Android6.0原始碼分析之藍芽顯示接收到的檔案
在藍芽介面有個menu：顯示接收到的檔案。本文分析顯示接收到的檔案
chapter one---顯示接收到的檔案
/android/packages/apps/Settings/src/com/android/settings/bluetooth/資料夾下的BluetoothSettings.java開始分析
case MENU_ID_SHOW_RECEIVED: MetricsLogger.action(getActivity(), MetricsLogger.ACTION_BLUETOOTH_FILES); Intent intent = new Intent(BTOPP_ACTION_OPEN_RECEIVED_FILES); getActivity().sendBroadcast(intent); return true;
當點選顯示接收到的檔案menu時會發送廣播,傳送的廣播為
private static final String BTOPP_ACTION_OPEN_RECEIVED_FILES =
"android.btopp.intent.action.OPEN_RECEIVED_FILES";通過程式碼搜尋定位到/android/packages/apps/Bluetooth/資料夾下的Androidmanifest.xml檔案中進行了定義
可以看到實在opp資料夾下的BluetoothOppReceiver中進行處理的
在Constants中定義了全域性變數
/** the intent that gets sent from the Settings app to show the received files */
public static final String ACTION_OPEN_RECEIVED_FILES = "android.btopp.intent.action.OPEN_RECEIVED_FILES";在BluetoothOppReceiver中當檢測到該action時會進行如下處理
else if (action.equals(Constants.ACTION_OPEN_RECEIVED_FILES)) { if (V) Log.v(TAG, "Received ACTION_OPEN_RECEIVED_FILES."); Intent in = new Intent(context, BluetoothOppTransferHistory.class); in.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TOP); in.putExtra("direction", BluetoothShare.DIRECTION_INBOUND); in.putExtra(Constants.EXTRA_SHOW_ALL_FILES, true); context.startActivity(in);
跳轉到BluetoothTransferHistory，在跳轉時對intent做了一些處理，首先是設定了一些flags，說明一下
Intent.FLAG_ACTIVITY_CLEAR_TOP：如果在棧中有該例項，就會去重用該例項，並且會清除掉該例項上方的所有activity，簡單舉個例子，如果在棧1中存在有三個例項，Acivity1，Activity2，Activity3。可以看到處於棧頂的是Activity3，也就是目前顯示的是視窗3，如果從視窗3跳轉到視窗2，則會銷燬Activity3，並且重用Activity2，也就是說目前棧中Activity存在情況如下Activity1，Activity2。
Intent.FLAG_ACTIVITY_NEW_TASK：如果在activity節點下存在taskAffinity屬性，首先看該屬性值有沒有進行設定
android:taskAffinity="">
如果沒有設定該屬性或者該屬性值預設為空，則直接壓入當前棧。在程式中未對BluetoothTransferHistory的該屬性進行設定。
接下來對BluetoothTransferHistory.java分析，該類位於\android\packages\apps\Bluetooth\src\com\android\bluetooth\opp
設計思路：對於顯示藍芽接受到的檔案是利用ContentProvider來訪問uri獲取到已接受到的檔案並顯示出來。
佈局檔案為bluetooth_transfers_page.xml
setContentView(R.layout.bluetooth_transfers_page);該佈局檔案所用到的節點有些特別，分析一下
<merge xmlns:android="http://schemas.android.com/apk/res/android">
<ListView
android:id="@+id/list"
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
<ViewStub
android:id="@+id/empty"
android:layout="@layout/no_transfers"
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
</merge>
首先最外層佈局為merge，接下來是兩個子view：ListView和ViewStub。ListView很常見，但很少用到merge和ViewStub佈局控制元件
關於這些的介紹想了解的可以看相關連結，在這裡不再多說
其中merge是預設的垂直的線性佈局，也就是說該佈局檔案中顯示一個listview列表，然後是一個動態佈局的ViewStub，所引用的layout檔案為no_transfers
no_transfers.xml
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:text="@string/no_transfers"
android:gravity="center"
android:textStyle="bold"
/>
顯示一個textview，
<string name="no_transfers" msgid="3482965619151865672">"沒有傳輸歷史記錄。"</string>listview顯示的傳輸檔案列表，佈局xml介紹完後進入對Java檔案的分析。
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.bluetooth_transfers_page);
mListView = (ListView)findViewById(R.id.list);
mListView.setEmptyView(findViewById(R.id.empty));
mShowAllIncoming = getIntent().getBooleanExtra(
Constants.EXTRA_SHOW_ALL_FILES, false);
String direction;
int dir = getIntent().getIntExtra("direction", 0);
if (dir == BluetoothShare.DIRECTION_OUTBOUND) {
setTitle(getText(R.string.outbound_history_title));
direction = "(" + BluetoothShare.DIRECTION + " == " + BluetoothShare.DIRECTION_OUTBOUND
+ ")";
} else {
if (mShowAllIncoming) {
setTitle(getText(R.string.btopp_live_folder));
} else {
setTitle(getText(R.string.inbound_history_title));
}
direction = "(" + BluetoothShare.DIRECTION + " == " + BluetoothShare.DIRECTION_INBOUND
+ ")";
}
String selection = BluetoothShare.STATUS + " >= '200' AND " + direction;
if (!mShowAllIncoming) {
selection = selection + " AND ("
+ BluetoothShare.VISIBILITY + " IS NULL OR "
+ BluetoothShare.VISIBILITY + " == '"
+ BluetoothShare.VISIBILITY_VISIBLE + "')";
}
final String sortOrder = BluetoothShare.TIMESTAMP + " DESC";
mTransferCursor = managedQuery(BluetoothShare.CONTENT_URI, new String[] {
"_id", BluetoothShare.FILENAME_HINT, BluetoothShare.STATUS,
BluetoothShare.TOTAL_BYTES, BluetoothShare._DATA, BluetoothShare.TIMESTAMP,
BluetoothShare.VISIBILITY, BluetoothShare.DESTINATION, BluetoothShare.DIRECTION
}, selection, sortOrder);
// only attach everything to the listbox if we can access
// the transfer database. Otherwise, just show it empty
if (mTransferCursor != null) {
mIdColumnId = mTransferCursor.getColumnIndexOrThrow(BluetoothShare._ID);
// Create a list "controller" for the data
mTransferAdapter = new BluetoothOppTransferAdapter(this,
R.layout.bluetooth_transfer_item, mTransferCursor);
mListView.setAdapter(mTransferAdapter);
mListView.setScrollBarStyle(View.SCROLLBARS_INSIDE_INSET);
mListView.setOnCreateContextMenuListener(this);
mListView.setOnItemClickListener(this);
}
mNotifier = new BluetoothOppNotification(this);
mContextMenu = false;
}關鍵程式碼都在onCreate中，可以看出來通過呼叫managedQuery方法按指定的條件查詢指定的uri，獲取到cursor後傳給adapter，並將adapter與listview繫結顯示資料。
首先是對傳輸列表資料來源的獲取----managedQuery
public final Cursor managedQuery(Uri uri, String[] projection, String selection,
String sortOrder) {
Cursor c = getContentResolver().query(uri, projection, selection, null, sortOrder);
if (c != null) {
startManagingCursor(c);
}
return c;
}managedQuery方法定義在Activity中，可以看到首先獲取到ContentResolver物件，然後呼叫query方法進行查詢指定uri的資料。有幾點需要注意，通過該方法獲取到的cursor無需去呼叫close方法將其關閉，因為activity會在合適的時候將其關閉。但是有一點，如果你的cursor物件呼叫了stopManagingCursor方法時，必須手動去呼叫cursor.close方法將其關閉，因為此時，activity不會自動去關閉
需要傳入四個引數
- uri : the uri of the content provider to query 所要查詢的contentProvider的uri
- projection : projection list of columns to return 查詢到後所要返回的cursor的列名，如果想要全部返回可以將引數置為null
- selection : selectio SQL WHERE clause 查詢條件
- sortOrder : sortorder SQL ORDER BY clause 按某種條件排序
所查詢的uri為
/**
* The content:// URI for the data table in the provider
*/
public static final Uri CONTENT_URI = Uri.parse("content://com.android.bluetooth.opp/btopp");<uses-permission android:name="android.permission.ACCESS_BLUETOOTH_SHARE" />查詢到後傳給adapter進行載入view
舉一個例子，在item上顯示遠端藍芽name的話可以使用如下程式碼
tv = (TextView)view.findViewById(R.id.targetdevice);
//獲取到本地藍芽介面卡
BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();
//獲取到索引
int destinationColumnId = cursor.getColumnIndexOrThrow(BluetoothShare.DESTINATION);
//獲取到本條資料中所對應的遠端裝置
BluetoothDevice remoteDevice = adapter.getRemoteDevice(cursor
.getString(destinationColumnId));
//獲取到name
String deviceName = BluetoothOppManager.getInstance(context).getDeviceName(remoteDevice);
tv.setText(deviceName);顯示接收到的檔案原始碼其實實現起來不難，就是藉助contentResolver來讀取uri的資料並顯示出來，那麼資料必須要通過contentprovider的方式儲存，但是接收到的檔案時儲存在哪個contentprovider？？如何進行儲存？會儲存哪些資訊？有哪些列？接下來就進行分析
首先根據uri---com.android.bluetooth.opp去查詢清單配置檔案
<provider android:name=".opp.BluetoothOppProvider"
android:authorities="com.android.bluetooth.opp"
android:exported="true"
android:process="@string/process">
<path-permission
android:pathPrefix="/btopp"
android:permission="android.permission.ACCESS_BLUETOOTH_SHARE" />
</provider>可以發現儲存所用的provider為BluetoothOppProvider.java，正好藉此機會分析下provider的用法。
chapter two-----儲存接收到的檔案的ContentProvider
該類位於\android\packages\apps\Bluetooth\src\com\android\bluetooth\opp資料夾下，直接繼承與ContentProvider。希望是在對contentProvider有一定的瞭解後閱讀如下分析
provider屬於元件，需要再清單配置檔案中進行配置
<provider android:name=".opp.BluetoothOppProvider"
android:authorities="com.android.bluetooth.opp"
android:exported="true"
android:process="@string/process">
<path-permission
android:pathPrefix="/btopp"
android:permission="android.permission.ACCESS_BLUETOOTH_SHARE" />
</provider>自定義一個provider需要新增如下屬性authorities：域名，如果需要訪問許可權，就規定所需要的訪問許可權
java程式碼中的處理如下
首先對於BluetoothOppProvider的uri進行解析
定義一個urimatcher物件，以供應用對uri進行訪問解析資料
/** URI matcher used to recognize URIs sent by applications */
private static final UriMatcher sURIMatcher = new UriMatcher(UriMatcher.NO_MATCH);/** URI matcher constant for the URI of the entire share list 返回整個資料列表*/
private static final int SHARES = 1;
/** URI matcher constant for the URI of an individual share 返回一條記錄*/
private static final int SHARES_ID = 2;
static {
sURIMatcher.addURI("com.android.bluetooth.opp", "btopp", SHARES);
sURIMatcher.addURI("com.android.bluetooth.opp", "btopp/#", SHARES_ID);
}緊接著看到原始碼中建立了資料庫，也就是說contentprovider將資料儲存到資料庫
資料庫的name為：btop.db
/** Database filename */
private static final String DB_NAME = "btopp.db";所建立的列包括14個，如下所示
private void createTable(SQLiteDatabase db) {
try {
db.execSQL("CREATE TABLE " + DB_TABLE + "(" + BluetoothShare._ID
+ " INTEGER PRIMARY KEY AUTOINCREMENT," + BluetoothShare.URI + " TEXT, "
+ BluetoothShare.FILENAME_HINT + " TEXT, " + BluetoothShare._DATA + " TEXT, "
+ BluetoothShare.MIMETYPE + " TEXT, " + BluetoothShare.DIRECTION + " INTEGER, "
+ BluetoothShare.DESTINATION + " TEXT, " + BluetoothShare.VISIBILITY
+ " INTEGER, " + BluetoothShare.USER_CONFIRMATION + " INTEGER, "
+ BluetoothShare.STATUS + " INTEGER, " + BluetoothShare.TOTAL_BYTES
+ " INTEGER, " + BluetoothShare.CURRENT_BYTES + " INTEGER, "
+ BluetoothShare.TIMESTAMP + " INTEGER," + Constants.MEDIA_SCANNED
+ " INTEGER); ");
} catch (SQLException ex) {
Log.e(TAG, "couldn't create table in downloads database");
throw ex;
}
}介紹一個小知識，在資料庫類的oncreate方法中可以直接並且只調用createTable方法，但是在更新資料庫時需要先將資料庫刪除然後再呼叫createTable建立，刪除資料庫方法如下
private void dropTable(SQLiteDatabase db) {
try {
db.execSQL("DROP TABLE IF EXISTS " + DB_TABLE);
} catch (SQLException ex) {
Log.e(TAG, "couldn't drop table in downloads database");
throw ex;
}
}然後就會provider對資料庫進行增刪改查操作--
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未完待續