线程未在android中运行

Question

I'm trying to connect my android application with mysql database using jdbc driver. I searched a lot and found that using thread or AsyncTask we can connect to the mysql directly. But i found difficult in asynctask, So i'm using thread to do that. Here is my code :

protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.search_customer);
    TextView t = (TextView) findViewById(R.id.Search_Customer_textView1);
    Button b = (Button) findViewById(R.id.Search_Customer_button1);
    b.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            Thread timer=new Thread(){
                public void run(){
                    try {
                        Class.forName("com.mysql.jdbc.Driver");
                        con = DriverManager.getConnection("jdbc:mysql://192.168.1.102:3306/outsidelaundry", "root", "");
                        Statement stmt = con.createStatement();
                        String query = "select Name from nonmember";
                        ResultSet rs = stmt.executeQuery(query);        
                        while(rs.next())
                        {
                            val = val + rs.getString(1) + "\n";
                        }
                        Toast.makeText(getApplicationContext(), val, Toast.LENGTH_LONG).show();
                        con.close();

                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            };
            timer.start();
            Toast.makeText(getApplicationContext(), "pressed", Toast.LENGTH_LONG).show();
        }
    });

    }

When i run the program thread is not starting/running. I didn't get any exception. Please help me with this.

Answer 1

You are displaying a Toast inside a thread. You should update ui on ui thread.

Inside thread's run method use runOnUiThread . runOnUiThread is a method of your activity class. Add @Override

    Thread timer=new Thread(){
        @Override
        public void run(){
          Log.i("Thread","Running"); 
          // you should see the log message if the thread runs
            try {

                    // do othere operations
                runOnUiThread(new Runnable() {
                        @Override 
                    public void run() {
                        // dispaly toast here;
                    }
                });

            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    };
    timer.start();

You can use asynctask also.

Answer 2

You need to call Toast on runOnUiThread() method

activity.runOnUiThread(new Runnable() {
    public void run() {
        Toast.makeText(getApplicationContext(), val, Toast.LENGTH_LONG).show();
    }
});

Answer 3

By Looking at your code, I can see that exception is getting generated but you have cached it so not as visible force close is happening while running the code.

Simple take on textbox in the layout and try to set the text for that as response. which confirms that you have no problem with JDBC or database.

and if that succeed then AsynTask is the best one to use here.

Answer 4

Try this...

  try{
     timer.join();
      }  
   catch (Exception e) {
                    e.printStackTrace();
                }

We have to wait until the thread finish it work.