线程在Android的UI更新 [英] Threading UI updates in Android

问题描述

我刚开始与Android的开发和更新UI真的窃听我：/

I've just started with android development and updating the UI is really bugging me :/

这是我所得到的工作，到目前为止 -

This is what I've got working so far -

package projects.Move;

import android.os.Bundle;
import android.view.View;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Color;

public class Move extends Activity {

    private float y = 0;
    private long now = 0;  
    private float delay = 75;
    private Paint paint = new Paint();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new SimpleMotion(this));
        paint.setColor(Color.BLACK);
    }
    private class SimpleMotion extends View {

        public SimpleMotion(Context context) {
            super(context);
        }

        @Override protected void onDraw(Canvas canvas) {

            float x = canvas.getWidth() / 2;
            canvas.drawColor(Color.WHITE);
            canvas.drawCircle(x, y, 30, paint);  
            if(System.currentTimeMillis() - now > delay) y++;    
            invalidate();
        }
    }
}

它工作正常，但每个人都表示，做你的图形在主线程，所以我想（和失败），以将其传递给另一个线程。麻烦的是，我完全不知道如何，因为我真的从来没有使用线程。

It works fine but everybody says that doing your graphics in the main thread, so I'm trying (and failing) to pass it off to another thread. Trouble is, I have absolutely no idea how since really I've never used Threads.

这是谷歌提供使用主题似乎没有例子是非常清楚的，我不能真正按照它为我想做的事情。请问有人在这里给我的我怎么能做到什么，我在这里做有效地使用线程最基本的例子吗？

The examples that Google gives on using Threads doesn't seem to be very clear and I couldn't really follow it for what I want to do. Could I ask somebody out here to give me the most basic example of how I could do what I'm doing here efficiently using Threads?

在此先感谢：）

推荐答案

嗯，我想有一些混乱怎么回事。你必须从主线程做你的图形用户界面的更新（也称为GUI线程） - 否则，你也得到类似异常，布拉布拉已经泄露视图

Well, I guess there is some confusion going on here. You HAVE TO do your GUI updates from the main thread (also called the GUI thread) - otherwise you well get something like "Exception, blabla has leaked a view".

我猜有误解的是昂贵的操作，如网络，应在不同的线程比主线程来完成。而如果你想更新从网线的图形用户界面，你会做的ArtWorkAD说（或他联系说的）。

I guess what have misunderstood is that expensive operations, such as networking, should be done in a different thread than the main thread. And if you would like to update the GUI from the network thread you would do as ArtWorkAD says (or his links says).

所以，你想要做什么，你可以用类似与以下替换您SimpleMotion类实现的：

So for what you want to do, you could achieve with something like replacing your SimpleMotion class with the following:

private class SimpleMotion extends View {

        public SimpleMotion(Context context) {
            super(context);

            new Thread(new Runnable() {
                public void run() {
                    while(true){
                        try {
                            Thread.sleep(75);
                            y++;
                            postInvalidate();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }
              }).start();
        }

        @Override protected void onDraw(Canvas canvas) {

            float x = canvas.getWidth() / 2;
            canvas.drawColor(Color.WHITE);
            canvas.drawCircle(x, y, 30, paint);  
//            if(System.currentTimeMillis() - now > delay) y++;    
//            invalidate();
        }
    }

使用具有的OnDraw 无效（）（）的旧code 你会continously被重绘即使没有改变它的图形用户界面。

With your old code of having invalidate() in onDraw() you would continously be redrawing the gui even while there are no change to it.

新的code中的重要组成部分，是 postInvalidate（）。这样就可以告诉GUI线程 - 从另一个线程 - 重绘GUI

The important part of the new code is postInvalidate(). This makes it possible to tell the GUI thread - from another thread - to redraw the GUI.

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