当我运行第一个活动时......没有错误 但是，当我尝试运行第二个活动ERROR时 “java.lang.RuntimeException：无法在未调用Looper.prepare（）的线程内创建处理程序”
没有循环问题的活动
package com.example.androidnotizer;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class LoginActivity extends Activity {
public static final String URL="jdbc:mysql://10.0.2.2/notizer";
public static final String USER="root";
public static final String PASSWORD="apple";
public static final String Driver_Class="com.mysql.jdbc.Driver";
public static final int RED=-65536;
Handler handler = new Handler();
Thread background;
String uid,pass;
int count=0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
TextView tv = (TextView)findViewById(R.id.textView4);
tv.setText("");
Button login = (Button) findViewById(R.id.button1);
login.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View arg0) {
EditText et1 = (EditText)findViewById(R.id.editText1);
EditText et2 = (EditText)findViewById(R.id.editText2);
uid=et1.getText().toString();
pass=et2.getText().toString();
TextView tv = (TextView)findViewById(R.id.textView4);
tv.setText("");
count=0;
doLogin();
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.login,menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.action_signup:
Intent i = new Intent(LoginActivity.this,SignUpActivity.class);
startActivity(i);
}
return true;
}
public void doLogin(){
background = new Thread(new Runnable(){
@Override
public void run(){
try{
Class.forName(Driver_Class);
Connection con = DriverManager.getConnection(URL, USER, PASSWORD);
Statement st = con.createStatement();
ResultSet rs =st.executeQuery("select * from login where user_id='"+ uid +"' and password='"+ pass +"'");
while(rs.next()){
count++;
}
}catch(Exception e){
e.printStackTrace();
}
Runnable r=new Runnable() {
@Override
public void run() {
if(count==0){
Toast.makeText(getApplicationContext(), "Unsuccessful Login", Toast.LENGTH_SHORT).show();
TextView tv = (TextView)findViewById(R.id.textView4);
tv.setText("Wrong user_id or password");
tv.setTextColor(RED);
}
else{
Intent i = new Intent(LoginActivity.this,NoticeActivity.class);
startActivity(i);
}
}
};
handler.post(r);
}
}
);
background.start();
}
}
活跃与循环问题
package com.example.androidnotizer;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.util.SparseBooleanArray;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;
public class StudentSignUpActivity extends Activity implements OnClickListener {
public static final String URL="jdbc:mysql://10.0.2.2/notizer";
public static final String USER="root";
public static final String PASSWORD="apple";
public static final String Driver_Class="com.mysql.jdbc.Driver";
Handler handler = new Handler();
Thread background;
Button button,combi;
ListView listView;
ArrayAdapter<String> adapter;
String fname,lname,mname,gender,mobile,designation,passPapers,roll,department,year;
int count=0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_student_sign_up);
Intent intent =getIntent();
fname = intent.getStringExtra("fname");
mname = intent.getStringExtra("mname");
lname = intent.getStringExtra("lname");
gender = intent.getStringExtra("gender");
mobile = intent.getStringExtra("mobile");
designation = intent.getStringExtra("designation");
roll = intent.getStringExtra("roll");
department = intent.getStringExtra("department");
year = intent.getStringExtra("year");
findViewById();
String[] sports = getResources().getStringArray(R.array.papers_array);
adapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_multiple_choice, sports);
listView.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
listView.setAdapter(adapter);
button.setOnClickListener(this);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.student_sign_up, menu);
return true;
}
private void findViewById() {
listView = (ListView) findViewById(R.id.dept_listView1);
button = (Button) findViewById(R.id.done);
}
@Override
public void onClick(View arg0) {
SparseBooleanArray checked = listView.getCheckedItemPositions();
passPapers="";
for (int i = 0; i < checked.size(); i++) {
int position = checked.keyAt(i);
if (checked.valueAt(i))
if((i+1) < checked.size()){
passPapers=passPapers+String.valueOf(adapter.getItem(position))+",";
}
else{
passPapers=passPapers+String.valueOf(adapter.getItem(position));
}
}
doSignUp();
}
public void doSignUp(){
Toast.makeText(getApplicationContext(),"Inside doSignUp()",Toast.LENGTH_LONG).show();
background = new Thread(new Runnable(){
@Override
public void run(){
try{
Toast.makeText(getApplicationContext(),"Inside try",Toast.LENGTH_LONG).show();
Class.forName(Driver_Class);
Connection con = DriverManager.getConnection(URL, USER, PASSWORD);
Statement st = con.createStatement();
//st.executeUpdate("insert into student(roll_no,fname,mname,lname,gender,mobile_no,department,year,pass_papers,desigantion) values('"+ roll +"','"+ fname +"','"+ mname +"','"+ lname +"','"+ gender +"','"+ mobile +"','"+ department +"','"+ year +"','"+ passPapers +"','"+ designation +"')");
st.executeUpdate("insert into login(user_id,password) values('"+ roll +"','"+ roll +"')");
count=1;
}catch(Exception e){
count=0;
e.printStackTrace();
Toast.makeText(getApplicationContext(),e.toString(),Toast.LENGTH_LONG).show();
}
Runnable r=new Runnable() {
@Override
public void run() {
if(count==1){
Toast.makeText(getApplicationContext(), "Successful Sign Up\nYour user_id : " + roll + "\nand password : " + roll, Toast.LENGTH_LONG).show();
Intent i = new Intent(StudentSignUpActivity.this,NoticeActivity.class);
startActivity(i);
}
else{
Toast.makeText(getApplicationContext(), "Unsuccessful Sign Up\nTry Again", Toast.LENGTH_LONG).show();
Intent i = new Intent(StudentSignUpActivity.this,SignUpActivity.class);
startActivity(i);
}
}
};
handler.post(r);
}
}
);
background.start();
}
}
logcat的
12-10 06:49:48.823: E/AndroidRuntime(5021): FATAL EXCEPTION: Thread-344
12-10 06:49:48.823: E/AndroidRuntime(5021): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
12-10 06:49:48.823: E/AndroidRuntime(5021): at android.os.Handler.<init>(Handler.java:197)
12-10 06:49:48.823: E/AndroidRuntime(5021): at android.os.Handler.<init>(Handler.java:111)
12-10 06:49:48.823: E/AndroidRuntime(5021): at android.widget.Toast$TN.<init>(Toast.java:324)
12-10 06:49:48.823: E/AndroidRuntime(5021): at android.widget.Toast.<init>(Toast.java:91)
12-10 06:49:48.823: E/AndroidRuntime(5021): at android.widget.Toast.makeText(Toast.java:238)
12-10 06:49:48.823: E/AndroidRuntime(5021): at com.example.androidnotizer.StudentSignUpActivity$1.run(StudentSignUpActivity.java:104)
12-10 06:49:48.823: E/AndroidRuntime(5021): at java.lang.Thread.run(Thread.java:841)
答案 0 :(得分：2)
您必须从UI线程本身运行Toast消息。使用此：
LoginActivity.this.runOnUiThread(new Runnable() {
public void run() {
if(count==1){
Toast.makeText(getApplicationContext(), "Successful Sign Up\nYour user_id : " + roll + "\nand password : " + roll, Toast.LENGTH_LONG).show();
Intent i = new Intent(StudentSignUpActivity.this,NoticeActivity.class);
startActivity(i);
}
else{
Toast.makeText(getApplicationContext(), "Unsuccessful Sign Up\nTry Again", Toast.LENGTH_LONG).show();
Intent i = new Intent(StudentSignUpActivity.this,SignUpActivity.class);
startActivity(i);
}
});
将此放在您创建的主题中。
答案 1 :(得分：0)
public void doSignUp(){
background = new Thread(new Runnable() {
@Override
public void run() {
String error = "-1";
try {
Class.forName(Driver_Class);
Connection con = DriverManager.getConnection(URL, USER, PASSWORD);
Statement st = con.createStatement();
st.executeUpdate("insert into login(user_id,password) values('"+ roll +"','"+ roll +"')");
count=1;
} catch(Exception e) {
count=0;
e.printStackTrace();
error = e.toString();
}
final String cause = error;
runOnUiThread(new Runnable() {
@Override
public void run() {
if(count==1) {
Toast.makeText(getApplicationContext(), "Successful Sign Up\nYour user_id : " + roll + "\nand password : " + roll, Toast.LENGTH_LONG).show();
Intent i = new Intent(StudentSignUpActivity.this,NoticeActivity.class);
startActivity(i);
} else {
Toast.makeText(getApplicationContext(), "Unsuccessful Sign Up\nTry Again (Cause : " + cause + ")", Toast.LENGTH_LONG).show();
Intent i = new Intent(StudentSignUpActivity.this,SignUpActivity.class);
startActivity(i);
}
}
});
}
});
background.start();
}
试试这个样本