實(shí)例講解Android多線程應(yīng)用開(kāi)發(fā)中Handler的使用

2020-04-11 10:52:55

字體：大中小

供稿：網(wǎng)友

其實(shí)可以理解Handler為主線程和另外的線程之間進(jìn)行數(shù)據(jù)更新的東東，并且Handler在主線程中，并在Handler直接調(diào)用線程的run方法

package com.Handler02;  import android.app.Activity; import android.os.Bundle; import android.os.Handler;  public class Handler02Activity extends Activity {   /** Called when the activity is first created. */   private Handler handler=new Handler();   @Override   public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     handler.post(thread1);     setContentView(R.layout.main);         System.out.println("================Main==============="+Thread.currentThread().getId());     System.out.println("============Main========="+Thread.currentThread().getName());   }   Runnable thread1=new Runnable() {          @Override     public void run() {       System.out.println("======thread1==============="+Thread.currentThread().getId());       System.out.println("========thread1============"+Thread.currentThread().getName());       try {         Thread.sleep(10000);       } catch (Exception e) {         // TODO: handle exception       }            }   }; }

結(jié)果是主線程等待10s后才顯示出來(lái)，并且線程ID

package com.Handler4;  import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.view.View; import android.widget.TextView;  public class Handler4Activity extends Activity {   /** Called when the activity is first created. */   private TextView textView;   private MyHandler myHandler=new MyHandler();   @Override   public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.main);     textView=(TextView)this.findViewById(R.id.textView1);   }   class MyHandler extends Handler{     //從消息隊(duì)列中取出并handleMessage處理消息     @Override     public void handleMessage(Message msg) {       textView.setText((String)msg.obj);     }   }   public void download(View view){     Thread thread=new Thread(new Runnable() {              @Override       public void run() {         try {           String s="zhangzhao";           Thread.sleep(5000);           //數(shù)據(jù)發(fā)送出來(lái)           //textView.setText(s);           Message message=Message.obtain();//最好不要new，這個(gè)obtain會(huì)節(jié)省資源           message.obj=s;           myHandler.sendMessage(message);//沒(méi)有指定looper那么就會(huì)發(fā)送給主線程中的looper                    } catch (InterruptedException e) {           // TODO Auto-generated catch block           e.printStackTrace();         }                }            });     thread.start();//會(huì)出錯(cuò)原因是在非UI線程里面直接操作UI     //主線程維護(hù)了一個(gè)消息對(duì)列，當(dāng)其他的線程有數(shù)據(jù)需要傳遞給主線程的時(shí)候，你就把數(shù)據(jù)封裝成一個(gè)Message對(duì)象，然后放在主線程的     //消息隊(duì)列中去，對(duì)應(yīng)消息的處理由Looper，子線程通過(guò)Handler把下載完的數(shù)據(jù)封裝到Message里面，然后把消息取出來(lái)交給Handler進(jìn)行處理     //通過(guò)Handle和Message實(shí)現(xiàn)兩個(gè)線程之間達(dá)到共享數(shù)據(jù)   } }

package com.Handler5;  import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.view.View; import android.widget.Button; import android.widget.ProgressBar; import android.widget.TextView;  public class Handler5Activity extends Activity {   /** Called when the activity is first created. */   private ProgressBar progressBar;   private Button button;   private TextView textView;   private MyHandler myHandler=new MyHandler();   int i=0;   @Override   public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);        setContentView(R.layout.main);     progressBar = (ProgressBar)this.findViewById(R.id.progressBar1);     textView=(TextView)this.findViewById(R.id.textView1);   }   class MyHandler extends Handler{     @Override     public void handleMessage(Message msg) {       int pos =(Integer)msg.obj;       progressBar.setProgress(pos);       textView.setText(pos+"%");            }   }   public void downLoad(View view){           new Thread(new Runnable() {              @Override       public void run() {         while(i<=100){           try {             Thread.sleep(300);             i+=10;             Message message=Message.obtain();             message.obj=i;             myHandler.sendMessage(message);           } catch (InterruptedException e) {             // TODO Auto-generated catch block             e.printStackTrace();           }                  }                }     }).start();   } }

效果：

2016131175347004.jpg (283×189)