Android5.0开发范例大全 读书笔记（四）

Android5.0开发范例大全 读书笔记（四）

（三）通信和联网

3.1显示Web信息

1.WebView通过loadUrl()方法直接访问网页时，点击跳转链接会打开系统默认的浏览器，若要拦截WebView事件，可为其添加WebViewClient

webView.setWebViewClient(new WebViewClient())

2.WebView默认不支持JavaScript，要通过setJavaScriptEnabled()进行设置

 Settings().setJavaScriptEnabled(true);

3.WebView可以直接显示Html内容

3.4下载图片文件

1.自定义一个ImageView控件，实现资源的下载与显示

  值得一提的是，设置本地资源应该提供2个方法，一个通过资源id获取，一个通过drawable获取

  网络下载可以通过asynctask实现，要注意不要在doInBackground()中更新UI线程

  下面附上完整代码

public class WebImageView extends ImageView {private Drawable mPlaceholder, mImage;public WebImageView(Context context) {this(context, null);}public WebImageView(Context context, AttributeSet attrs) {this(context, attrs, 0);}public WebImageView(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);}public void setPlaceholderImage(Drawable drawable) {mPlaceholder = drawable;if (mImage == null) {setImageDrawable(mPlaceholder);}}public void setPlaceholderImage(int resid) {mPlaceholder = getResources().getDrawable(resid);System.out.println(1);if (mImage == null) {System.out.println(2);setImageDrawable(mPlaceholder);}}public void setImageUrl(String url) {DownloadTask task = new DownloadTask();ute(url);}private class DownloadTask extends AsyncTask<String, Void, Bitmap> {@Overrideprotected Bitmap  params) {String url = params[0];try {URLConnection connection = (new URL(url)).openConnection();InputStream is = InputStream();return BitmapFactory.decodeStream(is);} catch (IOException e) {e.printStackTrace();return null;}}@Overrideprotected void onPostExecute(Bitmap bitmap) {mImage = new BitmapDrawable(getContext().getResources(), bitmap);setImageDrawable(mImage);}}
}

3.5完全在后台下载

1.DownloadManager适合处理和管理需要长时间运行的下载操作。其优点是即使在下载失败，链接改变甚至设备重启时，依然会继续尝试下载

2.首先实现一个广播接收者来监听下载状态

 private BroadcastReceiver receiver=new BroadcastReceiver() {@Overridepublic void onReceive(Context context, Intent intent) {queryDownloadStatus();}};private void queryDownloadStatus(){DownloadManager.Query query=new DownloadManager.Query();query.Long(DL_ID,0));Cursor c=dm.query(query);veToFirst()){int status&#ColumnIndex(DownloadManager.COLUMN_STATUS));switch (status){case DownloadManager.STATUS_PAUSED:case DownloadManager.STATUS_PENDING:case DownloadManager.STATUS_RUNNING:break;case DownloadManager.STATUS_SUCCESSFUL:try {ParcelFileDescriptor file=dm.Long(DL_ID,0));FileInputStream fis=new ParcelFileDescriptor.AutoCloseInputStream(file);imageView.setImageBitmap(BitmapFactory.decodeStream(fis));Toast.makeText(this,"download over!",Toast.LENGTH_SHORT).show();} catch (FileNotFoundException e) {e.printStackTrace();}break;case DownloadManager.STATUS_Long(DL_ID, 0));prefs.edit().clear().apply();break;}}}

3.接着获取系统服务

dm= (DownloadManager) getSystemService(DOWNLOAD_SERVICE);

4.最后，在onResume中注册广播并开始下载

 @Overrideprotected void onResume() {Resume();if(!ains(DL_ID)){Uri resource=Uri.parse(&#ji.mi.apk");DownloadManager.Request request=new DownloadManager.Request(resource);request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_MOBILE| DownloadManager.Request.NETWORK_WIFI);request.setTitle("Download Sample");request.setDescription("Download SSR!");request.setAllowedOverRoaming(false);long id&#queue(request);prefs.edit().putLong(DL_ID,id).apply();}else{queryDownloadStatus();}registerReceiver(receiver,new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));}

3.10发送短信

1.与之前的DownloadManager一样，发送短信的SmsManager也是系统级服务，二者的调用极为相似

2..首先实现广播接收者，发送短信一共有2个接受者，一个返回发送是否成功

private BroadcastReceiver sent = new BroadcastReceiver() {@Overridepublic void onReceive(Context context, Intent intent) {switch (getResultCode()) {case Activity.RESULT_OK:Toast.makeText(SendSmsActivity.this, "发送成功", Toast.LENGTH_SHORT).show();break;case SmsManager.RESULT_ERROR_GENERIC_FAILURE:case SmsManager.RESULT_ERROR_NO_SERVICE:case SmsManager.RESULT_ERROR_NULL_PDU:case SmsManager.RESULT_ERROR_RADIO_OFF:Toast.makeText(SendSmsActivity.this, "发送失败", Toast.LENGTH_SHORT).show();break;}}};

  另一个返回接收是否成功

private BroadcastReceiver delivered = new BroadcastReceiver() {@Overridepublic void onReceive(Context context, Intent intent) {switch (getResultCode()) {case Activity.RESULT_OK:Toast.makeText(SendSmsActivity.this, "传递成功", Toast.LENGTH_SHORT).show();break;case Activity.RESULT_CANCELED:Toast.makeText(SendSmsActivity.this, "传递失败", Toast.LENGTH_SHORT).show();break;}}};

3.接着，分别在resume和pause中注册和注销广播

 @Overrideprotected void onResume() {Resume();registerReceiver(sent, new IntentFilter(ACTION_SENT));registerReceiver(delivered,new IntentFilter(ACTION_DELIVERED));}

 @Overrideprotected void onPause() {Pause();unregisterReceiver(sent);unregisterReceiver(delivered);}

4.最后调用SmsManager即可

private void sendSms(String msg) {PendingIntent sIntent = Broadcast(this, 0, new Intent(ACTION_SENT),0);PendingIntent dIntent = Broadcast(this, 0, new Intent(ACTION_DELIVERED),0);SmsManager manager&#Default();manager.sendTextMessage(RECIPIENT_ADDRESS,null,msg,sIntent,dIntent);}

3.11蓝牙通信

1.蓝牙通信需要获取权限

 <uses-permission android:name="android.permission.BLUETOOTH" /><uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />

2.有时蓝牙并没有开启，所以要通过startActivityForResult启动

Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableIntent, REQUEST_ENABLE);

3.此时应该设置一个onActivityResult方法来获取蓝牙的启动情况

@Overrideprotected void onActivityResult(int requestCode, int resultCode, Intent data) {switch (requestCode) {case REQUEST_ENABLE:if (resultCode != RESULT_OK) {Toast.makeText(this, "蓝牙启动失败", Toast.LENGTH_SHORT).show();finish();}break;case REQUEST_DISCOVERABLE:if (resultCode == RESULT_CANCELED) {Toast.makeText(this, "蓝牙必须被设置为可见", Toast.LENGTH_SHORT).show();finish();} else {startListening();}break;default:break;}}

4.蓝牙功能分两方，一方让设备处于监听状态，监听其他设备的连入

listenButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {email = Text().toString();if (ScanMode() != BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE) {Intent discoverableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 3000);startActivityForResult(discoverableIntent, REQUEST_DISCOVERABLE);}startListening();}});

  监听时要用到唯一的UUID

private void startListening() {AcceptTask task = new AcceptTask();ute(MY_UUID);setProgressBarIndeterminateVisibility(true);}

5.另一方要让设备扫描可连入的设备，主要通过startDiscovery()方法

scanButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {email = Text().toString();mBtAdapter.startDiscovery();setProgressBarIndeterminateVisibility(true);}});

6.程序要使用2个AsyncTask来执行具体的功能，一个用来连接

private class AcceptTask extends AsyncTask<UUID, Void, BluetoothSocket> {@Overrideprotected BluetoothSocket  params) {String name = Name();mBtAdapter.setName(SEARCH_NAME);try {BluetoothServerSocket socket = mBtAdapter.listenUsingRfcommWithServiceRecord("BluetoothRecipe", params[0]);BluetoothSocket connected = socket.accept();mBtAdapter.setName(name);return connected;} catch (IOException e) {e.printStackTrace();mBtAdapter.setName(name);return null;}}@Overrideprotected void onPostExecute(BluetoothSocket bluetoothSocket) {mBtSocket = bluetoothSocket;ConnectedTask task = new ConnectedTask();ute(mBtSocket);}}

7.另一个用来传输数据

 private class ConnectedTask extends AsyncTask<BluetoothSocket, Void, String> {@Overrideprotected String  params) {InputStream in = null;OutputStream out = null;try {//发送数据out = params[0].getOutputStream();out.Bytes());//接受其他数据in = params[0].getInputStream();byte[] buffer = new byte[1024];in.read(buffer);String result = new String(buffer);mBtSocket.close();im();} catch (IOException e) {e.printStackTrace();return null;}}@Overrideprotected void onPostExecute(String result) {Toast.makeText(ExchangeActivity.this, result, Toast.LENGTH_SHORT).show();setProgressBarIndeterminateVisibility(false);}}

8.两个AsyncTask之间使用BroadCast进行连接

private BroadcastReceiver mReceiver = new BroadcastReceiver() {@Overridepublic void onReceive(Context context, Intent intent) {String action = Action();if (BluetoothDevice.ACTION_FOUND.equals(action)) {BluetoothDevice device = ParcelableExtra(BluetoothDevice.EXTRA_DEVICE);if (Name().equals(SEARCH_NAME)) {mBtAdapter.cancelDiscovery();try {mBtSocket = ateRfcommSocketToServiceRecord(MY_UUID);t();ConnectedTask task = new ConnectedTask();ute(mBtSocket);} catch (IOException e) {e.printStackTrace();}}} else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {setProgressBarIndeterminateVisibility(false);}}};

9.广播接收者分别在resume和pause中注册和注销

@Overrideprotected void onResume() {Resume();IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);registerReceiver(mReceiver, filter);filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);registerReceiver(mReceiver, filter);}

 requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);setContentView(R.layout.activity_exchange);mBtAdapter = DefaultAdapter();if (mBtAdapter == null) {Toast.makeText(this, "不支持蓝牙", Toast.LENGTH_SHORT).show();finish();}//开启蓝牙if (!mBtAdapter.isEnabled()) {Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);startActivityForResult(enableIntent, REQUEST_ENABLE);}emailField = (EditText) findViewById(ailField);

 @Overrideprotected void onDestroy() {Destroy();if (mBtSocket != null) {try {mBtSocket.close();} catch (IOException e) {e.printStackTrace();}}}

public static boolean isNetworkReachable(Context context) {final ConnectivityManager mManager = (ConnectivityManager) SystemService(Context.CONNECTIVITY_SERVICE);NetworkInfo current = ActiveNetworkInfo();return current != null && State() == NetworkInfo.State.CONNECTED;}

public static boolean isWifiReachable(Context context) {final ConnectivityManager mManager = (ConnectivityManager) SystemService(Context.CONNECTIVITY_SERVICE);NetworkInfo current = ActiveNetworkInfo();return current != null && Type() == ConnectivityManager.TYPE_WIFI;}