Android开发之自己主动登录功能的实现

时间：2022-07-24 15:17:59

在我们平时使用的手机应用都能够实现仅仅须要登陆一次账号后，第二次进入应用直接跳转到效果界面的效果，还有QQ的登陆框是怎样记忆我们的隐身登陆，保存账号选项的呢，这些都是通过使用SharedPreferences共享參数效果实现的，而无须使用数据库来存储。下面我们直接看具体代码分析。

package com.example.account.login;

import java.util.HashMap;

import java.util.Map;

import com.android.dao.MySQLiteOpenHelper;

import com.example.account.MainActivity;

import com.example.account.R;

import android.app.Activity;

import android.content.Context;

import android.content.Intent;

import android.content.SharedPreferences;

import android.database.Cursor;

import android.database.sqlite.SQLiteDatabase;

import android.database.sqlite.SQLiteOpenHelper;

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.EditText;

import android.widget.TextView;

import android.widget.Toast;

public class LoginActivity extends Activity {

	private EditText e1, e2;

	private SQLiteOpenHelper helper;

	private boolean flag, flag2, flag3;

	private HashMap<String, Object> map;

	@SuppressWarnings("unchecked")

	@Override

	protected void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.login);

		TextView textView = (TextView) this.findViewById(R.id.textView1);

		e1 = (EditText) this.findViewById(R.id.editText1);

		e2 = (EditText) this.findViewById(R.id.editText2);

		//从共享參数获取数据

		map = (HashMap<String, Object>) getMsg("login");

		if (map != null && !map.isEmpty()) {

			if ((Boolean) map.get("login2")) {

				//若值为true,用户无需输入password，直接跳转进入操作界面

				Intent intent = new Intent(LoginActivity.this,

						MainActivity.class);

				startActivity(intent);

			}

		}

		helper = new MySQLiteOpenHelper(this);

		textView.setText("登录界面");

		Button button = (Button) findViewById(R.id.button2);

		button.setOnClickListener(new OnClickListener() {

			@Override

			public void onClick(View v) {

				if (!e1.getText().toString().isEmpty()

						&& !e2.getText().toString().isEmpty()) {

					//从数据库获取账号信息

					SQLiteDatabase database = helper.getReadableDatabase();

					Cursor cursor = database.query("user", new String[] {

							"username", "password" }, null, null, null, null,

							null);

					while (cursor.moveToNext()) {

						flag = e1

								.getText()

								.toString()

								.equals(cursor.getString(cursor

										.getColumnIndex("username")));

						flag2 = e2

								.getText()

								.toString()

								.equals(cursor.getString(cursor

										.getColumnIndex("password")));

						if (flag && flag2) {

							Intent intent = new Intent(LoginActivity.this,

									MainActivity.class);

							startActivity(intent);

							//登陆跳转动画

							overridePendingTransition(R.anim.zoomin,

									R.anim.zoomout);

							Toast.makeText(LoginActivity.this, "登录成功",

									Toast.LENGTH_SHORT).show();

							flag3 = true;

							//登陆成功后将flag设置为ture存入共享參数中

							HashMap<String, Object> map = new HashMap<String, Object>();

							map.put("login2", flag3);

							saveMsg("login", map);

						}

					}

					if (!flag3) {

						Toast.makeText(LoginActivity.this, "您输入的帐号或password有误",

								Toast.LENGTH_SHORT).show();

					}

				} else {

					Toast.makeText(LoginActivity.this, "请正确输入您的帐号password",

							Toast.LENGTH_SHORT).show();

				}

			}

		});

		Button button2 = (Button) findViewById(R.id.button1);

		button2.setOnClickListener(new OnClickListener() {

			@Override

			public void onClick(View v) {

				Intent intent = new Intent(LoginActivity.this,

						RegisterActivity.class);

				startActivity(intent);

			}

		});

	}

   //将数据存储进入共享參数

	public boolean saveMsg(String fileName, Map<String, Object> map) {

		boolean flag = false;

		// 一般Mode都使用private,比較安全

		SharedPreferences preferences = getSharedPreferences(fileName,

				Context.MODE_PRIVATE);

		SharedPreferences.Editor editor = preferences.edit();

		// Map类提供了一个称为entrySet()的方法，这种方法返回一个Map.Entry实例化后的对象集。

		// 接着，Map.Entry类提供了一个getKey()方法和一个getValue()方法，

		// 因此，上面的代码能够被组织得更符合逻辑

		for (Map.Entry<String, Object> entry : map.entrySet()) {

			String key = entry.getKey();

			Object object = entry.getValue();

			// 依据值得不同类型，加入

			if (object instanceof Boolean) {

				Boolean new_name = (Boolean) object;

				editor.putBoolean(key, new_name);

			} else if (object instanceof Integer) {

				Integer integer = (Integer) object;

				editor.putInt(key, integer);

			} else if (object instanceof Float) {

				Float f = (Float) object;

				editor.putFloat(key, f);

			} else if (object instanceof Long) {

				Long l = (Long) object;

				editor.putLong(key, l);

			} else if (object instanceof String) {

				String s = (String) object;

				editor.putString(key, s);

			}

		}

		flag = editor.commit();

		return flag;

	}

	// 读取数据

	public Map<String, ?> getMsg(String fileName) {

		Map<String, ?> map = null;

		// 读取数据用不到edit

		SharedPreferences preferences = getSharedPreferences(fileName,

				Context.MODE_APPEND);

		//Context.MODE_APPEND能够对已存在的值进行改动

		map = preferences.getAll();

		return map;

	}

}

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