android面試四

1、android:process

解決訪問SharedPreferences，不在同一進程

private SharedPreferencesDB(Context cxt) {
		this.context = cxt;
		Context context;
		try {
			context = cxt.createPackageContext(cxt.getPackageName(), Context.CONTEXT_IGNORE_SECURITY);
			prefs = context.getSharedPreferences(PREFS_FILE, Context.MODE_WORLD_READABLE + Context.MODE_WORLD_WRITEABLE);//可讀可寫
		} catch (NameNotFoundException e) {
			e.printStackTrace();
		}

	}

如果該屬性指定名稱以“：”開頭，則一個新的專屬於該應用的進程將會被創建。

如果該進程名以小寫字母開頭，則爲該activity提供權限以讓其在一個全局的進程中運行。這樣會允許多個應用的不同組件共用一個進程，以便節省資源。

2、applicationContext與context的區別

applicationContext與application生命週期一致,儘量用它

3、notifyDataSetChanged與notifyDataSetInvalidated

notifyDataSetInvalidated：更新數據並把列表組件移到頂部

notifyDataSetChanged：容易使列表閃動

4、drawable-m與drawable-h

高清圖放入drawable-h不容易佔內存，若高清圖放入drawable-m則內存增大,若將低清圖放入drawable-h容易造成UI失真

5、應用存在時清緩存

清除緩存時會執行onSaveInstanceState方法

@Override
	protected void onSaveInstanceState(Bundle outState) {
		super.onSaveInstanceState(outState);
		outState.putString("key", "value");//緩存數據
	}

清除緩存後打開應用時，會再次執行onCreate(Bundle savedInstanceState)

在這個方法中把剛剛被清除的數據給找回

if (savedInstanceState != null) {
String str=savedInstanceState.getString("key"));
}

6、全局異常處理UncaughtExceptionHandler

在public void uncaughtException(Thread thread, Throwable ex) 方法中執行捕獲全局異常

7、android4.0前與後對於flash的處理

4.0需要硬件加速

mainfest.xml設置android:hardwareAccelerated="true"

8、加載圖片

TransitionDrawable td = new TransitionDrawable(new Drawable[] { new ColorDrawable(R.color.transparent),
new BitmapDrawable(resources, bitmap) });
holder.getInfoListImg().setImageDrawable(td);
td.startTransition(150);

9、防止睡眠

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

private void acquireWakeLock() {
		if (wakeLock == null) {
			PowerManager pm = (PowerManager) getActivity().getSystemService(Context.POWER_SERVICE);
			wakeLock = pm.newWakeLock(PowerManager.SCREEN_BRIGHT_WAKE_LOCK, this.getClass().getCanonicalName());
			wakeLock.acquire();
		}

	}

private void releaseWakeLock() {
		if (wakeLock != null && wakeLock.isHeld()) {
			wakeLock.release();
			wakeLock = null;
		}

	}

10、電話狀態監聽

TelephonyManager telephonyManager = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
		telephonyManager.listen(new MobliePhoneStateListener(), PhoneStateListener.LISTEN_CALL_STATE);

private class MobliePhoneStateListener extends PhoneStateListener {

		@Override
		public void onCallStateChanged(int state, String incomingNumber) {
			if (currentMusic == null)
				return;
			MediaPlayer mPlayer = playerMap.get(currentMusic.getPlayUrl());
			switch (state) {
			case TelephonyManager.CALL_STATE_IDLE: /* 無任何狀態時 */
				break;
			case TelephonyManager.CALL_STATE_OFFHOOK: /* 接起電話時 */
				break;
			case TelephonyManager.CALL_STATE_RINGING: /* 電話進來時 */
				break;
			default:
				break;

			}

		}

	}

11、監聽耳機插拔

IntentFilter filter = new IntentFilter(AudioManager.ACTION_AUDIO_BECOMING_NOISY);
		this.registerReceiver(new AudioBroadCastReceiver(), filter);

public class AudioBroadCastReceiver extends BroadcastReceiver {

		@Override
		public void onReceive(Context context, Intent intent) {
			if (AudioManager.ACTION_AUDIO_BECOMING_NOISY.equals(intent.getAction())) {/*耳機被拔出*/
				
			}
		}
	}

12、監控apk安裝

<receiver
            android:enabled="true"
            android:name="com.mobcent.ad.android.ui.activity.receiver.AdBootReceiver" >
            <intent-filter >
                <action android:name="android.intent.action.PACKAGE_ADDED" />
                <action android:name="android.intent.action.PACKAGE_REMOVED" />
                <action android:name="android.intent.action.PACKAGE_REPLACED" />
                <data android:scheme="package" />
            </intent-filter>
        </receiver>

@Override
	public void onReceive(Context context, Intent intent) {
		String action = intent.getAction();
		String packageName = intent.getData().getSchemeSpecificPart();
		adService = new AdServiceImpl(context);
		if (Intent.ACTION_PACKAGE_ADDED.equals(action)) {//添加
			
		}else if(Intent.ACTION_PACKAGE_REMOVED.equals(action)){//移除
			
		}else if(Intent.ACTION_PACKAGE_INSTALL.equals(action)){//安裝
			
		}

	}