Android studio的登录代码，登录后跳到一个新界面，新界面为一张课程表，课程表的布局使用gridview控件，并且控件下面有三个按钮，能对课程表做出修改，删除，查询，修改界面能修改课程时间，地点以及添加课程名称，课程时间，课程地点，删除界面能删除选定课程，并且更新修改后的课程表的代码以及界面布局代码

以下是一个简单的Android Studio登录代码，登录成功后跳转到课程表界面：

### LoginActivity.java

public class LoginActivity extends AppCompatActivity {

    private EditText etUsername, etPassword;
    private Button btnLogin;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        etUsername = findViewById(R.id.et_username);
        etPassword = findViewById(R.id.et_password);
        btnLogin = findViewById(R.id.btn_login);

        btnLogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String username = etUsername.getText().toString();
                String password = etPassword.getText().toString();

                // TODO: 进行登录验证

                Intent intent = new Intent(LoginActivity.this, CourseActivity.class);
                startActivity(intent);
                finish();
            }
        });
    }
}

### activity_login.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <EditText
        android:id="@+id/et_username"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="用户名"
        android:inputType="text" />

    <EditText
        android:id="@+id/et_password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/et_username"
        android:hint="密码"
        android:inputType="textPassword" />

    <Button
        android:id="@+id/btn_login"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/et_password"
        android:text="登录" />

</RelativeLayout>

接下来是课程表界面的布局和代码：

### CourseActivity.java

public class CourseActivity extends AppCompatActivity {

    private GridView gridView;
    private Button btnAdd, btnModify, btnDelete;

    private List<Course> courseList;
    private CourseAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_course);

        gridView = findViewById(R.id.grid_view);
        btnAdd = findViewById(R.id.btn_add);
        btnModify = findViewById(R.id.btn_modify);
        btnDelete = findViewById(R.id.btn_delete);

        courseList = new ArrayList<>();
        adapter = new CourseAdapter(this, courseList);
        gridView.setAdapter(adapter);

        // TODO: 加载课程表数据

        btnAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // TODO: 打开添加课程界面
            }
        });

        btnModify.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // TODO: 打开修改课程界面
            }
        });

        btnDelete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // TODO: 删除选中课程
            }
        });
    }
}

### activity_course.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <GridView
        android:id="@+id/grid_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:numColumns="5"
        android:horizontalSpacing="1dp"
        android:verticalSpacing="1dp"
        android:stretchMode="columnWidth" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/grid_view"
        android:orientation="horizontal">

        <Button
            android:id="@+id/btn_add"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="添加" />

        <Button
            android:id="@+id/btn_modify"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="修改" />

        <Button
            android:id="@+id/btn_delete"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="删除" />

    </LinearLayout>

</RelativeLayout>

最后是课程表的适配器和数据模型：

### CourseAdapter.java

public class CourseAdapter extends BaseAdapter {

    private Context context;
    private List<Course> courseList;

    public CourseAdapter(Context context, List<Course> courseList) {
        this.context = context;
        this.courseList = courseList;
    }

    @Override
    public int getCount() {
        return courseList.size();
    }

    @Override
    public Object getItem(int position) {
        return courseList.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = LayoutInflater.from(context).inflate(R.layout.item_course, parent, false);
        }

        TextView tvName = convertView.findViewById(R.id.tv_name);
        TextView tvTime = convertView.findViewById(R.id.tv_time);
        TextView tvLocation = convertView.findViewById(R.id.tv_location);

        Course course = courseList.get(position);
        tvName.setText(course.getName());
        tvTime.setText(course.getTime());
        tvLocation.setText(course.getLocation());

        return convertView;
    }
}

### Course.java

public class Course {

    private String name;
    private String time;
    private String location;

    public Course(String name, String time, String location) {
        this.name = name;
        this.time = time;
        this.location = location;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }

    public String getLocation() {
        return location;
    }

    public void setLocation(String location) {
        this.location = location;
    }
}

希望这份代码能够帮到你。