首先呢，看到这么长的标题，是不是感觉这些功能有点难以实现呢，哈哈，其实并没有想象中的那么复杂，下面就跟着笔者来一起学习一下这些功能是怎么实现的吧！
1.建立一个所有活动的父类，继承自AppcompatAvtivity类，用来实现全局广播，与强制下线功能相关联：
package com.example.pc_ly.dl;import android.app.Activity;import android.content.BroadcastReceiver;import android.content.Context;import android.content.DialogInterface;import android.content.Intent;import android.content.IntentFilter;import android.os.Bundle;import android.support.v7.app.AlertDialog;import android.support.v7.app.AppCompatActivity;/*** Created by pc_ly on /10/29.*/public class BaseActivity extends AppCompatActivity {//所有活动继承的一个类，用来实现全局广播，Intent aa=getIntent();private Focreof receiver;protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);ActivityCollector.addAvtivity(this);}protected void onResume(){super.onResume();IntentFilter intentFilter=new IntentFilter();intentFilter.addAction("com.example.office");receiver=new Focreof();registerReceiver(receiver,intentFilter);}protected void onPause(){super.onPause();if(receiver!=null){unregisterReceiver(receiver);receiver=null;}}protected void onDestroy(){super.onDestroy();ActivityCollector.removeActivity(this);}class Focreof extends BroadcastReceiver{//当广播成功响应时，弹出一个对话框，显示一些信息，并且之后会回到登录的界面public void onReceive(final Context context, final Intent intent){;AlertDialog.Builder builder=new AlertDialog.Builder(context);builder.setTitle("警告");builder.setMessage("Dear:"+intent.getStringExtra("t")+"! You are forced to be offline. Please try to login again.");builder.setPositiveButton("OK",new DialogInterface.OnClickListener(){public void onClick(DialogInterface dialog,int which){ActivityCollector.finishAll();Intent intent=new Intent(context,MainActivity.class);context.startActivity(intent);}});builder.show();}}}
2.建立一个管理所有活动的类：
package com.example.pc_ly.dl;import android.app.Activity;import java.util.ArrayList;import java.util.List;/*** Created by pc_ly on /10/29.*/public class ActivityCollector {//管理所有活动public static List<Activity> activities=new ArrayList<>();public static void addAvtivity(Activity activity){activities.add(activity);}public static void removeActivity(Activity activity){activities.remove(activity);}public static void finishAll(){for(Activity activity:activities){if(!activity.isFinishing()){activity.finish();}}activities.clear();}}
3.建立一个初始化数据库的类，并创建对应的表
package com.example.pc_ly.dl;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import android.widget.Toast;import java.sql.SQLClientInfoException;/*** Created by pc_ly on /11/20.*/public class DateBaseHelper extends SQLiteOpenHelper {public static final String CREATE_BOOK="create table userData ("+ "id text, "+"password text)";//创建表的语句private Context mContext;public DateBaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory,int version){//初始化一个数据库super(context,name,factory,version);mContext=context;}public void onCreate(SQLiteDatabase db){db.execSQL(CREATE_BOOK);//执行创建表的语句Toast.makeText(mContext,"Create succeed",Toast.LENGTH_SHORT).show();}public void onUpgrade(SQLiteDatabase db,int oldVersion,int newVersion){}}
4.先将登录的界面通过代码写出来，这个比较简单，我就直接上代码了
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="/apk/res/android"xmlns:tools="/tools"android:orientation="vertical"android:id="@+id/activity_main"android:layout_width="match_parent"android:layout_height="match_parent"><LinearLayoutandroid:orientation="horizontal"android:layout_width="match_parent"android:layout_height="60dp"><TextViewandroid:layout_width="90dp"android:layout_height="wrap_content"android:layout_gravity="center_vertical"android:textSize="18sp"android:text="Account:"/><EditTextandroid:id="@+id/account"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:layout_gravity="center_vertical"android:drawableRight="@drawable/jiantou"/></LinearLayout><LinearLayoutandroid:orientation="horizontal"android:layout_width="match_parent"android:layout_height="60dp"><TextViewandroid:layout_width="90dp"android:layout_height="wrap_content"android:layout_gravity="center_vertical"android:textSize="18sp"android:text="Password: "/><EditTextandroid:id="@+id/password"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:layout_gravity="center_vertical"android:inputType="textPassword"/></LinearLayout><LinearLayoutandroid:orientation="horizontal"android:layout_width="match_parent"android:layout_height="wrap_content"><CheckBoxandroid:id="@+id/rember_1"android:layout_width="wrap_content"android:layout_height="wrap_content" /><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:textSize="18sp"android:text="记住密码"/></LinearLayout><Buttonandroid:id="@+id/button_1"android:layout_width="match_parent"android:layout_height="60sp"android:text="Login"/><Buttonandroid:id="@+id/zhuce_"android:layout_width="match_parent"android:layout_height="60sp"android:text="注册账号"/></LinearLayout>
效果大致是这个样子：
其中的记住密码的复选框是有checkbox定义的，然后下拉箭头是一张图片，大家可以去网上下载，然后利用Drawableright属性把它添加到账号框里面去，然后这个界面就做好啦。
5.这一步呢就是将登录界面要实现的功能的代码写出来，代码如下：
package com.example.pc_ly.dl;import android.content.Intent;import android.content.SharedPreferences;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.preference.Preference;import android.preference.PreferenceManager;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.support.v7.widget.ListPopupWindow;import android.view.MotionEvent;import android.view.View;import android.widget.AdapterView;import android.widget.ArrayAdapter;import android.widget.Button;import android.widget.CheckBox;import android.widget.EditText;import android.widget.PopupWindow;import android.widget.TextView;import android.widget.Toast;import java.util.ArrayList;public class MainActivity extends BaseActivity{private SharedPreferences pref;//利用sharePREfreences来保存数据private SharedPreferences.Editor editor;//用来保存密码的private DateBaseHelper dphelp;private ListPopupWindow listPopupWindow;private EditText accountEdit;private EditText passwordEdit;private Button login;private Button zhuce;private CheckBox rember;private String list[];protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);dphelp=new DateBaseHelper(this,"Userss.db",null,1);//数据库的初始化rember=(CheckBox)findViewById(R.id.rember_1) ;//这个是复选框，用来选择是否选中密码的login=(Button)findViewById(R.id.button_1);zhuce=(Button)findViewById(R.id.zhuce_);//初始化//list.add("li");listPopupWindow=new ListPopupWindow(MainActivity.this);accountEdit=(EditText)findViewById(R.id.account) ;passwordEdit=(EditText)findViewById(R.id.password) ;pref=PreferenceManager.getDefaultSharedPreferences(this);Boolean isrember=pref.getBoolean("rember_pass",false);//初始设置记住密码为falseDateBaseHelper database=new DateBaseHelper(this,"Userss.db",null,1);if(isrember){int username=perf.getInt("username",0)-1;String id=pref.getString("account"+username,"");String pass=pref.getString("password"+username,"");accountEdit.setText(id);passwordEdit.setText(pass);//把保存的账号和密码读取出来rember.setChecked(true);}zhuce.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {//点击注册跳到注册的页面Intent intent=new Intent(MainActivity.this,Zhuche.class);startActivity(intent);}});login.setOnClickListener(new View.OnClickListener(){public void onClick(View v){accountEdit=(EditText)findViewById(R.id.account);//与相应的文本框对应起来passwordEdit=(EditText)findViewById(R.id.password);String userName=accountEdit.getText().toString();//获取文本框的数据String passWord=passwordEdit.getText().toString();if (login(userName,passWord)) {Toast.makeText(MainActivity.this, "登陆成功，欢迎来到新的世界", Toast.LENGTH_SHORT).show();//成功了弹出登陆成功editor=pref.edit();if(rember.isChecked()){//复选框是否被选中int username=pref.getInt("username",0);editor.putBoolean("rember_pass",true);//把记住密码设置为trueeditor.putString("account"+username,userName);editor.putString("password"+username,passWord);//把密码和账号分别保存到account和password里面editor.putInt("username",username+1);}else{editor.clear();//清空editor保存的东西}editor.apply();//启用editoyString data=userName;Intent intent=new Intent(MainActivity.this,denglv.class);intent.putExtra("ex",data);//把当前登陆成功的账号的数据传递给下一个活动，用来显示是谁登陆成功了startActivity(intent);}else {Toast.makeText(MainActivity.this, "登陆失败", Toast.LENGTH_SHORT).show();//失败，弹出登陆失败}}});accountEdit.setOnTouchListener(new View.OnTouchListener() {@Overridepublic boolean onTouch(View view, MotionEvent event) {//设置监听事件final int DRAWABLE_LEFT = 0;final int DRAWABLE_TOP = 1;final int DRAWABLE_RIGHT = 2;final int DRAWABLE_BOTTOM = 3;if (event.getAction() == MotionEvent.ACTION_UP) {if (event.getX() >= (accountEdit.getWidth() - accountEdit.getCompoundDrawables()[DRAWABLE_RIGHT].getBounds().width())) {//当点击了箭头位置的时候回调用下面的函数，显示出下拉框accountEdit.setCompoundDrawablesWithIntrinsicBounds(null, null, getResources().getDrawable(R.drawable.jiantou), null);showListPopulWindow();return true;}}return false;}});}public void showListPopulWindow(){//用来显示下拉框final String acc[]=new String[pref.getInt("username",0)];//定义一个账号数组，长度为选择记住密码的登录成功的账号个数final String pas[]=new String[pref.getInt("username",0)];//定义一个密码数组，长度为选择记住密码的登录成功的账号个数for(int a=0;a<pref.getInt("username",0);a++){acc[a]=pref.getString("account"+a,"");//初始化账号数组，把已保存的账号放到数组里面去pas[a]=pref.getString("password"+a,"");//初始化密码数组，把已保存的密码放到数组里面去}listPopupWindow = new ListPopupWindow(MainActivity.this);listPopupWindow.setAdapter(new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, acc));//把账号的数据显示到下拉列表里面去listPopupWindow.setAnchorView(accountEdit);listPopupWindow.setModal(true);listPopupWindow.setOnItemClickListener(new AdapterView.OnItemClickListener() {//设置项点击监听@Overridepublic void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {accountEdit.setText(acc[i]);//当选中下拉框的某一个选项的时候，把选择的选项内容展示在EditText上passwordEdit.setText(pas[i]);//将选中的账号的密码显示出来，显示在面板上，listPopupWindow.dismiss();//如果已经选择了，隐藏起来}});listPopupWindow.show();}public boolean login(String username,String password) {//验证此账号密码是否正确SQLiteDatabase db = dphelp.getWritableDatabase();String sql = "select * from userData where id=? and password=?";//将登录时填的账号和密码在数据库里面进行查询，如果存在该数据，则返回true，否则返回falseCursor cursor = db.rawQuery(sql, new String[] {username, password});if (cursor.moveToFirst()) {cursor.close();return true;}return false;}}
上面的注释比较详细，就不一一介绍啦
6.将注册的界面通过代码写出来：
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="/apk/res/android"xmlns:tools="/tools"android:orientation="vertical"android:id="@+id/activity_zhuche"android:layout_width="match_parent"android:layout_height="match_parent"android:paddingBottom="@dimen/activity_vertical_margin"android:paddingLeft="@dimen/activity_horizontal_margin"android:paddingRight="@dimen/activity_horizontal_margin"android:paddingTop="@dimen/activity_vertical_margin"tools:context="com.example.pc_ly.dl.Zhuche"><LinearLayoutandroid:orientation="horizontal"android:layout_width="match_parent"android:layout_height="60dp"><TextViewandroid:layout_width="90dp"android:layout_height="wrap_content"android:layout_gravity="center_vertical"android:textSize="18sp"android:text="Account:"/><EditTextandroid:id="@+id/account111"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:layout_gravity="center_vertical"android:drawableRight="@drawable/jiantou"/></LinearLayout><LinearLayoutandroid:orientation="horizontal"android:layout_width="match_parent"android:layout_height="60dp"><TextViewandroid:layout_width="90dp"android:layout_height="wrap_content"android:layout_gravity="center_vertical"android:textSize="18sp"android:text="Password: "/><EditTextandroid:id="@+id/password111"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:layout_gravity="center_vertical"android:inputType="textPassword"/></LinearLayout><Buttonandroid:id="@+id/button_111"android:layout_width="match_parent"android:layout_height="60sp"android:text="注册"/></LinearLayout>
7.将注册界面要实现的功能通过代码写出来：
package com.example.pc_ly.dl;import android.content.ContentValues;import android.content.Intent;import android.content.SharedPreferences;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.Button;import android.widget.EditText;import android.widget.Toast;public class Zhuche extends BaseActivity {private DateBaseHelper dphelper;private EditText a,b;private Button an1;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_zhuche);dphelper=new DateBaseHelper(this,"Userss.db",null,1);an1=(Button)findViewById(R.id.button_111);an1.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {//dphelper.getWritableDatabase();a=(EditText)findViewById(R.id.account111);b=(EditText)findViewById(R.id.password111) ;String newname =a.getText().toString();String password=b.getText().toString();Log.d("Zhuche","sss");if (CheckIsDataAlreadyInDBorNot(newname)) {Toast.makeText(Zhuche.this,"该用户名已被注册，注册失败",Toast.LENGTH_SHORT).show();}else {if (register(newname, password)) {Toast.makeText(Zhuche.this, "恭喜您 注册成功，即将返回登录界面", Toast.LENGTH_SHORT).show();Intent intent=new Intent(Zhuche.this,MainActivity.class);startActivity(intent);}}}});}//向数据库插入数据public boolean register(String username,String password){SQLiteDatabase db= dphelper.getWritableDatabase();/*String sql = "insert into userData(name,password) value(?,?)";Object obj[]={username,password};db.execSQL(sql,obj);*/ContentValues values=new ContentValues();values.put("id",username);values.put("password",password);db.insert("userData",null,values);db.close();//db.execSQL("insert into userData (name,password) values (?,?)",new String[]{username,password});return true;}//检验用户名是否已存在public boolean CheckIsDataAlreadyInDBorNot(String value){SQLiteDatabase db=dphelper.getWritableDatabase();String Query = "Select * from userData where id =?";Cursor cursor = db.rawQuery(Query,new String[] { value });if (cursor.getCount()>0){cursor.close();return true;}cursor.close();return false;}}
8.登录成功之后，会跳到一个新的界面，界面的布局代码如下：
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="/apk/res/android"android:orientation="vertical"xmlns:tools="/tools"android:id="@+id/activity_denglv"android:layout_width="match_parent"android:layout_height="match_parent"><TextViewandroid:id="@+id/text_1"android:gravity="center"android:layout_gravity="center"android:layout_width="match_parent"android:layout_height="wrap_content"android:textSize="24sp"android:text="HI! haha"/><Buttonandroid:id="@+id/button_2"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="强制下线"/></LinearLayout>
9.当点击按钮之后，会实现强制下线的功能，代码如下：
package com.example.pc_ly.dl;import android.content.Intent;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.Button;import android.widget.TextView;public class denglv extends BaseActivity{private DateBaseHelper hp;private TextView textView;@Overrideprotected void onCreate(Bundle savedInstanceState) {Intent intent=getIntent();super.onCreate(savedInstanceState);setContentView(R.layout.activity_denglv);Button force=(Button)findViewById(R.id.button_2);textView=(TextView)findViewById(R.id.text_1) ;textView.setText("Hi,"+intent.getStringExtra("ex"));//显示你的名字出来force.setOnClickListener(new View.OnClickListener(){public void onClick(View v){Intent aa=getIntent();String data=aa.getStringExtra("ex");Intent intent=new Intent("com.example.office");intent.putExtra("t",data);sendBroadcast(intent);//点击按钮会强制退出，并利用intent传递数据}});}}
然后代码差不多就是这个样子啦，最后再贴几张效果图：
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欢迎各位访问哦，这次就到这里啦！
Android编写一个登录界面 利用数据库实现记住密码 注册账号 强制下线 以及类似QQ的下拉列表登录功能
