多表格合并一起
2022
2022-05-28
Android 通過廣播監聽USB連接狀態的改變
一、原理講解
Android通過廣播監聽USB連接狀態的改變的動作在UsbManager.java文件里，為ACTION_USB_STATE。然而在UsbManager中，該常量的注釋中包含{@hide}，該注釋是控制該API是否開放用的。未開發的API意味著google可以隨時調整該API的定義或實現方式，而不用保證向下兼容。
所以盡量避免調用未開發的API，因為一旦系統升級導致其實現方式改變，程序很有可能就直接崩潰了。
注意：
目前仍未發現 ACTION_USB_ACCESSORY_XXX 這種廣播
插拔手機與電腦之間的USB線：ACTION_USB_STATE（主要參數是 Boolean connected）
插拔U盤發送的是OTG廣播：ACTION_USB_DEVICE_XXX，XXX代表了ATTACH 或 DETACH，這種情況是手機是主，u盤是從，手機給U盤供電。
二、代碼如下
1、MyUsbManager.java
package com.example.testapp; public class MyUsbManager { /** * Broadcast Action: A sticky broadcast for USB state change events when in device mode. * This is a sticky broadcast for clients that includes USB connected/disconnected state, *
- *
- {@link #USB_CONNECTED} boolean indicating whether USB is connected or disconnected. *
- {@link #USB_CONFIGURED} boolean indicating whether USB is configured. currently zero if not configured, one for configured. *
- {@link #USB_FUNCTION_ADB} boolean extra indicating whether the adb function is enabled *
- {@link #USB_FUNCTION_RNDIS} boolean extra indicating whether the RNDIS ethernet function is enabled *
- {@link #USB_FUNCTION_MTP} boolean extra indicating whether the MTP function is enabled *
- {@link #USB_FUNCTION_PTP} boolean extra indicating whether the PTP function is enabled *
- {@link #USB_FUNCTION_PTP} boolean extra indicating whether the accessory function is enabled *
- {@link #USB_FUNCTION_AUDIO_SOURCE} boolean extra indicating whether the audio source function is enabled *
- {@link #USB_FUNCTION_MIDI} boolean extra indicating whether the MIDI function is enabled *
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2、UsbActivity.java
package com.example.testapp; import android.app.Activity; import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; import android.content.IntentFilter; import android.content.pm.PackageManager; import android.hardware.usb.UsbAccessory; import android.hardware.usb.UsbDevice; import android.hardware.usb.UsbManager; import android.os.Bundle; import android.widget.LinearLayout; import android.widget.ScrollView; import android.widget.TextView; public class UsbActivity extends Activity { private TextView textView; private UsbManager usbManager; private BroadcastReceiver receiver; private IntentFilter intentFilter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ScrollView scrollView = new ScrollView(this); LinearLayout linearLayout = new LinearLayout(this); linearLayout.setOrientation(LinearLayout.VERTICAL); textView = new TextView(this); scrollView.addView(linearLayout); linearLayout.addView(textView); setContentView(scrollView); usbManager = (UsbManager) getSystemService(Context.USB_SERVICE); receiver = new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { String action = intent.getAction(); addText("action : " + action); if(intent.hasExtra(UsbManager.EXTRA_PERMISSION_GRANTED)) { boolean permissionGranted = intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false); addText("permissionGranted : " + permissionGranted); } switch(action) { case UsbManager.ACTION_USB_ACCESSORY_ATTACHED: case UsbManager.ACTION_USB_ACCESSORY_DETACHED: //Name of extra for ACTION_USB_ACCESSORY_ATTACHED and ACTION_USB_ACCESSORY_DETACHED broadcasts containing the UsbAccessory object for the accessory. UsbAccessory accessory = intent.getParcelableExtra(UsbManager.EXTRA_ACCESSORY); addText(accessory.toString()); break; case UsbManager.ACTION_USB_DEVICE_ATTACHED: case UsbManager.ACTION_USB_DEVICE_DETACHED: //Name of extra for ACTION_USB_DEVICE_ATTACHED and ACTION_USB_DEVICE_DETACHED broadcasts containing the UsbDevice object for the device. UsbDevice device = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE); addText(device.toString()); break; case MyUsbManager.ACTION_USB_STATE: /* *
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三、運行截圖
四、ACTION_USB_DEVICE_ATTACHED 和 ACTION_USB_DEVICE_DETACHED的缺點
廣播是去監測U盤插入和拔出的，也就意味著，你只要一插入或者一拔出U盤，就是收到這兩個廣播。它不會管你的設備有沒有準備好，有沒有mounted或者unmounted。
因此就需要引入一個新的廣播 android.os.storage.extra.VOLUME_STATE。
這個廣播就是用來監聽Volume狀態的。當外置Usb設備在Mounted或者UnMounted的時候則就可以用來做監聽 int 類型的 VolumeInfo.EXTRA_VOLUME_STATE。
注意：android.os.storage.extra.VOLUME_STATE 一定要聲明讀寫權限，否則是收不到的。
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Android API
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