使用SharedPreferences记住密码的功能

本案例实现的功能：强制下线和记住密码的功能。

强制下线的实现思路：用户通过用户名和密码登录主界面，点击主界面按钮，发送一条广播，通知程序强制下线。广播接收器接收广播信息，强制用户下线。

记住密码的实现思路：点击记住密码选项框，将密码信息存入到SharedPreferences中，下次登陆时直接从SharedPreferences中读取信息，显示在EditText中。

1、定义登录界面activity_login.xml，使用的TableLayout布局

<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:stretchColumns="1">
    <TableRow>
        <TextView
            android:id="@+id/Account"
            android:layout_height="wrap_content"
            android:text="Account:"/>
        <EditText
            android:id="@+id/account_text"
            android:layout_height="wrap_content"
            android:hint="Input your account"/>
    </TableRow>
    <TableRow>
        <TextView
            android:id="@+id/Password"
            android:layout_height="wrap_content"
            android:text="Password:"
           />
        <EditText
            android:id="@+id/password_text"
            android:layout_height="wrap_content"
            android:hint="Input your password"/>
    </TableRow>
    <TableRow>
        <CheckBox
            android:id="@+id/remember_pass"
            android:layout_height="wrap_content"/>
        <TextView
            android:layout_height="wrap_content"
            android:text="Remember password"/>
    </TableRow>
    <TableRow>
        <Button
            android:id="@+id/login"
            android:layout_height="wrap_content"
            android:layout_span="2"
            android:text="Login"/>
    </TableRow>
</TableLayout>

2、定义主界面activity_main.xml，主界面只有一个按钮是发送广播的。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <Button
        android:id="@+id/force_offline"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Send force offline broadcast"/>
</LinearLayout>

3、定义一个活动集合类，来管理所有的活动。

public class ActivityCollector {
    public static List<Activity> activities=new ArrayList<Activity>();
    public static void addActivity(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();
            }
        }
    }
}

4、定义一个BaseActivity将活动从集合类中添加或删除。

public class BaseActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.requestWindowFeature(Window.FEATURE_NO_TITLE);//去掉标题栏
        ActivityCollector.addActivity(this);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        ActivityCollector.removeActivity(this);
    }
}

5、实现LoginActivity的类

public class LoginActivity extends BaseActivity {

    private SharedPreferences pref;
    private SharedPreferences.Editor editor;
    private EditText accountEdit;
    private EditText passwordEdit;
    private Button login;
    private CheckBox rememberPass;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        pref= PreferenceManager.getDefaultSharedPreferences(this);
        accountEdit=(EditText)findViewById(R.id.account_text);
        passwordEdit=(EditText)findViewById(R.id.password_text);
        rememberPass=(CheckBox)findViewById(R.id.remember_pass);
        login=(Button)findViewById(R.id.login);
        boolean isRemember=pref.getBoolean("remember_password", false);
        if(isRemember)
        {
            String account=pref.getString("account","");
            String password=pref.getString("password","");
            accountEdit.setText(account);
            passwordEdit.setText(password);
            rememberPass.setChecked(true);
        }
        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String account=accountEdit.getText().toString();
                String password=passwordEdit.getText().toString();
                if(account.equals("admin")&&password.equals("123456"))
                {//在登录的时候判断，记住密码的选项框有没有选中，选中了则将信息存入到SharedPreference中
                    editor=pref.edit();
                    if(rememberPass.isChecked())
                    {
                        editor.putBoolean("remember_password",true);
                        editor.putString("account",account);
                        editor.putString("password",password);
                    }else
                    {
                        editor.clear();//通过调用clear方法将SharedPreferences文件中的数据全部清除掉。
                    }
                    editor.commit();
                    Intent intent=new Intent(LoginActivity.this,MainActivity.class);
                    startActivity(intent);
                    finish();
                }else{
                    Toast.makeText(LoginActivity.this, "account or password is invalid", Toast.LENGTH_SHORT).show();
                }
            }
        });

    }
}

6、实现MainActivity，发送一条广播，通知强制下线。

public class MainActivity extends BaseActivity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button forceOffline=(Button)findViewById(R.id.force_offline);
        forceOffline.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent=new Intent("cn.sict.rememberpassword.FORCE_OFFLINE");
                sendBroadcast(intent);
            }
        });
    }
}

7、在广播接收器中实现强制下线的功能。

public class ForceOfflineReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(final Context context, Intent intent) {
        AlertDialog.Builder dialogBuilder=new AlertDialog.Builder(context);
        dialogBuilder.setTitle("Warning");
        dialogBuilder.setMessage("You are forced to be offline.Please try to login again");

        dialogBuilder.setCancelable(false);
        dialogBuilder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                ActivityCollector.finishAll();//销毁所有的活动
                Intent intent = new Intent(context, LoginActivity.class);
                intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                context.startActivity(intent);//重新启动LoginActivity
            }
        });

        AlertDialog alertDialog=dialogBuilder.create();
        alertDialog.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);
        alertDialog.show();
    }
}

实验结果如下所示：