如何用android studio实现生成验证码

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

et_phoneCode = (EditText) findViewById(R.id.et_phoneCodes);
Button but_toSetCode = (Button) findViewById(R.id
.but_forgetpass_toSetCodes);
but_toSetCode.setOnClickListener(this);
iv_showCode = (ImageView) findViewById(R.id.iv_showCode);
//将验证码用图片的形式显示出来
iv_showCode.setImageBitmap(Code.getInstance().createBitmap());
realCode = Code.getInstance().getCode();
iv_showCode.setOnClickListener(this);
}

Xml代码

android:id="@ id/iv_showCode"
android:layout_width="100dp"
android:layout_marginLeft="10dp"
android:layout_height="match_parent" />