handler更新UI主线程

示例：下面代码的功能是修改UI主线程TextView的内容

public class MainActivity extends Activity {

    private Button btn_start;

    private TextView numTxtView;

    int i = 2;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        numTxtView = (TextView) this.findViewById(R.id.numTxtView);

        btn_start = (Button)this.findViewById(R.id.btn_start);

        final Handler handler = new Handler() {

            @Override

            public void handleMessage(Message msg) {

                if (msg.what == 0x1233) {

                    //修改主线程中TextView所显示的内容

                    numTxtView.setText("" + i);

                    i++;

                }

            }

        };

        btn_start.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                //定义一个计时器，让改计时器周期性地执行指定任务

                new Timer().schedule(new TimerTask() {

                    @Override

                    public void run() {

                        //发送空消息

                        handler.sendEmptyMessage(0x1233);

                    }

                }, 0,1000);

            }

        });

    }

}