在Service中弹出Toast和Dialog

众所周知，Toast必须在UI主线程上才能正常显示，而在Service中是无法获得Acivity的Context的，在service中想显示出Toast只需将show的消息发送给主线程Looper就可以了

Handler handler = new Handler(Looper.getMainLooper());              handler.post(new Runnable() {  
                public void run() {  
                    Toast.makeText(getApplicationContext(), "存Service is runing!",  
                            Toast.LENGTH_SHORT).show();  
                }  
            });  

此时便可显示Toast

Dialog的用法与此类似，但是要多加个权限

在manifest中添加此权限以弹出dialog

<uses-permission Android:name="android.permission.SYSTEM_ALERT_WINDOW" />

Builder builder = new AlertDialog.Builder(getApplicationContext())                      .setIcon(android.R.drawable.ic_dialog_info)                      .setTitle("service中弹出Dialog了")                      .setMessage("是否关闭dialog？")                      .setPositiveButton("确定",                              new DialogInterface.OnClickListener() {                                  public void onClick(DialogInterface dialog,                                          int whichButton) {                                                                        }                              })                      .setNegativeButton("取消",                              new DialogInterface.OnClickListener() {                                  public void onClick(DialogInterface dialog,                                          int whichButton) {                                    }                              });              final AlertDialog dialog = builder.create();              dialog.getWindow().setType(                      (WindowManager.LayoutParams.TYPE_SYSTEM_ALERT));              Handler handler = new Handler(Looper.getMainLooper());              handler.post(new Runnable() {                  public void run() {                      dialog.show();                  }              });  

来自：http://blog.csdn.net/nmzkchina/article/details/15506373