編輯:關於android開發
android最後一個組件便是service了,終於學習到最後一個組件了,從年前的開發環境的搭建,到現在學到最後一個組件花了三周的時間,期間記錄的點點滴滴,照著書本學習編寫的代碼都受益匪淺,這裡要感謝第一行代碼這本書。三個星期除了三十和初一沒有學習,其余時間堅持每天學習一個知識點,總算慢慢地學習了個大概,接下去繼續學習其他的東西。說了這麼多還是開始學習Service組件吧。
Service從字面上理解就是服務的意思,也就是為應用程序提供服務,比如我們在播放一首歌的時候,我又想把它下載下來,那麼我們就可以把他交給Service去處理。播放歌曲是在後台運行的,那麼它也是個服務,還是來個例子吧。先新建工程ServiceTest。編寫布局如下:
<!--{cke_protected}{C}%3C!%2D%2D%3Fxml%20version%3D%221.0%22%20encoding%3D%22utf-8%22%3F%2D%2D%3E--> <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" android:orientation="vertical" android:layout_margin="10dp" android:padding="10dp" tools:context="com.example.jared.servicetest.MainActivity"><button android:id="@+id/startService" android:text="啟動Service" android:layout_width="match_parent" android:layout_height="wrap_content" android:textallcaps="false"></button><button android:id="@+id/stopService" android:text="停止Service" android:layout_width="match_parent" android:layout_height="wrap_content" android:textallcaps="false"></button></linearlayout>這裡實現了兩個按鈕啟動和停止Service。接著新建一個MyService類,繼承Service,代碼如下:
package com.example.jared.servicetest; import android.app.Service; import android.content.Intent; import android.os.IBinder; import android.support.annotation.Nullable; import android.util.Log; import android.widget.Toast; /** * Created by jared on 16/2/18. */ public class MyService extends Service{ private static final String TAG = "MyService"; @Nullable @Override public IBinder onBind(Intent intent) { return null; } @Override public void onCreate() { super.onCreate(); Log.d(TAG, "onCreate is called"); Toast.makeText(MyService.this, "onCreate is called",Toast.LENGTH_SHORT).show(); } @Override public int onStartCommand(Intent intent, int flags, int startId) { Log.d(TAG, "onStartCommand is called"); Toast.makeText(MyService.this, "onStartCommand is called",Toast.LENGTH_SHORT).show(); return super.onStartCommand(intent, flags, startId); } @Override public void onDestroy() { super.onDestroy(); Log.d(TAG, "onDestroy is called"); Toast.makeText(MyService.this, "onDestroy is called",Toast.LENGTH_SHORT).show(); } }這裡重寫了onCreate方法,onStartCommand方法和onDestroy方法,這裡在各個方法裡加了些調試信息,接著我們再實現MainActivity的代碼:
package com.example.jared.servicetest; import android.content.Intent; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.view.View; import android.widget.Button; public class MainActivity extends AppCompatActivity { private Button mStartServiceBtn; private Button mStopServiceBtn; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mStartServiceBtn = (Button)findViewById(R.id.startService); mStopServiceBtn = (Button)findViewById(R.id.stopService); mStartServiceBtn.setOnClickListener(new myOnClickListener()); mStopServiceBtn.setOnClickListener(new myOnClickListener()); } private class myOnClickListener implements View.OnClickListener { @Override public void onClick(View view) { switch (view.getId()) { case R.id.startService: Intent mStartIntent = new Intent(getApplicationContext(), MyService.class); startService(mStartIntent); break; case R.id.stopService: Intent mSopIntent = new Intent(getApplicationContext(), MyService.class); stopService(mSopIntent); break; default: break; } } } }
從上可知先調用了onCreate方法,然後調用onStartCommand方法。然後我們看下在運行著的服務,打開手機的setting下的apps裡的running:
從圖可知ServiceTest已經在了,然後這個時候我們再點擊啟動Service的話,是不會再調用onCreate方法的,只會調用onStartCommand方法,只有stop了Service才可以,那我們先stop掉Service,效果如下:
如圖調用了onDestroy方法。接著再啟動Service的話,就和上述一樣了。
上面代碼中還有個方法那就是onBind方法了,從字面可以理解到這個方法是把Activity和Service綁定了,那樣就可以通過Activity控制Service了。下面實現下代碼,修改layout如下:
<!--{cke_protected}{C}%3C!%2D%2D%3Fxml%20version%3D%221.0%22%20encoding%3D%22utf-8%22%3F%2D%2D%3E--> <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" android:orientation="vertical" android:layout_margin="10dp" android:padding="10dp" tools:context="com.example.jared.servicetest.MainActivity"><button android:id="@+id/startService" android:text="啟動Service" android:layout_width="match_parent" android:layout_height="wrap_content" android:textallcaps="false"></button><button android:id="@+id/stopService" android:text="停止Service" android:layout_width="match_parent" android:layout_height="wrap_content" android:textallcaps="false"></button><button android:id="@+id/startDownloadService" android:text="綁定Service Download" android:layout_width="match_parent" android:layout_height="wrap_content" android:textallcaps="false"></button><button android:id="@+id/stopDownloadService" android:text="解綁Service Download" android:layout_width="match_parent" android:layout_height="wrap_content" android:textallcaps="false"></button><button android:id="@+id/startGetProgressService" android:text="綁定Service GetProgress" android:layout_width="match_parent" android:layout_height="wrap_content" android:textallcaps="false"></button><button android:id="@+id/stopGetProgressService" android:text="解綁Service GetProgress" android:layout_width="match_parent" android:layout_height="wrap_content" android:textallcaps="false"></button></linearlayout>
package com.example.jared.servicetest; import android.app.Service; import android.content.Intent; import android.os.Binder; import android.os.IBinder; import android.support.annotation.Nullable; import android.util.Log; import android.widget.Toast; /** * Created by jared on 16/2/18. */ public class MyService extends Service{ private static final String TAG = "MyService"; private DownloadBinder mDownloadBinder = new DownloadBinder(); class DownloadBinder extends Binder { private int progress = 0; public void startDownload() { Log.d(TAG, "startDownload is called"); Toast.makeText(MyService.this, "startDownload is called",Toast.LENGTH_SHORT).show(); progress = 0; new Thread(new Runnable(){ @Override public void run() { for (int i=0; i<=100; i++) { try { Thread.sleep(1000); progress++; } catch (InterruptedException e) { e.printStackTrace(); } } } }).start(); } public int getProgress() { Log.d(TAG, "getProgress is called"); Toast.makeText(MyService.this, "getProgress is called",Toast.LENGTH_SHORT).show(); return progress; } } @Nullable @Override public IBinder onBind(Intent intent) { return mDownloadBinder; } @Override public void onCreate() { super.onCreate(); Log.d(TAG, "onCreate is called"); Toast.makeText(MyService.this, "onCreate is called",Toast.LENGTH_SHORT).show(); } @Override public int onStartCommand(Intent intent, int flags, int startId) { Log.d(TAG, "onStartCommand is called"); Toast.makeText(MyService.this, "onStartCommand is called",Toast.LENGTH_SHORT).show(); return super.onStartCommand(intent, flags, startId); } @Override public void onDestroy() { super.onDestroy(); Log.d(TAG, "onDestroy is called"); Toast.makeText(MyService.this, "onDestroy is called",Toast.LENGTH_SHORT).show(); } }
package com.example.jared.servicetest; import android.content.ComponentName; import android.content.Intent; import android.content.ServiceConnection; import android.os.Bundle; import android.os.IBinder; import android.support.v7.app.AppCompatActivity; import android.view.View; import android.widget.Button; import android.widget.Toast; public class MainActivity extends AppCompatActivity { private Button mStartServiceBtn; private Button mStopServiceBtn; private Button mBindService1Btn; private Button mUnbindService1Btn; private Button mBindService2Btn; private Button mUnbindService2Btn; private MyService.DownloadBinder downloadBinder; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mStartServiceBtn = (Button)findViewById(R.id.startService); mStopServiceBtn = (Button)findViewById(R.id.stopService); mBindService1Btn = (Button)findViewById(R.id.startDownloadService); mUnbindService1Btn = (Button)findViewById(R.id.stopDownloadService); mBindService2Btn = (Button)findViewById(R.id.startGetProgressService); mUnbindService2Btn = (Button)findViewById(R.id.stopGetProgressService); mStartServiceBtn.setOnClickListener(new myOnClickListener()); mStopServiceBtn.setOnClickListener(new myOnClickListener()); mBindService1Btn.setOnClickListener(new myOnClickListener()); mUnbindService1Btn.setOnClickListener(new myOnClickListener()); mBindService2Btn.setOnClickListener(new myOnClickListener()); mUnbindService2Btn.setOnClickListener(new myOnClickListener()); } private class myOnClickListener implements View.OnClickListener { @Override public void onClick(View view) { switch (view.getId()) { case R.id.startService: Intent mStartIntent = new Intent(getApplicationContext(), MyService.class); startService(mStartIntent); break; case R.id.stopService: Intent mSopIntent = new Intent(getApplicationContext(), MyService.class); stopService(mSopIntent); break; case R.id.startDownloadService: Intent mBindIntent = new Intent(getApplicationContext(), MyService.class); bindService(mBindIntent, startDownloadInService, BIND_AUTO_CREATE); break; case R.id.stopDownloadService: unbindService(startDownloadInService); break; case R.id.startGetProgressService: Intent mGetProgress = new Intent(getApplicationContext(), MyService.class); bindService(mGetProgress, getProgressInService, BIND_AUTO_CREATE); break; case R.id.stopGetProgressService: unbindService(getProgressInService); break; default: break; } } } private ServiceConnection startDownloadInService = new ServiceConnection() { @Override public void onServiceConnected(ComponentName componentName, IBinder iBinder) { downloadBinder = (MyService.DownloadBinder)iBinder; downloadBinder.startDownload(); } @Override public void onServiceDisconnected(ComponentName componentName) { } }; private ServiceConnection getProgressInService = new ServiceConnection() { @Override public void onServiceConnected(ComponentName componentName, IBinder iBinder) { downloadBinder = (MyService.DownloadBinder)iBinder; String progressValue = String.valueOf(downloadBinder.getProgress()); Toast.makeText(getApplicationContext(), "ProgressNow is:"+progressValue, Toast.LENGTH_SHORT).show(); } @Override public void onServiceDisconnected(ComponentName componentName) { } }; }這裡實例化了ServiceConnection,當通過bindService方法的時候,會通過ServiceConnection的onServiceConnected方法來調用Service中剛創建的下載類的方法。運行看下效果,先啟動下載,再獲取progress,運行效果如下:
這裡要注意的是,服務是單例的,所謂單例就是只有一個實例,只能被new一次,不同進程也只能調用一次。當我們調用bind download的時候會直接調用Service的onCreate,當我們解綁的時候,也會調用Service的onDestroy方法。不過當我們調用了啟動Service,又調用了binder的話,那就得ubind和stop方法都得調用。
上述當我們獲取progress的時候,如果不解綁,那麼之後的都是無效的。只有獲取了一次,解綁了,再獲取才有效。
android系統當內存不夠的時候會自動回收優先級比較低的服務,所以為了讓服務可以一直保存運行狀態,而不會由於內存不足的原因導致被回收,就需要使用前台服務。前台服務就是一直運行並在狀態欄顯示,類似音樂播放器就會在狀態欄一直保存著。簡單修改Service代碼如下:
package com.example.jared.servicetest; import android.app.PendingIntent; import android.app.Service; import android.content.Intent; import android.os.Binder; import android.os.IBinder; import android.support.annotation.Nullable; import android.support.v4.app.NotificationCompat; import android.util.Log; import android.widget.Toast; /** * Created by jared on 16/2/18. */ public class MyService extends Service{ private static final String TAG = "MyService"; private static final int NOTIFICATION_ID = 1; private DownloadBinder mDownloadBinder = new DownloadBinder(); class DownloadBinder extends Binder { private int progress = 0; public void startDownload() { Log.d(TAG, "startDownload is called"); Toast.makeText(MyService.this, "startDownload is called",Toast.LENGTH_SHORT).show(); progress = 0; new Thread(new Runnable(){ @Override public void run() { for (int i=0; i<=100; i++) { try { Thread.sleep(1000); progress++; } catch (InterruptedException e) { e.printStackTrace(); } } } }).start(); } public int getProgress() { Log.d(TAG, "getProgress is called"); Toast.makeText(MyService.this, "getProgress is called",Toast.LENGTH_SHORT).show(); return progress; } } @Nullable @Override public IBinder onBind(Intent intent) { return mDownloadBinder; } @Override public void onCreate() { super.onCreate(); Log.d(TAG, "onCreate is called"); Toast.makeText(MyService.this, "onCreate is called",Toast.LENGTH_SHORT).show(); NotificationCompat.Builder notification = new NotificationCompat.Builder(this); notification.setSmallIcon(R.mipmap.ic_launcher); notification.setContentTitle("前台服務"); notification.setContentText("這是個前台服務"); Intent intent = new Intent(this, MainActivity.class); PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, 0); notification.setContentIntent(pendingIntent); startForeground(NOTIFICATION_ID, notification.build()); } @Override public int onStartCommand(Intent intent, int flags, int startId) { Log.d(TAG, "onStartCommand is called"); Toast.makeText(MyService.this, "onStartCommand is called",Toast.LENGTH_SHORT).show(); return super.onStartCommand(intent, flags, startId); } @Override public void onDestroy() { super.onDestroy(); Log.d(TAG, "onDestroy is called"); Toast.makeText(MyService.this, "onDestroy is called",Toast.LENGTH_SHORT).show(); stopForeground(true); } }這裡用到了notification,然後通過startForegroid方法來啟動一個前台服務,運行看下效果:
從上圖可知,當啟動了前台服務的時候,在狀態欄有個圖標顯示,當activity退出的時候,還是存在,只有當停止服務的時候才消失,那麼就可以理解了為什麼qq音樂退出了還在播放歌曲,還可以通過前台服務點擊進入app。其實就是這個道理了。
關於Service就先學習到這裡了。總算把Service學習好了。接下去繼續學習別的知識點了。
Android junit單元測試,androidjunit軟件測試的分類* 黑盒測試 * 測試邏輯業務* 白盒測試 * 測試邏輯方法 根據測試粒度 * 方法測試:fun
Activity的四種啟動模式,activity四種模式在多Activity開發中,有可能是自己應用之間的Activity跳轉,或者夾帶其他應用的可復用Activity。
android之文件操作——讀取assets和raw文件下的內容,androidassets1.分別創建assets文件夾和res/raw文件夾:(要注意的raw文件是在
Menu創建菜單,menu創建 菜單是用戶界面中最常見的元素之一,使用非常頻繁,在And