Question

线程似乎不起作用我试过sysout并检查logcat，我试图改变textview

package com.android.wakey;

import java.text.SimpleDateFormat;
import java.util.Calendar;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

public class finallytime extends Activity implements Runnable{

    boolean n = true;
    TextView tv;
    Thread t;
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fullscreen);
        tv= (TextView) findViewById(R.id.fullscreen_content);
        System.out.println("=======>>>>>> DONE");

        t = new Thread();

        t.start();

}
    @Override
    protected void onPause() {
        // TODO Auto-generated method stub
        super.onPause();
        n=false;
    }
    @Override
    protected void onResume() {
        // TODO Auto-generated method stub
        super.onResume();
        n=true;
    }

    @Override
    public void run() {
        System.out.println("====================>>>>>>>>>>>>>>>>>>>>>>\n==============================>>>>>>>>>>>>>>>>>>>>>>>" + n);
        // TODO Auto-generated method stub
        while(n){

        tv.findViewById(R.id.fullscreen_content);
        tv.setText("THis must work");
        Calendar cal = Calendar.getInstance();
        cal.getTime();
        SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss a");
        tv.setText((sdf.format(cal.getTime())).toString());

        try {
            t.sleep(1000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
}
    }}

这是我建立的android的一个小代码，但线程似乎不起作用文本视图不会更改，仍会显示默认文本。

请帮助

Answer 1

这里实际上有两个问题，一个是你永远不会为线程调用runnable

t = new Thread(this);
t.start();

接下来是您尝试在单独的线程中更新UI元素，而这是您无法做到的。所以在线程中你需要使用runOnUiThread()方法来更新textview

Answer 2

尝试

t = new Thread(this); // missing this

您正在从线程更新ui。

tv.setText("THis must work");

你应该从ui线程更新ui。使用runOnUiThread

将cal和sdf声明为类成员。

Calendar cal;
SimpleDateFormat sdf;

然后

@Override
public void run() {

    while(n){
    cal = Calendar.getInstance();
    cal.getTime();
    sdf = new SimpleDateFormat("HH:mm:ss a");
    runOnUiThread(new Runnable() {
        @Override
        public void run() {
            tv.setText((sdf.format(cal.getTime())).toString());
        }
    });
    try {
        t.sleep(1000);
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
   }
}

线程不工作

2 个答案: