详解Android Studio实现用户登陆界面demo（xml实现）

<LinearLayout
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="vertical"
  android:paddingLeft="55px"
  android:paddingRight="50px"
  tools:context=".MainActivity">
  <TextView
    android:id="@+id/message"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="@dimen/activity_horizontal_margin"
    android:layout_marginLeft="@dimen/activity_horizontal_margin"
    android:layout_marginTop="@dimen/activity_vertical_margin"
    android:text="Hello Word！"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintTop_toTopOf="parent" />
  <View
    android:layout_width="match_parent"
    android:layout_height="2px"
    android:layout_marginTop="16px"
    android:background="#000000" />
  <TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="28dp"
    android:layout_gravity="center_horizontal"
    android:layout_marginTop="20px"
    android:text="登陆界面" />
<LinearLayout
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:orientation="horizontal"
  >
  <EditText
    android:id="@+id/et1"
    android:layout_width="280dp"
    android:layout_height="wrap_content"
    android:layout_marginTop="30dp"
    android:paddingLeft="10dp"
    android:hint="请输入账号"
    android:inputType="text"/>
  <ImageView
    android:id="@+id/bt1"
    android:layout_width="25dp"
    android:layout_height="25dp"
    android:layout_marginTop="37dp"
    android:src="@drawable/delete" />
</LinearLayout>
  <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:paddingLeft="8px">
  <EditText
    android:id="@+id/et2"
    android:layout_width="280dp"
    android:layout_height="wrap_content"
    android:layout_marginTop="26dp"
    android:hint="请输入密码"
    android:inputType="textPassword" />
    <ImageView
      android:id="@+id/bt2"
      android:layout_width="25dp"
      android:layout_height="25dp"
      android:layout_marginTop="33dp"
      android:src="@drawable/delete" />
</LinearLayout>
    <Button
      android:id="@+id/btn_login"
      android:layout_width="match_parent"
      android:layout_height="48dp"
      android:background="@color/bbutton_danger_disabled_edge"
      android:layout_marginTop="30dp"
      android:text="登 陆"
      android:textSize="30dp"
      android:textColor="@color/bbutton_danger"/>
  <Button
  android:id="@+id/bbt1"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:textSize="15dp"
  android:layout_gravity="right"
  android:layout_marginTop="20px"
  android:background="@color/bbutton_danger"
  android:text="Adapter" />
  </LinearLayout> 

/**
 * 用于实现点击叉叉时 , 清空输入框的内容
 */

 class EditTextUtils {

  public static void clearButtonListener(final EditText et, final View view) {

    // 取得et中的文字

    String etInputString = et.getText().toString();

    // 根据et中是否有文字进行X可见或不可见的判断

    if (TextUtils.isEmpty(etInputString)) {

      view.setVisibility(View.INVISIBLE);
    } else {

      view.setVisibility(View.VISIBLE);
    }

    //点击X时使et中的内容为空

    view.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View view) {
        et.setText("");
        et.requestFocusFromTouch();
      }
    });
    //对et的输入状态进行监听
    et.addTextChangedListener(new TextWatcher() {
      @Override
      public void onTextChanged(CharSequence s, int start, int before, int count) {
      }
      @Override
      public void beforeTextChanged(CharSequence s, int start, int count, int after) {
      }
      @Override
      public void afterTextChanged(Editable s) {

        if (s.length() == 0) {
          view.setVisibility(View.INVISIBLE);
        } else {
          view.setVisibility(View.VISIBLE);
        }
      }
    });
  }
}

private TextView mTextMessage;
@Override
protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  EditText et1 = (EditText) findViewById(R.id.et1);
  EditText et2 = (EditText) findViewById(R.id.et2);
  View bt = findViewById(R.id.bt1);
  View iv = findViewById(R.id.bt2);
  EditTextUtils.clearButtonListener(et1, bt);
  EditTextUtils.clearButtonListener(et2, iv);

  Button btn1 = (Button) findViewById(R.id.bbt1);
  btn1.setOnClickListener(new View.OnClickListener(){
    @Override
    public void onClick(View v){
      //Intent是一种运行时绑定（run-time binding）机制，它能在程序运行过程中连接两个不同的组件，在存放资源代码的文件夹下下，
      Intent i = new Intent(MainActivity.this , Main2ActivityAdapterDemo.class);
      //启动
      startActivity(i);
      }
  });

  mTextMessage = (TextView) findViewById(R.id.message);
  BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
  navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
}

<resources>
  <!-- Default screen margins, per the Android Design guidelines. -->
  <dimen name="activity_horizontal_margin">16dp</dimen>
  <dimen name="activity_vertical_margin">16dp</dimen>
  <dimen name="text_size_16">22dp</dimen>
  <dimen name="space_8">8</dimen>
  <dimen name="space_16">16</dimen>
  <dimen name="fab_margin">16dp</dimen>
</resources>

<?xml version="1.0" encoding="utf-8"?>
<resources>
  <color name="colorPrimary">#008577</color>
  <color name="colorPrimaryDark">#00574B</color>
  <color name="colorAccent">#D81B60</color>
  <color name="main_gray">#CCCCCC</color>
  <color name="main_black">#000000</color>
  <color name="bbutton_danger_disabled_edge">#00CC33</color>
  <color name="bbutton_danger">#FFFFFF</color>
</resources>