照着书《第一行代码》打的代码,但是书上的代码发送广播和接收广播都是在同一个进程里面,所以书上的注册广播在onResume(),解除广播在onPurse()。但是我现在要实现的是要在两个不同的进程里面的广播,所以,这里是一个坑,简单到你自己都意识不到的坑。
如果照着书上的代码,你会发现,你无法接收到另一个进程的广播,这是因为什么。根据Activity的生命周期,当你把接收广播的进程切换到发送广播进程的时候,已经调用了onPurse()方法,你的广播已经解除了,所以你不能收到发送广播的广播。所以,我的意思就是说,这里你要把你的注册广播以及解除广播放在onCreate()和onDestory()中。代码如下:
发送广播者:
public class MainActivityextends AppCompatActivity {
private Buttonforce_offline;
private static final StringBROADCAST_ACTION="android.intent.action.FORCE_OFFLINE";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
force_offline = findViewById(R.id.force_offline);
force_offline.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent =new Intent(BROADCAST_ACTION);
Log.e("OFFLINE", "onClick: 点击了强制下线" +intent.toString());
sendBroadcast(intent);
Toast.makeText(MainActivity.this, "发送了广播", Toast.LENGTH_SHORT).show();
}
});
}
}
xml:就是一个按钮,点击按钮发送一个广播
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
android:id="@+id/force_offline"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:text="@string/offline"/>
</LinearLayout>
接收者:
public class BaseActivityextends AppCompatActivity {
private ForceOfflineReceiverreceiver;
private static final StringBROADCAST_ACTION ="android.intent.action.FORCE_OFFLINE";
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (receiver ==null) {
IntentFilter intentFilter =new IntentFilter(BROADCAST_ACTION);
receiver =new ForceOfflineReceiver();
registerReceiver(receiver, intentFilter);
Toast.makeText(this, "注册广播接收器", Toast.LENGTH_SHORT).show();
}else {
Toast.makeText(this, "已经注册广播接收器", Toast.LENGTH_SHORT).show();
}
}
class ForceOfflineReceiverextends BroadcastReceiver {
ForceOfflineReceiver() {
Toast.makeText(BaseActivity.this, "创建ForceOfflineReceiver对象", Toast.LENGTH_SHORT).show();
}
@Override
public void onReceive(final Context context, Intent intent) {
if (intent !=null) {
String action = intent.getAction();
Toast.makeText(BaseActivity.this, "接收到的广播:" + action, Toast.LENGTH_SHORT).show();
Log.e("OFFLINE", "onReceive: 收到了强制下线广播:" + action);
AlertDialog.Builder builder =new AlertDialog.Builder(context);
builder.setTitle("下线通知")
.setMessage("您有另外一台移动设备登陆叻此账号,需要下线")
.setCancelable(false)
.setPositiveButton("退出", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
ActivityCollector.finishAll();
context.startActivity(new Intent(context, LoginActivity.class));
}
})
.create()
.show();
}
}
}
@Override
protected void onDestroy() {
if (receiver !=null) {
unregisterReceiver(receiver);
receiver =null;
Toast.makeText(this, "解注册广播接收器", Toast.LENGTH_SHORT).show();
}else {
Toast.makeText(this, "还没有注册广播接收器", Toast.LENGTH_SHORT).show();
}
Log.e("BaseActivity", "onDestroy: " +this.toString());
super.onDestroy();
}
}
其实就是一个很小的细节性问题,记录一下。
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