如何延迟衍生的线程时UI线程的Runnable运行是不是一种选择？ [英] How to delay spawned thread when a Runnable run on UI thread isn't an option?

问题描述

我曾与一个previous的问题，我不能肯定我的code是否有内存泄漏问题。它被UI线程上运行，因此阻断几个答案担心。这是真实的，它运行在UI线程并不会产生一个新的..

I had issues with a previous question where I was unsure whether my code had a memory leak. A few answers were concerned with it being run on the UI thread and so blocking. It is true, it runs on the UI thread and doesn't spawn a new one..

所以要解决它，我用发而不是处理程序产卵UI之外一个新的线程。现在的问题是，我不能管理我一样在用户界面线程中有一个人跑去做耽误了。

So to solve it I use Thread instead of Handler to spawn a new thread outside of UI. The problem now is that I can't manage to delay it like I did with the one ran in the UI thread.

这是我的previous问题在我的原来的UI线程code是：的是内存泄漏这个Runnable的安全和以下是更新code这产生一个新的线程：

This is my previous question where my original UI thread code is: Is this Runnable safe from memory leak? and the following is the updated code which spawns a new thread:

package com.example.helloworld;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.widget.TextView;
import android.util.Log;
import java.lang.ref.WeakReference;

public class HelloWorldActivity extends Activity
{

    private static TextView txtview;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        txtview = (TextView) findViewById(R.id.mainview);

        Thread t = new Thread(new WeakRunnable(txtview));
        t.start();
    }

    private static final class WeakRunnable implements Runnable {
        private final WeakReference<TextView> mtextview;

        protected WeakRunnable(TextView textview){
            mtextview = new WeakReference<TextView>(textview);
        }

            @Override
            public void run() {
                TextView textview = mtextview.get();
                if (textview != null) {

                    try {
                        Thread.sleep(1500);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    int test = 5*5;
                    txtview.setText("Hola Mundo"+test);
                }
                Log.d("com.example.helloworld", "" + Thread.currentThread().getName()); // Outputs "Thread-<num>" if not running on UI thread
            }
    }           

}

它只是设置视图文本和追加的结果 5 * 5 。

当我启动它退出本身应用程序，我不知道为什么。有个声音告诉我，我推迟了错误的方式或者使用 runOnUiThread 错了。即使在更改 txtview.setText（世界报霍拉+测试）; 到 runOnUiThread（txtview.setText（世界报霍拉+测试））; 不会编译给错误：无效类型这里不允许。

As soon as I start the app it quits itself and I don't get why. Something tells me I'm delaying it the wrong way or using runOnUiThread wrong. Even changing txtview.setText("Hola Mundo"+test); to runOnUiThread( txtview.setText("Hola Mundo"+test) ); doesn't compile giving error: 'void' type not allowed here.

在一言以蔽之：计算（ 5 * 5 在这种情况下）应该在一个单独的线程来完成，以避免阻塞主要（UI）线程和文本应在服用computated项目从单独的线程的用户界面进行设置。你自己的一个简单的例子就可以了了。

In a nutshell: Computation (5*5 in this case) should be done on a separate thread to avoid blocking the main (UI) thread, and the text should be set on the UI taking the computated item from the separate thread. A simple example of your own would be fine too.

更新
我已经发布的答案，我自己的问题实施的AsyncTask 。

推荐答案

您可以使用状态，直到它被满足，而不是使用Thread.sleep代码（）;

You can use condition until it is met instead of using thread.sleep();

 Condition.wait(new Callable<Boolean>() {
            @Override
            public Boolean call() throws Exception {
                return textview != null;
            }
        });

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