總結(jié)Android中多線程更新應(yīng)用的頁(yè)面信息的方式

更新時(shí)間：2016年02月26日 17:00:04 作者：時(shí)光微涼

這篇文章主要介紹了總結(jié)Android中多線程更新應(yīng)用的頁(yè)面信息的方式,文中共總結(jié)了runOnUiThread、Handler、AsyncTask異步以及View直接在UI線程中更新的方法,需要的朋友可以參考下

一、runOnUiThread的用法
runOnUiThread是Activity的內(nèi)部方法，使用時(shí)最好指定當(dāng)前的環(huán)境變量（Context）。

new Thread(new Runnable() {

    @Override
    public void run() {
      runOnUiThread(new Runnable() {
        public void run() {
          Toast.makeText(mainActivity.this,"UI操作。。。",0).show();
        }
      });

    }
  }).start();

執(zhí)行runOnUiThread這個(gè)方法會(huì)調(diào)用父類中的

public final void runOnUiThread(Runnable action){
 if(Thread.currentThread()!=mUiThread){
 mHandler.post(action);
 }else{
  action.run();
 }
}

二、新線程中View直接在UI線程中更新的方法

textView.postDelayed(new Runnable() {

    @Override
    public void run() {
      textView.setText("Test View.post(Runnable)");

    }
  }, 1000);
-

 textView.post(new Runnable() {

    @Override
    public void run() {
      textView.setText("Test View.postDelay(Runnable，long)");

    }
  });

三、Handler(消息傳遞機(jī)制)使用

Handler myHandler = new Handler(){
 public void handleMessage(Message msg){
  super.handleMessage(msg); 
  }
};

也可以繼承handler

class MyHandler extends handler{
  public MyHandler(){

 }
 @Override
 public void handleMessage(Message msg){
  super.handleMessage(msg);
 }
}

分發(fā)Message或者Runnable對(duì)象到handler所在的線程中一般handler在主線程中。

handler中一些分發(fā)消息的方法：

post（Runnable）
postAtTime(Runnable,long)
postDelay(Runnable,long)
sendEmptyMessage(int what)
sendMessage(Message)
senMessageAtTime(Message，long)
sendMessageDelayed(Message,long)

post方式添加一個(gè)實(shí)現(xiàn)Runnable接口的匿名對(duì)象到消息對(duì)列中，在目標(biāo)收到消息后就可以以回調(diào)的方式在自己的線程中執(zhí)行

Message對(duì)象所具有的屬性：

屬性	類型	描述
arg1	int	用來(lái)存放整型數(shù)據(jù)
arg2	int	用來(lái)存放整型數(shù)據(jù)
obj	Object	用來(lái)存放發(fā)送給接收器的Object任意對(duì)象
replyTo	Messager	用來(lái)指定此Message發(fā)送到何處的可選Message對(duì)象
what	int	用于指定用戶自定義的消息代碼這樣接受者就可以了解這個(gè)消息的信息

Message message = Message.obtain();
message.arg1 = 1;
message.arg2 = 2;
message.obj = "Demo";
message.what = 3;
Bundle bundle = new Bundle();
bundle.putString( "name","Lucy");
message.setData(bundle);

下面貼上一段示例代碼（開(kāi)啟新線程實(shí)現(xiàn)電子廣告牌）

public class MainActivity extends Activity implements Runnable {

  private ImageView iv;
  private TextView tv;

  private Handler handler;
  private int[] path = new int[]{R.drawable.img01,R.drawable.img02,R.drawable.img03,R.drawable.img04,
      R.drawable.img05,R.drawable.img06};
  private String[] title = new String[]{"編程詞典系列","高效開(kāi)發(fā)","快樂(lè)分享","用戶人群","快速學(xué)習(xí)","全方位查詢"};
  private int index =0;
  @Override
  protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    iv = (ImageView) findViewById(R.id.imageView1);
    tv = (TextView) findViewById(R.id.textView1);


    Thread t = new Thread(this);
    t.start();
    handler = new Handler(){
      public void handleMessage(Message msg){
        if (msg.what ==1) {
          tv.setText(msg.getData().getString("title"));
          iv.setImageResource(path[msg.arg1]);
        }
        super.handleMessage(msg);
      }
    };


  }

  @Override
  public void run() {

    while(!Thread.currentThread().isInterrupted()){
      index = new Random().nextInt(path.length);
      Message m = handler.obtainMessage();
      m.arg1 = index;
      Bundle bundle = new Bundle();
      m.what = 1;
      bundle.putString("title", title[index]);
      m.setData(bundle);
      handler.sendMessage(m);
      try {
        Thread.sleep(2000);
      } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
      }      
    }    

  }

  }

四、AsyncTask異步任務(wù)的用法

AsyncTask實(shí)際上是一個(gè)線程池，在代碼上比handler要輕量級(jí)但是實(shí)際上要比Handler要耗資源，Handler僅僅發(fā)送了一個(gè)消息隊(duì)列，連線程池對(duì)沒(méi)有開(kāi)。
onPreExecute()，（可選方法）最新用戶調(diào)用excute時(shí)的接口，任務(wù)執(zhí)行之前調(diào)用該方法，可以在這里顯示進(jìn)度對(duì)話框。
doInBackground(Params...),后臺(tái)執(zhí)行比較好使的操作，不能直接操縱UI。在該方法中使用publishProgress（progress...）來(lái)更新任務(wù)的進(jìn)度。
onProgressUpdate(Progress...),在主線程中執(zhí)行，顯示進(jìn)度條
onPostExecute(Result),此方法可以從doinbackground得到的結(jié)果來(lái)操作UI，在主線程中執(zhí)行，執(zhí)行的結(jié)果作為參數(shù)返回。
onCancelled(Object)調(diào)用此方法可以隨時(shí)取消操作。

AsyncTask定義的三種泛型

params: 啟動(dòng)任務(wù)執(zhí)行的輸入?yún)?shù)，如：http請(qǐng)求的URL
progress:后臺(tái)任務(wù)執(zhí)行的百分比
result:返回結(jié)果，如：String、list集合等

 private class MyTask extends AsyncTask<params, progress, result> { ... }

示例代碼：

  private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
   protected Long doInBackground(URL... urls) {
     int count = urls.length;
     long totalSize = 0;
     for (int i = 0; i < count; i++) {
       totalSize += Downloader.downloadFile(urls[i]);
       publishProgress((int) ((i / (float) count) * 100));
       // Escape early if cancel() is called
       if (isCancelled()) break;
     }
     return totalSize;
   }

   protected void onProgressUpdate(Integer... progress) {
     setProgressPercent(progress[0]);
   }

   protected void onPostExecute(Long result) {
     showDialog("Downloaded " + result + " bytes");
   }
  }

獲取網(wǎng)絡(luò)圖片的示例代碼：

 public class MainActivity extends ActionBarActivity {
  private ImageView iv;
  private Button bt;
  private String imagePath = "http://192.168.1.1/sa";
  private ProgressDialog dialog;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    iv = (ImageView) findViewById(R.id.imageView1);
    bt = (Button) findViewById(R.id.button1);
    dialog = new ProgressDialog(this);
    dialog.setTitle("提示信息：");
    dialog.setMessage("正在下載。。。");
    bt.setOnClickListener(new OnClickListener() {

      @Override
      public void onClick(View v) {
        new MyTask().execute(imagePath);

      }
    });
  }
  public class MyTask extends AsyncTask<String, Void, Bitmap>{

    @Override
    protected Bitmap doInBackground(String... params) {
      HttpClient httpClient = new DefaultHttpClient();
      HttpGet httpGet = new HttpGet(params[0]);
      Bitmap bitmap = null;
      try {
        HttpResponse httpResponse = httpClient.execute(httpGet);
        if (httpResponse.getStatusLine().getStatusCode()==200) {
          HttpEntity httpEntity = httpResponse.getEntity();
          byte[] data = EntityUtils.toByteArray(httpEntity);
          bitmap= BitmapFactory.decodeByteArray(data, 0, data.length);
        }
      } catch (Exception e) {

        e.printStackTrace();
      }

      return bitmap;
    }

    @Override
    protected void onPreExecute() {      
      super.onPreExecute();
      dialog.show();
    }

    @Override
    protected void onPostExecute(Bitmap result) {      
      super.onPostExecute(result);
      iv.setImageBitmap(result);
      dialog.dismiss();
    }    
   }  
  }

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