android：登录界面，输入框输入数量达到了之后自动隐藏键盘。

一、前言：这篇文章是关于当我们输入账号密码时，达到11位（自定义）时，自动隐藏键盘。

二、上代码：

界面布局：

对应的Activity：LoginMainActivity

public class LoginMainActivity extends AppCompatActivity implements RadioGroup.OnCheckedChangeListener {

    private TextView tv_password;
    private EditText et_password;
    private Button btn_forget;
    private CheckBox ck_remember;
    private EditText et_phone;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login_main);
        RadioGroup rg_login = findViewById(R.id.rg_login);
        tv_password = findViewById(R.id.tv_password);
        et_phone = findViewById(R.id.et_phone);
        et_password = findViewById(R.id.et_password);
        btn_forget = findViewById(R.id.btn_forget);
        ck_remember = findViewById(R.id.ck_remember);
        //给rg_login设置单选监听器
        rg_login.setOnCheckedChangeListener(this);
        //给et_phone添加文本变更器
        et_phone.addTextChangedListener(new HideTextWatcher(et_phone,11));
        //给et_password添加文本变更器
        et_password.addTextChangedListener(new HideTextWatcher(et_password,6));
    }

    @Override
    public void onCheckedChanged(RadioGroup radioGroup, int i) {
        switch (i){
            //选择密码登录
            case R.id.rb_password:
                tv_password.setText(getString(R.string.login_password));
                et_password.setHint(getString(R.string.input_password));
                btn_forget.setText(getString(R.string.foget_password));
                ck_remember.setVisibility(View.VISIBLE);
                break;
                //选择验证码登录
            case R.id.rb_verifycode:
                tv_password.setText(getString(R.string.verifycode));
                et_password.setHint(getString(R.string.input_verifycode));
                btn_forget.setText(getString(R.string.get_verifycode));
                ck_remember.setVisibility(View.GONE);
                break;
        }
    }

    //定义一个编辑框监听器，在输入文本达到指定长度时自动隐藏输入法
    private class HideTextWatcher implements TextWatcher {
        private  EditText mView;
        private int mMaxLength;
        public HideTextWatcher(EditText v, int maxLength) {
            this.mView = v;
            this.mMaxLength = maxLength;

        }

        @Override
        public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {

        }

        @Override
        public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {

        }

        //在编辑框的输入文本变化后触发
        @Override
        public void afterTextChanged(Editable s) {
          //获得已输入的文本字符串
            String str = s.toString();
            if (str.length() == mMaxLength){
                //隐藏输入法软键盘
                ViewUtil.hideOneInputMethod(LoginMainActivity.this,mView);
            }
        }
    }
}

新建一个工具类：ViewUtil

public class ViewUtil {
    public static void hideOneInputMethod(Activity act, View v){
        //从系统服务中获取输入法管理器
        InputMethodManager imm = (InputMethodManager) act.getSystemService(Context.INPUT_METHOD_SERVICE);
        //关闭屏幕上的输入法软键盘
        imm.hideSoftInputFromWindow(v.getWindowToken(),0);
    }
}