android studio handler

来源：互联网发布：淘宝上在哪申请信用卡编辑：程序博客网时间：2024/06/18 11:50

handler用来更新ui，同时封装了消息传递机制。

不使用handler，而新建线程，是会引起错误的：

public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        final TextView textView=(TextView)findViewById(R.id.text);        new Thread(){            @Override            public void run() {                super.run();                try {                    Thread.sleep(1000);                    textView.setText("hi");                } catch (InterruptedException e) {                    e.printStackTrace();                }            }        }.start();    }}

原因是不能在非ui线程中更新ui。

使用handler：

public class MainActivity extends AppCompatActivity {    private Handler handler=new Handler();    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        final TextView textView=(TextView)findViewById(R.id.text);        new Thread(){            @Override            public void run() {                super.run();                try {                    Thread.sleep(1000);                    handler.post(new Runnable() {                        @Override                        public void run() {                            textView.setText("hi");                        }                    });                } catch (InterruptedException e) {                    e.printStackTrace();                }            }        }.start();    }}

handler实现图片轮播：

public class MainActivity extends AppCompatActivity {    private Handler handler=new Handler();    private ImageView imageView;    private int[] images={R.drawable.x,R.drawable.y,R.drawable.z};    private int index=0;    class RN implements Runnable{        @Override        public void run() {            index++;            System.out.println(index);            index=index%3;            imageView.setImageResource(images[index]);            handler.postDelayed(new RN(),1000);        }    }    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        final TextView textView=(TextView)findViewById(R.id.text);        imageView=(ImageView)findViewById(R.id.image);        handler.postDelayed(new RN(),1000);    }}

传递message：

public class MainActivity extends AppCompatActivity {    private Handler handler=new Handler(){        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            textView.setText(""+msg.arg1+"/"+msg.arg2+"/"+msg.obj);        }    };    private TextView textView;    private ImageView imageView;    private int[] img={R.drawable.x,R.drawable.y,R.drawable.z};    private int index;    private myRunnable runnable=new myRunnable();    class myRunnable implements Runnable{        @Override        public void run() {            index++;            index=index%3;            imageView.setImageResource(img[index]);            handler.postDelayed(runnable,1000);        }    }    class Person{        public int age;        public String name;        @Override        public String toString() {            return "Person{" +                    "age=" + age +                    ", name='" + name + '\'' +                    '}';        }    }    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        textView=(TextView)findViewById(R.id.text);        imageView=(ImageView)findViewById(R.id.image);        handler.postDelayed(runnable,1000);        new Thread(){            @Override            public void run() {                super.run();                try {                    Thread.sleep(1000);                    Message message=new Message();                    message.arg1=0;                    message.arg2=100;                    Person person=new Person();                    person.age=20;                    person.name="hehe";                    message.obj=person;                    handler.sendMessage(message);                } catch (InterruptedException e) {                    e.printStackTrace();                }            }        }.start();    }}
threadhandler:

public class Main2Activity extends AppCompatActivity {    private HandlerThread thread;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main2);        thread=new HandlerThread("handler thread");        thread.start();        Handler handler=new Handler(thread.getLooper()){            @Override            public void handleMessage(Message msg) {                super.handleMessage(msg);                System.out.println("thread----"+Thread.currentThread());            }        };        handler.sendEmptyMessage(1);    }}

0 0