我开发了一个连接到数据库的Android应用程序。登录功能已成功完成。当我添加注册功能时，应用程序停止工作。 APK文件已成功构建，主要活动也成功启动，但是当我点击任何按钮时，应用程序停止。这是主要的活动代码：`public class MainActivity扩展AppCompatActivity {
SQLiteDatabase db;
String url;
EditText emailText, passText;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
getSupportActionBar().hide();
final TextView registerText = (TextView) findViewById(R.id.registertext);
final Button loginbtn = (Button) findViewById(R.id.login);
db = openOrCreateDatabase("User", Context.MODE_PRIVATE, null);
db.execSQL("CREATE TABLE IF NOT EXISTS Login(ID VARCHAR, NAME VARCHAR, pass VARCHAR);");
registerText.setOnClickListener(
new TextView.OnClickListener() {
public void onClick(View view){
Intent intent = new Intent(MainActivity.this, Register.class);
startActivity(intent);
}
}
);
loginbtn.setOnClickListener(
new Button.OnClickListener(){
public void onClick(View view) {
//check connection
ConnectivityManager cm = (ConnectivityManager) getSystemService(getBaseContext().CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getNetworkInfo(0);
url = "http://skillsexchangecyprus.com/SEC/SkillsLogin.php";
//Check fields
RelativeLayout relativeLayout = (RelativeLayout) findViewById(R.id.activity_main);
final TextView alert = (TextView)findViewById(R.id.alert);
if (emailText.getText().toString().matches(" ") || passText.getText().toString().matches(" ")) {
Snackbar snackbar = Snackbar.make(relativeLayout, "Fill In Empty Fields", Snackbar.LENGTH_LONG);
snackbar.show();
} else {
new BackgroundTasks(alert).execute(url);
}
}});}
class BackgroundTasks extends AsyncTask <String, Void, String> {
TextView alert;
public BackgroundTasks(TextView textview) {
this.alert = textview;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
alert.setVisibility(View.VISIBLE);
alert.setText("Loading...");
}
String emtxt= emailText.getText().toString();
String passtxt= passText.getText().toString();
@Override
protected String doInBackground(String... strings) {
String result = "";
try {
URL url = new URL(strings[0]);
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setDoOutput(true);
ArrayList<NameValuePair> params = new ArrayList<NameValuePair>();
final EditText emailText = (EditText) findViewById(R.id.email);
final EditText passText = (EditText) findViewById(R.id.password);
params.add(new BasicNameValuePair("email", emtxt));
params.add(new BasicNameValuePair("password", passtxt));
OutputStream os = urlConnection.getOutputStream();
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os, "UTF-8"));
writer.write(getQuery(params));
writer.flush();
writer.close();
os.close();
InputStream inputStream = new BufferedInputStream(urlConnection.getInputStream());
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
StringBuilder builder = new StringBuilder();
String inputString;
while ((inputString = bufferedReader.readLine()) != null) {
builder.append(inputString);
}
result = String.valueOf(builder.toString());
urlConnection.disconnect();
} catch (IOException e) {
e.printStackTrace();
}
return result;
}
@NonNull
private String getQuery(List<NameValuePair> params) throws UnsupportedEncodingException {
StringBuilder out = new StringBuilder();
boolean first = true;
for (NameValuePair pair : params) {
if (first)
first = false;
else
out.append("&");
out.append(URLEncoder.encode(pair.getName(), "UTF-8"));
out.append("=");
out.append(URLEncoder.encode(pair.getValue(), "UTF-8"));
}
return out.toString();
}
@Override
protected void onPostExecute(String temp) {
if (temp.trim().matches("Empty")) {
alert.setText("Invalid username or password");
} else {
alert.setVisibility(View.GONE);
String[] Split = temp.split("_");
db.execSQL("INSERT INTO Login values(' " + Split[1] + " ' , ' " + Split[0] + " ', ' " + Split[3] + " ')");
Intent intent = new Intent(MainActivity.this, FindSkill.class);
startActivity(intent);
}
}
}
}`
这里是注册码：
public class Register extends AppCompatActivity {
String url;
EditText name,email,pass;
Button registerBtn;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.register);
registerBtn.setOnClickListener(
new Button.OnClickListener(){
public void onClick(View view) {
ConnectivityManager cm = (ConnectivityManager) getSystemService(getBaseContext().CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getNetworkInfo(0);
url="http://skillsexchangecyprus.com/SEC/SkillsRegister.php";
RelativeLayout relativeLayout = (RelativeLayout) findViewById(R.id.regLayout);
name = (EditText) findViewById(R.id.namereg);
email = (EditText) findViewById(R.id.emailreg);
pass = (EditText) findViewById(R.id.passwordreg);
final TextView alert = (TextView)findViewById(R.id.alert);
if (name.getText().toString().matches("")||email.getText().toString().matches("")||pass.getText().toString().matches("")) {
Snackbar snackbar = Snackbar
.make(relativeLayout, "Fill in Empty Fields", Snackbar.LENGTH_LONG);
snackbar.show();
} else {
new BackgroundTasks(alert).execute(url);
}
}});}
class BackgroundTasks extends AsyncTask<String, Void, String> {
TextView alert;
public BackgroundTasks(TextView textview) {
this.alert = textview;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
alert.setVisibility(View.VISIBLE);
alert.setText("Saving....");
}
String nametxt = name.getText().toString();
String emtxt = email.getText().toString();
String passtxt = pass.getText().toString();
@Override
protected String doInBackground(String... strings) {
String task = "";
try {
URL url = new URL(strings[0]);
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setDoOutput(true);
ArrayList<NameValuePair> params = new ArrayList<>();
params.add(new BasicNameValuePair("nameReg", nametxt));
params.add(new BasicNameValuePair("emailReg", emtxt));
params.add(new BasicNameValuePair("passwordReg", passtxt));
OutputStream os = urlConnection.getOutputStream();
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os, "UTF-8"));
writer.write(getQuery(params));
writer.flush();
writer.close();
os.close();
InputStream stream = new BufferedInputStream(urlConnection.getInputStream());
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(stream));
StringBuilder builder = new StringBuilder();
String inputString;
while ((inputString = bufferedReader.readLine()) != null) {
builder.append(inputString);
}
task = String.valueOf(builder.toString());
urlConnection.disconnect();
} catch (IOException e) {
e.printStackTrace();
}
return task;
}
@NonNull
private String getQuery(List<NameValuePair> params) throws UnsupportedEncodingException {
StringBuilder result = new StringBuilder();
boolean first = true;
for (NameValuePair pair : params) {
if (first)
first = false;
else
result.append("&");
result.append(URLEncoder.encode(pair.getName(), "UTF-8"));
result.append("=");
result.append(URLEncoder.encode(pair.getValue(), "UTF-8"));
}
return result.toString();
}
@Override
protected void onPostExecute(String temp) {
if (temp.trim().matches("Success")) {
alert.setText("Successfully saved");
} else {
String msg = "NOT FOUND";
alert.setVisibility(View.VISIBLE);
alert.setText("Try again");
}
}
}
}
现在Logcat充满了错误和警告!!!
答案 0 :(得分：0)
你在做什么是错的。
String emtxt= emailText.getText().toString();
String passtxt= passText.getText().toString();
@Override
protected String doInBackground(String... strings) {
String result = "";
try {
URL url = new URL(strings[0]);
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setDoOutput(true);
ArrayList<NameValuePair> params = new ArrayList<NameValuePair>();
final EditText emailText = (EditText) findViewById(R.id.email);
final EditText passText = (EditText) findViewById(R.id.password);
您正在尝试在后台方法中创建视图对象，并且您尝试在此之前从它们获取值。相应地重新格式化代码并检查。