实现强制下线功能的思路就是弹出一个对话框，让用户无法进行任何操作，必须选择对话框中的确定按钮，然后Intent跳转到Login页面即可。现在存在这样一个问题，我们被通知强制下线的时候可能处于任何一个页面，难道我们需要在每个界面上都编写一个弹出对话框的逻辑？我们可以借助广播，来轻松实现这一功能。
首先我们考虑强制下线功能需要先关闭掉所有的活动，然后回到登录界面，怎么实现关闭所有活动的功能呢？我们可以先创建一个ActivityCollector类用于管理所有的活动：
<p>package com.example.forceoffline;</p><p>import java.util.ArrayList;
import java.util.List;</p><p>import android.app.Activity;</p><p>public class ActivityCollector {
public static List<Activity> activities = new ArrayList<Activity>();</p><p> public static void addActivity(Activity activity) {
activities.add(activity);
}</p><p> public static void removeActivity(Activity activity) {
activities.remove(activity);
}</p><p> public static void finishAll() {
for (Activity activity : activities) {
if (!activity.isFinishing()) {
activity.finish();
}
}
}</p><p>}
</p>
然后创建BaseActivity类作为所有活动的父类。
package com.example.forceoffline;
import android.app.Activity;
import android.os.Bundle;
public class BaseActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ActivityCollector.addActivity(this);
}
@Override
protected void onDestroy() {
ActivityCollector.removeActivity(this);
super.onDestroy();
}
}
登录login.xml代码如下：
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.forceoffline.LoginActivity"
tools:ignore="MergeRootFrame" >
<TableRow>
<TextView
android:layout_height="wrap_content"
android:text="Account:" />
<EditText
android:id="@+id/account"
android:layout_height="wrap_content"
android:minWidth="50dp" />
</TableRow>
<TableRow>
<TextView
android:layout_height="wrap_content"
android:text="Password:" />
<EditText
android:id="@+id/password"
android:layout_height="wrap_content"
android:inputType="textPassword"
android:minWidth="50dp" />
</TableRow>
<TableRow>
<Button
android:id="@+id/login"
android:layout_height="wrap_content"
android:layout_span="2"
android:text="Login" />
</TableRow>
</TableLayout>
新建LoginActivity继承BaseActivity:
package com.example.forceoffline;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class LoginActivity extends BaseActivity {
private EditText accEditText = null;
private EditText passEditText = null;
private Button loginButton = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.login);
this.accEditText = (EditText) super.findViewById(R.id.account);
this.passEditText = (EditText) super.findViewById(R.id.password);
this.loginButton = (Button) super.findViewById(R.id.login);
this.loginButton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
String account = accEditText.getText().toString();
String passwordString = passEditText.getText().toString();
if (account.equals("admin") && passwordString.equals("admin")) {
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();
}
}
});
}
}
main.xml代码如下：
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.forceoffline.LoginActivity"
tools:ignore="MergeRootFrame" >
<Button
android:id="@+id/offline"
android:layout_height="wrap_content"
android:layout_span="2"
android:text="Offline" />
</TableLayout>
MainActivity.java如下：
package com.example.forceoffline;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class MainActivity extends BaseActivity {
private Button offlineButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
this.offlineButton = (Button) super.findViewById(R.id.offline);
offlineButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
Intent intent = new Intent("com.example.offline.FORCE_OFFLINE");
sendBroadcast(intent);
}
});
}
}
接下来我们要创建一个广播接收器了：
package com.example.forceoffline;
import android.app.AlertDialog;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.view.WindowManager;
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 arg0, int which) {
ActivityCollector.finishAll();
Intent intent = new Intent(context, LoginActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
context.startActivity(intent);
}
});
AlertDialog alertDialog = dialogBuilder.create();
alertDialog.getWindow().setType(
WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);
alertDialog.show();
}
}
最后不要忘了配置manifest：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.forceoffline"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="19" />
<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.example.forceoffline.LoginActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".MainActivity" >
</activity>
<receiver android:name="com.example.forceoffline.ForceOfflineReceiver" >
<intent-filter>
<action android:name="com.example.offline.FORCE_OFFLINE" />
</intent-filter>
</receiver>
</application>
</manifest>
运行实例：
输入正确的用户名和密码后进入Main：
点击offline:
点击OK后返回登录界面，实现简单的下线功能。
最后推荐一下我开发的应用：http://openbox.mobilem.360.cn/index/d/sid/2966005
应用看起来很简单，却也用到了不少技术，希望初学者及安卓开发爱好者下载后与我交流学习，谢谢支持。