AndroidHandler原理分析及实例代码-创新互联

Android Handler 原理分析

Handler一个让无数android开发者头疼的东西，希望我今天这边文章能为您彻底根治这个问题

今天就为大家详细剖析下Handler的原理

Handler使用的原因

1.多线程更新Ui会导致UI界面错乱
2.如果加锁会导致性能下降
3.只在主线程去更新UI,轮询处理

Handler使用简介

其实关键方法就2个一个sendMessage，用来接收消息

另一个是handleMessage，用来处理接收到的消息

下面是我参考疯狂android讲义，写的一个子线程和主线程之间相互通信的demo

对原demo做了一定修改

public class MainActivity extends AppCompatActivity { 
  public final static String UPPER_NUM="upper_num"; 
  private EditText editText; 
  public jisuanThread jisuan; 
  public Handler mainhandler; 
  private TextView textView; 
  class jisuanThread extends Thread{ 
    public Handler mhandler; 
    @Override 
    public void run() { 
      Looper.prepare(); 
      final ArrayList al=new ArrayList<>(); 
      mhandler=new Handler(){ 
        @Override 
        public void handleMessage(Message msg) { 
 
          if(msg.what==0x123){ 
            Bundle bundle=msg.getData(); 
            int up=bundle.getInt(UPPER_NUM); 
            outer: 
            for(int i=3;i<=up;i++){ 
              for(int j=2;j<=Math.sqrt(i);j++){ 
                if(i%j==0){ 
                  continue outer; 
                } 
              } 
              al.add(i); 
            } 
            Message message=new Message(); 
            message.what=0x124; 
            Bundle bundle1=new Bundle(); 
            bundle1.putIntegerArrayList("Result",al); 
            message.setData(bundle1); 
            mainhandler.sendMessage(message); 
          } 
        } 
      }; 
      Looper.loop(); 
    } 
  } 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    editText= (EditText) findViewById(R.id.et_num); 
    textView= (TextView) findViewById(R.id.tv_show); 
    jisuan=new jisuanThread(); 
    jisuan.start(); 
    mainhandler=new Handler(){ 
      @Override 
      public void handleMessage(Message msg) { 
        if(msg.what==0x124){ 
          Bundle bundle=new Bundle(); 
          bundle=msg.getData(); 
          ArrayList al=bundle.getIntegerArrayList("Result"); 
          textView.setText(al.toString()); 
        } 
      } 
    }; 
    findViewById(R.id.bt_jisuan).setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
        Message message=new Message(); 
        message.what=0x123; 
        Bundle bundle=new Bundle(); 
        bundle.putInt(UPPER_NUM, Integer.parseInt(editText.getText().toString())); 
        message.setData(bundle); 
        jisuan.mhandler.sendMessage(message); 
      } 
    }); 
  } 
}