第二个作业

首先是最简单的布局

<LinearLayout

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical"

tools:context="com.example.zhdn.a1.MainActivity">

<TextView

android:layout_width="match_parent"

android:layout_height="50dp"

android:gravity="center"

android:text="登录界面"

android:textSize="22sp" />

<EditText

android:id="@+id/ev_userName"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="请输入用户名" />

<EditText

android:id="@+id/ev_password"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="请输入密码" />

<Button android:id="@+id/btn_login"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:gravity="center"

android:text="写入"

android:textSize="20sp"

android:onClick="onClick"

android:layout_gravity="center"/>

<Button

android:id="@+id/btn_b"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:gravity="center" android:text="读取"

android:textSize="20sp"

android:onClick="onClick"

android:layout_gravity="center"/>

</LinearLayout>

接下来是java

public class MainActivity extends AppCompatActivity

{

private EditText ev_userName;

private EditText ev_password;

private Button btn_login;

private Button btn_b;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

ev_userName = (EditText) findViewById(R.id.ev_userName);

ev_password = (EditText) findViewById(R.id.ev_password);

btn_login = (Button) findViewById(R.id.btn_login);

btn_b=(Button)findViewById(R.id.btn_b);

}

public void onClick(View view){ switch (view.getId())

{

case R.id.btn_login: String username = ev_userName.getText().toString();

String password = ev_password.getText().toString();

write(username,password);

break;

case R.id.btn_b: read(); break;

}

}

private void read()

{

SharedPreferences prefs = getSharedPreferences("data.text", MODE_PRIVATE);

 String username = prefs.getString("username", "");

 String password = prefs.getString("password", "");

Toast.makeText(MainActivity.this, "用户名："+username+"密码："+password, Toast.LENGTH_LONG).show();

}

private void write(String username, String password)

{

SharedPreferences.Editor editor = getSharedPreferences("data.text", MODE_PRIVATE).edit();

 editor.putString("username",username );

 editor.putString("password",password);

editor.commit();

editor.clear();

Toast.makeText(MainActivity.this, "保存成功!", Toast.LENGTH_LONG).show();

}

}