第二个作业

实现按两次退出(查资料得出)

public class MainActivity extends AppCompatActivity {
    private boolean isExit = false;
    private Handler mHandler = new Handler() {
    };

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    //监听手机的物理按键点击事件
    public boolean onKeyDown(int wqm, KeyEvent event) {
        if (wqm == KeyEvent.KEYCODE_BACK) {
            if (!isExit) {
                isExit = true;
                Toast.makeText(getApplicationContext(), "再按一次退出程序",
                        Toast.LENGTH_SHORT).show();
                mHandler.sendEmptyMessageDelayed(0, 3000);
            } else {
                finish();
                System.exit(0);
            }
        }
        return false;

    }

显示坐标

 public boolean onTouchEvent(MotionEvent event) {
        if (event.getAction() == MotionEvent.ACTION_MOVE) {
            float x = event.getX();
            float y = event.getY();
            String pos = "x坐标" + x + "y坐标" + y;
            Toast.makeText(this, pos, Toast.LENGTH_LONG).show();
        }
        return super.onTouchEvent(event);
    }
}

加入能拖动的图片不太会，希望老师在课堂上讲一下