.disclosure_scots.disclosure_scots.RegisterActivity.registerUser(RegisterActivity.java:194)
at com.disclosure_scots.disclosure_scots.RegisterActivity.access$300(RegisterActivity.java:34)
at com.disclosure_scots.disclosure_scots.RegisterActivity$1.onClick(RegisterActivity.java:90)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
它所引用的RegisterActivity中的行也是
AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
}
所涉及的活动包括:
注册活动
package com.disclosure_scots.disclosure_scots;
import android.app.ProgressDialog;
import android.content.Intent;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import com.disclosure_scots.disclosure_scots.AppConfig;
import com.disclosure_scots.disclosure_scots.AppController;
import com.disclosure_scots.disclosure_scots.SQLiteHandler;
import com.disclosure_scots.disclosure_scots.SessionManager;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.HashMap;
import java.util.Map;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;
import com.android.volley.Request.Method;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;
public class RegisterActivity extends ActionBarActivity {
private static final String TAG = RegisterActivity.class.getSimpleName();
private Button btnRegister;
private EditText inputFullName;
private EditText inputEmail;
private EditText inputPassword;
private EditText inputTel_No;
private EditText inputHome_Add;
private EditText inputPostcode;
private CheckBox inputPostal;
private ProgressDialog pDialog;
private SessionManager session;
private SQLiteHandler db;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
inputFullName = (EditText) findViewById(R.id.editTextName);
inputEmail = (EditText) findViewById(R.id.editTextEmail);
inputPassword = (EditText) findViewById(R.id.editTextPass);
inputTel_No = (EditText) findViewById(R.id.editTextPhone);
inputHome_Add = (EditText) findViewById(R.id.editTextPost);
inputPostcode = (EditText) findViewById(R.id.editTextPostcode);
inputPostal = (CheckBox) findViewById(R.id.PostalcheckBox);
btnRegister = (Button) findViewById(R.id.btnRegister);
// Progress dialog
pDialog = new ProgressDialog(this);
pDialog.setCancelable(false);
// Session manager
session = new SessionManager(getApplicationContext());
// SQLite database handler
db = new SQLiteHandler(getApplicationContext());
// Check if user is already logged in or not
if (session.isLoggedIn()) {
// User is already logged in. Take him to Legal disclaimer activity
Intent intent = new Intent(RegisterActivity.this,
LegalDiscActivity.class);
startActivity(intent);
finish();
}
// Register Button Click event
btnRegister.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
String name = inputFullName.getText().toString();
String email = inputEmail.getText().toString();
String password = inputPassword.getText().toString();
if (!name.isEmpty() && !email.isEmpty() && !password.isEmpty()) {
registerUser(name, email, password);
} else {
Toast.makeText(getApplicationContext(),
"Please enter your details!", Toast.LENGTH_LONG)
.show();
}
}
});
// Link to Login Screen
/*btnLinkToLogin.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Intent i = new Intent(getApplicationContext(),
LoginActivity.class);
startActivity(i);
finish();
}
});*/
}
/**
* Function to store user in MySQL database will post params(tag, name,
* email, password) to register url
* */
private void registerUser(final String name, final String email,
final String password) {
// Tag used to cancel the request
String tag_string_req = "req_register";
pDialog.setMessage("Registering ...");
showDialog();
StringRequest strReq = new StringRequest(Method.POST,
AppConfig.URL_REGISTER, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
Log.d(TAG, "Register Response: " + response.toString());
hideDialog();
try {
JSONObject jObj = new JSONObject(response);
boolean error = jObj.getBoolean("error");
if (!error) {
// User successfully stored in MySQL
// Now store the user in sqlite
String uid = jObj.getString("uid");
JSONObject user = jObj.getJSONObject("user");
String name = user.getString("name");
String email = user.getString("email");
String created_at = user
.getString("created_at");
// Inserting row in users table
db.addUser(name, email, uid, created_at);
// Launch login activity
Intent intent = new Intent(
RegisterActivity.this,
LoginActivity.class);
startActivity(intent);
finish();
} else {
// Error occurred in registration. Get the error
// message
String errorMsg = jObj.getString("error_msg");
Toast.makeText(getApplicationContext(),
errorMsg, Toast.LENGTH_LONG).show();
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.e(TAG, "Registration Error: " + error.getMessage());
Toast.makeText(getApplicationContext(),
error.getMessage(), Toast.LENGTH_LONG).show();
hideDialog();
}
}) {
@Override
protected Map<String, String> getParams() {
// Posting params to register url
Map<String, String> params = new HashMap<String, String>();
params.put("tag", "register");
params.put("name", name);
params.put("email", email);
params.put("password", password);
return params;
}
};
// Adding request to request queue
AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
}
private void showDialog() {
if (!pDialog.isShowing())
pDialog.show();
}
private void hideDialog() {
if (pDialog.isShowing())
pDialog.dismiss();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_register, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
package com.disclosure\u scots.disclosure\u scots;
导入android.app.ProgressDialog;
导入android.content.Intent;
导入android.support.v7.app.ActionBarActivity;
导入android.os.Bundle;
导入android.util.Log;
导入android.view.Menu;
导入android.view.MenuItem;
导入com.disposition\u scots.disposition\u scots.AppConfig;
导入com.disposition\u scots.disposition\u scots.AppController;
导入com.disposition\u scots.disposition\u scots.SQLiteHandler;
导入com.disposition\u scots.disposition\u scots.SessionManager;
导入org.json.JSONException;
导入org.json.JSONObject;
导入java.util.HashMap;
导入java.util.Map;
导入android.view.view;
导入android.widget.Button;
导入android.widget.CheckBox;
导入android.widget.EditText;
导入android.widget.Toast;
导入com.android.volley.Request.Method;
导入com.android.volley.Response;
导入com.android.volley.VolleyError;
导入com.android.volley.toolbox.StringRequest;
公共类注册活动扩展了ActionBarActivity{
私有静态最终字符串标记=RegisterActivity.class.getSimpleName();
专用按钮BTN注册表;
私有编辑文本输入全名;
私人编辑文本输入电子邮件;
私有编辑文本输入密码;
私人编辑文本输入号码;
私人编辑文本输入puthome_Add;
私人编辑文本输入邮政编码;
私人支票输入邮政;
私人对话;
私人会话管理器会话;
私有SQLiteHandler数据库;
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity\u寄存器);
inputFullName=(EditText)findViewById(R.id.editTextName);
inputEmail=(EditText)findViewById(R.id.editTextEmail);
inputPassword=(EditText)findViewById(R.id.editTextPass);
Inputel_No=(EditText)findViewById(R.id.editTextPhone);
inputHome_Add=(EditText)findViewById(R.id.editTextPost);
inputPostcode=(EditText)findViewById(R.id.editTextPostcode);
inputPostal=(复选框)findViewById(R.id.PostalcheckBox);
btnRegister=(按钮)findViewById(R.id.btnRegister);
//进度对话框
pDialog=新建进度对话框(此对话框);
pDialog.setCancelable(假);
//会话管理器
session=newsessionmanager(getApplicationContext());
//SQLite数据库处理程序
db=新的SQLiteHandler(getApplicationContext());
//检查用户是否已登录
if(session.isLoggedIn()){
//用户已登录。请将其带到法律免责声明活动
意向意向=新意向(RegisterActivity.this,
Legaldisc(活动类);
星触觉(意向);
完成();
}
//注册按钮点击事件
btnRegister.setOnClickListener(新视图.OnClickListener(){
公共void onClick(视图){
字符串名称=inputFullName.getText().toString();
字符串email=inputEmail.getText().toString();
字符串密码=inputPassword.getText().toString();
如果(!name.isEmpty()&&&!email.isEmpty()&&&!password.isEmpty()){
注册者(姓名、电子邮件、密码);
}否则{
Toast.makeText(getApplicationContext(),
“请输入您的详细信息!”,Toast.LENGTH\u LONG)
.show();
}
}
});
//链接到登录屏幕
/*btnLinkToLogin.setOnClickListener(新视图.OnClickListener(){
公共void onClick(视图){
意图i=新意图(getApplicationContext(),
物流活动(类);
星触觉(i);
完成();
}
});*/
}
/**
*在MySQL数据库中存储用户的函数将发布参数(标签、名称、,
*电子邮件、密码)以注册url
* */
私有无效注册器(最终字符串名称、最终字符串电子邮件、,
最终字符串(密码){
//用于取消请求的标记
String tag_String_req=“req_register”;
pDialog.setMessage(“注册…”);
showDialog();
StringRequest strReq=新的StringRequest(Method.POST,
AppConfig.URL\u寄存器,新的Response.Listener(){
@凌驾
公共void onResponse(字符串响应){
Log.d(标记,“寄存器响应:+Response.toString());
hideDialog();
试一试{
JSONObject jObj=新的JSONObject(响应);
布尔错误=jObj.getBoolean(“错误”);
如果(!错误){
//用户成功存储在MySQL中
//现在将用户存储在sqlite中
stringuid=jObj.getString(“uid”);
JSONObject user=jObj.getJSONObject(“用户”);
字符串名称=user.getString(“名称”);
String email=user.getString(“电子邮件”);
在=用户处创建的字符串
.getString(“创建于”);
//在用户表中插入行
db.addUser(姓名、电子邮件、uid、创建地址);
//启动登录活动
意图=新意图(
package com.disclosure_scots.disclosure_scots;
/**
* Created by Administrator on 09/05/2015.
*/
import android.app.Application;
import android.text.TextUtils;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.Volley;
public class AppController extends Application {
public static final String TAG = AppController.class.getSimpleName();
private RequestQueue mRequestQueue;
private static AppController mInstance;
@Override
public void onCreate() {
super.onCreate();
mInstance = this;
}
public static synchronized AppController getInstance() {
return mInstance;
}
public RequestQueue getRequestQueue() {
if (mRequestQueue == null) {
mRequestQueue = Volley.newRequestQueue(getApplicationContext());
}
return mRequestQueue;
}
public <T> void addToRequestQueue(Request<T> req, String tag) {
req.setTag(TextUtils.isEmpty(tag) ? TAG : tag);
getRequestQueue().add(req);
}
public <T> void addToRequestQueue(Request<T> req) {
req.setTag(TAG);
getRequestQueue().add(req);
}
public void cancelPendingRequests(Object tag) {
if (mRequestQueue != null) {
mRequestQueue.cancelAll(tag);
}
}
}
<application
android:name="(your app package).app.AppController" // <--this line
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
...../>