public class MainActivity extends AppCompatActivity {
    private Button mButton;
    private TextView mTextView;
    @Override
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mButton = (Button) findViewById(R.id.btn_button
 
);
        mTextView = (TextView) findViewById(R.id.tv_show);
        mButton.setOnClickListener(new View.OnClickListener() {
            @Override
public void onClick(View view) {
                new Thread(new Runnable() {
                    @Override
public void run() {
                        mTextView
 
.setText("1321456");
                    }
                }).start();
            }
        });
    }

}

這個程式碼表示不能線上程裡邊更新UI，

下面的程式碼展示更新UI 宣告一個靜態常量 ，新增了一個handle物件 重寫handleMessage()

public static final int UPDATE_TEXT = 1;
private Button mButton;
private TextView mTextView;
private Handler handle = new 
 
Handler(){
    public void handleMessage(Message msg){
        switch (msg.what){
            case UPDATE_TEXT:
                //在這裡進行UI更新
mTextView.setText("123456");
                break;
            default:
                break;
        }
    }
};
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mButton = (Button) findViewById(R.id.btn_button);
    mTextView = (TextView) findViewById(R.id.tv_show);
    mButton.setOnClickListener(new View.OnClickListener() {
        @Override
public void onClick(View view) {
            new Thread(new Runnable() {
                @Override
public void run() {
                    Message message = new Message();
                    message.what = UPDATE_TEXT;
                    handle.sendMessage(message);
                }
            }).start();
        }
    });
}