Android 多线程

Question

我正在尝试在 Android 中开发简单的多线程应用程序。 这是我的代码如下：

package com.sudarshan.mythread;
import android.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.EditText;

public class MainActivity extends AppCompatActivity implements Runnable {

EditText t;
StringBuffer buffer = new StringBuffer();
@Override

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    t=(EditText) findViewById(R.id.editText);
    int n = 8; // Number of threads
    for (int i=0; i<n; i++)
    {
        Thread object = new Thread(new MainActivity());
        object.start();
        t.setText(buffer.toString());
    }
}
public void run()
{
    try
    {
        // Displaying the thread that is running


        buffer.append ("Thread " +
                Thread.currentThread().getId() +
                " is running");

    }
    catch (Exception e)
    {
        // Throwing an exception
        showMessage("Error","Error Message");
    }
}
public void showMessage(String title,String Message)
{
    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setCancelable(true);
    builder.setTitle(title);
    builder.setMessage(Message);
    builder.show();
} }

并且我正在尝试在 stringbuffer 缓冲区中显示数据。每次运行线程时都应将数据附加到 Stringbuffer 中。但是通过编辑文本没有显示任何内容。我做错了什么？

Answer 1

你已经写了t.setText(buffer.toString()); 线程启动后立即。 但到那时，缓冲区可能尚未更新。 因此，在更新缓冲区后更新EditText 。

buffer.append ("Thread " +
            Thread.currentThread().getId() +
            " is running");
// Note: If you want to update UI from background thread, you should do it the following way.
runOnUiThread(new Runnable() {
    public void run(){
        t.setText(buffer.toString());
    }
});

另外，正如@Bek 所说，您应该用this替换new MainActivity() 。