项目需求
（1）实现四个页面：首页、登录页、注册页、登陆成功页。
排版和跳转关系如图：
（2）注册页实现注册功能；登录页实现使用注册过的账号密码登录功能，登录成功后转到登录成功页；登录成功页有注销功能。
（3）具体功能：用户名必须为纯数字；注册页密码有二次验证功能；标题栏有返回键；成功登陆界面的文本根据用户名显示。
工程框架
主要实现代码
均在onActivityCreated（）方法实现，布局文件代码省略。
没有的事
MainActivity
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| package com.example.myapplication;
import androidx.appcompat.app.ActionBar;
import androidx.appcompat.app.AppCompatActivity;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.ui.NavigationUI;
import android.app.Activity;
import android.os.Bundle;
import android.view.MenuItem;
import android.view.Window;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
NavController controller = Navigation.findNavController(this,R.id.fragment);
NavigationUI.setupActionBarWithNavController(this,controller);
}
@Override
public boolean onSupportNavigateUp(){
NavController controller = Navigation.findNavController(this,R.id.fragment);
return controller.navigateUp();
}
}
|
user(首页)部分
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| public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
login_user = getView().findViewById(R.id.login_user);
login_user.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v){
NavController controller = Navigation.findNavController(v);
controller.navigate(R.id.action_user_to_login);
}
});
register_user = getView().findViewById(R.id.register_user);
register_user.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v){
NavController controller = Navigation.findNavController(v);
controller.navigate(R.id.action_user_to_register);
}
});
}
|
register（注册）部分
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|
registerBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String name = name_register.getText().toString().trim();
String password = password_register.getText().toString().trim();
String repass = pass_register.getText().toString().trim();
databaseHelper = new MyDatebaseHelper(getActivity(), DATABASE_NAME, null, DATABASE_VERSION);
db = databaseHelper.getReadableDatabase();
Cursor cursor = db.query(TABLE_NAME, new String[]{"name"}, "name=?", new String[]{name}, null, null, null);
if (name.matches("[0-9]*")) {
if (cursor != null && cursor.getCount() >= 1) {
Toast.makeText(getActivity(), "此用户已存在", Toast.LENGTH_LONG).show();
NavController controller = Navigation.findNavController(v);
controller.navigate(R.id.action_register_self);
} else {
if (!name.isEmpty() && !password.isEmpty() && !repass.isEmpty() && name.length() < 11 && password.length() < 11) {
if (password.equals(repass)) {
db.execSQL("insert into username (name,password) values(?,?)", new String[]{name, repass});
Toast.makeText(getActivity(), "注册成功,请登录", Toast.LENGTH_LONG).show();
NavController controller = Navigation.findNavController(v);
controller.navigate(R.id.action_register_to_login);
} else {
Toast.makeText(getActivity(), "两次密码不一致", Toast.LENGTH_SHORT).show();
}
} else {
Toast.makeText(getActivity(), "用户名和密码长度为1-10", Toast.LENGTH_SHORT).show();
}
}
} else {
Toast.makeText(getActivity(), "账号仅由数字组成", Toast.LENGTH_SHORT).show();
}
}
});
}
|
login（登录）部分
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| loginBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String name = name_login.getText().toString().trim();
String pass = pass_login.getText().toString().trim();
if (!name.isEmpty() && !pass.isEmpty()) {
databaseHelper = new MyDatebaseHelper(getActivity(), DATABASE_NAME, null, DATABASE_VERSION);
db = databaseHelper.getReadableDatabase();
try {
Cursor cursor = db.query(TABLE_NAME, new String[]{"name", "password"}, "name=?", new String[]{name}, null, null, "password");
if (cursor != null && cursor.getCount() >= 1) {
while (cursor.moveToNext()) {
String password = cursor.getString(cursor.getColumnIndex("password"));
if (pass.equals(password)) {
new AlertDialog.Builder(getActivity()).setTitle("密码正确")
.setMessage("成功登录").setPositiveButton("确定", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
Bundle args = new Bundle();
args.putString("username",name);
NavController controller = Navigation.findNavController(v);
controller.navigate(R.id.action_login_to_login_successful,args);
}
}).show();
break;
} else {
Toast.makeText(getActivity(), "密码错误", Toast.LENGTH_SHORT).show();
}
}
}else{
Toast.makeText(getActivity(), "该用户不存在", Toast.LENGTH_SHORT).show();
}
}catch (Exception e) {
e.printStackTrace();
}
}else {
Toast.makeText(getActivity(), "请填写完整", Toast.LENGTH_SHORT).show();
}
}
});
|
login_successful(登录成功页)部分
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| @Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
name_su = getView().findViewById(R.id.name_successful);
Intent intent = getActivity().getIntent();
String name = intent.getStringExtra("name");
name_su.setText(name);
exitBtn = getView().findViewById(R.id.exitBtn);
Bundle args = getArguments();
String user = args.getString("username");
name_su.setText("欢迎您："+user);
exitBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
NavController controller = Navigation.findNavController(v);
controller.navigate(R.id.action_login_successful_to_user);
}
});
}
|
数据库类
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| package com.example.myapplication;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import java.util.ArrayList;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
class MyDatebaseHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME="sql.db";
private static final int DATABASE_VERSION=1;
public MyDatebaseHelper(Context context, String name, CursorFactory factory, int version) {
super(context, DATABASE_NAME, factory, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table username( name varchar(30) primary key,password varchar(30))");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
|
标题栏自定义
左上方返回键
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| @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
NavController controller = Navigation.findNavController(this,R.id.fragment);
NavigationUI.setupActionBarWithNavController(this,controller);
}
@Override
public boolean onSupportNavigateUp(){
NavController controller = Navigation.findNavController(this,R.id.fragment);
return controller.navigateUp();
}
|
属性
（1）设置标题栏的文字：在nav_graph_xml中，选中单个fragment，在Attributes中设置它的label即可。
（2）设置颜色：在themes.xml中找到<item name="colorPrimary">@color/purple_500</item>，在color.xml找到对应的<color name="purple_500">#FF00BFFF</color>，修改其中的颜色值即可。
总结
（1）可以增加登录输入验证码的功能。
（2）UI设计可以更加丰富。
