Handler类的简单使用与进度条的更新

我们废话少说直接上代码：
下面是activity_main_xml布局文件

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:orientation="horizontal" >    <ProgressBar        android:id="@+id/progress"        style="?android:attr/progressBarStyleHorizontal"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:layout_alignParentLeft="true"        android:layout_below="@+id/textView1"        android:layout_marginTop="72dp" />    <TextView        android:id="@+id/textView1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignParentTop="true"        android:layout_centerHorizontal="true"        android:layout_marginTop="38dp"        android:text="进度条测试"        android:textSize="20sp" /></RelativeLayout>

下面是Handler类消息处理机制

Handler handler=new Handler(){    @Override    public void handleMessage(Message msg){        super.handleMessage(msg);        switch (msg.what) {        case INC:            bar.incrementProgressBy(5);            Log.d("TAGGAG", "Thread id "+Thread.currentThread().getId()+",handler INC");            break;        case DEC:            bar.incrementProgressBy(-5);            Log.d("TAGGAG", "Thread id "+Thread.currentThread().getId()+",handler DEC");        break;        default:            Log.d("TAGGAG", "Thread id "+Thread.currentThread().getId()+",handler default");            break;        }    }};

接下来我们来是进度条的实现，写在onStart()里

@Override    protected void onStart(){        super.onStart();        bar=(ProgressBar)findViewById(R.id.progress);        bar.setProgress(0);        Thread handlerBarThread=new Thread(new Runnable() {            @Override            public void run() {                // TODO Auto-generated method stub                for(int i=0;i<20&&is_running;i++){                    try {                        Thread.sleep(1000);                        Message msg=new Message();                        msg.what=INC;                        handler.sendMessage(msg);                        Log.d("TAGGAG", "Thread id "+Thread.currentThread().getId()+",sendMessage INC");                    } catch (Exception e) {                        // TODO: handle exception                    }                }                    for(int j=0;j<20&&is_running;j++){                        try {                            Thread.sleep(1000);                            Message msg=new Message();                            msg.what=DEC;                            handler.sendMessage(msg);                            Log.d("TAGGAG", "Thread id "+Thread.currentThread().getId()+",sendMessage DEC");                        } catch (Exception e) {                            // TODO: handle exception                        }                    }                }        });        is_running=true;        handlerBarThread.start();    }

好了，运行下程序如下：